Acid-treated Clay Research Articles

Comparison of the Effect of Kaolin and Bentonite Clay (Raw, Acid-Treated, and Metal-Impregnated) on the Pyrolysis of Waste Tire.

This study investigates the effectiveness of kaolin and bentonite catalysts in improving liquid hydrocarbon yields during the pyrolysis of waste tires. Raw clay, nitric acid-treated clay, and mono- or bimetal-impregnated clay were used as catalysts in the pyrolysis of waste tire. Acid-treated kaolin produced a higher yield of liquid hydrocarbons (43.24-47%) compared to acid-treated bentonite (35.34-41.85%). This improvement in the liquid yield can be attributed to the higher specific surface area and pore diameter of the acid-treated clay in comparison to raw kaolin (39.48%) and raw bentonite (31.62%). Moreover, the use of metal-impregnated catalysts, such as Fe/kaolin and Ni/Fe/kaolin, resulted in higher liquid yields (47%) compared to the 3 M HNO3-treated kaolin catalyst (43.24%). Gas chromatography-mass spectrometry (GC-MS) analysis confirmed the presence of limonene, a crucial ingredient for commercial perfume production, in the liquid products. The calorific values of oil obtained through kaolin and bentonite catalysis were measured at 13,922 and 10,174 kcal/kg, respectively, further highlighting the potential of these catalysts in waste tire valorization.

Linear and nonlinear investigations for the adsorption of paracetamol and metformin from water on acid-treated clay

Natural clays are considered a safe, low-cost, and sound sorbent for some pharmaceutical and body care products from water. Metformin (MF) and paracetamol (PA) are of the most consumable drugs worldwide. A portion of natural clay was treated with distilled water, and another part was treated with hydrochloric acid. The water-treated clay (WTC) and the acid-treated clay (ATC) were characterized by scanning electron microscopy-energy dispersive spectroscopy, X-ray diffraction, Fourier transforms infrared spectroscopy, and nitrogen adsorption isotherm. Batch experiments were employed to investigate the influence of contact time and solution parameters on the adsorption of PA and MF on WTC and ATC. 30 min attained the equilibrium for all sorbent-sorbate systems. Both sorbents fitted the pseudo-second-order kinetic model with a preference to the nonlinear fitting, and the mechanism of adsorption partially fitted the liquid-film diffusion model. The PA and MF adsorption on WTC and ATC fitted the Freundlich model in preference to nonlinear fitting. The adsorption of pollutants on both sorbents was spontaneous, exothermic, and physisorption in nature. Even at low concentrations, both WTC and ATC showed efficiency above 80% in removing PA and MF from tab water, groundwater, and Red seawater. These findings nominated natural clay as an alternative to the costly nanomaterials as sorbents for removing pharmaceutical contaminants from water.

Developing an Efficient Catalyst Based on Thermal and Acid-Treated Clay for the Removal of Trace Olefins From Aromatic Compounds

AbstractBentonite is used as a catalyst in the removal of olefins from aromatic compounds and the present study was designed to investigate how its performance might be improved by various treatments. Bentonite from Semnan mine, Iran, was used in the study following initial characterization. In order to investigate the effect of acid and thermal treatments on the removal of olefins from aromatic compounds, bentonite samples were modified using HNO3 at different concentrations (0.15, 0.3, 0.5, 0.7, 1, and 2 M) and were also at temperatures between 100 and 340°C for 3 h. To examine the catalytic activity of bentonite-based catalysts, the samples were evaluated after running batch and continuous experiments. The optimum catalyst was characterized using thermo-programmed desorption (TPD) of NH3 to examine the acidic sites. Scanning Electron Microscopy (SEM) images, nitrogen adsorption-desorption isotherms (BET analysis), and X-ray diffraction (XRD) patterns were used to study the structural changes of the bentonite produced by the acid and thermal activation. The removal of olefins by the catalysts in batch and continuous systems revealed that the sample modified with 0.3 M Nitric acid at 150°C had superior catalytic activity, with olefin conversion remaining at >50% for up to 20 h. Nitrogen adsorption-desorption isotherms showed that acid treatment can produce a mesoporous structure. On the other hand, the TPD analysis indicated that during weak acid treatment, some cations, such as Al3+ and Fe3+, were leached from octahedral sheets and the interlayers of the clay mineral resulting in weak acid sites being generated. Finally, a novel method was proposed and tested for measuring the Bromine Index (BI) using potentiometric titration.

Effect of Acid Treatment on the Chemical Properties of Clays from Selected Sites in Murang’a and Nyeri counties, Kenya

Assessing improvement on the quality of clay has been conducted by treatment with different concentrations of hydrochloric and oxalic acid. This project intended to assess the effect of acid treatment on the elemental composition of clays from selected sites. The clays were leached using hydrochloric and oxalic acid separately at a concentration of 0.0, 0.1, 0.25, 0.5, 1, and 2M. The elemental composition of raw and acid-treated clays was determined using AAS. Elemental composition of the acid-treated clays, in oxide form were in the ranges of 40.80-65.16 % SiO 2 , 7.16 -30.33 % Al 2 O 3 , 0.33-7.62 %TiO 2 , 0.24-2.65 % K 2 O, 0.01-1.82 % MgO. The findings of this study showed that the quality of clays could be improved by acid treatment hence the clays can be used as a source of raw materials for industrial applications. Keywords: Acid-treatment, Elemental, raw materials DOI: 10.7176/JNSR/11-22-05 Publication date: November 30 th 2020

Structural and composition enhancement of Indian Kachchh kaolin clay: characterisation and application as low-cost catalyst

ABSTRACT The effect of acid treatment on kaolin clay from the Kachchh region of Gujarat, India, was explored to prepare a low-cost (−$0.6/kg) catalyst. The clay was treated with 10 M H2SO4 which increased the Si/Al ratio from 1.3 to 2.4, surface area from 10.322 to 54.193 m2/g and pore volume from 0.041 to 0.152 cm3/g. The XRF analysis indicated that the metal oxides in treated clay decreased with increasing acid strength; consequently increasing the SiO2 content. SEM micrographs displayed gradual disaggregation and decrease in the size of clay structure with an increase in acid strength. TG-DTA study confirmed the removal of structural water. FTIR and X-ray diffraction analysis indicated metal removal creating a large degree of structural disorder resulting in reduced crystallinity and leading towards the amorphous phase. BET study confirmed the formation of additional mesopores. The acid-treated clay was applied as a catalyst for the esterification of succinic acid (SA) with ethanol. The conversion of SA increased from 27% to 56% revealing higher activity and selectivity in terms of higher yield (96%) of valuable diester. The catalyst was reused up to three cycles with a slight loss of catalytic activity.

Preparation of poly(acrylic acid) exfoliated clay composite by in-situ polymerisation for decolouration of methylene blue from wastewater

ABSTRACT Acid treated locally available Bijoypur white clay was exfoliated with dodecyl amine to facilitate in-situ polymerisation of acrylic acid (AA) using N, N′‐methylenebisacrylamide (MBA) crosslinker and ammonium persulphate as the initiator for the preparation of a novel adsorbent. In order to obtain poly(acrylic acid)-graft-modified clay composite (PAA-g-MC), the growing PAA chain was ‘grafted onto’ the modified clay surface. The structural properties of the composite adsorbent were studied by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray fluorescence (XRF), and scanning electron microscope (SEM). Thermal properties of the composites were measured by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The effect of different process parameters such as pH of dye solution, contact time, initial concentration of dye, and adsorbent amount on the removal efficiency of methylene blue (MB) from aqueous solution was evaluated by batch experiments. Characteristics data from XRD and XRF for raw clay and acid-treated clay showed that Bijoypur clay is rich in kaolinite, which contains a significant amount of quartz. However, treatment with HCl reduces 55% of quartz and increases the percentage of kaolinite that made it suitable for adsorbent used. Adsorption results showed that PAA-g-MC composite showed a maximum adsorption of 162.3 mg g−1 of 100 mg L−1 MB dye solution at pH 7.25 after 80 min of adsorption using 0.03 g L−1 of the adsorbent. Langmuir and Freundlich adsorption isotherms were studied and the equilibrium adsorption data were found to be well fitted with the Langmuir adsorption isotherm. The interaction between adsorbent and MB molecules was explained by chemisorption, as suggested by the pseudo-second-order kinetic model. Maximum monolayer adsorption of 168.4 mg g−1 was calculated from the Langmuir adsorption isotherm which is very close to the experimental value of 162.3 mg g−1.

Physico-chemical Characterization of Hydrochloric Acid-treated Kaolin Clay: An Industry Approach as a Potential Catalyst.

This study explains the FT-IR, XRD, XRF, SEM/EDX, TGA, and DSC/DTA characterization of commercially available kaolin clay. The objective of this paper is to explore the prominent utilization of kandites clay and useful chemical aspects for the modification of kaolin clay minerals. The untreated kaolin sample has been procured in this experimental work from AksharChem, Gujrat, India. The kaolin clay was treated with 4M hydrochloric acid. FT-IR, XRD, XRF, SEM/EDX, TGA, and DSC/DTA characterization methods have been used. Loss on ignition was found at 10.89%. The fingerprint region of the acid-treated sample has broad and more bending vibrations than untreated samples. The high weight percentage of Ti and CaCO3 were spotted in the scanning electron micrograph by both atomic % and weight %. The FT-IR revealed the functional group of Al-O, A1-OH, and Si-O. The morphology indicates that the presences of large particles are in the form of agglomerates. It was found that impurity like scandium vanished and manganese traced by the same atomic % 0.01 of zinc which had no presence after acid treatment. Thermogravimetric analysis indicates the sharp increments in heat flow in-between temperatures 0°C to 200°C and consequently increments in between 500°C to 550°C, a suitable range for the pyrolysis. Low amount of alumina and high amount of silica has been found out. TGA and DTA analysis satisfy the waste plastic valorization temperature ranges.

Acid-treated Clay Minerals as Catalysts for Dehydration of Methanol and Ethanol

AbstractThe purification of clay minerals prior to their use as catalysts can escalate processing costs so methods are needed whereby less purification is necessary. One such potential method is acid treatment of the unpurified clay minerals. The main objectives of the present study were to develop the optimal acid-treatment conditions and to determine how the acidic properties of the modified clay samples influenced their catalytic capability toward the dehydration of ethanol and methanol. Clay mineral samples – allophane, palygorskite, and sepiolite, without purification – were acid treated (0.8 M HNO3; 95°C; 2, 8, or 24 h) and after calcination (500°C; 6 h) tested as catalysts for the conversion of methanol to dimethyl ether and of ethanol to diethyl ether and ethene. The changes in chemical and structural compositions as well as surface acidity of the mineral samples were analyzed and correlated with their catalytic performance. Among the samples studied, allophane was the most catalytically active in the dehydration of methanol to dimethyl ether. Acid treatment of this mineral sample decreased methanol conversion slightly. An opposite effect was found for ethanol dehydration to diethyl ether, where acid treatment increased catalytic activity of allophane. The differences in catalytic performance of the mineral samples were discussed with respect to the nature and concentration of acid sites.

Intrinsic affinity of acid-activated bentonite towards hydrogen and carbon dioxide

The effect of acid activation on bentonite affinity toward carbon dioxide (CO2) and hydrogen (H2) was investigated at ambient conditions. Characterization through X-ray diffraction and fluorescence, thermal gravimetric analysis, nitrogen adsorption-desorption isotherms, Fourier Transform Infrared spectroscopy and differential scanning calorimetry allowed correlating newly induced textural and structural features with adsorptive properties. Optimum acid treatment improved the specific surface area and porosity. The resulting decrease in dehydration temperature indicates decay in hydrophilic character. The affinity improvement towards hydrogen was due to Brønsted acidity suppression and surface basicity attenuation, which are essential requirements for adsorption on aluminosilicates (AS) via weak Lewis Acid-Base interactions, but excessive acid attack was detrimental. Low Si/Al surfaces should be suitable for CO2 capture, while moderately acid-treated clays should be interesting candidates as hydrogen adsorbents. This allows envisaging promising prospects for low-cost AS-based materials intended for selective CO2-free capture and storage of hydrogen without energy and safety constraints.

Physical and chemical properties of gamma-irradiated styrene–butadiene rubber/vermiculite clay nanocomposites modified using maleic anhydride

In this work, nanoparticle vermiculite clay was prepared by acid treated with hydrochloric acid at room temperature for and dried at 300 °C for different time intervals. The untreated (VMT) and acid-treated (DVMT) vermiculite clay were characterized by X-ray diffraction (XRD), FT-IR, and transmission electron microscopy. The DVMT and maleic anhydride (MA) at different concentrations (parts per hundred of rubber) were mixed with styrene–butadiene rubber (SBR) to obtain SBR/DVMT/MA nanocomposites. The SBR/VMT composites and SBR nanocomposites were subjected to gamma irradiation at different doses from 25 to 150 kGy. As a comparison, the gamma-irradiated SBR composites with VMT and nanocomposites with DVMT/MA were characterized in terms of XRD, physico-chemical and thermal properties. The results indicated that the incorporation of DVMT nanoparticles and MA improved the physico-chemical and thermal properties of the SBR/clay nanocomposite. The improvement was achieved when the contents of both DVMT and MA were 10 phr and irradiation dose of 100 kGy.

Characterization of a Fine-Grained Interstratification of Turbostratic Talc and Saponite

Interstratifications of talc and trioctahedral smectites from different provenances are used as indicators for geological environments and for geotechnical and technical applications. However, comprehensive layer characterization of these interstratifications is rare. Sample EX M 1694, a clay with red-beige appearance from the Madrid basin was studied by X-ray diffraction analysis, X-ray fluorescence analysis, Fourier transformation infrared spectroscopy, simultaneous thermal analysis, gas adsorption measurements, cation exchange capacity, and environmental scanning electron microscopy. More than 95% of particles in EX M 1964 belong to the clay fraction <2 µm. It contains 75% interstratification of 30% turbostratic talc, and 70% saponite type III and 25% turbostratic talc. The turbostratic talc(0.3)/saponite interstratification is characterized by a low number of layers per stack (3), small lateral dimension of layers (60–80 nm) and, accordingly, a high specific surface area (283 m2/g) with nearly equal surface area of micro- and mesopores. Thus, the studied material can be used as mined for adsorption, in contrast to acid-treated clays that produce hazardous waste during production. Low particle size of the interstratification drastically reduced thermal stability and dehydroxylation was superimposed by recrystallization of high temperature phases already at 816 °C, which is low for trioctahedral 2:1 layer minerals.

Catalytic Hydrolysis of Pretreated Sugarcane Bagasse over Acid-Activated Vermiculite Catalysts

Aiming at obtaining glucose, we studied the chemical pretreatment (NaOH + H2SO4) and the hydrolysis of sugarcane bagasse using as catalyst the acid-treated vermiculite clay. Samples of the bagasse before and after the treatment were characterized as to the fiber content and XRD. It has been found that the chemical pretreatment showed satisfactory results providing a decrease of 40% in the lignin content and of 43% in the hemicellulose content, regarding to the bagasse in natura. Catalytic tests in aqueous solution were performed at 200°C, to evaluate the use of vermiculite treated as a catalyst for the hydrolysis of sugarcane bagasse. The reaction product was filtered and the supernatant was analyzed by high performance liquid chromatography. A yield of 6.18% in glucose was achieved.

Acid treated clays: preparation, characterization and catalytic activity for synthesis of quinoxaline derivatives

The preparation, characterization, and catalytic properties of acid treated clay (ATC) are reported. ATC has been characterized by XRD (basal spacing, 14.82 A), specific surface area (66 m2/g), pore volume and pore width using BET method, UV–Vis DRS, TGA, SEM, and surface acidity by TPD of NH3. The activity of was investigated by the reaction of benzil with o-phenylene diamine. Among the catalysts, ATC was found to be more active. The reaction of various substituted o-phenylenediamines with benzil was studied on ATC to obtain corresponding quinoxalines in good yields. The regeneration and reusability of ATC has also been investigated.

Changes in the characteristics of acid-treated clay after the inclusion of proteins

Changes in the characteristics of acid-treated clay after the inclusion of proteins

Modification of Sodium Bentonitic Clay Used in Zinc Ion Adsorption

In this study, it was evaluated the potential use of commercial sodium bentonitic clay, called Fluidgel, chemically and thermally treated, as an adsorbent in the removal of zinc ions from aqueous effluents. The chemical treatment was carried out with 10 g of clay dispersed in 100 mL of acetic acid 4 %. The heat treatment was obtained by calcination at 750 °C for 24 hours in muffle. The adsorption experiments were performed in thermostatic bath system and fixed bed, both based on preliminary study of metallic cationic speciation. The kinetics of zinc ions adsorption by acid-treated clay was rapid, requiring a minimum time of 60 min to reach equilibrium. The adsorbed amount and percentage of total zinc removal, at equilibrium time, was 0.06 mmol/g and 45 %, respectively, using the acid-treated clay. There was no removal of zinc by Fluidgel calcined clay in bath system, but in fixed bed it was obtained the total amount of zinc removal of 0.11 mmol/g and 41 % of percentage of removal.

Chromate adsorption on acid-treated and amines-modified clay

Acid-treated montmorillonite-rich clay and amines (methylamine, morpholine, and aniline)-modified clay adsorbents were investigated and their abilities to remove chromate from aqueous solution were studied. For the later purpose, kinetic studies were carried out under different operating conditions (chromate concentration, adsorbent content, and temperature), and adsorption isotherm measurements were performed. It was found that the kinetic of adsorption was fast and the data followed the pseudo-second rate equation. The rate of adsorption was controlled by the intra-particle diffusion and mass transfer through the liquid film, and the relative importance of these limiting steps depended on the operating conditions. Chromate adsorption was an endothermic process and took place spontaneously by physisorption. The free energy at 25 ≤ T ≤ 40 °C varied from −1.5 to −46 kJ/mol. Adsorption isotherms of Na+-saturated clay (AN), acid-treated clay (AA), and methylamine–clay and morpholine–clay (A–Me, A–Mo) were type V, whereas those of aniline–clay (A–An) were type III. The estimated maximum uptakes were 105, 29, 15, 11, and 10 mmol/kg for A–An, AN, A–Mo, AA, and A–Me, respectively. The mechanism of chromate adsorption was discussed based on the shape of the isotherms. Considering for instance the most efficient absorbent (A-An), the isotherm followed the Freundlich equation and hydrogen chromate (the main stable form at working pH) adsorbed to solid particles once aniline species were entirely desorbed.

Impact of mesoporous structure of acid-treated clay on nickel dispersion and carbon deposition for CO methanation

Nickel catalysts supported on different acid-treated clays were prepared by the impregnation method in order to investigate the effect of the pore structures of supports on the dispersion and the chemical states of nickel species, and thus on the carbon depositions resulted from the dissociation of the CO molecules adsorbed on different active nickel sites. The catalysts and supports were characterized by the X-ray diffraction (XRD), the transmittance electron microscopy (TEM), the H2 temperature-programmed reduction (H2-TPR), the nitrogen adsorption–desorption, and the thermogravimetry and differential thermal analysis (TG-DTA). The CO methanation performance of the catalyst was investigated at a temperature range from 300 °C to 500 °C. The results indicated that the dispersion and the states of the nickel species on the support were influenced strongly by the pore structures of the acid-treated clays, and only the mesopores composed by partly damaged clay layers were conducive to forming the active nickel species, and thus reducing the deposition of the inactive carbon and improving the stability of the catalyst. The carbon species deposited on different active sites was slightly different in the oxidative properties when it was oxidized in air. A fraction of aluminum in the clays was leached out by acid, which decreased the possibility of forming the spinel phase of nickel aluminate in the catalyst. The highly dispersed nickel species showed little relevance to the high activity of the catalyst, but it exhibited a strong relation to the nickel sites from the bulk nickel species.

Thermoanalytical study of acid-treated clay containing amino acid immobilized on its surface

The aim of this study is to investigate the incorporation of amino acid molecules in an acid-activated montmorillonite by means of solid characterization after the incorporation of these biomolecules. The acid activation procedure was carried out for the purpose of increasing the acid sites in the clay as well as the impurity elimination in the mineral. Cysteine, aspartic, and glutamic acids were adsorbed on montmorillonite K10 which was previously treated with a hydrochloric acid solution. The clay was put in contact with amino acid solutions at two different concentrations. Each amino acid was adsorbed at identical conditions, with the pH fixed to ensure the charge of molecules and surface clay. The solid was characterized by means of X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, and nitrogen adsorption at 77 K. After the amino acid adsorption, the powders showed changes in their characteristics as well as in their thermal behavior, which depended on both the concentration and the nature of the adsorbed amino acid. The thermal decomposition and elimination of cysteine occurred at a higher temperature than the aspartic and glutamic acid; the complete removal of glutamic acid molecules was not observed at 850 °C. The differences observed in the solid characteristic after the adsorption of each amino acid were discussed. Both the thermoanalytical study and characterization of materials after the interaction with amino acid molecules can be useful to understand the adsorption mechanism of biomolecules on solid surfaces.

The effects of microstructural changes on montmorillonite–microbial interactions

Clay minerals are important natural adsorbents of soil organic matter (SOM) and therefore are natural modulators of soil-atmospheric carbon fluxes. Although such effects have been reported, little is known about the spatial distribution of organic matter (OM) on the surfaces of soil minerals and even less is known about the effects of microstructural changes on clay–organo interactions. Here we employ acid hydrolysis to induce varying degrees of microstructural changes to montmorillonite clay mineral as a function of time and combine IR spectroscopy, X-ray diffraction, and SEM-EDX as primary techniques to independently provide molecular-level information on the effects these changes on microbial interactions with the mineral. We observed that progressive dissolution of octahedral cations and the simultaneous enrichment of amorphous silica are prominent structural changes induced by hydrolysis, and that the adsorption of microbial-derived components (in particular lipids) on the surfaces of acid-treated clay decreases with increasing acid dissolution time. Although the precise mechanism(s) of interactions remains unclear, we speculate that this adsorption behavior is most likely due to spatial co-variation of microbial-derived OM with octahedral cations in the mineral, acid erosion of biochemically active binding sites, and/or a progressive increase in the hydrophilicity of the mineral surfaces by acid attack over time.

Optimization by Response Surface Methodology of the adsorption of Coomassie Blue dye on natural and acid-treated clays

The effect of acid treatment on natural agalmatolite (AN) and natural kaolinite (KN) was investigated, together with the influence of those modifications on the removal of Coomassie Blue (CB) dye. The process was optimized using the Response Surface Methodology (RSM) developed by the application of the quadratic model associated with the Central Composite Design. Adsorption was promoted by initial CB concentration of 25 mg L−1, pH 2 and adsorbent mass of 0.1 g. The adsorption kinetics study carried out in optimized conditions established that the equilibrium times were 1 h for AN and AA (treated agalmatolite), 4 h for KN and 2 h for KA (treated kaolinite). The kinetics data for AN, KN and KA were best fitted to the pseudo second order model, whilst for AA, the result pointed to the pseudo first order model. In the isotherm of adsorption the maximum quantities were obtained with reference to 11.29 mg g−1, 9.84 mg g−1, 22.89 mg g−1 and 30.08 mg g−1 for the samples AN, AA, KN and KA respectively. The data fitting showed that the Sips model was the most satisfactory for all the adsorbents. The calculated thermodynamic parameters showed that the process was spontaneous in all the adsorbents, endothermic for the KN and KA samples, exothermic for AN and AA, involved the disorganization of the adsorption system for the KN and KA and its organization for the AN and AA samples. The results showed that the KN and KA samples were more appropriate for use as adsorbents.