Electrodialysis of a sodium sulphate solution with experimental bentonite-modified bipolar membranes

The aim of this work is to study the characteristics of the electrodialysis of a sodium sulphate solution with experimental bipolar membranes based on the MA-41 anion exchange membrane and a liquid sulphonated cation-exchanger modified with bentonite clays. The conversion of sodium sulphate was conducted by electrodialysis with bipolar membranes obtained by applying a liquid sulphonated cation-exchanger containing particles of bentonite clay to the MA-41 anion-exchange membrane.To increase the performance of membranes in terms of hydrogen and hydroxyl ions, we carried out organomodifications of bentonite with alkyldimethylbenzylammonium chloride and stearic acid at various concentrations. The bipolar membrane with the addition of bentonite modified with alkyldimethylbenzylammonium chloride (2 wt%) showed a higher performance in terms of H+-ions. The bipolar membrane with bentonite modified with stearic acid (3 wt%) added to its cation-exchangelayer is the most effective in terms of obtaining a flux of OH--ions. It was shown that a combination ofalkyldimethylbenzylammonium chloride (2 wt%) and stearic acid (3 wt%) used to modify bentonite can increase the performance of the bipolar membrane during the conversion of sodium sulphate, both in terms of the acid and alkali.

Fifteen shades of clay: distinct microbial community profiles obtained from bentonite samples by cultivation and direct nucleic acid extraction

Characterizing the microbiology of swelling bentonite clays can help predict the long-term behaviour of deep geological repositories (DGRs), which are proposed as a solution for the management of used nuclear fuel worldwide. Such swelling clays represent an important component of several proposed engineered barrier system designs and, although cultivation-based assessments of bentonite clay are routinely conducted, direct nucleic acid detection from these materials has been difficult due to technical challenges. In this study, we generated direct comparisons of microbial abundance and diversity captured by cultivation and direct nucleic acid analyses using 15 reference bentonite clay samples. Regardless of clay starting material, the corresponding profiles from cultivation-based approaches were consistently associated with phylogenetically similar sulfate-reducing bacteria, denitrifiers, aerobic heterotrophs, and fermenters, demonstrating that any DGR-associated growth may be consistent, regardless of the specific bentonite clay starting material selected for its construction. Furthermore, dominant nucleic acid sequences in the as-received clay microbial profiles did not correspond with the bacteria that were enriched or isolated in culture. Few core taxa were shared among cultivation and direct nucleic acid analysis profiles, yet those in common were primarily affiliated with Streptomyces, Micrococcaceae, Bacillus, and Desulfosporosinus genera. These putative desiccation-resistant bacteria associated with diverse bentonite clay samples can serve as targets for experiments that evaluate microbial viability and growth within DGR-relevant conditions. Our data will be important for global nuclear waste management organizations, demonstrating that identifying appropriate design conditions with suitable clay swelling properties will prevent growth of the same subset of clay-associated bacteria, regardless of clay origin or processing conditions.

INFLUENCE OF BENTONITE CLAYS ON THE MINERAL COMPOSITION OF RED TABLE WINES

Использование суспензий бентонитовых глин при обработке виноматериалов в процессе их осветления и стабилизации оказывает влияние на минеральный состав вин. Виноматериалы могут обогащаться катионами металлов, оказывающими разнонаправленное влияние на качество и розливостойкость вина. Исследованы изменения элементного состава виноматериалов в результате их обработки 32 образцами бентонитовых глин различных торговых марок. Объектами исследования были образцы виноматериалов из винограда сортов Каберне-Совиньон, Мерло и Молдова, собранного на территории Краснодарского края в 2019 г. Методами ИСП-АЭС и ИСП-МС определен элементный состав виноматериалов до обработки суспензиями бентонитовых глин и после нее. Установлено, что обработка бентонитовыми глинами привела к изменению концентраций практически всех определяемых элементов в образцах виноматериалов. Во всех образцах виноматериалов после обработки снизились концентрации B, Cu, Zn и увеличились концентрации Ag, Al, Cd, Ni, Na, Sb, Sn, Pb, Ti, Fe. As и Hg не были обнаружены ни в исходных, ни в обработанных образцах виноматериалов. Концентрации As, Cd, Hg, Pb, которые регламентируются в Российской Федерации, во всех обработанных образцах виноматериалов были существенно ниже установленного максимального уровня. Концентрации других элементов – Ag, B, Cu, Na, Zn, Ni, нормируемых в документах ЕС и МОВВ, в исследованных обработанных образцах виноматериалов оказались также значительно ниже нормативов. Таким образом, все исследованные бентонитовые глины могут быть рекомендованы к использованию при производстве вин. The use of suspensions of bentonite clays in the processing of wines in order to clarify and stabilize them has a significant effect on the mineral composition of wines. In this case, wines can be enriched with metals cations, which have a different effect on the quality and persistence of wine. Changes in the elemental composition of wine materials as a result of their treatment with 32 samples of bentonite clays of various brands were studied. The objects of the study were samples of wine materials from grapes of the varieties Cabernet Sauvignon, Merlot and Moldova, collected on the territory of the Krasnodar region in 2019. The methods of ICP-NPP and ICP-MS were used to determine the elemental composition of wine materials before and after treatment with bentonite clay suspensions. It was found that the treatment with bentonite clays led to a change in the concentrations of almost all detectable elements in the samples of wine materials. In all samples of wine materials after treatment, the concentrations of B, Cu, Zn decreased and the concentrations of Ag, Al, Cd, Ni, Na, Sb, Sn, Pb, Ti, Fe. As and Hg were not detected in either the initial or treated samples of wine materials. The concentrations of As, Cd, Hg, Pb, which are regulated in the Russian Federation, in all processed samples of wine materials were significantly lower than the established maximum level. The concentrations of other elements – Ag, B, Cu, Na, Zn, Ni, normalized in the EU and the International Organization of Vine and Wine documents, in the studied processed samples of wine materials were also significantly lower than the standards. Thus, all the studied bentonite clays can be recommended for use in the production of wines.

Fifteen shades of clay: distinct microbial community profiles obtained from bentonite samples by cultivation and direct nucleic acid extraction

Characterizing the microbiology of swelling bentonite clays can help predict the long-term behaviour of deep geological repositories (DGRs), which are proposed as a solution for the management of used nuclear fuel worldwide. Such swelling clays represent an important component of several proposed engineered barrier system designs and, although cultivation-based assessments of bentonite clay are routinely conducted, direct nucleic acid detection from these materials has been difficult due to technical challenges. In this study, we generated direct comparisons of microbial abundance and diversity captured by cultivation and direct nucleic acid analyses using 15 reference bentonite clay samples. Regardless of clay starting material, the corresponding profiles from cultivation-based approaches were consistently associated with phylogenetically similar sulfate-reducing bacteria, denitrifiers, aerobic heterotrophs, and fermenters, demonstrating that any DGR-associated growth may be consistent, regardless of the specific bentonite clay starting material selected for its construction. Furthermore, dominant nucleic acid sequences in the as-received clay microbial profiles did not correspond with the bacteria that were enriched or isolated in culture. Few core taxa were shared among cultivation and direct nucleic acid analysis profiles, yet those in common were primarily affiliated with Streptomyces, Micrococcaceae, Bacillus, and Desulfosporosinus genera. These putative desiccation-resistant bacteria associated with diverse bentonite clay samples can serve as targets for experiments that evaluate microbial viability and growth within DGR-relevant conditions. Our data will be important for global nuclear waste management organizations, demonstrating that identifying appropriate design conditions with suitable clay swelling properties will prevent growth of the same subset of clay-associated bacteria, regardless of clay origin or processing conditions.

Investigation of the insulating properties of the Cherkasy deposit clays for the creation of underlying screens of radioactive waste at the ‘Vector’ site

The lack of scientifically substantiated requirements, comprehensively developed and approved in a prescribed manner, for the usage of clays as a barrier material poses risks for the safe disposal of radioactive waste in facilities at the ‘Vector’ site for the period of their operation and closure. The bentonite clay from Ukraine’s largest Cherkasy deposit of bentonite and palygorskite clays is considered the most durable as the main component of the insulating (underlying) screens of radioactive waste disposal facilities. The main properties and compositional features of the Cherkasy natural bentonite clay (Dashukovskaya site, layer II) and its variety such as alkaline earth bentonite (activated soda bentonite), which provide isolation of radioactive waste in disposal, are considered. It is shown that the Cherkasy field has good waterproofing and barrier properties, including a high sorption capacity with respect to 90Sr and 137Cs, which is one of the main characteristics that ensure the safe disposal of radioactive waste. The alkaline earth bentonite absorbs 90Sr and 137Cs more efficiently than natural bentonite does. However, 90Sr is sorbed in larger quantities than 137Cs on both types of bentonite. With increasing time of interaction with an aqueous solution, both types demonstrate a redistribution of the mobile (exchangeable) and immobile (non-replaceable) forms of radionuclides. The contribution of the stationary form that does not participate in migration processes also increases. A comprehensive analysis of the bentonite clays of the Cherkasy deposit was carried out, taking into account the significance of recoverable reserves and the potential for improving the technical and economic parameters of clays. Thus, the Cherkasy bentonite clays can be recommended as an additional anti-migration engineering barrier for ground/near-surface facilities for the disposal of radioactive waste. When choosing the type of bentonite clay for use as a barrier in a radioactive waste disposal facility, one could take into account the data published in the article, but the question of applying the bentonite clays of the Cherkasy deposit to ensure the safe disposal of radioactive waste remains to be further studied.

Sorption of 90Sr and 137Cs on clays used to build safety barriers in radioactive waste storage facilities

The purpose of the work was to investigate the sorptive capacity of natural clay samples with respect to 90Sr and 137Cs to assess the possibility of using these as components of protective barriers at radioactive waste isolation facilities. Bentonite clays of the Zyryanskoye and Desyaty Khutor deposits and high-melting clay of the Kampanovskoye deposit were selected for the investigation. The capacity of clays for sorption through ionic exchange is characterized by the value of the cation exchange capacity (CEC). In the process of sorption experiments, all of the test clays displayed a high rate of extracting strontium and cesium radionuclides from aqueous solutions. It was shown that the sorption of 90Sr is affected by the content of montmorillonite in the samples: bentonite clays absorb up to 98–99% of the initial radionuclide content in the solution, while about 80% of strontium is sorbed by high-melting clay. Cesium is practically fully sorbed by the tested samples and the degree of sorption amounts to over 99%, the highest value of the distribution coefficient having been recorded for the Kampanovskoye sample (Kd = 5.0×103 cm3/g). The method of sorbed radionuclides fixation on the clay samples were identified by selective desorption using the modified Tessier methodology. It was shown that strontium ions are more mobile than ions of cesium up to 97% of which is retained by clays.

Local Cuban bentonite clay: composition, structure and textural characterization

The Cuban bentonite clays have a specific surface area of 79.9098 m2.g-1, a pore volume of about 0.077612 cm3.g-1 and both isotherms exhibited a hysteresis loop of IV type. X-ray diffractogram of raw bentonite shows that the main mineralogical component is montmorillonite (> 90%). The mineral object study presents the first endothermic peak, characteristic of montmorillonite, in 48.11 ºC and others less accentuated (80.81, 94.01, 119.81 ºC) characteristic of calcium montmorillonite, that corresponds to the loss of water, and can be extended up to 250 ºC. The FTIR spectra showed the existence of Si-OH, Al-Al-OH, Al-Fe-OH, Al-Mg-OH and Si-O-Si functional groups in all clay samples, confirmed the presence of hydrated aluminosilicate in the clay, bands between 1120 and 461 cm-1 correspond to phyllosilicate structures and OH stretching vibrations were observed. The pH at the point of zero charge (pHPZC) obtained has a value of 8.1, which allows montmorillonite to be classified as basic. The structural formula for one-layer unit of montmorillonite was determined as (Na3.99Al0.01)(Al1.11Fe3+0.49Mg0.18Ti0.07)(Ca0.24Na0.15K0.01)O10(OH)2, indicate the location of the different cations in metal oxide octahedrons or tetrahedrons, respectively. From the results obtained by different methods and the analysis of the calculated structural formula, it can be concluded that the bentonite under study is a calcium montmorillonite, with a low specific surface area and little porosity.