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Compacted bentonite is part of the multi-barrier system of radioactive waste repositories. The assessment of the long-term performance of the barrier requires using reactive transport models. Here we present a multiphase flow and reactive transport benchmark for radioactive waste disposal. The numerical model deals with a 1D column of unsaturated bentonite through which water, dry air and CO 2 (g) may flow and with the following reactions; aqueous complexation, calcite and gypsum dissolution/precipitation, cation exchange and gas dissolution. INVERSE-FADES-CORE V2, DuMu X , TOUGHREACT and iCP were benchmarked with 6 test cases of increasing complexity, starting with conservative tracer transport under variably unsaturated conditions and ending with water flow, gas diffusion, minerals and cation exchange. The solutions of all codes exhibit similar trends. Small discrepancies are found in conservative tracer transport due to differences in hydrodynamic dispersion. Computed CO 2 (g) pressures agree when a sufficiently refined grid is used. Small discrepancies in CO 2 (g) and pH are found near the no-flow boundary at early times which vanish later. Discrepancies are due differences in the formulations used for gas flow at nearly water-saturated conditions. Computed CO 2 (g) pressures show a fluctuation between 10 - 4 and 10 - 3 years which slows down the in-diffusion of CO 2 (g) . This fluctuation is associated with chemical reactions involving CO 2 . There are discrepancies in solute concentrations due to differences in the Debye–Hückel (DH) formulation. They are overcome when all codes use the same DH formulation. The results of this benchmark will contribute to increase the confidence on multiphase reactive transport models for radioactive waste disposal. [ABSTRACT FROM AUTHOR]

The improper disposal of uranium mine tailings and smelting wastewater poses significant environmental hazards, including contamination of water bodies and soil, and potential health risks to humans through the accumulation of uranium in bones and organs. This study examines the removal of hexavalent uranium (U(VI)) from water using biochar derived from agricultural waste enhanced by hydrogen peroxide (H2O2) and magnetization modifications involving the incorporation of Fe3O4 nanoparticles onto the biochar surface. The adsorption capacities were evaluated through batch experiments, and the mechanisms were analyzed using SEM, FT-IR, XPS, and BET surface analysis. These modifications were found to significantly increase the biochar's specific surface area from 17.606 m2/g to 195.62 m2/g and pore volume from 0.037 cm3/g to 0.132 cm3/g, and surface enrichment with oxygen-containing functional groups, particularly carboxyl groups. The inherent adsorption efficiency of biochar for U(VI) is significantly enhanced by these modifications, with the adsorption capacities of H2O2-modified (HBC) and magnetized HBC (MBC) reaching 69.50 mg/g and 77.58 mg/g, respectively. The adsorption mechanisms of BC, HBC, and MBC for U(VI) involve complexation reactions where hydroxyl and carboxyl groups, among other oxygen-containing functional groups on the biochar, interact with uranyl ions. HBC and MBC exhibit enhanced complexation due to higher carboxyl content, leading to improved U(VI) adsorption. Additionally, the presence of iron-containing functional groups on the surface of MBC contributes to electrostatic interactions and facilitates complexation reactions between Fe-O and uranyl ions, enhancing the overall adsorption process. These findings highlight the potential of modified biochar for the removal of U(VI) from water, particularly for the treatment of mine tailings and smelting wastewater, with significant implications for industrial applications in environmental remediation. [ABSTRACT FROM AUTHOR]

Wastewater produced in beryllium mining seriously affects ecological balance and causes great environmental pressure. We designed a novel porous lotus leaf biochar modified with PO43−/NH4+ multifunctional groups (MLLB) and used it for beryllium(Be) removal from beryllium mining wastewater. Kinetic and thermodynamic experiments showed that the adsorption capacity (Qe) of Be with MLLB from the simulated beryllium mining wastewater could reach 40.38 g kg−1 (35 °C, pH = 5.5), and the adsorption process was spontaneous and endothermic. The dispersion coefficient Kd of Be with MLLB was 2.6 × 104 mL g−1, which proved that MLLB had strong selective adsorption capacity for Be. Phosphoric acid, ammonia, and hydroxyl groups on the MLLB surface would complex with Be to form Be(OH)2 and Be(NH4)PO4 complexation products, which implied that surface complexation and precipitation reactions might co-existed in the adsorption process. The above results showed that MLLB could effectively adsorb Be and prevent beryllium exposure in a beryllium mining process. [ABSTRACT FROM AUTHOR]

The application of low-cost biosorbent of bamboo in methylene blue (MB) removal treatment is limited by its poor adsorption performance. In this study, bamboo parenchyma cell (BP) was isolated from bamboo powder by facile method of water separation and then incorporated with natural non-toxic vermiculite (VE) to prepare bamboo parenchyma cell-vermiculite (VEBP) composites. Much more nanopores were formed and more active adsorbed sites were introduced by filling with VE in BP lumen, which is favorable for improving the MB adsorption capacity. The MB adsorption isotherm of VEBP was preferably fitted with Langmuir model, yielding the highest equilibrium MB adsorption capacity of approximately 422 mg/g. As-obtained adsorption capacity is much higher than that of BP and various kinds of biosorbents in previous researches. Besides, the adsorption kinetics was closer to the pseudo-second-order model, indicating the dominant chemisorption process. Thermodynamic parameters implied the endothermic and spontaneous as well as entropy-governed adsorption process. Based on the analysis of adsorption behavior together with characterizations of VEBP, it can be confirmed that the predominant mechanisms for MB adsorption may involve electrostatic attraction, ion exchange, hydrogen bonding, pore filling, complexation reaction, and π-π interactions. Furthermore, the VEBP exhibited excellent reusability with MB removal efficiency of more than 80% after five cycles. Therefore, this study successfully provides a facile method for preparation of bamboo-based adsorbent with efficient MB adsorption performance. [ABSTRACT FROM AUTHOR]

A new sustainable heterogeneous catalyst for the effective synthesis of 4H-pyran derivatives under mild reaction conditions was investigated. This heterogeneous catalyst was prepared through the complexation reaction between the naturally obtained chitosan from Callinectes sapidus shells and zinc(II) ions (Zn(II)/Chitosan), and characterized using a variety of techniques, including thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and infrared spectroscopy (IR). The corresponding 4H-pyran derivatives were obtained in good to excellent yields (58–96%) in the presence of Zn(II)/chitosan catalyst using water as solvent at 60°C for only 20 min. The catalyst was easily separated from the reaction mixture by simple filtration, resulting in the desired products with excellent purity. In comparison to numerous other catalyst systems for the synthesis of 4H-pyran derivatives, Zn(II)/chitosan, a new sustainable heterogeneous catalyst, demonstrated remarkable efficacy in an environmentally benign solvent, allowing the desired products to be produced under more environmentally friendly reaction conditions. [ABSTRACT FROM AUTHOR]

Excessive oxidative stress (OS) in the peri-implant environment is commonly considered to be an important reason for poor implant osseointegration, and numerous approaches have been developed for improving antioxidant capability of implants. However, it remains challenging to alleviate multiple OS factors in the peri-implant environment. Herein, we reported a facile and effective surface modification method to construct a mussel-inspired epigallocatechin gallate (EGCG)/nano-ceria coating with multiple antioxidant capacities on the titanium surface based on the combination of polyphenol–metal complexation and hydrothermal reaction, which consisted of antioxidative EGCG and CeO2 nanoenzyme to mimic the multiple antioxidant mechanisms of living organisms. The effects of preparation conditions on the morphology, structure, multiple enzyme-like activities, and free radical scavenging ability of the coatings were investigated. The optimized EGCG/nano-ceria coating demonstrated good inhibition efficacy on multiple OS factors, non-toxicity, and improved osteogenetic activities with upregulated alkaline phosphatase expression and calcium deposition even under the simulated OS environment. The results indicated that EGCG/nano-ceria coating with multiple antioxidant capacities showed great potential for enhancing osteogenesis of titanium implants, and also suggested a promising bio-inspired surface modification strategy for improving the biological function of implant materials. [ABSTRACT FROM AUTHOR]

Heavy metals are particularly damaging contaminants in the environment, and even trace concentrations represent a risk to human health due to their toxicity. To detect the heavy metals of Mn2+ and Co2+ ions, a novel selective reusable paper-based Fluorescence naked-eye sensor based on naphthalene cationic Schiff base (NCSB) was synthesized and confirmed using FT-IR, 1 H-NMR, and MS tools. Based on a blue to colorless color change in the aqueous solution, the NCSB sensor is utilized to Mn2+ and Co2+ cations selectively among other metal ions (Fe2+, Cu2+, Mg2+, Ni2+, Zn2+, Cd2+, Hg2+, Pb2+, Sn2+ and Cr3+). In the aqueous medium, the NCSB sensor displayed high sensitivity, with limits of detection (LOD) values of 0.014 µM (14.08 nM) and 0.041 µM (41.47 nM) for Mn2+ and Co2+ cations, respectively. The paper-based sensor naked-eye detected Mn2+ and Co2+ cations in water at concentrations as low as 0.65 µM (65 nM) and 0.086 µM (86 nM), respectively. It was discovered that 5 min of incubation time and a pH range of 7 to 11 were optimal for the complexation reaction between the Mn2+ and Co2+ ions and the NCSB sensor. Through a static quenching process, the interaction of the different metal ions with the Schiff base group in the NCSB molecule results in the development of a ground-state non-fluorescent complex. NCSB sensor was also successfully applied in analysis of Mn2+ and Co2+ in environmental water with good recoveries of 94.8–105.9%. The theoretical calculations based on density functional theory (DFT) studies are in support of experimental interpretations. The links between the input factors and the anticipated response were evaluated using the quadratic model of the response surface methodology (RSM) modeling. [ABSTRACT FROM AUTHOR]

Lead(II) complexation reactions were studied in the presence of salts of the closo-decaborate anion [B10H10]2– and azaheterocyclic ligands 2,2'-bipyridyl (bipy) or 1,10-phenanthroline (phen) in water and organic solvents (acetonitrile, DMF). Binuclear complex Pb(bipy)2[B10H10] and polymer complex [Pb(phen)[B10H10]] were isolated. The effect of solvents and reagent ratios on the composition and structures of the final complexes was studied. The complex compounds were identified by elemental analysis, IR spectroscopy, and X-ray powder diffraction. The structure of complex [Pb(bipy)2[B10H10]]2·2CH3CN (CCDC no. 2325841) was determined by single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

Developing multifunctional engineered adsorbents is an effective strategy for decontaminating the environment from various pollutants. In this study, a polyfunctionalized carbon-framework composite, MSC-CFM, was synthesized. The composite comprises an aromatic carbon framework enriched with various functional groups, including magnetic nanoparticles, hydroxyl, and amino groups. MSC-CFM was used to decontaminate Cr(VI) and polycyclic aromatic nitrides (p-dimethylaminoazobenzene sulfonate (DAS) and diphenyl-4, 4 '-di [sodium (azo-2 -) -1-amino-naphthalene-4-sulfonate] (DANS)) from acidic wastewater. The adsorption capacities of MSC-CFM for Cr(VI), DAS and DANS, quantified using the Langmuir isotherm model, were 161.28, 310.83, and 1566.09 mg/g, respectively. Cr(VI) and PAHs (DAS and DANS) were monolayer adsorbed controlled by chemisorption. MSC-CFM could maintain good adsorption efficiency after up to 6 adsorption and desorption cycles. The presence of polycyclic aromatic nitrides promoted the adsorption of Cr(VI) in the Cr(VI)-DAS/DANS binary systems. Removal of pollutants by MSC-CFM involved a variety of unreported reaction mechanisms, such as electrostatic attraction, redox reaction, anion exchange, intermolecular hydrogen bonding, complexation reaction, π-π interaction, and anion-π interaction. MSC-CFM, enriched with a variety of functional groups, is a promising new material for environmental protection. It has good potential for practical application in treating polluted wastewater. [ABSTRACT FROM AUTHOR]

Background: Positron emission tomography (PET) is a highly sensitive method that provides fine resolution images, useful in the field of clinical diagnostics. In this context, Zirconium-89 (89Zr)-based imaging agents have represented a great challenge in molecular imaging with immuno-PET, which employs antibodies (mAbs) as biological vectors. Indeed, immuno-PET requires radionuclides that can be attached to the mAb to provide stable in vivo conjugates, and for this purpose, the radioactive element should have a decay half-life compatible with the time needed for the biodistribution of the immunoglobulin. In this regard, 89Zr is an ideal radioisotope for immuno-PET because its half-life perfectly matches the in vivo pharmacokinetics of mAbs. Results: The main objective of this work was the design and synthesis of a series of bifunctional octadentate pseudopeptides able to generate stable 89Zr complexes. To achieve this, here we investigated hydroxamate, N-methylhydroxamate and catecholate chelating moieties in complexing radioactive zirconium. N-methylhydroxamate proved to be the most effective 89Zr-chelating group. Furthermore, the increased flexibility and hydrophilicity obtained by using polyoxyethylene groups spacing the hydroxamate units led to chelators capable of rapidly forming (15 min) stable and water-soluble complexes with 89Zr under mild reaction conditions (aqueous environment, room temperature, and physiological pH) that are mandatory for complexation reactions involving biomolecules. Additionally, we report challenge experiments with the competitor ligand EDTA and metal ions such as Fe3+, Zn2+ and Cu2+. In all examined conditions, the chelators demonstrated stability against transmetallation. Finally, a maleimide moiety was introduced to apply one of the most promising ligands in bioconjugation reactions through Thiol-Michael chemistry. Conclusion: Combining solid phase and solution synthesis techniques, we identified novel 89Zr-chelating molecules with a peptide scaffold. The adopted chemical design allowed modulation of molecular flexibility, hydrophilicity, as well as the decoration with different zirconium chelating groups. Best results in terms of 89Zr-chelating properties were achieved with the N-methyl hydroxamate moiety. The Zirconium complexes obtained with the most effective compounds were water-soluble, stable to transmetallation, and resistant to peptidases for at least 6 days. Further studies are needed to assess the potential of this novel class of molecules as Zirconium-chelating agents for in vivo applications. [ABSTRACT FROM AUTHOR]

Trace metals (Mn, Ni, Cu, Zn and Pb) dynamics in the system soil–soil solution—uncultivated grass vegetation was investigated by experimental analytical studies of natural soil samples, uncultivated grass vegetation samples, as well as aqueous soil extracts prepared in laboratory. Additionally, thermodynamic modeling was applied to calculate the trace metals chemical species in these extracts. Two thermodynamic models were used—the classical ion-association model for calculating the inorganic metal species and the Stockholm Humic Model (SHM) accounting for the complexation reactions of trace metals with organic matter. The computer program Visual Minteq was used. Experimental data for the total concentrations of major and trace metals, dissolved organic carbon and pH were used as input data for the calculations. The highest mobility was registered for Mn, followed by Zn and Cu. No mobile Ni and Pb were extracted in water. The metal-organic species with fulvic acids were calculated to be dominant in the case of Cu and Zn, while inorganic species, mainly free ions and carbonates, were the dominant ones for Mn. The highest phytoaccumulation coefficients in the uncultivated grass vegetation were calculated for Cu and Zn, exceeding that of Mn by 1–2 orders of magnitude. Hence, it may be assumed that the domination of metal-organic species of Cu and Zn probably facilitates their phytoaccumulation in the examined vegetation. Despite the high Mn content in the aqueous soil extracts, its phytoavailability was very low, since organic complexes did not dominate for Mn. [ABSTRACT FROM AUTHOR]

Conventional neutralization treatment for manganese (Mn)-bearing mine drainage provides a challenge of cost-efficiency, and new approaches should be explored for efficient removal of Mn. We focused on Mn neutralization sludge, a by-product of the Mn-bearing drainage treatment process, which was assumed to be useful as a water purification material. Mn and zinc (Zn) removal tests in simulated drainage were performed using Mn neutralization sludge, and the reaction mechanism was elucidated using geochemical modeling and X-ray absorption fine structure (XAFS) analysis. The results showed that the addition of sludge enabled to lower the Mn and Zn concentration below Japanese effluent standard (10 mg dm−3 for Mn; 2 mg dm−3 for Zn) within 1 h. Furthermore, heavy metal immobilization was achieved at neutral pH (7–8) with the sludge addition, while the conventional neutralization process without adding the sludge requires higher pH (>10) to lower Mn concentration. These removal behaviors were not explainable by considering only well-known phenomena: hydroxide precipitation, surface complexation reaction onto δ-MnO2, and autocatalytic Mn oxidation. Hence, we advanced the geochemical model for simulation, suggesting that a surface complexation reaction onto γ-MnOOH greatly contributed to the removal of Mn. Besides, Zn was calculated to be predominantly precipitated as ZnMn2O4. Solid residue analysis by XAFS measurement supported the result of above calculation, validating the reliability of the constructed geochemical model. Overall, we concluded that the advanced geochemical model would be useful in predicting the Mn and Zn behavior during mine drainage treatment with Mn neutralization sludge. [ABSTRACT FROM AUTHOR]

A.Z. El-Sonbati et al., in their article "Synthesis, characterization of Schiff base metal complexes and their biological investigation" (Appl. Organometal. Chem. 2019, 33, e5048) reported on the synthesis of a new Schiff base named (E)-2-(((3-aminophenyl)imino)methyl)phenol (also known as N-salicylidene-m-phenylenediamine, HL), which was obtained through condensation reaction of m-phenylenediamine and salicylaldehyde in a 1:1 molar ratio. The reported Schiff base HL was involved in the complexation reaction with a series of metal cations named Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II). Although no crystal structures of either the parent ligand HL or its complexes with the mentioned metal cations were reported, the newly synthesized compounds were characterized by means of elemental analysis, IR-, UV-vis- and 1H NMR spectroscopy, mass-spectrometry, magnetic susceptibility, conductivity and thermal analyses. The antimicrobial activity of the discussed compounds, together with the molecular docking results, were also reported. Additionally, both the Schiff base HL and its metallocomplexes were thoroughly examined by quantum chemical calculations. Despite a plethora of different methods being applied to characterize the obtained compounds, herein, I argue that discussion of the results is doubtful. Furthermore, the results of quantum chemical calculations are dubious and must be reconsidered. Although numerous synthetic attempts failed in this work, the hypothetically possible Schiff base HL was revisited using quantum chemical calculations. A.Z. El-Sonbati et al., in their article "Synthesis, characterization of Schiff base metal complexes and their biological investigation" (Appl. Organometal. Chem. 2019, 33, e5048) reported on a new Schiff base (E)-2-(((3-aminophenyl)imino)methyl)phenol (also known as N-salicylidene-m-phenylenediamine, HL) and its metallocomplexes. Herein, I argue that the discussion of the results is doubtful. [ABSTRACT FROM AUTHOR]

Rare-earth elements are widely used in the study of source tracing and geochemical characteristics, which can reflect the degree of influence of human activities on water environment. In order to reveal the additive effects of various human activities on the geochemical characteristics of rare-earth elements in the surface water environment, the content of rare-earth elements in the river in the coal grain composite area of eastern China was determined by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that all water samples were alkaline, ΣREE content ranged 0.18–0.88 μg·L−1, with an average value of 0.28 μg·L−1. All the water samples showed significant enrichment of light rare-earth elements due to a combination of natural processes and external inputs. The spatial distribution and fractionation characteristics of rare-earth elements show that rare-earth elements (especially Ce) are prone to adsorption/complexation reactions with colloidal particles, resulting in their removal from rivers, Eu anomaly is related to plagioclase crystallization and human activities (coal development, agricultural production, urbanization process), and Gd anomaly is only related to human activities. The research results can provide scientific reference for revealing the distribution of rare-earth elements and geochemical environmental behavior in rivers environment under the superimposed influence of various human activities. [ABSTRACT FROM AUTHOR]

Cyanocobalamin (CNCbl), a medicinal form of vitamin B12, is resistant to glutathione (GSH), and undergoes intracellular processing via reductive decyanation producing the Co(II)-form of Cbl (Cbl(II)) mediated by the CblC-protein. Alteration of the CblC-protein structure might inhibit CNCbl processing. Here, we showed that introducing a bromine atom to the C10-position of the CNCbl corrin ring facilitates its reaction with GSH leading to the formation of Cbl(II) and cyanide dissociation. In a neutral medium, the reaction between C10-Br-CNCbl and GSH proceeds via the complexation of the reactants further leading to dimethylbenzimidazole (DMBI) substitution and electron transfer from GSH to the Co(III)-ion. The reaction is accelerated upon the GSH thiol group deprotonation. The key factors explaining the higher reactivity of C10-Br-CNCbl compared with unmodified CNCbl towards GSH are increasing the electrode potential of CNCbl two-electron reduction upon meso-bromination and the substantial labilization of DMBI, which was shown by comparing their reactions with cyanide and the pKa values of DMBI protonation (pKa base-off). Aquacobalamin (H2OCbl) brominated at the C10-position of the corrin reacts with GSH to give Cbl(II) via GSH complexation and subsequent reaction of this complex with a second GSH molecule, whereas unmodified H2OCbl generates glutathionyl-Cbl, which is resistant to further reduction by GSH. [ABSTRACT FROM AUTHOR]

An in vitro study was carried out to examine the impact of UV exposure on metal-dissolved humic material (M-DHM) complexes in aqueous systems at different pH. Complexation reactions of dissolved M (Cu, Ni, and Cd) with DHM increased with the increasing pH of the solution. Kinetically inert M-DHM complexes dominated at higher pH in the test solutions. Exposure to UV radiation did affect the chemical speciation of M-DHM complexes at different pH of the systems. The overall observation suggests that exposure to increasing UV radiation increased the lability, mobility, and bioavailability of M-DHM complexes in aquatic environments. The dissociation rate constant of Cu-DHM was found to be slower than Ni-DHM and Cd-DHM complexes (both before and after UV exposure). At a higher pH range, Cd-DHM complexes dissociated after exposure to UV radiation and a part of this dissociated Cd precipitated out from the system. No change in the lability of the produced Cu-DHM and Ni-DHM complexes after UV radiation exposure was observed. They did not appear to form new kinetically inert complexes even after 12 h of exposure. The outcome of this research has important global implications. The results of this study helped to understand DHM leachability from soil and its effect on dissolved metal concentrations in the Northern Hemisphere water bodies. The results of this study also facilitated to comprehend the fate of M-DHM complexes at photic depths (where pH changes are accompanied by high UV radiation exposure) in tropical marine/freshwater systems during summer. [ABSTRACT FROM AUTHOR]

The complexation of 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin and 5,10,15,20-tetrakis(2,6-difluorophenyl)porphyrin and metal exchange reactions of their cadmium complexes with manganese(II) chloride in DMF were studied with the goal of finding optimal conditions for the synthesis of manganese(II) and manganese(III) complexes with tetrapyrrole macrocyclic compounds. ortho-Substituted manganese com-plexes were synthesized by prolonged heating of the corresponding porphyrins with excess MnCl2 in boiling DMF. Metal exchange reactions of cadmium(II) 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin and cadmium(II) 5,10,15,20-tetrakis(2,6-difluorophenyl)porphyrin with MnCl2 in DMF produced the corresponding manganese(III) tetraphenylporphyrins. In contrast, the complexation of tetraphenylporphyrins substituted at both pyrrole and phenyl rings with manganese(II) chloride in DMF under mild conditions afforded manga-nese(II) 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin, which was oxidized to a mixture of manganese(II) and manganese(III) porphyrins on exposure to air, and manganese(II) 2,3,7,8,12,13,17,18-octachloro-5,10,15,20-tetrakis(2,6-difluorophenyl)porphyrin. The synthesized compounds were identified by electronic absorption spectroscopy, 1H NMR, and mass spectrometry. The metal exchange reactions of ortho-substituted cadmium(II) tetraphenylporphyrins and the complexation of 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin with manganese(II) chloride in DMF were studied by spectrophotometry, and their kinetic and activation parameters were determined. A significant effect of β- and ortho-substitution on the complexation and metal exchange reactions was revealed. [ABSTRACT FROM AUTHOR]

Sediment, consisting of different aggregation fractions, is a hotspot site for transport and transformation of various pollutants including antibiotics. However, the fate of different antibiotics in aquatic sediments mediated by sediment aggregation fraction adsorption and the mechanism behinds are still unclear. In this study, we investigated the adsorption behavior of two fluoroquinolone antibiotics (ciprofloxacin and ofloxacin) on four aggregation fractions separated from the sediment of Taihu Lake, a typical lake contaminated by antibiotics in China. The results showed that the adsorption of ciprofloxacin and ofloxacin fitted the Freundlich model, irrespective of sediment aggregation size. The adsorption of ciprofloxacin and ofloxacin was depended on the size of sediment aggregation fractions, and the macroaggregation (> 200 μm) exhibited the strongest capacity, followed by large microaggregation (63–200 μm), medium microaggregation (20–63 μm), and small and primary microaggregation (< 20 μm). This fraction size-dependent effects of sediment aggregations on antibiotic adsorption might be closely related to the differences in their specific surface areas, organic matter contents, and surface functional groups. The adsorption of ciprofloxacin and ofloxacin by sediment aggregation fractions was characterized by a combination of chemical and physical adsorptions, with the former being the dominant process. Compared with ofloxacin, ciprofloxacin could be more rapidly and easily absorbed by four sediment aggregation fractions, and more readily complexed with carboxyl groups on macroaggregation surface. The adsorption of two antibiotics by extracellular polymeric substance showed that tryptophan and tyrosine protein-like, humic-like substance on the surface of sediment could bind to both antibiotics through a complexation reaction. The π-π electron donor–acceptor interaction and hydrogen bonds were responsible for the antibiotic adsorption by sediment aggregation. [ABSTRACT FROM AUTHOR]

Hydrogeochemical processes and water–rock interactions of a geothermal system are important for understanding of the hydrochemical evolutionary process and genetic mechanisms of the geothermal system. The hydrochemistry, hydrogen and oxygen isotopes, and rare-earth elements (REEs) are discussed to reveal the hydrochemical characteristics and processes of these geothermal systems in Kahui and Gezha geothermal waters in the Ganzi–Litang fault in western Sichuan, China. The results show that the geothermal waters are Na-HCO3 type and influenced by combination of evaporite dissolution and silicate weathering. The isotopic compositions of δ2H and δ18O indicate that the geothermal water is recharged by atmospheric precipitation, and the oxygen isotope drifts in the Gezha geothermal water may be caused by water–rock interactions. The total REE content of the geothermal water is 0.059‒0.547 ug/L, and the REE contents are significantly influenced by pH and HCO3−, Na+, and Mn minerals. The chondrite-normalized REE pattern show geothermal water, cold springs, and surrounding rocks are rightward. The fractionation of rare-earth elements is affected by HCO3− complexation reactions, the dissolution of Mn minerals, and alternating cation adsorption. Moreover, the geothermal water exhibited positive Eu anomalies, which may be caused by the dissolution of feldspar minerals in surrounding rocks. In addition, the complexation patterns of REEs in geothermal water and cold springs in the Ganzi–Litang fault mainly include Ln(CO3)2− and LnCO3+, and the changes in the complexation patterns are influenced by the stability constants of complexation reactions and pH. [ABSTRACT FROM AUTHOR]

A series of 60-day soil immobilized incubations were performed to explore the impacts of various factors (incubation time, chitosan modified magnetic sawdust hydrochar (CMSH) dosages, initial pH values, moisture contents, and humic acid (HA)) on CMSH immobilization of Pb and Zn. DTPA and BCR extraction techniques were undertaken to study the distribution of form transformations of Pb and Zn. CMSH showed significant immobilization ability for both DTPA-Pb and DTPA-Zn, and the highest removal rates were shown to be 57.40% and 90.00% for Pb and Zn respectively. After 60 days of incubation, the residual Pb was enhanced by 34–61% and residual Zn increased by 25–41%, which indicated that CMSH was effective in immobilizing Pb and Zn. Meanwhile, the immobilization efficiency improved with increasing incubation time, CMSH dosage, HA dosage, and initial solution pH. In particular, 5% HA application increased the soil TOC and accelerated the metal stabilization processes, with the residual forms of Pb and Zn eventually reaching a maximum of 73% and 71%, respectively. In addition, the alkaline initial solution promoted the ion exchange, surface complexation reaction, and cationic-π interaction, resulting in a better immobilization of Pb and Zn by CMSH. Finally, according to the orthogonal analysis of BCR results, HA dosage was the major factor affecting Pb and Zn immobilization by CMSH compared to soil pH and moisture content in this study. [ABSTRACT FROM AUTHOR]

The need for a mild, low-cost, green environment that is able to produce exotic properties of output nanostructures is appealing nowadays. Employing these requirements, the copper (Cu)—based oxide nanostructures have been successfully synthesised via one-pot reaction using biocompatible natural polyphenol, tannic acid (TA) as both the reducing agent and stabiliser at 60, 70 and 80 °C. The structural and optical studies disclosed the effect of TA on the surface morphology, phase purity, elemental composition, optical microstrain and optical intrinsic energy of this mixed Cu2O and CuO nanostructures. The optically based method describes the comparative details of the multi-band gap in the presence of more than one element with overlapping spectra from the first-derivative absorbance curve Δ E Δ A and the exponential absorbance of Urbach tail energy E U towards the conventional Tauc bandgap. The Δ E Δ A demonstrates that the pronounced effect of TA that Cu2O and CuO nanostructures creates much sensitive first-derivative bandgap output compared to the Tauc bandgap. The results also show that the E U reduced as the temperature reaches 70 °C and then experienced sudden increase at 80 °C. The change in the pattern is parallel to the trend observed in the Williamson–Hall microstrain and is evident from the variations of the mean crystallite size D m which is also a cause response to the change in temperature or pH. Therefore, the current work has elucidated that the structural and optical correlations on the as-synthesised Cu2O and CuO nanostructures in the presence of TA were the combined reaction of pH change and the ligand complexation reactions. The acquired results suggest a more comprehensive range of studies to further understand the extent relationship between the physical and optical properties of TA functionalised Cu-based oxide nanostructures. [ABSTRACT FROM AUTHOR]

Metal-salt-modified clay minerals are widely used for endogenous phosphorus control in eutrophic lakes because of its high efficiency of P adsorption, but changes in water quality due to material dosing limit their practical remediation performance. In this study, lanthanum was embedded in thermally-treated calcium-rich attapulgite (TCAP) to strengthen its P uptake ability, and a novel and efficient phosphorus fixation material lanthanum-modified attapulgite (La-TCAP) was synthesized. Batch adsorption experiment indicated that the maximum P sorption capacity of La-TCAP can reach as high as 9.777 mg P/g, which was more than twice that of TCAP. The P removal rate of La-TCAP was maintained between 55.62% and 68% at 4–10 pH. La-TCAP exhibits strong resistance to interfering ions including SO42−, NO3−, Cl−, and HCO3− during phosphorus adsorption. The characterization analysis of La-TCAP showed that the adsorption of phosphate on La-TCAP was mainly based on the surface complexation reaction. Sediment P immobilization studies demonstrated that the coverage of La-TCAP contributed the P recession of 30% to 58.8% in overlying water during the aerobic and anaerobic incubation. Meanwhile, other water quality indicators in the overlying water had hardly changed. The content of Mobile-P in the surface sediments (0–4 cm) was drastically reduced, while the content of Al-P and Ca-P was greatly increased. The results of this study suggest that La-TCAP is a promising P immobilization material for sediment P control in urban eutrophic lake. [ABSTRACT FROM AUTHOR]

Surfactant-polymer (SP) flooding is considered an efficient technique to increase the recovery of oil, especially from carbonates reservoirs, because of their complex nature. The objective of this study is to analyze the effect of polymer drive composition on surfactant retention. We developed a geochemical model that uses various surface complexation reactions at the mineral/brine interface, oil/brine interface, surfactant/brine interface, and oil/surfactant interface. We also incorporated four new surface complexation reactions that honor oil/surfactant geochemical interaction to determine the influence of polymer composition on surface retention for the first time. Then we validated the developed geochemical model against coreflooding experimental data. Additionally, we investigated the influence of various parameters of polymer drive on surface retention under high temperature and salinity using the suggested surface complexation model. The findings showed that our surface complexation model can estimate surfactant retention and its concentration in the effluent with a certain accuracy during polymer drive. The developed geochemical model is validated against single-phase and two-phase coreflooding experimental data. The findings revealed that for a more representative and accurate estimation of surfactant retention in chemical flooding, it is important to consider the oil/surfactant surface complexation reactions. Moreover, the detailed and comprehensive analysis showed that with the increase in temperature of the polymer drive, the retention of surfactant increases, and its concentration in the effluent decreases. The latter shows that surfactant retention is a more chemical process as opposed to physio-retention. It is also shown that the injection of a specific composition of polymer drive after a surfactant slug could decrease the surfactant retention, which is related to the force of repulsion between the ionic species and the rock surface. Moreover, the effect of hard ions (calcium and magnesium) in polymer drive is significant where the increase in the concentration of hard ions increases the retention of surfactant. Furthermore, it is important to mention that the lowest level of surfactant retention was achieved through a certain composition of polymer drive, thus the polymer solution dilution is not an effective approach. This is the first study to test a novel formulation of surface complexation modeling that considers the oil/surfactant effect on surfactant retention corresponding to the composition of polymer drive. The suggested framework to determine surfactant retention is conducted for harsh reservoir conditions of temperature and salinity and suggests that the surface complexation reactions for all rock-forming minerals must be considered. [ABSTRACT FROM AUTHOR]

A green flow injection spectrophotometric technique for the determination of ascorbic acid was described based on the redox and complexation reactions. Iron(III) was reduced to iron(II) by ascorbic acid with subsequent complexation reaction of remaining iron(III) with a natural reagent extracted from Areca catechu L. at pH 5.0 yielding a dark-blue color. Absorbance decreased with increasing ascorbic acid concentration. A linear range of 1–10 mg/L for ascorbic acid was obtained with r2 of 0.9986. Limit of detection and limit of quantification were 0.3 and 0.9 mg/L, respectively. Relative standard deviation was less than 5.0%. This method was utilized to quantify ascorbic acid in pharmaceuticals and soft drinks with a sampling rate of 40 h−1. Ascorbic acid contents of 96–100% in pharmaceutical samples were obtained, while recoveries for spiked ascorbic acid standard at 3 mg/L in soft drinks were 92–113%. [ABSTRACT FROM AUTHOR]

The results of studying the complexation of a number of metal ions on the surface of silica chemically modified by various functional analytical groups are systematized in the review. Examples of the influence of the matrix of sorbents (silica) on the thermodynamic and kinetic parameters of surface complexation reactions with metals are presented. Specific features of using finely dispersed silicas with complexing functional groups in high performance complexation metal ion chromatography are considered. [ABSTRACT FROM AUTHOR]

In this paper, we prepared the modified polyethersulfone-g-poly(N-vinyl-2-pyrrolidone) ultrafiltration membrane by gamma-ray irradiation in a homogenous solution. The cross-section and surface micromorphology of the membrane prepared with different polyethersulfone mass fractions were analyzed by scanning electron microscope. Meanwhile, based on polymer-enhanced ultrafiltration technology combined with our self-made membrane performance testing system, the effects of polymer/metal ion mass ratio and pH value of the aqueous solution on membrane permeation flux and Ce3+ rejection rate were analyzed. According to these experimental results, a reasonable complexation reaction between polyethyleneimine and Ce3+, and the mechanism of the membrane's separation of Ce3+ from an aqueous solution were proposed. [ABSTRACT FROM AUTHOR]

Mercuric ion (Hg2+), a poisonous metal ion that remained in water ecosystems, can severely damage the human central and peripheral nervous system and kidneys. Consequently, rapid and highly sensitive methods to determine trace Hg2+ are meaningful to discuss. In recent years, methods for detecting heavy metals by complexation reactions have emerged one after another. We have proposed a novel approach of surface-enhanced Raman scattering (SERS) for the quantitative analysis of Hg2+ in water samples using dithizone (DTZ) as a Raman reporter. DTZ-modified silver nanoparticles (AgNPs) produced a strong SERS signal. In the presence of Hg2+, the DTZ can capture Hg2+ composing a stable structure, resulting in DTZ leaving the surface of the AgNPs, with an accompanying decrease in the signal. The proposed SERS assay showed a linear range of 10–4–10–8 M, with a limit of detection of 9.83 × 10–9 M. The sensor has low detection cost, rapid detection speed, and uncomplicated sample pretreatment. Furthermore, this method can be successfully utilized to detect Hg2+ rapidly in water samples, which sheds new light on the detection of Hg2+ in the environment. [ABSTRACT FROM AUTHOR]

Red mud/biochar composite material (RMBC), which was applied as heavy metal passivator in this research, was prepared with red mud (the bauxite residue) and cornstalk under anoxic sintering condition. Based on the batch experiments in Pb contaminated soil, the passivating properties of several materials, including red mud (RM), biochar (BC), RMBC and phosphate-containing RMBC (PRMBC), were investigated in comparison with each other. Some interesting results are as follows: through anoxic thermal activation, a rough and porous structure of RMBC was obtained. Substances such as Fe3O4 and metal-organic complexes generated in RMBC provided effective sites for Pb passivation; and the mechanisms were speculated as the precipitation between Pb2+ and the carbonate (or hydroxide), as well as the complexation reaction between Pb and metal organic complexes through ligand bonding. The pot experiments showed the promotion effects of four passivators on the growth of red onion were in the following order: PRMBC > RMBC > BC > RM. PRMBC stabilized Pb content in soil significantly due to the formation of insoluble substances, with the minimum transfer factor and bioconcentration factor for plant growth. The evidences above implied the composite materials (PRMBC and RMBC) would be potential passivators for heavy metal-contaminated soil. [ABSTRACT FROM AUTHOR]

The large amounts ofheavy metal from landscape wastewater have become serious problems of environmental pollution and risks for human health. The development of efficient novel adsorbent is a very important for treatment of heavy metal. The functionalized porous nanoscale Fe3O4 particles supported biochar from peanut shell (PS-Fe3O4) for removal of Pb(II) ions from aqueous solution was investigated. The characterization of PS-Fe3O4 composites showed that biochar was successfully coated with porous nanoscale Fe3O4 particles. The pseudo second-order kinetic model and Langmuir model were more fitted for describing the adsorption process of Pb(II) ions in solution. The adsorption process of Pb(II) ions removal by PS-Fe3O4 composites was a spontaneous and endothermic process. The adsorption mechanisms of Pb(II) ions by PS-Fe3O4 composites were mainly controlled by the chemical adsorption process. The maximum adsorption capacity of Pb(II) ions removal in solution by PS-Fe3O4 composites reached 188.68 mg/g. The removal mechanism included Fe–O coordination reaction, co-precipitation, complexation reaction, and ion exchange. PS-Fe3O4 composites were thought as a low-cost, good regeneration performance, and high efficiency adsorption material for removal of Pb(II) ions in solution. [ABSTRACT FROM AUTHOR]

A nanocomposite of α-Fe2O3/alkalinized C3N4 (α-Fe2O3/A-C3N4) electrocatalyst for oxygen reduction reaction (ORR) was synthesized by a simple in situ electrostatic adsorption of A-C3N4 and iron-based ionic liquid [Omim]FeCl4 complexation reaction using sonication treatment followed by pyrolysis process. The as-prepared α-Fe2O3/A-C3N4 nanocomposite can act as a superior electrocatalyst for ORR in terms of excellent ORR activity with onset potential of 0.82 V vs. reversible hydrogen electrodes (RHE), current density of 5.2 mA cm−2 and outstanding methanol resistance. This cost-effective starting materials and simple preparation method paves the way to large-scale fabrication of low-cost and highly active noble metal-free electrocatalyst and promotes their practical applications in electrochemical power conversion and storage system. [ABSTRACT FROM AUTHOR]

The adsorption of metal ions from wastewater using Schiff base cellulose bearing pendulant heterocyclic chelating groups (MC-Tz) as a sorbent is the subject of this paper. Solid state 13C-NMR, FT-IR, SEM, and XRD spectroscopy, as well as TGA and XRD were utilized to examine the adsorbent. The batch sorption process used pH, adsorbent dose, initial adsorbate concentration, temperature, as well as contact time to calculate the metal ion levels. The optimum pH-6.0, with the complexation reaction and ion exchange phase as the mechanisms at work. To investigate the equilibrium concentration and temperature-dependent rate constants, various models, such as the Langmuir, Freund, Temkin, and Redlich–Peterson adsorption isotherm were utilized. Maximum adsorption capacity of the modified cellulose (MC-Tz) towards Lead(II), Copper(II), Nickel(II), and Cadmium(II) were found to be 453.2, 485.5, 473.2, and 455.6 mg/g respectively. A Kinetic study shows that the Langmuir is more in agreement with the Pseudo-second order Kinetic model. Adsorption–Desorption experiments over four cycles demonstrated the feasibility of the sorbent's regeneration potential and the measured values of enthalpy and entropy explain the essence of the adsorption process. The objective of this research is to discover non-toxic, environmentally friendly adsorbent biodegradable components and to conduct evaluations to determine their use in wastewater treatment. [ABSTRACT FROM AUTHOR]

Iron species that occur in natural surface water could affect the photochemical behavior of pollutants. Complexation between iron species and polycarboxylate or heavy metals has been widely reported, where the ligands could be oxidized via ligand-to-metal charge transfer (LMCT) by light inducement. Such complexation and photochemical reactions might also occur for low valance metal-containing organic compounds, which is worthy of investigation. This work studied the phototransformation of p-arsanilic acid (ASA), an organic arsenic compound that is widely used as a feed additive in the poultry industry, by colloidal ferric hydroxide (CFH) using black light lamps (λ = 365 nm) as the light source. The results revealed the contribution to ASA transformation at circumneutral conditions by CFH through an LMCT process, which is the same as that for As(III). The complexation between ASA and CFH was investigated using UV–vis spectroscopy. The estimated equilibrium constant for the CFH–ASA complex was log Kf271 = 4.22. The analysis of the photoproducts found the generation of both inorganic and organic arsenic. Our findings confirmed the similarities in the photochemical mechanisms of ASA and As(III) in the presence of CFH. The results help in further understanding the fate of organoarsenicals in the surface water environment. [ABSTRACT FROM AUTHOR]

The release of potentially toxic metals, such as copper (Cu), into the water column is of concern during polymetallic nodule mining. The bioavailability and thus toxicity of Cu is strongly influenced by its speciation which is dominated by organic ligand (L) complexation in seawater, with L-complexes being considered less bioavailable than free Cu2+. The presence of CuL-complexes in deep-sea sediments has, however, not been systematically studied in the context of deep-sea mining. We thus analyzed the Cu-binding L concentration ([L]) in deep-sea pore waters of two polymetallic nodule provinces in the Pacific Ocean, the Peru Basin and the Clarion-Clipperton-Zone, using competitive ligand equilibration–adsorptive stripping voltammetry. The pore-water dissolved Cu concentration ([dCu]) ranged from 3 to 96 nM, generally exceeding bottom water concentrations (4–44 nM). Based on fitting results from ProMCC and Excel, Cu was predominantly complexed by L (3–313 nM) in bottom waters and undisturbed pore waters. We conclude that processes like deep-sea mining are unlikely to cause a release of toxic Cu2+ concentrations ([Cu2+]) to the seawater as > 99% Cu was organically complexed in pore waters and the [Cu2+] was < 6 pM for 8 of 9 samples. Moreover, the excess of L found especially in shallow pore waters implied that even with a Cu release through mining activities, Cu2+ likely remains beneath toxic thresholds. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to evaluate de influence of protein–sugar complexation on the stability and functionality of C-reactive protein, after exposure to constant high temperatures, in order to develop highly stable positive controls for in-vitro diagnostic tests. C-reactive protein is a plasmatic protein used as a biomarker for the diagnosis of a series of health problems such as ulcerative colitis, cardiovascular diseases, metabolic syndrome, due to its essential role in the evolution of chronic inflammation. The sugar–protein interaction was investigated using steady state and time resolved fluorescence. The results revealed that there are more than two classes of tryptophan, with different degree of accessibility for the quencher molecule. Our study also revealed that sugar–protein complexes have superior thermostability, especially after gamma irradiation at 2 kGy, the protein being stable and functional even after 22 days exposure to 40 °C. [ABSTRACT FROM AUTHOR]

Nitrogen-grafting through the addition of glycine (Gly) was performed on a metal- phenolic network (MPN) of copper (Cu2+) and gallic acid (GA) to increase its adsorption capacity. Herein, we reported a one-step synthesis method of MPN, which was developed according to the metal–ligand complexation principle. The nitrogen grafted CuGA (Ng-CuGA) MPN was obtained by reacting Cu2+, GA, and Gly in an aqueous solution at a molar ratio of 1:1:1 and a pH of 8. Several physicochemical measurements, such as Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), N2 sorption, X-ray diffraction (XRD), and thermal gravimetry analysis (TGA), were done on Ng-CuGA to elucidate its characteristics. The analysis revealed that the Ng-CuGA has non-uniform spherical shaped morphology with a pore volume of 0.56 cc/g, a pore size of 23.25 nm, and thermal stability up to 205 °C. The applicational potential of the Ng-CuGA was determined based on its adsorption capacity against methylene blue (MB). The Ng-CuGA was able to adsorb 190.81 mg MB per g adsorbent at a pH of 6 and temperature of 30 °C, which is 1.53 times higher than the non-grafted CuGA. Detailed assessment of Ng-CuGA adsorption properties revealed their pH- and temperature-dependent nature. The adsorption capacity and affinity were found to decrease at a higher temperature, demonstrating the exothermic adsorption behavior. [ABSTRACT FROM AUTHOR]

Transition metals such as Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Zn(II), Cd(II), and Hg(II) have been reacted with gibberellic acid (HGA) to give novel complexes, and those have been characterized by physical, spectral and analytical methods. The plant hormone gibberellate acts as a deprotonated bidentate ligand in the complexation reaction with central metal ions in the ratio 1 : 2 (Mn+ : GA). The complexes [M(GA)2(H2O)2], where [M = Mn(II), Co(II), and Ni(II)] form octahedral structures, while [M(GA)2] complexes [M = Zn(II), Cd(II), and Hg(II)] display four-coordination geometry. The octahedral structures of Cr(III) and Fe(III) complexes are characterized by the general formula [M(GA)2(H2O)(Cl)]. Computational study carried out has determined possible interactions of the complexes with COVID-19 (6LU7). [ABSTRACT FROM AUTHOR]

Copper(II) complexation of the [B10H10]2– anion has been studied in the presence of 2,2′-bipyridyl (bipy) in organic solvents. The reaction between CuCl, bipy, and (Et3NH)[Ag[B10H10]] in DMF leads to copper(II) complex [Cu2(bipy)4(µ-CO3)][B10H10]·2DMF·H2O. The copper complexation reaction has been performed under the redox conditions Cu(I) → Cu(II) in the presence of silver(I) compounds. When [Cu2(bipy)4(µ-CO3)][B10H10]·2DMF·H2O has been heated in DMSO, the monosubstituted derivative [2-B10H9OH]2– has been isolated as complex [Cu2(bipy)4(µ-CO3)][2-B10H10O0.17]·2DMSO·H2O consisting of the [B10H10]2– anion and its monosubstituted derivative [2-B10H9OH]2– cocrystallized in the 0.83:0.17 ratio. The metal-promoted process of exopolyhedral substitution of terminal hydrogen atoms in the [B10H10]2¬ anion in the presence of Cu(II) compounds has been discussed. Complexes synthesized have been studied by elemental analysis, IR, 1H and 11B NMR spectroscopy; the X-ray diffraction studies were performed for [Cu2(bipy)4(µ-CO3)][B10H10]·2DMF·H2O and [Cu2(bipy)4(µ-CO3)][2-B10H10O0.17]·2DMSO·H2O. [ABSTRACT FROM AUTHOR]

A quartz crystal adsorbent coated with 5,10,15,20-tetrakis(4-methylphenyl) porphyrin was used to examine the complexation phenomenon of three metallic ions [aluminum(III), iron(III) and indium(III)]. The aim is to select the appropriate adsorbate for metalloporphyrin fabrication. The equilibrium adsorption isotherms of tetrakis(4-methylphenyl) porphyrin were performed at four temperatures (from 300 to 330 K) through the quartz crystal microbalance (QCM) method. Subsequently, the experimental data were analyzed in order to develop a thorough explanation of the complexation mechanisms. The experimental results indicated that the aluminum(III) chloride is the adequate material for metalloporphyrin application. Theoretical investigation was established through physics adsorption models in order to analyze the experimental isotherms. The AlCl3 isotherms were modeled via a single-layer adsorption model which is developed using the ideal gas law. Whereas, the FeCl3 isotherms were interpreted via a single-layer adsorption which includes the lateral interactions parameters (real gas law), indicating the lowest stability of the formed iron-porphyrin complex. The participation of the chloride ions in the double-layers adsorption of InCl3 was interpreted via layer by layer formulation. Interestingly, the physicochemical investigation of the three adopted models indicated that the tetrakis(4-methylphenyl) porphyrin adsorption was an endothermic process and that the aluminum(III) chloride can be recommended for an industrial application because it presents the highest adsorption energy (chemical bonds with porphyrins). [ABSTRACT FROM AUTHOR]

This study investigated the influence of tartaric acid (TA) on the early hydration of NaOH-activated ground-granulated blast-furnace slag (GGBS) paste. Early hydration process of the paste with or without TA was characterized by the hydration heat using an isothermal calorimeter. In addition, inductively coupled plasma spectroscopy, X-ray diffraction, Fourier transform IR spectroscopy and scanning electron microscopy analyses were used as auxiliary tests. The results reveal that TA has a significant retarding effect on the hydration of NaOH-activated GGBS paste, finally leading to the initial setting time increasing with increasing TA. The complexation reaction of Al rather than Ca is the main reason for the observed retardation effect. The Al-complexed carboxylate salts formed by the complexation reaction of Al inhibit the depolymerization of the Si–Al phase, which leads to extend the time for SiO32− and Al3+ to reach the saturation point in pore solution. And it subsequently delays the crystallization and nucleation of the main hydration products. However, TA has a little effect on the hydration products of NaOH-activated GGBS paste. The application of TA maintains the variety of main crystal products and the constant structure of gel products. The gel product still remains C–(A)–S–H with a primarily Q2 structure. Therefore, TA is an effective retarder for the NaOH-activated GGBS system. [ABSTRACT FROM AUTHOR]

Biological macroscopic assemblies have inspired researchers to utilize molecular recognition to develop smart materials in these decades. Recently, macroscopic self-assemblies based on molecular recognition have been realized using millimeter-scale hydrogel pieces possessing molecular recognition moieties. During the study on macroscopic self-assembly based on molecular recognition, we noticed that the shape of assemblies might be dependent on the host–guest pair. In this study, we were thus motivated to study the macroscopic shape of assemblies formed through host–guest interaction. We modified crosslinked poly(sodium acrylate) microparticles, i.e., superabsorbent polymer (SAP) microparticles, with β-cyclodextrin (βCD) and adamantyl (Ad) residues (βCD(x)-SAP and Ad(y)-SAP microparticles, respectively, where x and y denote the mol% contents of βCD and Ad residues). Then, we studied the self-assembly behavior of βCD(x)-SAP and Ad(y)-SAP microparticles through the complexation of βCD with Ad residues. There was a threshold of the βCD content in βCD(x)-SAP microparticles for assembly formation between x = 22.3 and 26.7. On the other hand, the shape of assemblies was dependent on the Ad content, y; More elongated assemblies were formed at a higher y. This may be because, at a higher y, small clusters formed in an early stage can stick together even upon collisions at a single contact point to form elongated aggregates, whereas, at a smaller y, small clusters stick together only upon collisions at multiple contact points to give rather circular assemblies. On the basis of these observations, the shape of assembly formed from microparticles can be controlled by varying y. [ABSTRACT FROM AUTHOR]

Seven homo- and hetero-bimetallic macromolecular complexes (BMCs) were prepared via an in-situ multi-step complexation reaction of CuII, NiII and FeIII metal centers with imine- oxime π-conjugated ditropic spacer (1,4-phenylene-bis(2,3-butanedeimineoxime, L2−). The structures of the obtained [M-L2-M]x, [M'-L2-M']x, [M-L2-M']x and their μ-oxo-[M-L2-Fe]x BMCs (M = CuII, NiII; M' = FeIII) were elucidated using different spectroscopic (UV–Vis, FT-IR), powder X-ray diffraction (p-XRD) and microscopic (SEM) techniques. The SEM images indicate that the obtained BMCs exhibit nano/micro globular and rod-like textures. The electrical and magnetic characteristics of the obtained BMCs can be described as magneto-semiconducting materials. The structural, electrical, and magnetic properties inherited in the prepared regime demonstrate that the examined semiconducting π-spacer has clear ability to semi-conduct electron transport and delocalize spin leading to antiferromagnetic coupling, thus offering a favorable magnetic exchange pathway between the paramagnetic metal sites. However, ferromagnetic enhancement is observed in the μ-oxo-[M-L2-Fe]x BMCs where the μ-oxo-bridge overplays the role of the π-spacer. A magnetic responsive thin film was conveniently obtained by solvent casting of the μ-oxo-[Ni-L2-Fe]x BMC in a transparent poly(methamethylacrylate) matrix. [ABSTRACT FROM AUTHOR]

Monoiodo- and dibromsubstituted dipyrromethenes HL1 – HL3 were described as a highly sensitive and selective «Off-On» fluorescent chemosensor for Zn2+ based on the chelation-enhanced fluorescence (CHEF) effect. Сoordination reactions of HL1 – HL3 with Zn2+ cations are accompanied by a significant (124 to 215-fold) increase in fluorescence intensity against the background of other metal ions in the binary propanol-1/cyclohexane mixture (1:30). The fluorometric detection limit of Zn2+ ions using HL1 – HL3 sensors is from 3.0∙10−8 to 3.3·10−9 mol/L. The presence of Na+, K+, Ca2+, Mg2+, Mn2+, Ni2+, Co2+, Pb2+ cations does not interfere with the detection of Zn2+. Complexation reactions are accompanied by a visual change in the color of the solution from yellow-orange to pink-raspberry so that the HL1 – HL3 ligands can also be used as a «naked-eye» indicators of the presence of Zn2+ ions. [ABSTRACT FROM AUTHOR]

Acetohydroxamic acid (AHA) is a hydrophilic organic complexing agent with excellent masking or stripping effects on the tetravalent actinides in the extraction operations. Therefore, AHA is a promising reagent for the spent nuclear fuel reprocessing. In the reprosessing of spent uranium-aluminum fuel with a high U-235 enrichment which is used in research reactor, the dissolver solution contains a high concentration of Al(NO3)3, several orders of magnitude higher than that of minor actinides such as plutonium, and dilute tri-n-butyl phosphate(TBP)/n-dodecane is adopted as the extractant. In this research, complexation of Pu(IV) with AHA under the condition of U-Al fuel reprocessing is investigated. Results show that Al(NO3)3 insignificantly affects the mentioned complexation reaction. Further, the possibility of uranium purification against Pu(VI) is also investigated by using AHA in the presence of a high concentration of Al(NO3)3 by simulating some experiments on the separation process. [ABSTRACT FROM AUTHOR]

Neochlorogenic acid, a less-studied isomer of chlorogenic acid, has been seen to posses antioxidant, antifungal, anti-inflammatory and anticarcinogenic effects, which makes it an interesting candidate for incorporation in functional foods. However, its poor solubility in water and susceptibility to oxidation make such a task difficult. To overcome that, its encapsulation in cyclodextrins (CDs) is proposed. The fluorescence of neochlorogenic acid in different pH conditions was analyzed, and caffeic acid was proved to be the fluorescent moiety in the molecule. An encapsulation model whereby the ligand poses two potential complexation sites (caffeic and D-(-)-quinic moieties), showed that α-CD and HP-β-CD formed the best inclusion complexes with neochlorogenic acid, followed by M-β-CD, β-CD and γ-CD. Molecular docking with the two best CDs gave better scores for α-CD, despite HP-β-CD providing stabilization through H-bonds. The encapsulation of chlorogenic acid led to a similar CD order and scores, although constants were higher for α-CD, β-CD and M-β-CD, lower for HP-β-CD, and negligible for γ-CD. The protonation state affected these results leading to a different order of CD preference. The solubility and the susceptibility to oxidation of neochlorogenic acid improved after complexation with α-CD and HP-β-CD, while the antioxidant activity of both isomers was maintained. [ABSTRACT FROM AUTHOR]

Iron (Fe) is well known as a limiting factor to control primary productivity especially in high-nutrient and low chlorophyll area such as the subarctic Pacific. The solubility of Fe is believed to be controlled by its complexation with natural organic ligands, while the distribution of organic ligands is poorly understood. Here, we report that dissolved (< 0.2 µm) organic ligands were unevenly distributed between the western and eastern stations in the subarctic Pacific. The concentration of dissolved organic ligands around the lower part of subarctic Pacific intermediate water was higher in the western station, suggesting that Fe complexation with these organic ligands supports a lateral transport within the water mass. However, a more detailed size-fractionated treatment indicated no significant difference in the soluble (< 1000 kDa) ligands' distribution between the western and eastern stations. These results suggest that organic and inorganic colloid formations are potentially essential for Fe transport mechanisms in the subarctic Pacific. [ABSTRACT FROM AUTHOR]

This work continues a series of studies devoted to complex formation of ions of biogenic metals with the flavonoid dihydroquercetin (DHQ). The interaction of Со2+ ions with DHQ in aqueous solutions has been investigated. It has been found that, at different pH of a solution, complex compounds (CC) with different stoichiometry are formed; a variation of the pH value of a solution from 6.0 to 7.0 results in the formation of compounds (1)–(3) with the metal : flavonoid ligand ratio (Met : L) from 1 : 2 at рН 6.0 (1), through 2 : 3 at pH 6.4–6.7 (2), to 1 : 1 at рН 6.8–7.0 (3). By using the thermogravimetric method and the data of the elemental analysis, the most probable composition of the compounds with the determination of the amount of bound water has been proposed: [CoL2(H2O)4] for (1), [Co2L3(ОН)(H2O)4] for (2), and [CoL(ОН)(H2O)2] for (3). Conditions for the optimization of product yield in the complexation reaction of Со2+ ions with DHQ in an aqueous solution have been determined for compound (2): the рН value of solution 6.7; the reaction time 15 min; the temperature of the reaction solution 90°С; the molar ratio of the initial reagents DHQ : Со2+ 1 : 1.5; the initial concentration of DHQ 0.020 mol/L and that of Со2+ 0.030 mol/L; and the use of CoSO4 ⋅ 7H2O as a source of cobalt ions. The yield of the product is 81.8%. [ABSTRACT FROM AUTHOR]

The solution state of a new antituberculosis drug 1,6-bis(hydrazidomethylsulflnyl)hexane (L) and its complexation with copper(II) were investigated by spectrophotometry, pH-potentiometry (T = 25 °C; at variable ionic strength), and mathematical modeling. The dissociation constants of the protonated and imidol forms of compound L were determined. Complexation reactions in the Cu2+—L system result in mononuclear complexes [CuL]2+ and [CuL2]2+ with the amide form of the ligand provided that the redox reactions are excluded. The most probable (optimized) structures of 1,6-bis(hydrazidomethylsulfinyl)hexane and its complexes were obtained from quantum chemical calculations within the framework of the density functional theory (PBE/6-311G (d) method). Compound L adopts a folded conformation. The coordination site of the 1:1 complex includes six oxygen atoms from two carbonyl groups, two sulfoxide groups, and two water molecules. In the 1:2 complex, each ligand molecule is coordinated in bidentate mode through the carbonyl oxygen atom and the primary amino nitrogen of a hydrazide fragment. [ABSTRACT FROM AUTHOR]

Reactions of the inclusion complexation of β- and γ-cyclodextrins (β-CD and γ-CD) with benzoic acid (BA) in water-dimethyl sulfoxide media have been investigated at pH 3.6 and 1.65 and T = 298.15 K using isothermal titration calorimetry and UV-Vis spectroscopy. The standard thermodynamic parameters (lgK°, ΔrH°, ΔrG°, and TΔrS°) have been estimated for the formation of [BAβ-CD] and [BAγ-CD]. It was found that when H2O-DMSO mixtures were used as the solvent instead of pure water, the stability of complexes slightly decreased. [ABSTRACT FROM AUTHOR]

In recent papers, it is found that the silver-[6]Helicene complex can be used as a cancer drug but the interaction silver-hexaHelicene has not yet proven. The idea of this paper is to investigate the complexation process of the [6]Helicene by the silver metal (Ag+) using three types of adsorbates. Indeed, the adsorption of silver chloride, silver nitrate and silver sulfide into the sensor films deposited on the QCM electrode are measured at three temperatures (293–333 K). Films of the [6]Helicene were deposited on the QCM resonators using spin coating method in order to obtain uniform and homogenous sensor surface. Experimental results indicated that the [6]Helicene can form a stable complex with the silver ion and that the AgCl is the appropriate adsorbate for the complexation achievement. Actually, an advanced modeling analysis by means of statistical physics adsorption models is applied to explore the new vision of the complextion system. The values of the models parameters are deduced from fitting the experimental data with the developed models. They result in confirming the experimental findings by comparing the complexation energies of the three examined systems. In particular, for the silver nitrate, the Van-der-Waals parameters explained the isotherms drop at high concentration through the lateral interactions between the adsorbates. The adsorption energies analysis showed the highest interaction AgCl-[6]Helicene. Density functional theory (DFT) simulations showed that chemical bonds take place during the adsorption of silver chloride on hexaHelicene which confirms that the [6]Helicene can function as a chiral molecular tweezer of the univalent cationic silver. [ABSTRACT FROM AUTHOR]

Published and authors' own data have been used to create a unified mathematical model describing the distribution of uranyl nitrate, nitric acid, and tetravalent elements in TBP with consideration for its dilution in their distribution in neutral and acid systems in a wide range of component concentrations. As the base values of the concentration equilibrium constants were taken their values calculated for pure TBP. In this case, raising the diluent concentration leads to a linear dependence of the logarithms of the extraction constants on the TBP concentration with a parameter a the value of which reflects the influence exerted by the nature of a diluent. It is assumed that, simultaneously, there occur several complexation reactions in the aqueous and organic phases and a nonstoichiometric physicochemical interaction of the components. The values of the equilibrium constants of the extraction reactions and the corresponding parameters a were determined for tetravalent thorium, uranium, plutonium, neptunium, zirconium, and hafnium, which made it possible to describe their extraction with TBP solutions in a hydrocarbon diluent at concentration of the extractive agent of 5 to 100 vol %. The error in calculations of the distribution coefficients in terms of the model does not exceed 12%. [ABSTRACT FROM AUTHOR]