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Methods for obtaining efficient sorption materials based on highly porous melamine and polyurethane matrices modified with reduced graphene oxide were developed. These materials are promising for solving environmental problems such as water pollution with organic products by sorption treatment. Reduced graphene oxides (rGOs) were synthesized from graphene oxide suspensions using potassium hydroxide, ascorbic acid or hydrazine hydrate. Composites with obtained rGO and melamine and polyurethane foam were produced for further characterization. The composites demonstrate high sorption of organic pollutants (oil, diesel fuel and gasoline) and low sorption of water. The composites were comprehensively analyzed by physicochemical techniques (SEM, XPS, Raman spectroscopy, UV–Vis) to elucidate the mechanism of sorption. [ABSTRACT FROM AUTHOR]

Sorption of Pu(VI) onto synthesized goethite under oxidizing and normal conditions was investigated, which revealed its pH dependence on different solid/liquid ratios. Pu speciation upon sorption on the solid phase was characterized via extended X-ray absorption fine structure (EXAFS) spectroscopy, while that in solution was assessed using ultraviolet–visible (UV–Vis) spectroscopy and liquid–liquid extraction. The obtained results demonstrate differences in plutonium behavior in the studied systems. Pu(VI) remains hexavalent on the goethite surface and in solution under oxidizing conditions. While Pu(IV) is stabilized on the mineral and Pu(V) is found in solution under normal conditions. This study provides the thermodynamic descriptions of these reactions. [Display omitted] • Under oxidizing conditions Pu(VI) can be sorbed without changing oxidation states. • Thermodynamic model describes plutonium sorption with redox processes was constructed. • Upon plutonium reducing sorption on redox inactive minerals, Pu(V) remains in solution, which was also modeled. • It is shown that Pu(V) can also be present on the surface of minerals. [ABSTRACT FROM AUTHOR]

The sorption of U(VI), Am(III)/Eu(III) and Cs(I) radionuclides by graphene oxides (GOs) synthesized by Hummers's, Brodie's and Tour's methods was studied through a combination of batch experiments with characterization by microscopic and spectroscopic techniques such as X-ray photoelectron spectroscopy (XPS), attenuated total reflection fourier-transform infrared spectroscopy (ATR-FTIR), high-energy resolution fluorescence detected X-Ray absorption spectroscopy (HERFD-XANES), extended X-ray absorption fine structure (EXAFS) and high resolution transmission electron microscopy (HRTEM). Remarkably different sorption capacity and affinity of radionuclides was found towards GOs synthesized by Hummers's and Brodie's methods reflecting different structure and oxidation state of these materials. Mechanism underlying GO – radionuclide interaction is determined using variety of experimental techniques. For the first time it is shown here that GO - radionuclides interaction takes place on the small holes or vacancy defects in the GO sheets. Mechanism of GO's interaction with radionuclides was analyzed and specific functional groups responsible for this interaction were identified. Therefore, a new strategy to produce improved materials with high capacity for radionuclides suggests the use perforated and highly defected GO with a larger proportion of carboxylic functional groups. Image 1 [ABSTRACT FROM AUTHOR]

Here we provide evidence that the formation of PuO2 nanoparticles from oxidized PuVI under alkaline conditions proceeds through the formation of an intermediate PuV solid phase, similar to NH4PuO2CO3, which is stable over a period of several months. For the first time, state‐of‐the‐art experiments at Pu M4 and at L3 absorption edges combined with theoretical calculations unambiguously allow to determine the oxidation state and the local structure of this intermediate phase. [ABSTRACT FROM AUTHOR]

Here we provide evidence that the formation of PuO2 nanoparticles from oxidized PuVI under alkaline conditions proceeds through the formation of an intermediate PuV solid phase, similar to NH4PuO2CO3, which is stable over a period of several months. For the first time, state‐of‐the‐art experiments at Pu M4 and at L3 absorption edges combined with theoretical calculations unambiguously allow to determine the oxidation state and the local structure of this intermediate phase. [ABSTRACT FROM AUTHOR]

Precipitates formed by the neutralisation of Pu(iii), Pu(iv), Pu(v), and Pu(vi) solutions were characterised by HRTEM, SAXS, and XRD in the suspensions. PuO2 nanoparticles uniform in size (typical diameter around 2.5 nm) and phase composition were observed in all cases under equilibrium conditions. For Pu(vi), the precipitation reactions proceed via an intermediate product. [ABSTRACT FROM AUTHOR]

In this work, we study different clay samples to examine the effect of structural features of clay minerals (2:1 and 1:1 structures), interlayer cations (Na/Ca/Li forms of montmorillonite), surface area and presence of accessory minerals (iron oxides, calcite, quartz) on Np(V) sorption at trace concentrations. Various techniques, e.g., XRD, XRF, DTG, FTIR, BET absorption and Mossbauer spectroscopy, were used to characterize these clays. The presence of iron oxide as an accessory mineral has a strong effect on Np(V) sorption. Sorption of Np(V) onto different clay minerals with different surface areas, interlayer cations and structures is very similar at a pH range of 4.5–11.5. [ABSTRACT FROM AUTHOR]

Batch sorption experiments on thoroughly characterized bentonites and thermodynamic modeling studies were conducted to reveal the role of iron-containing accessory phases on the interfacial behavior of Np(V). Bentonite clays from different industrial deposits with varying total iron contents were selected for the studies. The samples were characterized by XRD, Mossbauer spectroscopy, XRF, HRTEM, SEM-EDX and other techniques, and wherever possible, the accessory iron phases were identified and quantified. Thermodynamic modeling using available surface complexation data revealed the dominant role of the goethite accessory phase, which was present as nanoparticles, in Np(V) sorption at trace level concentrations (10 −14 M). This fact is independently supported by the combination of SEM-EDX and α-track radiography. These studies illustrate the important role that accessory minerals can play in radionuclides sorption data. This is important to the understanding and modeling of the molecular-level speciation of radionuclides. [ABSTRACT FROM AUTHOR]

The effect of ionic strength, pH value, and particles morphology on the Am iii sorption onto LnPO 4 with different crystalline structures, i.e ., monazite, xenotime, and rhabdophane, was established. The sorption capacity of the LnPO 4 was found to be independent of its crystal structure and equal to ca . 1 μmol m –2 . [ABSTRACT FROM AUTHOR]

The present study was focused on the sorption of Eu(III) onto kaolinite. Two kaolinite samples with different origins and compositions were studied. A high-purity natural sample of kaolinite was used to obtain the sorption behavior: dependence of sorption on the ionic strength, pH, and radionuclide concentrations. It was compared with the data for another kaolinite sample containing admixtures of other clay minerals (illite and smectite). In addition, the effect of cations leaching from clay on the sorption was observed. Collected experimental results allowed to develop of a thermodynamic sorption model of Eu(III) sorption onto kaolinite accounting ion-exchange and surface complexation reaction as well competition with the sorption of Al3+. The model was also successfully tested on the available literature data for other kaolinite samples. • A robust model describing different experimental data on sorption of Eu3+ onto kaolinite was made. • Competition of Al3+ with Eu3+ towards ion exchange onto kaolinite was founded and modeled. • The dependence of sorption on edge site with the specific surface area was approved. [ABSTRACT FROM AUTHOR]

It has been found that leaching of Am III from the surface after the sorption is characterized by slow kinetics; over 10 days are required to reach a dynamic equilibrium in the system. The leaching process is accompanied by the formation of Am-containing phosphate phase on the sorbent surface. Annealing the sample at 400 °C for 5 h after sorption results in incorporation of the sorbed cation into the sorbent structure, which allows subsequent leaching to be reduced considerably. [ABSTRACT FROM AUTHOR]

237Np isotope is one of the long-lived and hazardous components of the accumulated liquid radioactive waste (LRW). The potential for environmental contamination when the LRW is directly disposed of in deep geological stratum is a matter of concern. Np(V) is highly mobile in the groundwater, and numerous studies are focused on its interaction with natural geological systems and prospective engineered barriers for the radioactive waste repositories. In this work, we studied the neptunium behavior in simulated conditions of acidic liquid radioactive waste injection to the deep permeable stratum collector. To determine components of the host rock preferentially binding the neptunium, and to estimate the effect of elevated temperature on its mobility, a series of laboratory experiments on sorption and leaching of neptunium was carried out using synthetic acid LRW solution and real stratum-collector sand along with individual component simulants. It was found that neptunium sorption on stratum collector sands in the conditions of acidic waste injection is quite low. Clay minerals turned out to be the sorption-dominating components of the host rock for neptunium. Increase in temperature significantly enhances the retention of neptunium on solid phase. Solid-bound neptunium species are sufficiently stable over the two-year experimental time under ambient conditions. [Display omitted] • Neptunium sorption in simulated injection conditions is quite low. • Clay minerals are sorption dominating components of deep stratal bedrock. • Increase in temperature significantly enhances sorption. • Solid-bound at 150°С Np species are sufficiently stable over time even after cooling. [ABSTRACT FROM AUTHOR]

Highlights: [•] TiO2 microspheres different in porosity were synthesized and characterized. [•] Kinetics and pH sorption edges for Am3+/Eu3+ onto TiO2 were studied. [•] The surface stability constants were determined and fitted by LFER. [•] Crystallinity of the sample is determined to be the major factor governing cation sorption. [•] No or small effect of pore size distribution is established on Am3+ sorption. [Copyright &y& Elsevier]

Abstract: It has been recognized that natural aquatic colloids can readily sorb actinide elements, including plutonium, whose behavior is complicated by its multiple valence states and the possibility of redox reactions under environmental conditions. In this paper, the sorption and surface-mediated redox transformations of hexavalent plutonium on synthetic well-characterized hematite colloids are studied in a series of batch sorption experiments. The variation in the kinetics of the Pu–hematite interactions, Pu-L3-XAFS, and HRTEM over a broad range of total concentrations of Pu have been studied in an attempt to define the molecular-level speciation of Pu. The surface-mediated slow reduction of Pu(V/VI) results in the formation of crystalline nanoparticles of PuO2+ x ·nH2O approximately 1.5nm in size at [Pu]tot ⩾10−9 M. This result is confirmed independently by HRTEM images of Pu-containing particles and through the identification in the EXAFS of a Pu neighbor shell at 3.8Å. The formation of such nanoparticles potentially influences the colloid-mediated transport of Pu in the subsurface environment because of the very slow leaching of Pu from the hematite colloids. [Copyright &y& Elsevier]

Sequential extraction tests were used to study partitioning of U in the bottom sediments of two reservoirs that have been used for the temporary storage of nuclear waste at the "Mining and Chemical Combine" (Zheleznogorsk, Krasnoyarsk region, Russia). Various sequential extraction protocols were applied to the bottom sediment samples and the results compared with those obtained for laboratory-prepared simulated samples with different speciation and partitioning, e.g., U(VI) sorbed onto various inorganic minerals and organic matter, as well as uranium oxides. The distributions of uranium in fractions extracted from simulated and actual contaminated samples were compared to shed light on the speciation of U in the bottom sediments. X-ray absorption spectroscopy, X-ray diffraction, and scanning electron microscopy were also used to analyze the partitioning of U in contaminated sediments. We also compared the results obtained using the spectroscopic and microscopic techniques, as well as sequential extraction. Image 1 • U partitioning in two liquid nuclear waste reservoirs in Russia was studied. • Sequential extraction of samples simulating U forms in environmental objects were investigated. • Four extraction procedures were probed to both model samples and contaminated sediments. • Results of spectroscopic and microscopic methods and sequential extraction were compared. [ABSTRACT FROM AUTHOR]

Rücktitelbild: A Novel Metastable Pentavalent Plutonium Solid Phase on the Pathway from Aqueous Plutonium(VI) to PuO2 Nanoparticles (Angew. Keywords: Actinoidchemie; Elektronenstrukturberechnungen; Pentavalentes Plutonium; Plutoniumdioxid-Nanopartikel; Pu M4 HERFD Actinoidchemie, Elektronenstrukturberechnungen, Pentavalentes Plutonium, Plutoniumdioxid-Nanopartikel, Pu M4 HERFD. [Extracted from the article]

We studied the interaction between bovine serum albumin (BSA) and lanthanide ions in aqueous solution in the 4.0 ÷ 9.5 pH range. A strong increase of the solution turbidity was observed at pH values exceeding 6, which corresponds to the formation of Ln(OH) 3 nanoparticles, while no changes were observed near the isoelectric point of BSA (pH 4.7). The results of the dynamic light scattering and protein adsorption measurements clearly demonstrated that the observed turbidity enhancement was caused by albumin sorption on the surface of Ln(OH) 3 and colloid particles bridging via adsorbed protein molecules. Upon pH increase from 4.5 to 6.5, albumin adsorption on lanthanide colloids was observed, while the following increase of pH from 6.5 to 9.5 led to protein desorption. The predominant role of the electrostatic interactions in the adsorption and desorption processes were revealed in the zeta-potential measurements. No reversibility was observed upon decreasing pH from 9.5 to 4.5 that was suggested to be due to the other interaction mechanisms present in the system. It was shown that while for all lanthanide ions the interaction mechanism with BSA was similar, its manifestation in the optical properties of the system was significantly different. This was interpreted as a consequence of the differences in lanthanides hydrolysis constants. [ABSTRACT FROM AUTHOR]

In the present study, the dissolution and microstructural transformation of CeO 2 nanoparticles (NPs) in a phosphate-containing milieu were investigated. The dissolution behaviour of 2 nm and 5 nm CeO 2 NPs in phosphate buffer solutions was found to differ markedly from that observed in 0.01 M NaClO 4. Through synchrotron X-ray diffraction analysis and X-ray absorption spectroscopy, the interaction between CeO 2 NPs and phosphate species was examined, revealing the transformation of the oxide into sodium-cerium double phosphate, with cerium predominantly existing in the Ce(IV) state. According to scanning and transmission electron microscopy observations, thus formed Na-Ce(IV) phosphate consists of spindle-like aggregates of nanocrystalline rods, presumably formed during phosphate anions sorption on the initial CeO 2 surface. Pair distribution function analysis revealed that Na-Ce(IV) phosphate has a three-dimensional framework crystal structure, similar to NaTh 2 (PO 4) 3 , as reported earlier, with large channels along the c-axis containing disordered sodium atoms. This study represents the first detailed analysis of phosphate-induced speciation and microstructural transformation of CeO 2 NPs, resulting in the formation of Ce(IV) phosphate. Similar processes may occur in natural ecosystems upon the introduction of CeO 2 NPs. [Display omitted] • CeO 2 NPs transform into Na-Ce(IV) phosphate in phosphate buffer. • Transformation rate and dissolved cerium concentration vary with NPs size. • Transformation mechanism involves phosphate sorption and new phase formation on CeO 2 surface. • Na-Ce(IV) phosphate morphology and crystal structure are thoroughly analysed. [ABSTRACT FROM AUTHOR]

The structural characterisation of actinide nanoparticles (NPs) is of primary importance and hard to achieve, especially for non‐homogeneous samples with NPs less than 3 nm. By combining high‐energy X‐ray scattering (HEXS) and high‐energy‐resolution fluorescence‐detected X‐ray absorption near‐edge structure (HERFD XANES) analysis, we have characterised for the first time both the short‐ and medium‐range order of ThO2 NPs obtained by chemical precipitation. By using this methodology, a novel insight into the structures of NPs at different stages of their formation has been achieved. The pair distribution function revealed a high concentration of ThO2 small units similar to thorium hexamer clusters mixed with 1 nm ThO2 NPs in the initial steps of formation. Drying the precipitates at around 150 °C promoted the recrystallisation of the smallest units into more thermodynamically stable ThO2 NPs. HERFD XANES analysis at the thorium M4 edge, a direct probe for f states, showed variations that we have correlated with the breakdown of the local symmetry around the thorium atoms, which most likely concerns surface atoms. Together, HEXS and HERFD XANES are a powerful methodology for investigating actinide NPs and their formation mechanism. [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]

Abstract The sorption of Cs+ onto raw Kutch clay (India) over a wide range of concentrations and pH levels was studied and compared with its sorption onto the well-studied FEBEX clay (Spain). The principal clay mineral in both samples is montmorillonite. Non-linear sorption isotherms were measured for both clays. The shapes of the isotherms prompted the use of a two-site exchange thermodynamic model to describe the experimental data. However, differences in the highly selective sorption sites (Type 1) were observed for the two studied clays. It was found that the presence of different cations (H+, Ca2+, Mg2+, etc.) in solution affected the sorption of Cs+. A model accounting for the competition process was developed for predicting the behavior of the raw clay in complex solutions. Highlights • Sorption of Cs+ onto Kutch clay was studied in a wide range of pH and concentration. • A thermodynamic model accounting of competition with cation was created. • The nature of different montmorillonites influences Cs+ sorption was observed. • The competition of different cations with Cs+ during the sorption was distinguished. [ABSTRACT FROM AUTHOR]

Porous carbons are not favorable for sorption of heavy metals and radionuclides due to absence of suitable binding sites. In this study we explored the limits for surface oxidation of "activated graphene" (AG), porous carbon material with the specific surface area of ∼2700 m2/g produced by activation of reduced graphene oxide (GO). Set of "Super-Oxidized Activated Graphene" (SOAG) materials with high abundance of carboxylic groups on the surface were produced using "soft" oxidation. High degree of oxidation comparable to standard GO (C/O=2.3) was achieved while keeping 3D porous structure with specific surface area of ∼700–800 m2/. The decrease in surface area is related to the oxidation-driven collapse of mesopores while micropores showed higher stability. The increase in the oxidation degree of SOAG is found to result in progressively higher sorption of U(VI), mostly related to the increase in abundance of carboxylic groups. The SOAG demonstrated extraordinarily high sorption of U(VI) with the maximal capacity up to 5400 μmol/g, that is 8.4 – fold increase compared to non-oxidized precursor AG, ∼50 –fold increase compared to standard graphene oxide and twice higher than extremely defect-rich graphene oxide. The trends revealed here show a way to further increase sorption if similar oxidation degree is achieved with smaller sacrifice of surface area. [Display omitted] • High surface area carbon materials can be oxidized to the same degree of standard graphene oxide. • The sorption of U(VI) increases proportionally to oxidation degree of material. • Super-oxidized "activated graphene" shows huge increase of U(VI) sorption up to 5400 μmol/g. • Sorption of U(VI) can be further increased by 2–3 times using general trend provided in our study. [ABSTRACT FROM AUTHOR]

Keywords: actinides; nanoparticles; thorium; X-ray absorption spectroscopy; X-ray scattering EN actinides nanoparticles thorium X-ray absorption spectroscopy X-ray scattering 1 1 1 01/06/21 20210104 NES 210104 B Oh, now I see b ! The precipitates formed during Th SP IV sp hydrolysis are ThO SB 2 sb nanoparticles, which in their initial stages of formation are a mixture of ultra-small nanoparticles and Th hexamer clusters. Actinides, nanoparticles, thorium, X-ray absorption spectroscopy, X-ray scattering. [Extracted from the article]

Invited for the cover of this issue is Lucia Amidani and co‐workers from the The European Synchrotron, Helmholtz Zentrum Dresden‐Rossendorf, Lomonosov Moscow State University, Kurchatov Institute, and the Université Grenoble Alpes. The image depicts the atomic structure of the sample being viewed through "atomic googles", which represent the X‐ray techniques used in this work. Read the full text of the article at 10.1002/chem.202003360. [ABSTRACT FROM AUTHOR]