The potential of a Na-bentonite to be used as liner material for the adsorption of Cu(II) and Ni(II) ions from mono, bi, and polycationic solutions was investigated by batch mode. pH and ionic strength effect on Cu(II) and Ni(II) sorption were evaluated. For isotherm sorption studies, metal solutions parameters (pH and ionic strength) were selected simulating common landfill leachate conditions in the acidogenic stage. The removal of these ions by the Na-bentonite is dominantly controlled by sorption (specifically, cation exchange) under acidic conditions, but it can be strongly enhanced by metal oxide/hydroxide precipitation under alkaline conditions. Adsorption equilibrium models for the single, binary, and multicomponent systems indicate that the Langmuir-type model can fit the experimental data very well for all of them. The co-presence of metals led to a decrease in the sorption of both metals due to competition for adsorption sites. Optimum conditions are obtained when the ionic strength of solution is low (<0.05 M), pH is higher than 6, and the metal concentration is lower than 20 mg/L. Adsorption rates indicate that in addition to its quality as a physical barrier this bentonite can also act as a chemical barrier, limiting the migration of heavy metals from security landfills

Collected samples of bentonite and associated facies from the Justina deposit of Cretaceous age (Anacleto Formation) have been studied. Facies analysis, mineralogical, and geochemical studies have been carried out using several techniques, including: XRD, FTIR, DTA-TGA, microscopy (OM, SEM-EDX), and chemical analysis. The deposit occurs in a shallow, saline lacustrine environment developed over a fluvial floodplain, with a thickness between 0.21 and 0.8 m intercalated between fine-grained siliciclastic facies. Three mineral assemblages were found. In assemblage 1, the bentonite has low content of detrital minerals and the smectite is sodic. In assemblage 2, the bentonite shows the occurrence of minor analcime and mica, slightly higher detrital mineral content and the smectite is sodic to sodic-calcic. The associated detrital facies (assemblage 3) is dominated by illite and a mixed layer of illite and calcic smectite (R0), subordinately kaolinite + chlorite, and locally low-ordered smectite. As inherited minerals are found: quartz, potassium feldspar, plagioclase, illite-mica, heavy minerals (monazite, zircon, apatite, titanomagnetite) and volcanic rock fragments (andesite, glass). Authigenic minerals are: sodium smectite, analcime, barite, celestine, gypsum, and hematite. A model for the formation of authigenic minerals is proposed, highlighting the formation of sodic smectite from the alteration of volcanic glass of trachyandesitic composition.

This study evaluated non-fibrous Mg-clays as potential adsorbents of emerging contaminants (ECs) from water. The materials were characterized, and their textural and structural properties were related to their ability to remove two model EC molecules: ciprofloxacin (CPX) and lidocaine (LID). The results showed that Ad-6 and Ad-7 are mixed-layer kerolite/stevensite, while Ad-5 and Ad-8 are mainly composed of smectite minerals like stevensite and saponite, respectively. Ad-8 exhibited the highest CPX-adsorption capacity (0.91 mmol·g⁻¹ clay), likely due to its saponite content. Mixed-layer materials also performed well, with Ad-6 and Ad-7 achieving an adsorption capacity of 0.8 and 0.55 mmol·g⁻¹ clay, respectively. Adsorption studies suggested that CPX is adsorbed through ion exchange in materials with high smectite content (Ad-8 and Ad-5), while interstratified materials showed enhanced retention due to kerolite presence, which improves their porous structures. Similar findings were observed for LID, indicating a cationic-exchange mechanism for LID adsorption in all the materials and suggesting that the molecular size of the EC could regulate the removal capacity of these materials. This work showed that the studied Mg-clays could be effectively used for the removal of pharmaceutical pollutants, expanding their commercial possibilities.

Adsorption studies of ciprofloxacine (CPX) and lidocaine (LID) emerging contaminants were performed on two fibrous Mg clays from the Madrid basin and Senegal. The samples were characterized by X-ray diffraction, ICP major element analysis, infrared spectroscopy, thermal analysis, optical petrography, scanning and transmission electron microscopy, cation exchange capacity (CEC), and N₂-BET analysis. Two mineral assemblages were established. Assemblage 1 mainly consists of sepiolite and minor trioctahedral smectite, while assemblage 2 is mostly composed of palygorskite, which is associated with dioctahedral smectite. The sorption was fast and reached equilibrium in 2 h. Fibrous Mg clays showed a higher adsorption capacity for CPX than for LID in the conditions studied. CPX adsorption on sepiolite and palygorskite can be the result of the combination of various mechanisms: ion exchange with permanently charged sites, electrostatic attractions with external surfaces, and an inner sphere complex with broken edges. LID adsorption mainly occurs by ion exchange and electrostatic interaction with the external surfaces of the clays. Dioctahedral smectite, as an associated phase, contributed to a higher removal percentage in palygorskite samples. By contrast, the trioctahedral smectite did not play a significant role in the adsorption of the samples with sepiolite. The mesoporous structure, high surface area, and moderate cation exchange of fibrous clays play a key role in the sorption process of CPX and LID.

Los yacimientos de bentonita del lago Pellegrini, provincia de Río Negro, constituyen el principal distrito productor de bentonita de la Argentina. Estos depósitos se alojan en la sección media de la Formación Allen (Cretácico Superior), integrada por facies pelíticas y niveles de ceniza volcánica alterada. La explotación se realiza en minas a cielo abierto que se encuentran afectadas por fallas normales, diques clásticos plegados y fallas inversas subordinadas como estructuras principales que condicionan la continuidad de los niveles bentoníticos subhorizontales. Las fallas normales conforman dos grupos principales con rumbos NE–SO y NO–SE, caracterizados por rechazos verticales de hasta 6 m y espaciamientos de hasta 60 m. Los diques clásticos y las fallas inversas presentan orientaciones concordantes con las fallas normales. Los diques clásticos tienen geometrías subverticales a inclinadas y plegamiento ptigmático. Para este conjunto de estructuras se propone un modelo deformacional dominado por procesos de compactación que iniciaría con la formación de diques durante estadios tempranos del soterramiento y que continuaría con las fallas normales durante la compactación progresiva de la secuencia arcillosa, acompañadas por escasas fallas inversas. Los parámetros estructurales como el rechazo vertical (RV) y el espaciamiento de fallas se proponen como herramientas para optimizar la explotación y estimar costos operativos de producción.