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Developing facile methods to modulate the structure and performance of photocatalysts plays a pivotal role in the potential large-scale application of photocatalytic hydrogen production. Herein, a series of uniformly sized and highly dispersed copper-doped cadmium sulfide (CdS) nanoparticles (NPs) were successfully synthesized through a facile cation exchange strategy. The resulting Cu-doped CdS samples exhibited a remarkable photocatalytic hydrogen production rate of 2459.3 μ mol·h−1g−1, nearly 11 times that of pure CdS. The introduction of Cu+ ions effectively reduced the band gap, leading to enhanced light absorption, as well as improved charge carrier separation and transfer efficiency. Meanwhile, the theoretical investigation further confirmed that Cu+ doping substantially decreased the free energy of hydrogen adsorption and provided more suitable active sites, thereby promoting the photocatalytic hydrogen production activity on CdS NPs. This work provides compelling evidence for the exploration of novel transition metal-doped photocatalysts for hydrogen production using the cation exchange method. [Display omitted] • Controllable Cu-doped CdS was prepared via cation-exchange approach. • Cu doping induced extended light absorption and accelerated charge separation. • HER was promoted by reduced free energy of hydrogen adsorption via Cu doping. • Photocatalytic hydrogen production of CdS was enhanced by 11 times. [ABSTRACT FROM AUTHOR]

To trace Critical Zone processes and to quantify Li fluxes from one Critical Zone compartment into another, we investigated the Li concentration and isotopic composition (δ7Li) of time-series water samples (including subsurface flow, groundwater and creek water), vegetation, bedrock (including separated minerals from bedrock), and regolith (including exchangeable fraction and clay-sized fraction of regolith) in a temperate forested headwater catchment in the Black Forest, Conventwald, Germany. Our estimation of the Li budget shows that atmospheric deposition and biological processes played minor roles in the Li cycle relative to chemical weathering. All water samples (δ 7Li value of 6.5 to 20.4 ‰) were enriched in 7Li compared to bedrock (-1.3 ‰) and regolith (∼-1.7 ‰), but δ7Li differed between water pathways: δ7Li variations in subsurface flow, creek water and groundwater were controlled by conservative mixing, exchangeable pool buffering and Li incorporation/adsorption, respectively. Fractionated heavy Li isotopes in water samples resulted from the formation of secondary solids which preferentially incorporated 6Li, with the separated clay-sized fraction of the regolith exhibiting more negative δ7Li values (-5.4 to −3.5 ‰) than the bulk regolith (∼-1.7 ‰). However, Li in secondary solids only accounted for 8 ± 6 % of the total Li hosted in bulk regolith, and consequently δ7Li in soil did not differ significantly from δ 7Li in bedrock. This is unexpected considering water is continuously removing 7Li in preference over 6Li from regolith. Mass balance calculations applied at the catchment scale point to an irreconcilable imbalance with our data. On one hand, the regolith's δ7Li values are not negative enough to balance the 7Li export by river water, and on the other hand Li in the riverine dissolved load only accounts for ∼ 30 % of the Li solubilized from regolith. Therefore, we suggest that there might be a "hidden export pathway" for Li at our site, possibly subsurface removal of fine particles enriched in 6Li. In light of increasingly frequent observations of such isotopic imbalances in the Critical Zone this phenomenon deserves increased attention. [ABSTRACT FROM AUTHOR]

Carbonate weathering plays a significant role in regulating global carbon budget at short time scales, and thus needs to be better constrained in the context of global warming. Riverine magnesium isotopes (δ26Mg) have the potential to trace carbonate weathering intensity (CWI) but require further testing under various climatic and geological settings. Cation exchange is an important mechanism buffering river water chemistry, especially in catchments characterized by high erosion. However, field evidence on the influence of cation exchange on riverine δ26Mg is rare. In this study, spatial riverine δ26Mg variation within the Three Rivers (i.e., the Jinsha Jiang, the Lancang Jiang, and the Nu Jiang), three extremely-high-erosion catchments in the southeastern Tibetan Plateau, was investigated to address this issue. The results showed that riverine δ26Mg values present a wide range from –1.11 ‰ to –0.59 ‰ in the Jinsha Jiang, from –1.39 ‰ to –0.65 ‰ in the Lancang Jiang, and from –1.19 ‰ to –0.50 ‰ in the Nu Jiang. An inversion model was used to partition riverine Mg2+ sources and confirmed that the riverine Mg2+ budget was dominated by carbonate weathering, followed by evaporite dissolution. However, conservative mixing could not explain riverine δ26Mg variation within the Three Rivers catchments, because measured δ26Mg values (δ26Mg measured) systematically deviated from the modeled ones (δ26Mg modeled), with Δ26Mg measured–modeled (δ26Mg measured – δ26Mg modeled) up to 0.79 ‰. The positive correlations between Δ26Mg measured–modeled and suspended particulate matter (SPM) concentrations indicate Mg isotopic fractionation was related to high suspended loads owing to extremely-high erosion rates. Given the significant cation exchange capacity of SPM, Mg2+-Na+ exchange is proposed for the first time as an explanation for the observed δ26Mg variations in the rivers draining the Tibetan Plateau, although the role of carbonate precipitation could not be excluded. The strong positive correlations between riverine δ26Mg and exchangeable Mg/Na ratios in the Three Rivers further support that light Mg isotopes may be preferentially retained in the riverine exchange pool during Mg2+-Na+ exchange, driving riverine δ26Mg towards higher values. Expanding our finding to global rivers, the negative correlation between riverine δ26Mg and CWI can be interpreted by a competition between the fast dissolution of carbonates leading to the enrichment of 24Mg in waters and Mg isotope fractionation induced by cation exchange leading to the depletion of 24Mg in the residual waters. This study provides new insight into cation exchange as a regulator of riverine δ26Mg and Mg cycling, highlighting the robustness of riverine δ26Mg in tracing CWI and constraining the carbon cycle. [ABSTRACT FROM AUTHOR]

Chemical weathering is one of the most important processes on the Earth's surface, and lithium isotopes have been used as a promising tracer of silicate weathering, as the secondary clay minerals precipitated during silicate weathering are thought to preferentially incorporate the lighter 6Li isotope. However, to utilize lithium isotopes as a geochemical tracer, it is essential to quantitatively understand the partitioning of Li in clay minerals, including structurally bound Li and exchangeable interlayer ions, as well as the associated isotope fractionation. With classical molecular dynamic simulations and thermodynamic calculations, the cation exchange between Na-/K-montmorillonite and solvated Li in environmental solution are disclosed under different aqueous activity conditions. The Li+ ion, whose hydration ability is stronger than Na+ and K+ ions, is easier to swell the montmorillonite and shows less affinity for the clay. And the calculated cationic selectivity coefficients between Na+/K+ and Li+ ions are K c (Li → Na) = 2.0, K c (Li → K) = 10.0 for Arizona-type montmorillonite and K c (Li → Na) = 1.0, K c (Li → K) = 4.0 for Wyoming-type montmorillonite, which are comparable to reported experiments. The cationic partition of Li in the clay interlayer decreases when the hydration states of montmorillonite transform from triple-layer to bilayer and then to monolayer. Based on the density functional theory, the Li isotope fractionations for Li in clay interlayer sites and structural octahedral sites are further derived by thermodynamic calculations with path integral molecular dynamic simulation, which deals with the quantum anharmonicity. The behaviors of Li isotope in the bilayer hydration state closely resembles that in the aqueous solution, and only a slight Li isotope fractionation is found between the monolayer hydrated octahedral-substituted clay and solution phase (Δ7Li monolayer-aq = −2.0‰). While Li isotope fractionation between aqueous solution and mica structural sites is significant (Δ7Li structural-aq = −10.4‰) and shows an obvious quantum anharmonicity, which indicates the importance of the anharmonic treatment for Li isotope fractionation calculations. The newly calculated Li equilibrium isotope fractionation between clay and aqueous solution deviates from the experimentally determined fractionation factor, which can be attributed to the kinetic effects. Moreover, on the basis of the surface kinetic reaction model, the Li isotope fractionation becomes more pronounced with higher clay growth rate. By integrating the cationic selectivity coefficient and Li isotope fractionation, it is possible to constrain the fluid composition during Li-clay deposit and diagenesis, and to evaluate the intensity of chemical weathering processes as well as the related carbon cycle. [ABSTRACT FROM AUTHOR]

• NaCl inhibited the growth and increased Na and Cl concentrations in rice leaves. • Application of Fe mitigated adverse effects of NaCl on rice growth. • Fe-supply enahnced plant antioxidant enzymatic activity in rice plants. • Fe-supply improved CEC of the soil and limited Na uptake by rice. Soil salinity affects plant growth and results in decreased agriculture productivity throughout the world. The present study was carried out to elucidate underlying mechanisms responsible for soil salinity tolerance in rice under the application of iron (Fe) as Fe(NH 4) 2 (SO 4) 2 ·6H 2 O. Rice seedlings were grown in pots containing soils (pH >8.0) and exposed to 0 and 150 mM (EC of 5.25 dS m−1) NaCl stress both with and without 0.5 mM Fe(NH 4) 2 (SO 4) 2 ·6H 2 O. Plant growth attributes like root length, shoot length, roots and shoots biomass, leaf chlorophyll contents, salt ions, plant mineral concentrations, plant antioxidant activities and cation exchange of soil were determined. Application of NaCl at the rate of 150 mM reduced the leaf chlorophyll contents (34%), root fresh and dry weights (39% and 45%), shoot fresh and dry weights (35% and 53%), grain yield (39%), potassium (K) (59% and 48%), calcium (Ca) (39% and 24%), and magnesium (Mg) (59% and 50%) concentrations in roots and leaves, whereas enhanced the sodium (Na) (537% and 500%) and chloride (Cl) (425% and 156%) accumulation both in roots and leaves as compared to control. Interestingly, Fe-supply enhanced the Fe uptake by rice plants and mitigated the adverse effects of salinity on rice growth and yield by 30%. Moreover, plant antioxidant enzymatic activity and cation exchange capacity (CEC) of soil (cmol Na+ kg−1) were enhanced by Fe-supply. In conclusion, Fe-application enhanced tolerance in rice due to down regulation of Na and up-regulation of Fe and antioxidant enzymatic activity in leaves. In addition, increased Na adsorption onto the surface of soils suggests that Fe competes with Na at soil-root interface, thereby limiting Na uptake by the plants. [ABSTRACT FROM AUTHOR]

To reduce the efflorescence extent of metakaolin (MK)-based geopolymer, this study introduced thermally activated modified calcium montmorillonite (MT) and 5 A zeolite (ZT) into MK-based geopolymer, and the optimal mixing ratio was acquired by response surface methodology. The effect of the two modified clay minerals on the microstructural and mechanical properties of the MT-ZT-MK geopolymer was explored by compressive strength testing, phase analysis (XRD and FTIR), pore structure analysis (MIP), and morphology analysis (SEM-EDS). To investigate the performance and mechanism of efflorescence inhibition of the ternary geopolymer, the cation concentration in the leaching solution was detected by inductively coupled plasma atomic emission spectrometry (ICP-OES), and the efflorescence area of the geopolymer was calculated using Image Pro Plus (IPP) software. The results of the experiment showed that the optimal mixing ratio, as determined by RSM, was 1.5 wt% of modified MT and 2.9 wt% of modified ZT, with the highest compressive strength at 65.1 MPa and the lowest degree of efflorescence after 28 days of curing. It can be concluded that the two clays gradually exhibit the effect of cation exchange and internal curing. The pore structure is optimized and (N, C)-A-S-H gels are formed with the extension of curing time. On the other hand, the lesser extent of efflorescence possibly is attributed to the restricted channels for Na+ in the matrix to undergo carbonation with CO 2 in the air. • Using thermally activated modified clay minerals to prepare ternary geopolymer. • The optimal mixing ratio of the ternary geopolymer is established by using RSM. • A proper content of modified clays is beneficial for the strength enhancement of geopolymers. • The mechanism of clay minerals to reduce efflorescence of geopolymers involves cation exchange and internal curing. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ionic liquid [HOEmim][NTf 2 ] can strengthen the extraction performance of TBP for Co2+. • The extraction efficiency of TBP/kerosene/[HOEmim][NTf 2 ] system for Co2+ is up to 99.6 %. • DFT calculations and FT-IR analysis indicate that Co2+ mainly binds to P=O in TBP. • A theoretical basis for removing Co2+ from waste water based on ionic liquids was laid. • ABSTRACT In order to achieve effective removal of radioactive Co(II) from the primary circuit wastewater of nuclear power plants and promote the safe use of nuclear energy, an efficient and eco-friendly method using ionic liquid as a co-extractant was proposed. The effects of ionic liquids 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C 2 mim][NTf 2 ]) or 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HOEmim][NTf 2 ]) as co-extractants on the extraction of Co(II) using tributyl phosphate (TBP) as an extractant were investigated in this work. The results reveal that the optimal extraction conditions for Co(II) are as follows: V TBP : V kerosene : V [HOEmim][NTf2] = 18:1:1, R(O/A) = 1, pH=4. Under these conditions, the extraction efficiency of Co(II) (E Co) reaches 99.6 %, with a distribution ratio (D Co) of 257. Notably, a single TBP or ionic liquid exhibits minimal ability to extract Co2+, while adding only 5 % (v/v) ionic liquid based on TBP/kerosene system can increase D Co by 104 times. The slope method and FT-IR analysis demonstrate that the TBP/kerosene/[HOEmim][NTf 2 ]/ system extracted Co2+ by a cation exchange mechanism. In addition, density functional theory (DFT) calculations were employed to explain the influence of different ionic liquid systems on the E Co , and further elucidate the extraction mechanism of Co2+. The striping results indicate that 92.2 % of Co2+ is stripped with 1.0 mol L−1 HNO 3. The extraction efficiency of Co(II) from the TBP/kerosene/[HOEmim][NTf 2 ] system remained at 98 % after 6 cycles. Therefore, the extraction system exhibits great practical potential in removing Co(II) from contaminated water. This work not only proposes an extraction system with excellent reusability and stability, but also lays a theoretical foundation for the ionic liquid-based cobalt extraction process. [ABSTRACT FROM AUTHOR]

The study presents a novel integrated three-compartment electrochemical continuous electrodeionization reactor that was constructed in a laboratory environment. In order to extract large amounts of carbon dioxide from naturally occurring oceanwater in the form of bicarbonate and carbonate, it develops a innovative electrolytic cation exchange process. At the same time, it produces hydrogen gas for possible hydrocarbon synthesis. The study employs the Box-Behnken experimental design approach implemented through the Design Expert software to investigate and optimize the performance of electrochemical hydrogen extraction from Ocean water from an integrated reactor. The integrated electrochemical continuous-type electrodeionization reactor comprises two cation-permeable membranes that operate as boundaries between three compartments: a central compartment and electrode compartments that house the cathode and anode, each of which may reverse polarity. These membranes are made of gel polystyrene cross-linked with divinylbenzene, which has acidic properties that allow cation transport while inhibiting anions. The integrated reactor's electrode chambers are enclosed in plexiglass end plates and contain distinct Plexiglass electrode compartments. These compartments have mesh and solid steel anode and cathode electrodes, with an electrode active area of 176.71 cm2. The influence of various factors, such as voltage and electrolyte amount, on the production of hydrogen synthesis is examined. The study results demonstrate a maximum hydrogen production rate of 2.2 mg/min and a hydrogen production efficiency of 7.82%. The lab testing was carried out using experimental equipment to determine viability. The tests included 35-min runs that measured hydrogen generation under various parameters, such as applied voltage, electrolyte concentration, and pH levels. The ocean salt solutions of 0.5M, 1M, and 2M were initially prepared and evaluated for hydrogen generation. Each concentration is assessed at a voltage range of 4–15V, with matching solution pH values ranging from 2 to 7. Optimization studies were conducted to enhance the hydrogen production rate. The results indicate that hydrogen production rises proportionally with applied voltage and electrolyte concentration but falls with pH growth. Within the Design Expert software, the statistical methods for response surface analysis and optimization are utilized accordingly. • The paper develops an integrated three-compartment system for hydrogen production. • The paper investigates the system overall efficiencies for assessment. • It discusses how varying voltage and concentration affects hydrogen production. [ABSTRACT FROM AUTHOR]

• Theoretical evaluation of protein separations by simultaneous independent pH & NaCl gradients. • Experimental demonstration of two dimensional LC pH & NaCl gradients. • Isocratic [NaCl] in pH gradients and vice versa vary MAb isoform retention times in WCX LC. • Separation of proteins by uncoupled pH and [NaCl] gradients enhances & improves resolution. • No one single set of uncoupled salt and pH gradients optimizes the resolution of all MAb isoforms. In previous publications we have described the pISep dual simultaneous, independent gradients (DSIGs) liquid chromatography (LC) for uncoupling gradients of non-buffering solute (NaCl, urea or acetonitrile) from externally generated pH gradients. In DSIGs the shape and slope of the [salute] gradient does not depend on the shape and slope of the pH gradient. The technique allows in a single run true simultaneous two dimensional LC separation of complex protein mixtures on various stationary phases including anion, cation exchangers (AEX, CEX), reversed phase (RP), mixed mode and mixed bed. Using a humanized IgG 1 (HIgG 1) monoclonal antibody (MAb) and a variety of pH & [NaCl] DSIGs, we show that most of MAb isoforms can be successfully separated from each other. These experimental observations are supported by an initial theoretical argument presented here predicting an overall improvement of all MAb isoforms separation by DSIGs of pH & [NaCl]. Theoretical calculations predict that, in general, there exists an optimal non-zero isocratic salt concentration in a pH gradient separation that will resolve isoforms close in binding energy, but a wide range of salt concentrations will be required for acceptable resolution of all isoforms. Theory also predicts better separation of weaker rather than stronger binding isoforms. Experimentally, we have found that no one set of DSIGs LC conditions could optimally baseline resolve all identifiable MAb isoforms in a single run of reasonable duration. The versatility and simplicity of the pH & [NaCl] pISep DSIGs LC allows fast, automated scouting of protein separations over any range of pH from 2.4 to 10.8 and [NaCl] from 0 to 1 M without changing the chemistry of the buffering system. Due to the universal applicability of the pISep buffering system in IEX LC, the researcher is given a powerful tool to easily develop pH & [NaCl] DSIGs protocols that vary mobile phase compositions to achieve high resolution separations of targeted proteins. [ABSTRACT FROM AUTHOR]

Currently, the deep geological repository approach for spent nuclear fuel is regarded as the most dependable and secure method for permanently disposing of this kind of waste. Among its key safety components is an engineered barrier made from compacted bentonite, which isolates the encapsulated waste from the surrounding host rock. As a result, understanding how bentonites react to varying compositions of groundwater is crucial. This is where numerical modelling becomes essential. It is generally approved by the scientific community to idealise bentonite as a material structured under a double porosity system composed of the macro and microstructure. In this context, this paper illustrates the capabilities of a double-porosity reactive transport model for bentonites fully implemented in the multiphysics COMSOL platform. For this purpose, different experimental tests were simulated based on the evaluation of diffusive ion transport, mineral dissolution and cation exchange processes in MX-80 bentonite, obtaining very satisfactory results. • A new reactive transport model for bentonites was implemented in COMSOL Multiphysics. • The model includes a geochemical system composed of 14 chemical species and gypsum. • The model considers diffusive-dispersive-advective transport in double-porosity media. • The model validation was run by 3 tests set in the Task Force on Engineered Barrier. [ABSTRACT FROM AUTHOR]

Targeted Alpha Therapy (TAT) has shown very high potential for the treatment of cancers that were not responsive to other therapy options (e.g., β− therapy and chemotherapy). The main constraint to the widespread use of TAT in clinics is the limited availability of alpha-emitting radionuclides. One of the most promising candidates for TAT is 225Ac (t 1/2 = 9.92 days), which can be used directly in combination with selective biomolecules (e.g., antibodies, peptides, etc.) or be a generator source of 213Bi (t 1/2 = 45.6 min), another shorter-lived TAT radionuclide. Several strategies are currently under investigation to increase the supply of 225Ac. One of the most attractive options is the irradiation of natural thorium-232 targets with high-energy protons (≥100 MeV). However, there are several challenges associated with this production method including the development of an efficient radiochemical purification method. During irradiation of natural thorium with proton energy above 100 MeV, several Ra isotopes (223,224,225Ra) are produced. 223Ra (t 1/2 = 11.43 days) is used for the treatment of bone metastases and can also be used as a generator source for 211Pb. Additionally, 225Ra (t 1/2 = 14.9 days) can be a valuable source of isotopically pure 225Ac. In the present work, we address the radiochemical separation aspects of isolating Ac and Ra isotopes from irradiated thorium targets. [Display omitted] • Actinium-225 (t 1/2 = 9.92 d) is one of the most promising candidates for Targeted Alpha Therapy (TAT) • The irradiation of natural thorium with high energy protons can provide clinically relevant amounts of 225Ac/213Bi and 223Ra • Ac and Ra can be isolated from the bulk mass of Th(IV) and co-produced fission products via cation exchange chromatography in trichloacetic acid • DN Resin allows the purification of Ac from lanthanides [ABSTRACT FROM AUTHOR]

Lithium (Li) isotopes have shown large potential in tracing weathering in various water bodies, but there is limited study on Li isotopes in subsurface conditions where CO 2 has been largely consumed. In this study, we use a thick sandstone aquifer in the Ordos Basin, NW China, as a natural setting to investigate the behaviors of Li isotopes in hydrogeochemical conditions with different concentrations of dissolved CO 2. For young groundwater in the recharge area (group R) where CO 2 is abundant (mean P CO2 = 10-2.5 atm), clay formation accompanying with weathering leads to the enrichment of 7Li in groundwater. The four deep samples in the recharge area have uniform Li/Na ratios (with a mean of 2.52 μmol/mmol) and δ7Li (with a mean of 25.0‰), corresponding to a mean Li removal rate of 81.2% compared with the sandstone leachate. For groundwater in the shallow part of the discharge area (group D1), Li was firstly removed by clay formation during weathering in the recharge area and was later removed by physisorption when CO 2 becomes much lower (mean P CO2 = 10-3.1 atm). Different degrees of weathering lead to a wide range of δ7Li varying from 19.7‰ in the deepest well to 33.0‰ in the shallowest well. The proportion of Li removal caused by physisorption is found to increase with groundwater age. After the stage of Li removal by adsorption, Li was released in the deeper part of the discharge area (group D2), and the positive correlation of δ7Li versus Li/Na is explained by a ternary mixing model. The endmember of water brought by cation exchange is inferred to have a heavier δ7Li than sandstone leachate, demonstrating that cation exchange could cause an enrichment of 7Li in water. This study enhances our understanding of the controlling factors of Li isotopes in deep groundwater with low dissolved CO 2 , which have implications for the application of Li isotopes in subsurface water. [ABSTRACT FROM AUTHOR]

In this study, Cu-doped ZnIn 2 S 4 nanosheets were synthesized through cation exchange reactions to enhance the dual-functional photocatalytic processes of CO 2 reduction and hydrogen evolution. The optimized Cu doping levels in Cu-ZIS samples significantly improved the photocatalytic performance, resulting in enhanced H 2 -evolution rates and increased selectivity in CO 2 reduction, particularly in the production of C 2 H 4 and CO. Characterization techniques confirmed the successful integration of Cu into the ZIS lattice, thereby improving charge transfer and separation within the material. Mechanistic studies indicated that Cu doping enhanced light absorption, charge transfer efficiency, and introduced shallow energy levels, consequently reducing charge carrier recombination and improving overall catalytic performance. These findings highlight the substantial potential of Cu-doped ZnIn 2 S 4 nanosheets for sustainable dual-functional applications in solar energy conversion. [Display omitted] [ABSTRACT FROM AUTHOR]

Ion composition in groundwater at the spent nuclear fuel repositories is a relevant uncertainty for predicting the shear behavior of the bentonite buffer. However, only a few studies investigated the range of shear strength variation with in-situ groundwater conditions. This paper examines the ultimate shear strength of compacted Wyoming-type bentonite, focusing on the effect of pore water salinity. Triaxial tests were performed under effective confining pressures up to 10 MPa with different types of pore water representing: 1) extremely low, 2) current, and 3) maximal salinity conditions at the repositories, while tracking the evolution of exchangeable cation composition. The results revealed that pore waters with typical Ca2+ concentrations at the repositories strengthen the sodium bentonite through Na+-Ca2+ cation exchange. The observed salinity-dependent strength of the bentonite was described by the ultimate shear strength line and its apparent mobilization in the deviatoric stress-mean effective stress plane. The upper limit of the increase in strength was found to be 0.74 MPa. Previous triaxial test results with deionized water were compared to refine the shape of the ultimate shear strength line. Lessons learned from the triaxial testing of saturated bentonite were elucidated to offer recommendations to address the challenges associated with high swelling potential and low permeability. The findings in this paper have implications for accurate assessment of shear behavior in the deep geological disposal system as well as effective laboratory measurements of the shear strength parameters of compacted bentonite. • Triaxial tests on a highly-swelling material under high confining pressure and pore water salinity are documented. • Shear strength dependency of a compacted bentonite on pore water salinity has been quantified. • Recommendations for triaxial testing of compacted bentonite are provided. [ABSTRACT FROM AUTHOR]

The hydrogeochemical signature of the discharged water can reveal significant information on the circulation and evolution of geothermal water, which can further guide the exploration and utilization of geothermal water resources. In this study, the source of major ions, reservoir temperature, and cycle time of geothermal fluids were clarified by the Ion relationship analysis, integrated multicomponent solute geothermometry method, and 14C isotope analysis, respectively, in the Wugongshan area of South China. Results show that the eastern and western parts of the Wugongshan area have distinct types of geothermal fluids, i.e. HCO 3 -Na and SO 4 HCO 3 -Na, respectively. The major source of HCO 3 − and Na+ is the hydrolysis of silicate minerals, partially accompanied by cation exchange. While gypsum hydrolysis and sulfide oxidation are the primary producers of SO 4 2−. Moreover, higher TDS, PH, and degree of cation exchange of geothermal fluids were found in the western part than that in the eastern part. The reservoir temperatures in the eastern and western portions are comparable (115–150 °C). However, the cycle time of the geothermal fluids in the western part (15,743 years on average) is much greater than in the eastern part (2160 years on average), which is considered to be the main reason for the difference in hydrogeochemical characteristics. This study can provide theoretical support for the rational development and usage of geothermal water resources. • The distinct geothermal water types were found in the Wugongshan area. • Gypsum hydrolysis and sulfide oxidation are the primary producers of SO 4 2−. • Higher TDS, PH, and degree of cation exchange were found in the western part. • The cycle time of geothermal fluids in the western part is much greater. [ABSTRACT FROM AUTHOR]

Selected layered clay minerals of smectite group with different chemical composition (e.g. synthetic hectorite, synthetic smectite and natural smectite) were modified by rare earth cations such as Er3+ and a stochiometric mixture of Er3+/Yb3+. Raw and modified smectites were systematically heated up to temperatures ensuring their dehydration (400 °C), dehydroxylation (800 °C) and formation of new high temperature phases (1200 °C). The products of heating were investigated by terahertz-time domain spectroscopy to follow changes of their dielectric properties in the far-infrared region. The frequency-dependent refractive index of raw and modified clays was determined in the range of 0.2–3.8 THz (6.6–126.5 cm−1). The heating at 800 °C and above resulted in increase frequency dependent index of refraction and decrease absorption coefficient in comparison to the raw clays. The ion-exchanged smectites by rare earth cations further decreased the absorption coefficient of the samples heated at 1200 °C. Raw natural smectite sample revealed a low frequency band at 0.86 THz, already reported in the literature, which shifted to 0.67 THz after sample modification by rare earth cations. Heating of modified JP to 1200 °C resolved a new absorption band at ∼3.40 THz in the ceramic phase produced from raw natural smectite. • Cation exchange reaction was used for modification of clays by selected rare earth elements. • Effect of sample heating up to 400, 800 and 1200 °C was studied. • Terahertz time domain spectroscopy was used to study the refractive index dispersion. • The frequency dependence of absorption in THz region resolved new typical absorption bands. • The high temperature treatment can be used for synthesis of new ceramic phosphor materials. [ABSTRACT FROM AUTHOR]

The knowledge of cation exchange parameters is important to understand and model the porewater chemistry in clayrocks. The Opalinus Clay (OPA) is a well-studied formation in view of its importance as host rock for radioactive waste repositories, but uncertainties exist regarding its cation exchange parameters, in particular its selectivity coefficients (K c). In fact, porewater chemistry models for OPA have so far been based on generic selectivity coefficients. Thanks to a recent extensive siting programme, involving eight vertical deep boreholes in northern Switzerland, a large number of porewater and cation exchange data from the OPA and its clay-rich confining units could be analysed. Thus, from the combination of porewater compositions (obtained from high-pressure squeezing and advective displacement), and exchangeable cation data (obtained from Ni ethylenediamine extraction), reliable selectivity coefficients could be derived. The values for K c Na/K, K c Na/Ca, K c Na/Mg are consistent with those obtained in parallel from the Mont Terri underground rock laboratory although the scatter is somewhat larger in the latter dataset. The derived selectivity coefficients indicate no dependency on ionic strength or in-situ temperature. Minor differences in K c values between OPA and confining units can be attributed to differences in clay mineralogy. The validity of a two-site cation exchange model including illite and smectite for estimating exchangeable Na, Ca and Mg from measured porewater compositions could be shown, while this simple model underpredicts the share of exchangeable K. The exchangeable cation extraction procedure induces the dissolution of Sr-bearing minerals whose amount is in the same range as exchangeable Sr, thus not enabling the derivation of selectivity coefficients for Sr. Finally, derived selectivity coefficients confirm results of previous studies, thus providing confidence in the applied experimental and modelling protocols on the one hand and in the outcome of those studies on the other hand. • Large porewater and cation exchange dataset for Opalinus Clay and confining units. • Robust selectivity coefficients consistent with previous work. • Derived selectivity coefficients are insensitive to temperature effects. • Two-site model with illite and smectite is partly successful. • Improved data for modelling is provided. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cd x Ag 2-x Se CQDs were chemically designed through partial cation exchange. • States of Ag ions were created for NIR absorption. • Surface traps induced by cation exchange were mitigated using a two-step process. • Traps were passivated via solution-phase ligand exchange and post-passivation. • High near-infrared responsivity (457 mA/W) was successfully achieved. Cation-exchange (CE) is a straightforward method for synthesizing colloidal quantum dots (CQDs) comprising multiple elements. However, the responsivity of photoconductors using cation-exchanged CQDs remains limited due to surface traps induced by the CE process. In this study a flexible near-infrared (NIR) photoconductive detector that exhibits the high responsivity (457 mA/W) under NIR light compared to reported Ag 2 Se CQD photodetector is fabricated using partially cation exchanged Cd x Ag 2-x Se CQDs. The as-synthesized CdSe CQDs were transformed into Cd x Ag 2-x Se CQDs through the introduction of an Ag precursor to enhance their NIR absorption characteristics and preserve their cubic structures. To mitigate surface traps associated with cation-exchanged CQDs, solution-phase ligand-exchange and post-treatment for surface passivation are incorporated using InBr 3. In and Br ions are utilized to fill the surface vacancies of the CQDs and passivate the dangling bonds, reducing nonradiative recombination sites. Structural and optical analyses confirm the passivation of trap states. In addition, indium passivation improves the Seebeck coefficient and mobility, resulting in enhanced responsivity. This study underscores the importance of surface passivation in the CE method, thereby contributing to the future CQDs development with multiple elements. [ABSTRACT FROM AUTHOR]

[Display omitted] • Zr(OBA) was synthesised with a high surface area and active binding sites to efficiently remove Sr2+ and Cs+ from solution. • The was stable in acid medium up to 4 M concentration of HNO 3 which is studied by PXRD. • This MOF shows distribution coefficients and record-high absorption capacities (Q m) of 353 mg/g for Sr2+ and 432.91 mg/g for Cs+ at pH 4. • The selectivity of Sr2+ and Cs+ ions in the simulated nuclear waste with sorption capacity of 112.75 mg/g for Sr2+ and 141.24 mg/g for Cs+ under 4 M HNO 3 circumstances, and 221.5 mg/g for Sr2+ and 253.77 mg/g for Cs+ from simulated seawater. • DFT computational simulation, the binding energy of strontium and caesium with MOF was estimated to be −87.31 kJ/mol for Sr2+ and −113.75 kJ/mol for Cs+, suggesting that Sr2+ bound with oxygen of linker OBA and the cationic exchange of [Me 2 NH 2 ]+ of Zr (OBA) by Sr2+ and Cs+ ions. • The regeneration and reusability of Zr(OBA) showed > 80 % of Sr2+ and Cs+ removal efficiency even after seven cycles. Herein we present acid stable [Zr 6 (µ 3 -O) 4 (µ 3 -OH) 4 (OBA) 4 (OH) 3 (H 2 O) 3 (Me 2 NH 2)] n (OBA = 4,4-oxy bis(benzoic acid)) (Zr(OBA) MOF) with the presence of cationic dimethyl ammonium groups were charge balanced with anionic Zr(OBA) n n– that is effective for removing Sr2+ and Cs+. This MOF shows distribution coefficients and record-high absorption capacities (Q m) of 353 mg/g for Sr2+ and 432.91 mg/g for Cs+ at pH 4, 112.75 mg/g for Sr2+ and 141.24 mg/g for Cs+ under 4 M HNO 3 circumstances, and 221.5 mg/g for Sr2+ and 253.77 mg/g for Cs+ from simulated seawater. It was demonstrated that a significant excess of complex cations had no substantial influence on the removal of Sr2+ and Cs+ from simulated seawater and nuclear waste, which have been included with Sr2+ and Cs+. The Langmuir isotherm was well suited for Sr2+ and Cs+ adsorption onto MOF, confirming the existence of monolayer adsorption. This finding was made possible by investigating the Langmuir, Freundlich, and Temkin adsorption isotherms. The results of the experiments agree very well with pseudo-second-order kinetic studies, which leads one to believe that chemisorption is the primary mechanism. The measurement of zeta potential has indicated an electrostatic connection between the negatively charged surface of the MOF and positively charged Sr2+/Cs+ at various pH values. This interaction demonstrates that the adsorption capacity is relatively high. SEM-EDS elemental mapping, IR, and XPS analysis confirm the presence of Sr2+ and Cs+ on MOF - of Zr(OBA)@Sr and Zr(OBA)@Cs MOF after adsorption studies. Sr2+/Cs+ exchanged MOF were improved in order to get a clear image of the ion exchange process, and the binding energies of −87.31 for Zr(OBA)@Sr and −113.75 kJ/mol for Zr(OBA)@Cs, respectively. The dose, initial concentration of metal ions, pH solution, contact time, and other ions of Na+, K+, Ca2+, and Mg2+ that were already present affected the adsorption of Sr2+ and Cs+. Recycle studies of Zr(OBA) MOF show 80 % recovery of Sr2+ and Cs+ even after eight cycles. [ABSTRACT FROM AUTHOR]

The Linta Basin, located in the Southwestern Madagascar, is a semi-arid area where groundwater in fractured media bedrock aquifer constitutes the main source of water supply. In the last two decades, highly mineralized groundwater was identified in this area; however, the origin of the salinity was not clear. The purpose of the study was to clarify the origin of salinity and to identify hotspots with groundwater unsuitable for water supply. Groundwater quality in this basin was investigated by hydrogeochemical and isotopic methods accompanied by mineralogical study. In total, 32 groundwater samples were collected and analyzed. The results showed that groundwater temperature varied from 25.2 °C to 31.7 °C. Values of pH and TDS varied from 6.55 to 8.24 and 221 to 5612 mg/L, respectively. The aquifer, which is mainly fractured, showed 7 groundwater types, namely Mg–HCO 3 ,Na–HCO 3 and also Na–C1, Mg–Cl, Na–Cl–HCO 3 , Mg–Cl–HCO 3 -, and Ca–Mg–HCO 3. Two groups of variables have been identified by factor analysis; the factor F1 comprises EC, Ca2+, Mg2+, SO 4 2−, and Cl− whereas the factor F2 comprises HCO 3 −, K+, and Na+, and they were interpreted in terms of hydrogeochemical processes. Values of saturation indices (SI) for carbonate minerals were generally positive, indicating their possible precipitation. Based on the Gibbs diagram and factor analysis, groundwater mineralization is affected by water-rock interactions and evaporation, respectively. The important role of evaporation is confirmed by enrichment of stable isotopes with δ18O values up to 1.2 ‰. Processes such as base ionic exchange process and reverse ionic exchange process may also be important locally. The main origin of groundwater mineralization is the hydrolysis of silicate minerals such as feldspars and micas coupled with evaporation. In several wells, salinity is too high for water supply and nitrate concentration is above the WHO limit for drinking water. Results of the study highlighted groundwater chemistry formation processes and are applicable in other African countries with bedrock aquifers. • Groundwater chemistry in bedrock aquifer in SW Madagascar was investigated. • Mineralization increases in flow direction and dominant groundwater types are Mg– HCO 3 and Na–HCO 3. • Principal processes affecting groundwater chemistry are dissolution of silicates and evaporation. • Hotspots with high salinity and nitrate concentration were identified. [ABSTRACT FROM AUTHOR]

The pilot plant extrusion was successfully utilized to manage a clay based solid waste deposited in the landfill of spent oil refinery through the conversion into the rod-like zeolite with LTA (Linde Type A) structure. The research was designed in combination with fusion, and hydrothermal processes to produce a packed bed with appropriate cation exchange capacity (CEC). However, the conversion of waste into the proper zeolite structure was the challenge of study due to lack of aluminum. To address this issue, boehmite, and sodium hydroxide were added to solid waste for compensation of aluminum lack before extrusion. The extradâtes were further consolidated by fusion at 800 °C, and then were converted into zeolite LTA by control of aging, and reaction periods in the hydrothermal step. The crystallinity, microstructure, and textural characteristics of waste, and fabricated rods were studied to examine the capability of process. The results revealed that the rod fabricated through the short aging period, 3 h, and longer reaction time, 9 h, represents the minimal CEC due to the recrystallization of hydroxysodalite. Although the textural characteristics of zeolites were found to be slightly affected by extrusion, the aging, and reaction periods of 9, and 6 h are beneficial to produce a packed bed with proper CEC, 214 mg g-1 demonstrating the potential of innovated technique. [ABSTRACT FROM AUTHOR]

[Display omitted] The pilot plant extrusion was successfully utilized to manage a clay based solid waste deposited in the landfill of spent oil refinery through the conversion into the rod-like zeolite with LTA (Linde Type A) structure. The research was designed in combination with fusion, and hydrothermal processes to produce a packed bed with appropriate cation exchange capacity (CEC). However, the conversion of waste into the proper zeolite structure was the challenge of study due to lack of aluminum. To address this issue, boehmite, and sodium hydroxide were added to solid waste for compensation of aluminum lack before extrusion. The extrudates were further consolidated by fusion at 800 °C, and then were converted into zeolite LTA by control of aging, and reaction periods in the hydrothermal step. The crystallinity, microstructure, and textural characteristics of waste, and fabricated rods were studied to examine the capability of process. The results revealed that the rod fabricated through the short aging period, 3 h, and longer reaction time, 9 h, represents the minimal CEC due to the recrystallization of hydroxysodalite. Although the textural characteristics of zeolites were found to be slightly affected by extrusion, the aging, and reaction periods of 9, and 6 h are beneficial to produce a packed bed with proper CEC, 214 mg g−1, demonstrating the potential of innovated technique. [ABSTRACT FROM AUTHOR]

Hydration tests were performed on geosynthetic clay liners (GCL) to examine the influence of subsoil water content (w subsoil) and mass per unit area (MPUA) on the cation exchange occurred during hydration. Increase in the w subsoil increased the final water content of GCL (w final). At MPUA of 4.0 kg/m2, w final increased from 70 to 109%. Such increase was less pronounced when MPUA was considered. Also, an inverse relation between MPUA and w final existed where w final increased as the MPUA decreased. The greatest w final was determined when w subsoil was ∼17% and MPUA of GCL was ∼3.0 kg/m2 (112%). The exchange reaction was the most favorable when w subsoil was ∼8% and MPUA of GCL was ∼3.0 kg/m2 (mole fractions of monovalent cations, X M , decreased from 0.81 to 0.65) and the least favorable when w subsoil was ∼17% and MPUA of GCL was ∼3.0 kg/m2 (X M decreased from 0.81 to 0.80). Combined influence of MPUA and w subsoil showed that although cation exchange depends on both factors, w subsoil had significant role in this reaction more than MPUA. The findings of cation exchange analyses were supported with swell index tests. The hydrated GCLs had lower swell indices than the virgin GCL (17.5–19.0 mL/2g vs. 21.5 mL/2g), indicating cation exchange. • Subsoil water content and mass per unit (MPUA) are of GCL affect the hydration behavior of GCLs. • Cation exchange is more favorable on drier subsoil conditions. • Subsoil pore fluid chemistry has an important role on cation exchange. • Subsoil water content has more influence on hydration and cation exchange than MPUA. [ABSTRACT FROM AUTHOR]

44Sc is of great interest as a positron emission tomography (PET) radionuclide due to its suitable nuclear characteristics: E β+max = 1.47 MeV, branching ratio 94.3% and convenient half-life of 3.97 h. Here, 44Sc was produced via the widely used reaction 44Ca (p,n)44Sc using natural calcium as a target. The irradiation was performed at TRIUMF using the 13 MeV cyclotron. The separation consisted of a combination of DGA branched resin and Dowex 50Wx8 (200–400 mesh). The distribution coefficients of Sc3+ on Dowex 50Wx8 (NH 4 + form, 200–400 mesh) with ammonium α-hydroxyisobutyrate (pH = 4.8) medium were determined in this study. The tested scheme allows both a reliable separation of 44Sc from the target material as well as from the other competitive metals and a final fraction with high specific activity. The achieved radiochemical yield was 95 ± 3%. [Display omitted] [ABSTRACT FROM AUTHOR]

The self-healing of a GCL with a circular hole is examined in experiments where the GCL, overlain by geomembrane, is hydrated from a silica sand subgrade (SSS) having three different pore water chemistries. Factors considered included: hole size, subgrade initial moisture content w fdn , GCL mass per unit area, and overburden stress (20–100 kPa). GCL self-healing is better for w fdn = 16% than for w fdn = 10%, which is better than for 5%, when the SSS pore water has negligible cations (ionic strength, I < 0.1 mM). However, only the 14.3 mm-diameter hole fully self-healed and only when w fdn = 16%. In contrast, when the GCL is hydrated from SSS with pore water having an ionic strength, I , of 20 and 30 mM, the self-healing for w fdn = 5% is better than for w fdn = 10%, which is better than for w fdn = 16%, although none of the holes self-healed. When a ~0.5 m hydraulic head was applied above the GCL under σ v = 20–100 kPa, a 38.1 mm-diameter hole self-healed with water having I < 0.1 mM, a 25.4 mm-diameter hole self-healed with pore water with I = 20 mM and 30 mM, but none self-healed with simulated synthetic landfill leachate (SSL). Post-hydration hydraulic conductivity (k) tests with SSL suggest that a hole up to 14.3 mm-diameter would not pose a significant adverse impact on the k compared to an intact GCL; however, this is not the case for the larger holes tested. • Hole D , GCL M A , w fdn , σ v , chemistry of subgrade pore water, ponded fluid and permeant all affect self-healing and k of GCL. • There is better self-healing with increasing w fdn for the GCL hydrated from SSS with DI pore water. • The self-healing was less with increasing w fdn when the GCL is hydrated from SSS with PW1 or PW2 pore water. • Other things being equal, self-healing improves with increasing M A of the GCL. • A hole as large as 14.3 mm self-heal at w fdn = 16% but not at w fdn = 5 and 10% upon hydration from SSS with DI pore water. • No hole examined (14.3 - 25.4 mm) completely self-heal upon hydration from SSS with PW1 or PW2 pore water. • The cations in pore water PW1 and PW2 inhibit the self-healing of holes in the GCL and result in a higher k. • All holes examined experience sufficient self-healing when permeated with TW or SSL to give k less than 2.4×10-9 m/s. [ABSTRACT FROM AUTHOR]

• Clay inhibition power of formation water is compared to NaCl and KCl solutions. • Swelling inhibition ability of formation water is near to the salts. • Formation water-based muds have acceptable filtration and rheological properties. • Similar morphology/texture of bentonite is seen exposed to formation water and KCl. • Clay-inhibitor, produced formation water, can reduce the need for commercial salts. This study focuses on the feasibility of reusing formation water as inhibitive base water for water-based drilling fluids (WBDFs) to reduce the need for freshwater and commercial salts. A real produced formation water (PFB) with known composition and a synthetic produced formation brine (SPFB) were compared to commercially available clay inhibitors, i.e., KCl and NaCl salts. Experiments show that the PFB and SPFB have acceptable free swelling indexes and sedimentation rates. According to the zeta potential measurements, they similarly decrease the charge of clay surfaces and reduce swelling of Na-bentonite. Besides, the cutting dispersion test illustrates that PFB and SPFB can reduce the interaction between the Pabdeh and Gurpi shales (Iranian formations) with drilling fluid. Drilling fluids made of the PFB and SPFB have rheological properties, including apparent viscosity, plastic viscosity, yield point, and gel strength less than a typical inhibitive WBDF made of NaCl. API filtration loss of both PFB- and SPFB-based drilling fluids at high bentonite concentrations (more than 12.5 wt.%) is similar to the same as the KCl-based drilling fluid, indicating their close inhibition power to the KCl solution. Finally, SEM analysis confirms that the texture/morphology of sodium bentonite exposed to the PFB and SPFB is close to that of the KCl solution and formation water inhibition power is more than NaCl and near to KCl. Eventually, formation water as a potential inhibitive water for water-based drilling fluids, is preferred to the commercial salts from both environmental and economic aspects. [ABSTRACT FROM AUTHOR]

In II-VI group, the doping in CdTe nanocrystals (NCs) is more difficult than other chalcogenides. In this communication, CdTe nanocrystals containing Cu impurities were carefully synthesized based on controlled reverse cation exchange process between as-prepared Cu 7 Te 5 nanocubes and Cd2+ ions. By well-defined Cu 7 Te 5 nanocubes, the obtained CdTe NCs kept the original morphology. The concentration of Cu impurities in CdTe NCs was controlled by the regulation such reverse cation exchange. Additionally, the regulation from band gap (BG) photoluminescence (PL) to the coexistence of the bandgap emission, dopant emission, and surface-state emission was realized. This tailoring from undoped to doped emission in the case of Cu impurities is helpful to study the Cu related doping in telluride NCs. [Display omitted] • Monodisperse CdTe nanocrystals containing Cu impurities have been successfully synthesized. • The bandgap photoluminescence of Cu doped CdTe have been tuned continuously from 585 ​nm to 721 ​nm. • The Cu dopant emission have been realized successfully. [ABSTRACT FROM AUTHOR]

Aromatic chlorinated compounds, such as 1,2-dichlorobenzene, are considered as precursors of dioxin formation and their removal from flue gas using adsorption technology could be a solution. Faujasite type zeolites seem to be the most promising adsorbent, as the size of its porosity matches the size of the molecule. Even though the cationic faujasites are hydrophilic, the strength of interaction of chlorinated aromatic compounds adsorbed in porosity are higher than with more silicic faujasite such as FAU-NaY. FAU-NaX commercial beads have been Nd3+ exchanged at different rates. Dichlorobenzene dynamic gas adsorption has been performed via a thermobalance with vapours at concentration of 938 ppm in nitrogen gas flow and the quantities absorbed have been recorded during time. Then, from the coupling of a thermobalance with an in-line mass spectrometer, the desorbed quantities and desorption temperatures have been measured for both water and dichlorobenzene. Total quantities of 1,2-dichlorobenzene adsorbed onto partially exchanged FAU-Nd-NaX zeolites increases with the exchange rate: it has been measured a capacity of 23.3 wt % (relative to activated zeolite) for the most exchanged FAU-Nd-NaX at exchange rate of 53.6 %. For that zeolite, 74.7 % of the 1,2-dichlorobenzene is adsorbed at high-energy bonds with cations, desorbable at temperatures higher than 160 °C. The desorption temperature of dichlorobenzene decreases from 380 to 310 °C for FAU-NaX and the FAU-Nd-NaX at exchange rate of 53.6 % and remains higher than that of water. So that, thermal-desorption remains a separative process between water and chlorinated molecules previously adsorbed on cationic faujasites. [Display omitted] • FAU-NaX beads have been partially exchanged by Nd3+ cations at different rates. • The amounts of 1,2-DCB adsorbed onto the exchanged FAU (X) beads increases with the Nd3+ exchange rate. • The desorption temperature of 1,2-DCB decreases from 380 to 310 °C with the Nd3+ exchange rate from 0 to ca. 54 %. • Different strengths of interaction of 1,2-DCB molecules with the zeolite framework are clearly identified by TG/MS analyses. [ABSTRACT FROM AUTHOR]

[Display omitted] • A silica-supported cation exchanger was successfully synthesized and well characterized. • The material showed fast adsorption kinetics and excellent separation performance. • The separation behaviors in batch and column modes were systematically investigated. • Hot test was conducted using 226Ra and 232Th, and 226Ra was separated from 232Th finally. 212Pb serves as one of the most important nuclides for targeted alpha therapy (TAT), with good potential in the treatment of malignant tumors. However, medical and clinical applications are seriously limited by its extremely short supply, which strongly depends on the acquisition of its parent nuclides such as 228Ra or 224Ra. To address this issue, we conducted a systematic investigation on the separation of trace radium from natural thorium using the ion exchange chromatography method, and a novel porous silica-based composite resin functionalized with sulfonic acid groups was prepared, characterized, and employed. Experimental results showed that the silica-supported resin was successfully prepared with the sulfonic acid groups, and possessed small particle size, mesoporous pore structure and large specific surface area. The resin exhibited high selectivity toward thorium compared with barium, and the separation factor reached 123 at low acidity and at low temperature. The resin demonstrated a fast adsorption speed and an excellent separation performance, and the adsorption mechanism was confirmed based on the ion exchange between the sodium carried and the target cations. On the basis, column experiments were further conducted and finally the separation of trace radium from thorium was realized using a small column filled with about 1.0 g resin. The chemical recovery of radium reached 97 %, and the decontamination factor for thorium exceeded 40,000. This work verifies the feasibility of directly extracting 228Ra and 224Ra from natural thorium using the sulfonic acid group functionalized materials in the dilute nitric acid solution, and presents an excellent material and systematic experimental data on the separation activities, rendering this study particularly significant. [ABSTRACT FROM AUTHOR]

Geopolymers (GP) are ceramic-like materials that can potentially be used in environmental applications to immobilize radionuclides (RNs) or toxic compounds. Although the literature reports that the sorption potential of a GP is influenced by its sorption capacity, especially for GPs produced from metakaolin (MK), the RN sorption mechanisms of these materials must be comprehensively studied together with their surface properties. In this study, the surface properties of a sodium-alkalinized MK-based GP (Na-MKGP), such as its surface protonation and cation exchange capacity (CEC), were characterized, and the sorption mechanisms of cesium (Cs+), strontium (Sr2+), and europium (Eu3+), which are important RNs for the safety assessment of high-level radioactive waste disposal, as functions of pH, ionic strength, and metal-ion concentration were investigated. The results were evaluated using the "two-site proteolysis no-electrostatics surface complexation/cation exchange (2SPNE SC/CE)" model by optimizing the selectivity coefficients and SC constants of the metal ions. Overall, this study provides a way to model the sorption of various cations to GP by a mechanistic model as is the case for clay minerals and makes the use of GP as a matrix of radioactive waste more attractive. • Cs+, Sr2+, Eu3+sorb on sodium alkalinized metakaolin-based geopolymer (Na-MKGP) by cation exchange and surface complexation, like as clay minerals. • Silicate plays significant role on europium sorption. • The distribution ratio of the sorbed metal ions modeled the selectivity coefficients and surface complexation constants are and optimized. • Surface deprotonation trend showed the point of zero charge of Na-MKGP is approximately pH 5.3. • Washing and drying improve the cation exchange capacity of Na-MKGP. [ABSTRACT FROM AUTHOR]

[Display omitted] • CE drove particulate carbon source dissolution by 34.72 % in 2-day treatment. • Remarkable carbon recovery rate of 21.37 % was achievable in 8-day fermentation. • 78.09–85.79 % of recoverable carbon sources were extracted by liquid separation. • CE-driven carbon migration and recovery were illustrated in negentropy pattern. Despite numerous treatments have been developed to enhance anaerobic fermentation of waste activated sludge, the innovative cation exchange (CE) approach has been rarely reported, little attempt was conducted to reveal carbon source fate. The interphase carbon balance was illustrated to clarify endogenous carbon dissolution, biotransformation,and recovery patterns. By CE-mediated divalent cation removal, almost 34.72 % of particulate carbon sources were dissolved in 2-day treatment, corresponding to soluble carbon content of 1165.58 mg C/L. Most of the originally dissolved carbon sources (58.01–66.81 %) were bio-transformed to volatile fatty acids with high bioavailability, while the further transformation to biogas was inhibited, contributing to recoverable carbon source accumulation. Overall, 21.38 % of total solid carbon sources were recovered through 8-day fermentation, the carbon extraction was implemented by solid–liquid separation with carbon loss of 14.21–22.91 %, manifesting the valid carbon recovery of 85.05–87.96 mg C/g VSS. Such CE-driven carbon recovery provided negentropy benefits in sustainable cycle economy. [ABSTRACT FROM AUTHOR]

The self-healing of a GCL with artificial defects (circular holes and rectangular slits, both with and without the carrier geotextile preserved below the holes) upon hydration on a Godfrey silty sand (GSS) subgrade with w fdn = 5, 10 and 16% under 2–100 kPa is examined. Circular holes with the carrier geotextile missing below holes with diameters up to 25.4 mm self-healed on the w fdn = 5% and 10% GSS but not on 16% GSS, while none self-healed when carrier geotextile was preserved below the holes. When DI water was introduced to the surface under 100 kPa, circular holes with diameter up to 38.1 mm self-healed. Neither the single 15 mm-wide slit nor double 15 mm-wide parallel slits with 20 mm-wide strip of undamaged GCL between them resting on w fdn = 10% GSS under 20 kPa fully self-healed. The introduction of simulated synthetic landfill leachate (SSL) to the GCL surface under 70 kPa did not result in self-healing. Post-hydration k tests found that GCL without a carrier geotextile below a hole up to 25.4 mm in diameter would not have a significant adverse effect on the hydraulic conductivity compared with an intact GCL provided the permeant was tap water rather than SSL. [ABSTRACT FROM AUTHOR]

• Bi3+ replaced by Ag+ in Bi 2 WO 6 nanosheets via liquid-phase cation exchange. • High CO generation rate (116.96 μmol g−1) with 95.7 % selectivity achieved. • Effects of Ag+ substitution studied through experiments and calculations. Creating useful chemicals based on artificial CO 2 photoreduction is considered to be an attractive approach to address the environmental and energy crises. Currently, its selectivity with high conversion efficiency is still a grand challenge. Here, we report the refined substitution of Bi3+ with Ag+ in ultrathin Bi 2 WO 6 nanosheets through a liquid-phase cation exchange process, favoring a high selectivity towards the photocatalytic production of CO from CO 2. The incorporation of Ag+ could not only significantly promote the adsorption of both CO 2 and H 2 O molecules, but also facilitate the transfer of photogenerated carriers. The as-fabricated photocatalyst achieves a high CO generation rate of 116.96 μmol g−1 with a superb selectivity of 95.7 % after 6 h reaction without any sacrificial agent, approximate 4.2 times higher than that of pure Bi 2 WO 6. The mechanism for photocatalytic CO 2 reduction is proposed, based on in-situ Fourier Transform Infrared spectrometry analyses and Density Functional Theory calculations. [ABSTRACT FROM AUTHOR]

In this work, Co-doped BiOBr prepared by cation-exchange strategy exhibits excellent photocatalytic performance under visible light in pure water. The Co-BiOBr-0.5 catalyst presents a better evolution rate of of CO 2 photoreduction to CO, reaching 11.71 μmol·g−1 h−1, which is 3.6 times higher than pure BiOBr. In addition, UV-Vis results show that the synthetized Co-doped BiOBr prepared by cation exchange strategy has wider visible light response. Meanwhile, TPR, EIS and PL results show that the cation exchange strategy can improve the electron-hole separation efficiency of BiOBr. This work might provide a simple method for preparing efficient photocatalysts for CO 2 reduction. [Display omitted] • Innovation in the use of cation-exchange strategy for the preparation of Co-BiOBr. • Cation-exchange strategy improves the light absorption and electron-hole separation efficiency of BiOBr. • The CO yield of Co-BiOBr-0.5 is as high as 11.71 μmolg−1h−1. • Cation exchange strategies offer new options for the preparation of high-performance catalysts. [ABSTRACT FROM AUTHOR]

Illite, smectite and illite/smectite mixed layers are major phases in various argillaceous rock formations foreseen as potential host rocks for the deep geological disposal of high-level radioactive waste and are important sorbents for cationic radionuclides potentially released in the repository. 226Ra is a critical radionuclide in the safety analysis and an important source of radioactivity in technically enhanced naturally occurring radioactive materials. A comprehensive study was carried out on the adsorption of Ba and Ra on purified homoionic Na-illite (Illite du Puy) over a wide range of experimental conditions (pH, concentration, ionic strength) allowing for the development of a quasi-mechanistic Ba/Ra adsorption model for illite. Ba adsorption isotherms obtained at fixed ionic strength and pH exhibit a non-linear behaviour in the Ba equilibrium concentration range between ∼10−7 and ∼10−2 M. The pH dependent adsorption of trace 226Ra and Ba was investigated at different ionic strengths and evidenced a more pronounced adsorption of 226Ra than Ba on illite. Finally, a competition experiment of trace 226Ra in the presence of increasing Ba concentrations showed an unexpected 226Ra adsorption behaviour which was not observed for montmorillonite in earlier studies. This large set of experimental data could be successfully modelled by Ba/226Ra exchange reactions against Na, together with selectivity coefficients, on two different site types, namely planar sites and high affinity sites. The modelling of the pH dependent adsorption of Ba and 226Ra at high ionic strength and high pH required an additional surface complexation reaction. Two additional exchange sites had to be introduced to quantitatively describe the 226Ra uptake on illite in the 226Ra/Ba competition experiment. The nature of these sites, however, remains unclear. The implementation of the 226Ra adsorption model into predictive transport modelling codes is of key importance for the safety analysis of deep geological disposal of radioactive waste. • 226Ra has stronger affinity for illite than Ba. • Adsorption of Ba and 226Ra on illite is mainly governed by cation exchange. • Surface complexation reaction is necessary to describe adsorption at high pH and high ionic strength. • Four cation exchange sites are necessary to quantitatively describe Ra uptake on illite. [ABSTRACT FROM AUTHOR]

The presence of antibiotics in soil and water raises great health concerns because they may increase the development of harmful antibiotic-resistant bacteria. In this study, composite beads prepared from 2:1 or 1:1 ratios of montmorillonite (Mt) and sodium alginate (SA) were used to adsorb tetracycline hydrochloride (TC), an antibiotic commonly found in aqueous systems. The equilibrium time for TC adsorption onto the Mt/SA was 8 h, and the kinetic data were consistent with the pseudo-second-order model. The adsorption isotherm was described with the Langmuir equation. The maximum amounts of TC adsorbed were 745, 689, and 445 mg g−1 for the 2:1- and 1:1-Mt/SA and the original Mt, respectively. The Mt/SA composite beads exhibited porous structures; however, this did not play a key role in TC removal, as previously reported. Cation exchange was the major adsorption mechanism, and electrostatic attraction and hydrogen bonding between the SA and TC also contributed to TC adsorption on the Mt/SA composite beads. In addition, the migration of a small amount of TC into the inner spaces of the beads led to the intercalation of the TC in the Mt interlayers and enhanced TC adsorption by the Mt/SA composite beads. • The porous structures of composite beads adsorbed remarkable amounts of tetracycline (TC) from water. • Cation exchange was the primary adsorption mechanism of TC. • Electrostatic attraction and hydrogen bonding between alginate and TC enhance TC adsorption. • The amine and dimethylamino groups of TC orient horizontally on the internal surface of composite beads. [ABSTRACT FROM AUTHOR]

Clay minerals, as biofriendly and low-cost materials, are highly essential for the modern industrial applications including the production of clean energy, its storage and conversion. Here, the capabilities of pure and cation exchanged rectorite, a regularly interstratified phyllosilicate from Beatrix Mine (South Africa) were explored and discussed. A comprehensive characterization was performed by means of high resolution solid-state NMR, electrochemical impedance spectroscopy and powder X-ray diffraction. 23Na MAS and 3QMAS NMR spectroscopy was used to characterize accessibility of interlayer space in rectorite for exchangeable cations. Three Na sites attributed to easily exchangeable Na+ on the surface or in large pores, Na+ in dehydrated micaceous interlayers and Na+ in hydrated smectite interlayers were identified. Differences in hydration states in smectitic interlayers depending on the type of intercalation were detected using 1H MAS NMR. A higher amount of hydrating water molecules in pure and Mg-exchanged rectorites was attributed to the higher hydration energy of Ca2+ and Mg2+. The temperature dependences of electrical conductivity in this work were best described using the empirical Vogel-Tammann-Fulcher equation with the temperature-dependent effective activation energy parameter. Significantly stronger change of activation energy in Mg2+ exchanged rectorite in the temperature range of 10 °C to 50 °C as compared to pure rectorite and its Na+, Li+ and NH 4 + modifications was related to an extensive H-bond network in the interlayers, which facilitated an effective proton transfer responsible for electric conductivity. The obtained resutls suggested a greater potential for the use of Mg-exchanged rectorite as ionic conductor at enhanced temperatures. [Display omitted] • Rectorite from Beatrix Mine was studied towards the structure – conducting properties relation. • Accessibility of interlayer space for exchangeable cations was characterized by solid state NMR. • Electrical conductivity in rectorite depends on interlayer cations, hydration and temperature. • Conductivity originates from proton transfer over the hydrating water network in the interlayers. • Mg-exchanged rectorite has a great potential as ionic conductor at enhanced temperatures. [ABSTRACT FROM AUTHOR]

In this study, magnetic composite microspheres (SCFP) were prepared by cross-linking chitosan (CS), sodium alginate (SA), poly(vinyl alcohol) (PVA), and ferric tetraoxide (Fe 3 O 4) in a CaCl 2 solution. CS and Fe 3 O 4 were encapsulated in gel spheres formed by cross-linking SA with Ca(II), while PVA facilitated the dispersion of CS in SA. SCFP was utilized as an adsorbent to remove Cu(II) from water. The effects of the initial pH of the solution, SCFP dosage, and initial Cu(II) concentration on the adsorption efficiency were investigated through batch experiments. The results demonstrated that the adsorption capacity reached 58.260 mg/g (removal rate = 97.1%) after 100 min of adsorption at a pH of 5. The removal rate remained above 90% even after 6 cycles of the cycling experiment. The incorporation of CS with other functional materials allowed SCFP to compensate for its inherent drawbacks such as low mechanical strength, poor acid resistance, and short service life. The pseudo-first-order kinetic model and Freundlich adsorption isotherm provided better descriptions of the adsorption process. A comprehensive analysis was conducted on the structure and adsorption mechanism of SCFP using characterization techniques such as SEM-EDS, FTIR, BET, XRD, etc. In summary, SCFP has the potential to be an excellent environmentally friendly material for the removal of Cu(II). [Display omitted] • SCFP was prepared by a simple method. • At pH 5 for 100 min, the adsorption capacity and removal rate for Cu(Ⅱ) reached 58.260 mg/g and 97.1%. • SCFP can be reused successfully in repeated adsorption-desorption cycles. • Adsorption mechanisms involved physical adsorption and chemical adsorption. [ABSTRACT FROM AUTHOR]

A series of organoclays were synthesized by modifying bentonite with lecithin under two pH reaction solutions, one acid and one basic. The products prepared using various surfactant concentrations (0.2–5.0CEC) were characterized by multiple experimental techniques. The conformational arrangement of the loaded surfactant, as well as the fluctuation in lecithin molecular properties and interlayer cation content in the organoclay were evaluated. According to the experimental results, the conformation of lecithin in the organoclay interlayer space undergoes a transition from flat-lying layer to a tilted paraffin-type-bilayer. This phenomenon happens for both pH but, interestingly, follows two different mechanisms. It can be observed that the cations content decreased during the addition of lecithin at pH = 1.0, suggesting that the surfactant intercalated into the interlayer space through cation exchange. On the contrary at pH = 9.0, the zwitterionic nature of lecithin allowed its intercalation in the interlayer space via ion-dipole interactions with the cations. Compared with the organoclay prepared at pH = 1.0, the organoclay prepared at pH = 9.0 also exhibited weaker hydrophobicity, clearly reflecting the difference in the interlayer conformation. [Display omitted] • The properties of organoclays prepared from lecithin-modified bentonite are pH dependent. • The lecithin conformationundergoes a transition from lying layer to a tilted paraffin-type-bilayer • The intercalation mechanism is cation exchange（pH = 1.0）while ion-dipole interactions （pH = 9.0）. [ABSTRACT FROM AUTHOR]

Perfluorooctanesulfonate (PFOS) is a hazardous chemical, and its presence in surface and groundwater poses a risk to environmental quality and human health. Containment is often applied to immobilize PFOS to stop or minimize the exposure. Mineral-based materials became promising adsorbents. However, there is scope to develop adsorbents using locally available minerals and understand their adsorption mechanisms. Here, we developed oleylamine-modified composites using naturally occurring Iranian zeolite and diatomaceous earth (DE). The mineralogy and surface properties of materials were fully characterized, and the adsorption of PFOS from simulated wastewater was linked to it. Clinoptilolite in zeolite sample, calcite and kaolinite in DE were main mineral assemblages. The raw samples also contained silica as a main constituent of them. Thermogravimetric analysis suggested that the materials were successfully modified with the oleylamine molecules in the material's structure and surfaces. These were further supported by scanning electronic microscopy (SEM), Fourier transmission infrared spectroscopy (FTIR), and surface and pore size analysis. After adsorption at various pHs, the isotherm of adsorption was also performed at ambient temperature. Modified DE and zeolite tend to adsorb PFOS (14.1 and 25.5 mg/g, respectively) more than their raw counterparts (4.72 and 0.39 mg/g, respectively). Adsorption models suggest monolayer and, in rare cases multilayer binding capacities and affinities toward PFOS. We analyzed the post-adsorption materials and discovered that electrostatic and hydrophobic interaction was likely the main cause of PFOS adsorbed to the material. This research helps to improve our knowledge of how PFOS adheres to untreated and surfactant-altered zeolite and DE in aquatic environments. [Display omitted] • Locally sourced Iranian zeolite and diatomite characterized mineralogically. • Materials modified with primary amine (oleylamine) without prior processing • Perfluorooctane sulfonate (PFOS) was removed from water by the modified minerals. • Amine-modified zeolite appears to be low cost and efficient adsorbent for PFOS. • Mechanistic study suggests adsorbent removed PFOS electrostatically and hydrophobically. [ABSTRACT FROM AUTHOR]

[Display omitted] • Significant vertical variation of hydrochemical and isotopic signatures categorise the aquifer system. • Cation exchange and mixing through various natural processes govern the groundwater chemistry. • The enrichment of NO 3 − and F− in groundwater is indicative of anthropogenic and natural control. The present study aims to understand the hydrochemical evolution of groundwater in the Ghaggar River Basin, representing a zone of excessive abstraction of groundwater in the northwestern Indo-Gangetic Basin. The study comprises a regional scale and high-resolution sampling of groundwater during pre- and post-monsoon seasons of 2013 and their analyses for major ions, δ 18O, δ 2H, and 3H. Variation in hydrochemical and isotopic data is found both in spatial and vertical scales. The significant vertical variation of TDS, NO 3 − and K+ allowed the classification of the aquifer system into two major groups: shallow (depth < 80 m bgl) and deep (depth > 80 m bgl). The depthwise variations of δ 18O and δ 2H support this categorization of the aquifers. The Ca-HCO 3 and Ca-Mg-Na-HCO 3 water facies with higher values of 3H in the proximal part of the basin characterize recharge areas under humid conditions. The dominance of Mg-Na-HCO 3 and Na-HCO 3 facies in shallow and deep aquifers in central part of the basin, illustrate the intermediate to advanced stages of hydrochemical evolution in the system. Dominance of brackish Ca-Mg-Cl-SO 4 and Na-Cl-SO 4 water types in the discharge areas is due to the prevailing geological conditions and anthropogenic activities. Geochemical modelling supports the reverse cation exchange and mixing during lateral and vertical flows, weathering of silicate minerals, dissolution of crustal salts, and evaporative enrichment are the natural processes governing the evolution of groundwater chemistry along the flowpaths. The developed process-based conceptual model will aid in the formulation of a suitable plan for groundwater resource management in the region. [ABSTRACT FROM AUTHOR]

• Retention of P in the soil increased with the addition of LDHs and in the presence of Ca2+ in comparison to K+. • Both breakthrough curves and retention profiles for P were simulated by Hydrous 1D. • A potential for Fe/Al oxides-facilitated transport of P under the change of soil solution chemistry. • The dissolution and transport of LDHs could be impeded in the presence of high cation valence and IS. Mg-Al layered double hydroxides (LDHs) were synthesized and applied to soils to control phosphorus (P) loss. Saturated soil column experiments and numerical modeling were conducted to investigate the transport, retention, and release behavior of P in natural soil with and without mixing LDHs under various solution chemistries. Retention of P in the soil increased with the addition of 0.5% LDHs and in the presence of Ca2+ in comparison to K+. The simulated results showed that irreversible retention of P is greater in the presence of Ca2+ than K+ in soil without LDHs and in the presence of 0.5% LDHs in comparison to the absence. The increase of ionic strength (IS) for K+ from 1 to 100 mM resulted in increased P retention in LDH-soil system due to more inner-sphere complexes and increased adhesive force. Near equilibrium retention on the reversible site occurred for all these experiments. The P was desorbed and the transport of dissolved P was improved with the reduction of IS in the presence of K+. On the other side, larger ion exchange and reduction of IS in the presence of Ca2+ induced the release of Fe/Al oxides which brought transport of P absorbed on those minerals, suggesting the potential for Fe/Al oxides-facilitated transport of P under the change of soil solution chemistry. Additionally, the transport and stability of LDHs in soil column were also investigated. The dissolution and transport of LDHs could be impeded in presence of high cation valence and IS. [ABSTRACT FROM AUTHOR]

• Overall excellent performance for CE modes and CEX. • Highest precision was observed for cation exchange chromatography. • Outstanding separation efficiency for capillary isoelectric focusing techniques. • Reliability and ease of use of CE systems are increasingly improved. Charge heterogeneity is an important critical quality attribute for the analysis of monoclonal antibodies (mAbs). For this, (imaged) capillary isoelectric focusing ((i)cIEF), ion exchange chromatography (IEC) and, recently, capillary zone electrophoresis (CZE) are the predominantly used techniques. In order to investigate which one is most suitable to answer a specific analytical question, here, the four aforementioned separation techniques were systematically evaluated using NISTmAb and Infliximab as test molecules. The performance parameters (precision, separation efficiency, linearity and sensitivity) were determined under comparable conditions. Moreover, important aspects for daily routine such as speed and ease of use were considered. Each technique has its own pros and cons. The (i)cIEF methodology is distinguished by its excellent separation efficiency. In addition, the native fluorescence mode in icIEF is a good tool to analyze small sample amounts (LOQ: 2.8 mg/l for Infliximab). Nevertheless, high performance liquid chromatography (HPLC) still has superior precision. CZE, and also micellar electrokinetic chromatography (MEKC), have emerged as further interesting alternatives. For all techniques, variations connected to the sample preparation strongly influence precision. Looking at the relative standard deviation (RSD) values of the relative peak areas, all techniques provide acceptable performance (RSD: 0.6–1.6%). [ABSTRACT FROM AUTHOR]

• Highly fluorescent and stable Cu-In-Zn-S/ZnS quantum dots (QDs) with tunable emission were aqueously synthesized. • Mild and rapid cation exchange was used for Cu2+ detection by utilizing the change of intrinsic optical properties of QDs. • The QD sensor exhibits wide pH resistance and comparable accuracy to ICP-AES method. Non-cadimum photoluminescent I−III−VI semiconductor nanocrystals have attracted increasing attention due to their low toxicity, extraordinary optical and electronic properties. Herein, water-soluble quaternary Cu-In-Zn-S quantum dots (CIZS QDs) with tunable emission from 535 nm to 645 nm were successfully synthesized via ecofriendly one-pot aqueous method. The full width at half-maximum (FWHM) of the emissions are about 68 nm–88 nm, which are rather narrow among Cu-based semiconductors and preferred to facilitate improving color purity. The photoluminescence of water-soluble QDs was enhanced by ZnS coating with the absolute quantum yield (QY) up to 30.8%. Further, a novel fluorescent sensor for Cu2+ detection was developed based on the alteration of intrinsic optical properties of the CIZS/ZnS QDs after cation exchange at room temperature within 10 min, presenting a linear range of 0.020–20 μM and a detection limit down to 6.7 nM. Mechanism studies revealed that the QDs served as the template for cation exchange, through UV–vis absorption and fluorescence spectra in combination with the chemical composition and time-resolved photoluminescence decay analysis. Ions interference experiments demonstrated the good selectivity of the QDs towards Cu2+ and the sensor showed comparable accuracy to ICP-AES method as well as good performance in real sample detection, manifesting the reliability of the current strategy for sensing Cu2+ mildly and rapidly. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • We demonstrate the first synthesis of ultra-small heavy-metal-free nanoplatelets. • Nanoplatelets exhibit lateral dimension of 6–10 nm with a quantum yield of 20%. • Nanoplatelet-based anode exhibits a saturated photocurrent density of ˜7.4 mA/cm2. • EIS analysis was used to determine the charge transfer resistances. • Nanoplatelets demonstrate potential as light-converter in solar-to-H 2 generation. Abstract Metal chalcogenide semiconducting nanoplatelets exhibit a broad absorption spectrum, as well as thickness-dependent optical and electronic properties. As such, they may be used as building blocks in a variety of optoelectronic devices. The direct synthesis of heavy-metal-free ultra-small sized nanoplatelets is still challenging, due to the inherent limits in existing synthetic approaches. Here, we report an efficient template-assisted cation-exchange route to synthesize heavy metal free metal chalcogenide nanoplatelets that are optically active in the near infrared. The SnSe nanoplatelets, whose lateral dimension is 6–10 nm, exhibit a quantum yield of 20%. The nanoplatelets are applied as light absorbers in a photoelectrochemical (PEC) system for hydrogen generation, leading to a saturated photocurrent density of 7.4 mA/cm2, which is a record for PEC devices using heavy metal-free colloidal quantum dots or nanoplatelets under identical measurement conditions. Our results indicate that quasi-zero-dimensional SnSe nanoplatelets hold great potential as efficient light absorbers for emerging optoelectronic technologies. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hydroxyapatite/biochar nanocomposites (HAP/BC-NCs) were hydrothermally synthesized. • HAP/BC-NCs were used for Cu(II) removal and exhibited high adsorption affinity. • The adsorption rate of Cu(II) was mainly controlled by film diffusion mechanism. • The maximum adsorption capacity was determined to be 99.01 mg/g at 298 K. • Adsorption mechanism involved cation exchange and inner-sphere surface complexation. Abstract In this study, hydroxyapatite/biochar nanocomposites (HAP/BC-NCs) were synthesized through a simple one-pot hydrothermal process and utilized as an adsorbent for the removal of copper(II) from aqueous media. Characterization results revealed that rod-shaped HAP nanoparticles were successfully incorporated on the surfaces of synthesized HAP/BC-NCs. A set of systematically designed batch experiments were carried out to determine the influences of adsorbent dosage, solution pH, ionic strength, and temperature on the adsorption behavior of the HAP/BC-NCs. Overall findings from batch experiments and extended X-ray absorption fine structure analysis demonstrated that the potential mechanisms responsible for the removal of Cu(II) from aqueous media are cation exchange between Cu2+ in solution and Ca2+ in the HAP on the surfaces of the as-synthesized nanocomposites and the formation of inner-sphere surface complexes on the surfaces of the HAP/BC-NCs. Kinetic studies revealed that the adsorption process follows the pseudo-second-order model and that the overall adsorption rate is controlled by film diffusion as the dominant mechanism and intraparticle diffusion as a secondary mechanism. Adsorption isotherms were accurately represented by a Langmuir isotherm model and the maximum adsorption capacity was determined to be 99.01 mg/g at 298 K, which represents a higher efficiency for Cu(II) adsorption compared to previously reported composite materials. Thermodynamic analysis indicated that the process is thermodynamically spontaneous and endothermic process. Overall, the findings presented in this paper suggest that HAP/BC-NCs have promising applicability for the removal of heavy metals from aqueous media as an alternative, low-cost, and eco-friendly adsorbent for environmental remediation. [ABSTRACT FROM AUTHOR]

• Uptake of Triethylenetetramine (TETA) on rectorite was via a complexation mechanism. • Uptake of Cu2+ and Cu-TETA on rectorite was via a cation exchange mechanism. • Interlayer cation Ca2+ complexed with TETA could be exchange with Cu2+. • Under high loading levels, Cu-TETA adoption a vertical bilayer configuration. • Results suggest that TETA-modified clay minerals could be used as sorbent for metals. Uptake of metals, organics, and formation of metal-organic complexes on the surface or in the interlayer of clay minerals had been studied extensively over the last half century. In this study, we investigated the uptake mechanisms of Cu2+, triethylenetetramine (TETA), and Cu-TETA on rectorite and its use for metal removal via metal-TETA complexation. The uptake of Cu2+, TETA, and Cu-TETA by rectorite occurred on the external as well as in the interlayer space, resulting in a change of d 001 -spacing due to differences in sizes of interlayer cations or complexes. Although the uptake of Cu2+ and Cu-TETA by rectorite was via a cation exchange process as evidenced by the stoichiometric desorption of dominant interlayer cation Ca2+, the uptake of TETA alone on rectorite was via complexation with interlayer cation Ca2+. Due to strong affinity of TETA for Cu2+, significant amounts of Cu2+ uptake occurred on TETA-rectorite. Desorption of Ca2+ from TETA-rectorite confirmed the replacement of interlayer cation Ca2+ by Cu2+. However, the replacement of Ca2+ by Cu2+ in TETA-rectorite did not involved in removal of TETA. As such, TETA-modified clay minerals may serve as a type of sorbents for the removal of selected heavy metals via surface or interlayer via complexation. [ABSTRACT FROM AUTHOR]

The sorption of Eu(III) onto montmorillonite samples from different deposits such as those of Kutch (India), 10th Khutor deposit (Russia), and Cortijo de Archidona (Spain) was studied over a wide range of experimental conditions by varying the total Eu concentration, pH, and ionic strength. Various bentonite samples showed quantitative sorption at all pH values at low ionic strengths of the solution because of ion exchange interactions. At a higher ionic strength (1 M NaClO 4), the sorption is pH-dependent because of the interaction with edge sorption sites and it differed from sample to sample. The difference in the mechanism of interaction at different ionic strengths was confirmed by time-resolved laser-induced fluorescence. Thermodynamic modeling was performed with all experimental data for montmorillonite samples from different sources to create a generalized model for describing their interaction with Eu(III). Unlabelled Image • Sorption of Eu(III) onto previously not studied montmorillonite is investigated. • Samples include new Kutch bentonite from India and Khakassia bentonite from Russia. • Admixture iron oxyhydroxide in Kutch bentonite influences Eu(III) sorption. • Thermodynamic model describing Eu(III)–montmorillonite interaction is proposed. • The constant for ion-exchange Eu(III) reaction with montmorillonite is calculated. [ABSTRACT FROM AUTHOR]