Adsorption Capacity Of Bentonite Research Articles

In vitro evaluation of the capacity of zeolite and bentonite to adsorb aflatoxin B1 in simulated gastrointestinal fluids

Anin vitro study using single concentration and isotherm adsorption was carried out to evaluate the capacity of Vietnamese produced zeolite and bentonite to adsorb aflatoxin B1 (AFB1) in simulated gastrointestinal fluids (SGFs), and a commercial sorbent hydrated sodium calcium aluminosilicate (HSCAS) was used as reference. In this study, AFB1 solution was mixed with sorbents (0.3, 0.4 and 0.5% w/v) in SGFs at pH 3 and pH 7 and shaken for 8 h, centrifuged and the supernatant measured by Vicam fluorometer. Adsorption of AFB1 onto zeolite and bentonite varied according to the pH of SGFs and was lower than HSCAS. Linearity between the increased amount of AFB1 adsorbed on sorbents and the decrease of sorbent concentration was observed for bentonite and HSCAS, except for zeolite in SGFs at pH 7. The observed maximum amounts of AFB1 adsorbed on bentonite and HSCAS were 1.54 and 1.56 mg/g, respectively. The adsorption capacities of bentonite and HSCAS for AFB1 were 12.7 and 13.1 mg/g, respectively, from fitting the data to the Freundlich isotherm equation. Improvement in processing and purification for bentonite is needed to enhance the surface area, which would probably result in better adsorptive capacity for this sorbent.

Smectite organofunctionalized with thiol groups for adsorption of heavy metal ions

The structural characteristics as well as the binding capacity of the functionalized bentonite from Campina Grande (PB), Brazil, were investigated. The sample was modified by acid treatment followed by immobilization of ligands containing thiol (–SH) groups by covalent grafting with surface and interlayer silanol groups. The modification was carried out under anhydrous conditions with (3-mercaptopropyl)trimethoxysilane. The functionalization process changed the hydrophilic nature of the clay mineral into hydrophobic. X-ray diffraction indicated that their original structure had been preserved. The DRIFT spectra demonstrated the presence of organic chains and thiol groups. The BET results indicated decreased porosity and specific surface area after grafting. Organic loading, calculated from TG data was 1.76 mmol g − 1 of bentonite. The thiol-functionalized bentonite presented binding capacity of Ag + ions about ten times higher compared to the ungrafted sample. These results support a mechanism of adsorption involving primarily ion complexation by the thiol groups (specific) instead of cation exchange (unspecific). The accessibility to the reactive centers was 60–75%. Thus, the adsorption capacity of bentonite can be enhanced by surface modification using organo-functional silane coupling agents. This new hybrid organic–inorganic material may be a good alternative for separation and pre-concentration of heavy metal ions.

Adsorption of malachite green onto bentonite: Equilibrium and kinetic studies and process design

The adsorption of malachite green onto bentonite in a batch adsorber has been studied. The effects of contact time, initial pH and initial dye concentration on the malachite green adsorption by the bentonite have been studied. Malachite green removal was seen to increase with increasing contact time until equilibrium and initial dye concentration, and the adsorption capacity of bentonite was independent of initial pH in the range 3–11. Four kinetic models, the pseudo first- and second-order equations, the Elovich equation and the intraparticle diffusion equation, were selected to follow the adsorption process. Kinetic parameters; rate constants, equilibrium adsorption capacities and correlation coefficients, for each kinetic equation were calculated and discussed. It was shown that the adsorption of malachite green onto bentonite could be described by the pseudo second-order equation. The experimental isotherm data were analyzed using the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich equations. Adsorption of malachite green onto bentonite followed the Langmuir isotherm. The thermodynamic parameters, such as Δ H ∘, Δ S ∘ and Δ G ∘, were also determined and evaluated. A single stage batch adsorber was designed for different adsorbent mass/treated effluent volume ratios using the Langmuir isotherm.

Study of adsorption of acid dye from aqueous solutions using bentonite

The removal of the dye cyanine acid blue (CAB) with bentonite clay was studied. The effect of various experimental parameters was investigated using a batch adsorption technique. Saturated sodium chloride treatment results in an increase in adsorption capacity of bentonite. A pH value of 2 is favorable for the adsorption of CAB. The maximum removal of CAB is obtained at a dosage of 2 g of bentonite. The use of Fe+3 ion (2.0 × 10−3 M) as a catalyst increased the percentage of dye removal. It was found that the Freundlich isotherm appears to fit the isotherm data better than the Langmuir isotherm. A fast adsorption rate was observed and could be well-described by a pseudo-second-order kinetics model.

The adsorption of caesium—137 on bentonites from the Carpathian basin

The adsorption of cesium was studied on the surface of bentonite rocks from the Carpathian basin. The adsorbed quantity at carrier-free concentration was measured using 137Cs, the adsorption capacity of bentonites for cesium ions was determined by X-ray fluorescence analysis. The relation of the cesium adsorption and mineral composition as well as the structural modifications of crystal structure was studied by X-ray diffraction spectrometry and thermoanalysis. The results show that the adsorbed quantity of cesium primarily depends on the montmorillonite content of bentonites.

The Role of Bentonite in Soil Sealing Applications

The use of bentonite as a natural soil sealant has experienced a phe­nomenal increase over the past 15 years. Swelling bentonites, which occur mainly in Wyoming, are exported all over the world for various uses, in­cluding the sealing of ponds, lagoons, and landfills and as a component of the slurry in slurry trenching. The natural swelling and adsorption capacity of bentonites are of tremendous value in the sealing off and containment of industrial waste sites. Landfills and lagoons are often constructed in areas where the natural soils have a permeability that is not consistent with safety standards. Admixing 5 to 15 percent bentonite into those soils will quickly reduce the natural permeability to the desired levels. All landfills require a cap once they are filled, to prevent the formation of a “bathtub” full of water and commensurate generation of excessive leachate. A cap consists of a 4 to 6 in. layer of soil-bentonite and two to three ft of natural soil, to allow for vegetation. Over the years, many hazardous waste sites have contaminated the ground water to such a degree that it is not fit for drinking. These sites can be encapsulated by constructing a slurry cut-off wall. These trenches are filled with a bentonite or cement-bentonite slurry during excavation and then backfilled with natural soil or a soil-bentonite mixture. The most important aspects of using bentonites as waste site sealants are the proper installation of the sealing systems and a knowledge of the limitations of bentonites regarding resistance to contamination. Types of bentonite, installation practices, and testing methods are discussed in this paper.

The adsorption and release of tylosin by clays and soils

The uptake and release of tylosin by Wyoming bentonite, Ca++ montmorillonite, illite (Fithian Illinois) and kaolin (china clay) was studied. The adsorption capacities of bentonite and montmorillonite for tylosin were found to be 190 and 65 μg mg−1 respectively, while the adsorption capacities of illite and kaolinite were found to be 22 and 6.5 μg mg−1. 7.6 and 7.4% respectively of the tylosin adsorbed by bentonite and montmorillonite, and 30 and 25% respectively of the tylosin adsorbed by illite and kaolinite, was released in phosphate buffer.