Clay Adsorbents Research Articles

Extraction of rare earth elements from ion adsorption clay using bio-based ionic liquid via COSMO-RS: computational and experimental validation

The study introduces eco-friendly leaching agents as alternatives to traditional rare earth element (REE) extraction solvents, addressing environmental concerns associated with ammonium sulfate. Bio-based ionic liquids (ILs), known for their non-toxic and biodegradable properties, were screened using the COSMO-RS software. Initially, 105 ILs involving 7 cations and 15 anions were computationally screened to find the best ILs for REE extraction. The chosen criteria were based on hydrogen bond formation, affinity screening, hydrophobicity, viscosity, and eco-toxicity test. Based on the COSMO-RS screening, choline oleate, choline decanoate, and choline hexanoate exhibit high solubility for REEs, with a chemical potential of 17.60, 17.01, and 18.37 kcal/mol at REE oxidation state +2. Choline glycinate, choline oleate, choline decanoate, choline hexanoate, choline lysinate, and choline leucinate were selected for their strong affinity to extract REE dissociate ions. Experimental results show slightly higher REE extraction from ammonium sulfate (3.17 ppm) compared to choline glycinate (3.15 ppm). For long-term applications, choline glycinate offers a promising eco-friendly and cost-effective alternative to traditional leaching agents, promoting economic feasibility and environmental friendliness.

Artificial Neural Network Modeling of the Removal of Methylene Blue Dye Using Magnetic Clays: An Environmentally Friendly Approach

In this study, the effectiveness of Fe3O4-based clay as a cost-effective material for removing methylene blue (MB) dye from aqueous solutions was evaluated. The structural properties of the clay and Fe3O4-based clay were analyzed using SEM, XRF, BET, XRD, FTIR, and TGA techniques. In this research, the effects of various aspects, such as adsorbent amount, contact time, solution pH, adsorption temperature, and initial dye concentration, on the adsorption of Fe3O4-based clay are investigated. The experiments aimed at understanding the adsorption mechanism of Fe3O4-based clay have shown that the adsorption kinetics are accurately described by the pseudo-second order kinetic model, while the equilibrium data are well represented by the Langmuir isotherm model. The maximum adsorption capacity (qm) was calculated as 52.63 mg/g at 25 °C, 53.48 mg/g at 30 °C, and 54.64 mg/g at 35 °C. All variables affecting the MB adsorption process were systematically optimized in a controlled experimental framework. The effectiveness of the artificial neural network (ANN) model was refined by modifying variables such as the quantity of neurons in the latent layer, the number of inputs, and the learning rate. The model’s accuracy was assessed using the mean absolute percentage error (MAPE) for the removal and adsorption percentage output parameters. The coefficient of determination (R2) values for the dyestuff training, validation, and test sets were found to be 99.40%, 92.25%, and 96.30%, respectively. The ANN model demonstrated a mean squared error (MSE) of 0.614565 for the training data. For the validation dataset, the model recorded MSE values of 0.99406 for the training data, 0.92255 for the validation set, and 0.96302 for the test data. In conclusion, the examined Fe3O4-based clays offer potential as effective and cost-efficient adsorbents for purifying water containing MB dye in various industrial settings.

Enhanced sequestration of ciprofloxacin from aqueous solution using composite montmorillonite-kaolin clay adsorbent

Clay minerals are low-cost and environmentally benign natural adsorbents with huge potential for removing micropollutants from aqueous solutions owing to their intrinsic surface properties. In this study, montmorillonite and kaolin clay minerals were activated using NaNO3 and HNO3 to develop activated montmorillonite- kaolin clay composites (AMKCC) material for the sequestration of ciprofloxacin (CIP) from aqueous solution. The developed AMKCC was characterized using X-ray fluorescence (XRF), Brunauer-emmett-teller (BET), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The BET analysis reveals an improved BET surface area, pore volume and pore diameter of 139.13 m2/g, 0.17 cm3/g and 2.18 nm, respectively. At optimum conditions, pH (3.56), initial concentration (16.74 mg/L), time (77.9 mins) and adsorbent dosage (0.4 g), the percentage of ciprofloxacin removed from aqueous solution was 97 %. The adsorption of ciprofloxacin (CIP) using AMKCC was spontaneous, feasible, endothermic, and followed Freundlich isotherm with pseudo-second-order kinetics. The maximum monolayer adsorption capacity of AMKCC is 344.82 mg/g. The desorption studies revealed HCl as the best eluent for AMKCC regeneration. Therefore, AMKCC has considerable potential for the adsorption of pharmaceuticals from aqueous solution.

Adsorption of Se(IV) on kaolinite and montmorillonite in the presence of fulvic acid

This study investigates the influence of fulvic acid, a representative of aquatic natural organic matter (NOM), on the pH-dependent adsorption of Se(IV) on kaolinite and montmorillonite. Given their negative charges in aqueous solutions, Se(IV) and fulvic acid compete for the limited and identical adsorptive sites of clay minerals, particularly in neutral to alkaline environments. This competition was most pronounced under acidic conditions, where both Se(IV) and fulvic acid adsorption are favored. At pH 3, the presence of 20–80 mg·L−1 fulvic acid reduced the Se(IV) adsorption by up to half on both clay adsorbents. However, in near-neutral to alkaline pH regions (pH 6 to 10), the competitive interaction between Se(IV) and fulvic acid was less pronounced, since the adsorption of both fulvic acid and Se(IV) decreased. In particular for kaolinite, a rise in Se(IV) adsorption was evident at lower fulvic acid concentrations (20 mg·L−1). This phenomenon arises from the absence of aqueous complexes between Se(IV) and fulvic acid under acidic conditions, contrasting with their strong interaction under alkaline conditions as observed in the ATR-FTIR spectra. This study sheds light on the influence of NOM on the mobility of Se(IV) in natural waters, an aspect yet to be thoroughly explored.

Adsorption of dibenzothiophene sulfone using Fe3+ and Fe6+-impregnated clay adsorbents

In this study, the adsorption of dibenzothiophene sulfone (DBTO) was investigated using clay minerals as adsorbents. Raw bentonite (BR) and raw activated clay (ACR) were impregnated with Fe3+ and Fe6+, creating bentonite-Fe3+ (BF3), bentonite-Fe6+ (BF6), activated clay-Fe3+ (ACF3), and activated clay-Fe6+ (ACF6). The surface functional groups, surface morphology, and surface area of the raw and modified adsorbents were studied through Fourier transform infrared spectroscopy, a scanning electron microscope, and Brunauer, Emmett, and Teller analysis, respectively. Batch experiments on simulated oil were done to test the effect of adsorption time (0.5–24 h), adsorption dosage (0.3–1.5 g), and adsorption temperature (30–50 °C). The results of the experiments showed the suitability of the pseudo-second order kinetic model on the clay adsorbent and sulfone system. This suggests that chemisorption is the rate-limiting step of the reaction. Equilibrium isotherms indicated the adherence of DBTO onto BR and BF3 to the Freundlich model, implying the heterogeneous adsorption of the sulfones onto the adsorbents. The systems of DBTO with BF6, ACR, ACF3, and ACF6 showed a better fit with the Dubinin-Radushkevich model. This denotes that adsorption happens through the filling of sulfones of the micropores on the adsorbent. Lastly, thermodynamic studies revealed the endothermic and non-spontaneous nature of the clay adsorbents and sulfone systems. The experiments showed that the impregnation of Fe3+ and Fe6+ lowered the desulfurization ability of the adsorbents. This could be due to the iron ions being hard acids and the sulfones being soft bases, thus showing lower compatibility than the raw counterparts of the adsorbents. Comparison with related studies showed that the prepared adsorbents, namely BF3 (5.1 mg g−1) and BF6 (6.4 mg g−1), had a higher adsorption capacity than Ni2+-loaded activated carbon (4.9 mg g−1) and activated clay (4.1 mg g−1). The study shows that BR (7.2 mg g−1) is the best-performing adsorbent, which can be set as the direction for future research. This study is a step toward the commercialization of oxidative desulfurization methods.

Tetrasodium iminodisuccinate modified montmorillonite for Pb and Cd adsorption from water: Characterization and mechanism

Heavy metal pollution is a huge hazard to the water environment and modified clay adsorbents have been widely used to remove heavy metals from water. Degradable anionic chelating agents have a greater potential for the immobilization of heavy metals, so tetrasodium iminodisuccinate (IDS) was introduced to modify montmorillonite (Mt) for Pb(II) and Cd(II) adsorption from water in this study. IDS was bound with Mt by sonication, heating, and acidity to form IDS-Mt, and characterized by XRD, FT-IR, SEM, and zeta potential analyzer. The batch adsorption experiments revealed that IDS-Mt5 had excellent adsorption capacity of Pb(II) and Cd(II) up to 214.73 mg/L and 104.07 mg/L, respectively. The adsorption process of IDS-Mt on Pb(II) and Cd(II) was consistent with the Sips model and PSO model, indicating that the adsorption was heterogeneous and chemical. The adsorption capacities of IDS-Mt in the second cycle remained above 76 % for Pb(II) and 69 % for Cd(II) of the initial ones, respectively. IDS was immobilized on the interlayer and edge surfaces of Mt through interactions or forming hydrogen bonds facilitated by ultrasonic under acidic heating conditions. Pb(II) and Cd(II) were immobilized by IDS-Mt through cation exchange, negative charge attraction at the edge surface, and IDS chelation. IDS-Mt was an excellent adsorbent with strong dispersibility and swelling properties for Pb(II) and Cd(II) removal from contaminated water. This study provides a new solution for the anionic modification of Mt and a new material for the treatment of heavy metal wastewater.

Recent Advances on the Adsorption of Pollutants from Aqueous Media Using Clay-Based Adsorbents

The sequestration of pollutants from wastewater remains an active research topic recently owing to persistent disposal of industrial wastewater to waterbodies without adequate management strategies available especially in the developing countries. Different technologies have been employed in which adsorption has found a wide range of application. Today, various low cost adsorbents have been developed and evaluated for the adsorption processes. Clay mineral is one of the low cost natural adsorbents requiring minimum modification to enhance its adsorptive capacities. To maintain a clean and safe environment the water bodies must be free of contaminants of emerging concern. The availability of potable water is a global effort, as two of the UN's seventeen Sustainable Development Goals (SDG) are centered on water which is not surprising. Goal 6 focuses on clean water and sanitation whereas Goal 14 focuses on life below the water. With this in view, the availability of potable water highlights the significance of this study, which analyzes the potential of clay minerals as a good precursor for water treatment. Therefore, this review focuses on the clay minerals, its availability in Nigeria, classification and modification of the clay adsorbent.

Sulfuric Acid Leaching of Carbonatite ore with High Calcite Content in Lugiin Gol under Ambient Condition

AbstractCarbonatite bearing rare earth elements are rich sources of rare earth elements and play a critical role in the global supply chain. While carbonatite deposits are less accessible compared to ion adsorption clays, their mineral composition makes them essential for rare earth element extraction. Extraction of rare earth elements from carbonatite ore involves acid leaching, a process that we aim to explore in this study using the carbonatite ore from Lugiin gol. Characterization of the raw material and solid residue post‐leaching was conducted using X‐ray diffractometry, inductively coupled plasma optical emission spectroscopy, and a zeta potential analyzer. These analytical techniques were utilized for kinetic modeling, assessing the influencing factors of leaching, and determining metal recovery in the pregnant solution. The results of the study highlight the significant role of surface charge formation on target particles during milling in the acidic leaching process. This finding shed light on the importance of understanding the surface properties of the particles in the extraction of rare earth elements from carbonatite ores. The surface of particles in the supernatant of rare earth elements’ ore was negatively charged, with the median zeta potential of the 0.025 mm fraction being at its minimum of −60.6 mV.

Natural and modified clays as low-cost and ecofriendly materials to remove salinomycin from environmental compartments

Antibiotics in the environment represent a substantial pollution threat. Among these emerging pollutants, ionophore anticoccidials are of special concern due to their potential ecological impact, persistence in the environment, and role in promoting antimicrobial resistance. To investigate the adsorption/desorption of the ionophore antibiotic salinomycin (SAL) on/from raw and modified clay adsorbents, batch-type experiments were performed using 0.5 g of clay adsorbent mixed with 10 mL of increasing doses of SAL solutions for each sample, at room temperature, with a contact time of 24 h. All measurements were conducted in triplicate employing HPLC-UV equipment. Three different natural (raw) and modified clay samples were investigated, which were denominated as follows: AM (with 51% calcite), HJ1 (with 32% kaolinite), and HJ2 (with 32% microcline). The experiments were carried out using three pH ranges: between 3.33 and 4.49 for acid-activated clays, 8.39–9.08 for natural clays, and 9.99–10.18 for base-activated clays. The results indicated that, when low concentrations of the antibiotic were added (from 5 to 20 μmol L−1), more than 98% of SAL was strongly adsorbed by almost all clays, irrespective of the physicochemical and mineralogical composition of the clays or their pH values. When higher SAL concentrations were added (40 and 100 μmol L−1), the adsorption of the antibiotic showed pH-dependent ligand adsorption mechanisms: (i) highly decreased as the pH raised (for the raw and base-activated AM and HJ1 clays), while (ii) slightly decreased as the pH decreased (on the acid-activated clays). Among the adsorption equations tested (Freundlich, Langmuir, and Linear), the Freundlich model was identified as the most suitable for fitting the data corresponding to SAL adsorption onto the studied clays. SAL desorption from clays was consistently below 10% for all the clay samples, especially for the acid-activated clays, due to cation bridging adsorption mechanisms, when the lowest concentration of the antibiotic was added. Additionally, it should be stressed that the desorption values can increase with rising SAL concentrations, but they always remain below 20%. Overall, the clays here investigated (both raw and modified) provide a cost-effective and efficient alternative for the removal of the veterinary anticoccidial antibiotic SAL, with potential positive and practical implications in environmental remediation and antibiotic pollution management, particularly by serving as amendments for contaminated soils to enhance their adsorption capacities against SAL. Additionally, using these clays in water treatment processes could improve the efficiency of mitigating antibiotic contamination in aquatic systems.

-Effects and mechanisms of acrylamide-based polymer containing N-vinylpyrrolidone on drilling fluids at high temperature

The exploration of ultra-deep oil and gas presents higher temperature resistance requirements for water-based drilling fluids. However, the lack of temperature resistance mechanism of drilling fluid polymers limits the development of key materials and drilling fluids. In this paper, by comparing the preparation of acrylamide polymers for drilling fluids, the influence of cyclic monomer N-vinylpyrrolidone (NVP) on the properties of polymers for drilling fluids was investigated, and the mechanism of NVP was deeply discussed. The results show that the NVP-containing copolymer PAAN has superior viscosity enhancement and filtration control in high-temperature drilling fluids. This is mainly due to the fact that PAAN has a more stable and complex polymer chain structure than PAA, the polymer that does not contain NVP, and its thermal stability is improved by 18.6 % up to 268°C. At the same time, NVP provides more adsorption spots, and the high-temperature clay adsorption capacity of PAAN in drilling fluids is increased by more than 66.9 % compared with that of PAA, which improves clay hydration and promotes clay dispersion, and ultimately reduces filtration of drilling fluids and stabilizes drilling fluids at high temperatures by more than 23.7 %. The introduction of NVP and the in-depth analysis of its action mechanism supplemented the anti-temperature mechanism of drilling fluid polymers, aiming to support the research and development of ultra-deep drilling fluid technology.

A hybrid adsorption / ultrafiltration membrane process for removal of Cs-137 from radioactive wastewater using natural clay adsorbent

The removal of radioactive cesium element (Cs-137) from wastewater is relatively challenging due to its high diffusion coefficient, short hydration radius, and the similarity between its chemical behavior to other alkali metals having high background concentrations, leading to a competition that reduces the removal efficiency of cesium (Cs-137). This study introduces an innovative treatment process using a submerged membrane adsorption hybrid system (SMAHS) using natural Iraqi clay minerals as adsorbents. The operational conditions were studied using the (SMAHS) continuous flow operation in stirred filtration mode experiments. The maximum operational conditions were achieved for the initial radioactivity concentration of Cs-137 at 7201.8 Bq/L, clay dose 1 g/L, the stirring speed at 700 rpm, pH =6, the transmembrane pressure (TMP) under 2 bar, and temperature at 25 °C. The SMAHS rejection percentage of Cs-137 was 93.6 % and the permeate flux was 105.6 L/m2.h at the best operational conditions. This study demonstrates that utilizing raw bentonite which is both environmentally friendly and locally available as an adsorbent in the SMAHS has proven its effectiveness for removing Cs-137 from wastewater. The hybrid method effectively immobilizes radioactive waste by converting it from liquid to solid state, leading to an extended and safer storage time.

Understanding adsorption selectivity in zirconium-pillared clays for biogas upgradation: the role of metal/clay ratio.

Biogas, as a sustainable energy source, encounters challenges in practical applications due to impurities, notably carbon dioxide (CO2), and nitrogen (N2). This study investigates the effect of metal/clay ratio on the adsorption selectivity of porous zirconium-pillared clay adsorbents for biogas upgradation. Comprehensive analyses including nitrogen adsorption/desorption, X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) were conducted to evaluate the physicochemical properties. Adsorption properties for Zr-pillared clays for biogas components such as CO2, CH4, and N2, at 25 °C under different pressures were investigated. The ideal adsorbed solution theory (IAST) was employed to assess selectivity for three binary gas mixtures (CO2/CH4, CO2/N2, and CH4/N2). Results revealed the substantial impact of Zr/Clay ratio on both adsorption capacity and selectivity of the prepared materials. For instance, the maximum adsorption capacity of gases varies as ZrPILC-4 > ZrPILC-2 > ZrPILC-8 > ZrPILC-1, whereas the adsorption selectivity for CO2/CH4 separation (at 1000kPa) varies as ZrPILC-1 > ZrPILC-2 > ZrPILC-8 > ZrPILC-4. Interestingly, the ZrPILC-8 with maximum surface area (147 m2∙g-1) did not show maximum adsorption capacity for all the three gases, which was attributed to its lower pore volume, and basal spacing, as compared to ZrPILC-4. Amongst all the pillared samples, the ZrPILC-1 exhibited highest selectivity for all binary mixtures (at 1000kPa), signifies increased nonspecific interactions due to its lower surface area. Its separation performance, particularly for CO2/CH4 mixture exceeded that of the parent clay by 1.5 times. A significant increase in the working capacity of the prepared samples underscores the efficacy of these pillared materials in separating biogas components. This study provides valuable insights into effects of Zr/clay ratio for developing robust pillared adsorbents, contributing to the advancement of sustainable biomethane production.

Study on mechanical properties and microstructure of metakaolin-slag-calcium carbide residue synergistic solidifying waste engineering mud

Utilizing MSC composite materials (M-Metakaolin(MK)), S-Slag, C-Calcium carbide residue (CCR)), the waste engineering mud produced through the drilling and grouting pile construction method was solidified.Through the analysis of unconfined compressive strength (UCS), X-ray diffraction (XRD), and scanning electron microscope (SEM) on solidified engineering mud test blocks, the influence of complex factors such as slag content, CCR content, and curing time on the solidification efficiency of engineering mud was investigated, and the microscopic mechanism was analyzed.Concurrently, supplementary tests were carried out to ascertain the pH and water content of the cured mud.The results indicated that the 7-day unconfined compressive strength of cured mud specimens could achieve 3 MPa when incorporating 12 % MK, 8 % slag, and 6 % CCR.The optimal pH for the curing mud is determined to be 11.25, correlating with a water content of 84 %.The destructive strains corresponding to the peak stresses of the cured mud at different curing times ranged from 1.6 % to 2.5 % and generally decreased with increasing peak stresses.The XRD and SEM analyses have demonstrated that the enhancement in the strength of the cured mud can be attributed to the processes of hydration and polymerization, resulting in the generation of gel products such as calcium silicate hydrate (CSH) and aluminosilicate-Na hydrate (NASH). These products are responsible for the adsorption of clay and bentonite particles, thereby efficiently occupying the structural voids.The research findings have the potential to provide theoretical support for the development of environmentally friendly and low-carbon MSC gelling materials, as well as their application in soil reinforcement, notably in the context of engineered mud solidification.

Classification of rare earths mineral resources using the Jequié/BA complex rock weathering chemical index

The most common economic mineral deposits of Rare Earths are associated to magmatic calc-alkaline to alkaline rocks and their products. This work presents data from drilling carried out in rocks of the Jequié/BA Complex, mineralized in rare earths, which were subjected to an intense weathering process, similar to what occurred in the Ion Adsorption Clays deposits in southern China. The interpretation of the survey data allowed the classification of rare earths mineral resources with similar, sometimes higher, levels than those of Chinese deposits, contained in the lateritic regolithic profile studied. The chemical index of rock alteration (CIA) was adopted as a classification tool, horizontally separating the mineralized weather profile into six zones. The data indicate that there was supergenic enrichment REO in the lower portions of the profile and sometimes in the upper zones. The average levels ranged between 0.09% and 0.22% REO, with maximum values of 1.6%. A model section representing the deposit of rare earths minerals of supergenic origin in rocks of the Jequié/BA Complex was developed.

In-vivo evaluation of the adverse effects of ochratoxin A on broiler chicken health and adsorption efficacy of indigenous and commercial clay of Balochistan, Pakistan

Mycotoxins in animal feed pose health risks and economic losses, but using various adsorbent types could potentially protect animals from mycotoxicosis. The study aimed to assess the effect of OTA on the health of broiler chickens and to envisage the ameliorative potential of clay adsorbents. The objectives of this in vivo study were to investigate the effects of OTA on productivity, biochemical parameters, fecal residues, and the preventive effects of indigenous and commercial clay of Balochistan as adsorbents to alleviate the adverse effects of exposure. Male broiler chickens (n = 160) were treated with 400 μg/kg OTA and 0.5 g/kg clay adsorbent for 42 days, with feed and water available in an ad libitum manner. The amount of OTA in diet and fecal residues was assessed through HPLC. The administration of OTA in the diet, resulted in a significant (p < 0.05) decrease in the average daily gain (ADG) and average daily feed intake (ADFI) while increasing the feed conversion ratio (FCR) as compared to the control group. Furthermore, no significant (p > 0.05) differences were found between the weight gain of broiler chickens fed without OTA (positive control) and that of chickens fed adsorbent. The group given a diet containing OTA without adsorbents as compared to the control and adsorbent-supplemented group has shown a significant (p < 0.05) increase in the relative weight of the liver, kidney, gizzard, and proventriculus while decreasing the relative weight of the spleen and bursa of Fabricius. Alterations in the levels of serum total protein (TP), cholesterol (CHL), serum urea (SU), enzymatic activity (aspartate aminotransferase (AST) and alanine transaminase (ALT)), and creatinine were observed in the OTA-intoxicated and adsorbent-supplemented groups as compared to the control group. Adsorbent supplementation resulted in a significantly (p < 0.05) higher OTA content in the faeces. It can be concluded from the results of this study, that OTA intoxication negatively affects the health of broiler chickens, and the clay of Balochistan has shown effective adsorption potential against OTA.

Origin of Grain-Coating Chlorite and Implications for Reservoir Quality in the Triassic Deep-Buried Volcaniclastic Sandstones, Central Junggar Basin, Northwestern China.

The occurrence and genesis of grain-coating chlorite were investigated in order to evaluate the impact of grain-coating chlorite on preserving porosity in the deep-buried Triassic Karamay volcaniclastic sandstones based on thin sections, scanning electron microscopy, and an electron probe. Grain-coating chlorite was formed during the eogenesis, originating from the precursor of smectite through the solid-state transformation (SST) mechanism. The hydration and dissolution of unstable, intermediately basic volcanic rock fragments provided essential Fe2+ and Mg2+ ions for the formation of grain-coating chlorite. Due to relatively high stability and low susceptibility to dissolution, acidic volcanic rock fragments could not promote chlorite formation but resulted in authigenic quartz and clays as pore-filling cements. This process would destroy reservoir properties. Under high hydraulic conditions, medium- to coarse-grained sandstone experienced saltation transport, creating significant velocity differentials and pressure differentials on grain surfaces. Subsequently, clay grains adhere to the surfaces, forming grain-coating chlorite during diagenesis with good continuity. In contrast, pebbly sandstone undergoes rolling transport, resulting in smaller velocity differentials on grain surfaces. This makes relatively ineffective clay adsorption and leads to discontinuous grain-coating chlorite in subsequent stages. Under weak hydraulic conditions, grains and clay particles in fine-grained sandstone undergo suspended transport, lacking mutual movement and velocity differentials. Clay particles cannot effectively cover particles but instead fill the pores between them. Therefore, continuous grain-coating chlorite is more commonly developed in the medium- to coarse-grained sandstones and is crucial for inhibiting quartz cementation with a coverage rate exceeding 80%. Inadequate coatings fail to inhibit quartz cementation effectively, while excessive coatings may block pore throats. Optimal protection of primary porosity could occur only when grain-coating chlorite is moderately developed.

Fractionation of biomass-burning smoke-derived dissolved organic matters on the surface of clay minerals: Variations of molecular properties and components

Biomass burning (e.g., wildfire) frequently occurs globally, inevitably produces abundant biomass-burning smoke-derived dissolved organic matters (BBS-DOMs) which eventually deposits on the surface environment. The adsorption and fractionation of BBS-DOMs on clays inevitably alter their biogeochemical process and environmental behaviors in the surface environment. It is therefore important to clarify the adsorption and fractionation of BBS-DOM on clay surfaces. This study found that the fractionation of BBS-DOMs on clays (montmorillonite and kaolinite) were controlled by their functional groups, aromaticity, molecular size and organic components. The spectral indexes (SUVA254 and S275–295) of BBS-DOMs in solution after clays adsorption suggested that with the increasing DOC concentration, the primary interaction between BBS-DOMs and clays changed from hydrogen bond to hydrophobic/pore filling effects, and the adsorption ratio of the large molecules increased, which were very different from natural fulvic acid. Furthermore, various BBS-DOMs and fulvic acid had different component fractionation behaviors during clay adsorption, because they had different abundances of protein-like matters (hydrogen bond donors), pyridine-N/pyrimidine-N (positive charge doners of electrostatic interaction), and fulvic-like matters (hydrophobic interaction and pore filling effect). Additionally, the increasing pH weakened the adsorption of bulk BBS-DOMs and enhanced the adsorption ratio of aromatic matters and smaller BBS-DOM molecules. Meanwhile, at a higher pH, the adsorption ratio of protein-like matters increased, while the adsorption ratio of humic- and fulvic-like matters decreased. The result was ascribed to the enhanced hydrogen bond between protein-like matters and clays as well as the enhanced electrostatic repulsion between humic−/fulvic-like matters and clays. This study is helpful for deeply understanding the multimedia-crossing environmental behavior of BBS-DOMs in the surface environment.

Exploring the Efficiency of Algerian Kaolinite Clay in the Adsorption of Cr(III) from Aqueous Solutions: Experimental and Computational Insights.

The current study comprehensively investigates the adsorption behavior of chromium (Cr(III)) in wastewater using Algerian kaolinite clay. The structural and textural properties of the kaolinite clay are extensively characterized through a range of analytical methods, including XRD, FTIR, SEM-EDS, XPS, laser granulometry, N2 adsorption isotherm, and TGA-DTA. The point of zero charge and zeta potential are also assessed. Chromium adsorption reached equilibrium within five minutes, achieving a maximum removal rate of 99% at pH 5. Adsorption equilibrium is modeled using the Langmuir, Freundlich, Temkin, Elovich, and Dubinin-Radushkevitch equations, with the Langmuir isotherm accurately describing the adsorption process and yielding a maximum adsorption capacity of 8.422 mg/g for Cr(III). Thermodynamic parameters suggest the spontaneous and endothermic nature of Cr(III) sorption, with an activation energy of 26.665 kJ/mol, indicating the importance of diffusion in the sorption process. Furthermore, advanced DFT computations, including COSMO-RS, molecular orbitals, IGM, RDG, and QTAIM analyses, are conducted to elucidate the nature of adsorption, revealing strong binding interactions between Cr(III) ions and the kaolinite surface. The integration of theoretical and experimental data not only enhances the understanding of Cr(III) removal using kaolinite but also demonstrates the effectiveness of this clay adsorbent for wastewater treatment. Furthermore, this study highlights the synergistic application of empirical research and computational modeling in elucidating complex adsorption processes.

Sequestration of divalent heavy metal ions from aqueous environment by adsorption using biomass-bentonite composites as potential adsorbent: Equilibrium and kinetic studies

Hybrid clay adsorbents have been investigated in recent studies as cheap and effective adsorbents for eliminating micropollutants, such as heavy metal ions from aqueous solution. Here, we modified bentonite (BEN) with palm kernel shell and groundnut shell by calcination to obtain palm kernel shell-modified bentonite (BPKS) and groundnut shell-modified bentonite (BGS). We studied the batch equilibrium adsorption of Pb2+, Cd2+ and Ni2+ ions under the influence of dosage, solution pH, contact time and concentration. Under these conditions, we found that the modified adsorbents (BGS and BPKS) had a higher equilibrium adsorption (qe) for the metal ions than unmodified BEN. BEN exhibited Langmuir adsorption capacities (Qo) of 32.47, 14.04 and 14.16 mg/g for Pb2+, Cd2+ and Ni2+, respectively. BGS and BPKS had Qo values of 29.15, 14.27, 16.61 and 31.75, 17.67, 15.625 mg/g for Pb2+, Cd2+, Ni2+, respectively. Investigations revealed that the rate of adsorption on the three adsorbents is best described by a pseudo-second-order kinetic model, with R2 values ≥ 0.9; the intra-particle diffusion model establishes a surface interaction mechanism involving the exchange of electrons between the surfaces of the adsorbents and the adsorbate. Scanning electron microscopy results suggest porous and heterogeneous adsorbent surfaces, indicating a physio-sorption phenomenon. The modifications increased the surface area of BEN from 78.435 to 194.850 and 140.650 m2/g in BGS and BPKS, respectively, using BET surface area analysis. However, the average pore width of BEN reduces from 3.8 to 3.3 nm in both BGS and BPKS. Also, the modification enhanced the cation exchange capacity in BPKS only. The findings from this study offered invaluable insights into how biomass can enhance the physicochemical properties of BEN, as needed for practical environmental application and/or optimization, during the removal of Pb2+, Cd2+ and Ni2+ ions from aqueous media.

Optimized Bentonite Clay Adsorbents for Methylene Blue Removal

This study addresses the urgent need for effective water treatment methods by synthesizing and characterizing activated bentonite clay (ABC) adsorbents to remove methylene blue (MB) from aqueous solutions efficiently. Conventional adsorbents often exhibit limitations in efficiency and regeneration capabilities, necessitating novel approaches to water treatment. The primary objective is synthesizing and characterizing high-quality ABC adsorbents capable of effectively removing MB. The activation process was optimized, and adsorbent performance was evaluated regarding MB removal efficiency and regeneration potential. Various activation dos-ages were investigated, and comprehensive physicochemical characterization was performed using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), BET (Brunauer–Emmett–Teller) analysis, X-ray fluorescence (XRF), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). The synthesized adsorbents demonstrated exceptional MB removal efficiency (99.593%) and impressive adsorption capacity (22.131 mg/g) when activated with 16 M sodium hydroxide. The adsorption process exhibited spontaneity and exothermicity, as validated by Freundlich and second-order kinetic models. Furthermore, the adsorbents showcased successful regeneration and reusability over three cycles, highlighting their potential for long-term application in water treatment. This study significantly advances water treatment by offering a novel approach to MB removal using base-activated bentonite clay (BABC) adsorbents, contributing to the development of sustainable water treatment solutions.