Adsorption Capacity Of Bentonite Research Articles

საქართველოსა და უცხოეთის ქვეყნების ზოგიერთი საბადოს ბენტონიტების შედარებითი ტექნოლოგიური შეფასება

An assessment of the technological characteristics of bentonites from some deposits in Georgia and foreign countries was carried out. The superiority of Georgian bentonite clays in terms of basic physical and chemical indicators is shown; of the bentonites from foreign countries, the sample from Hungary turned out to be the best. The adsorption capacity of bentonites in relation to methylene blue (MB) has been studied. It has been established that heat treatment at a temperature of 500 0C leads to a decrease in the adsorption activity of bentonites towards MB.

Valorization of Cherry By-Products as Coagulant/Flocculants Combined with Bentonite Clay for Olive Mill Wastewater Treatment

In this study, two by-products resulting from the processing of cherry (stems and pits) were used as natural coagulants to promote the valorization of these wastes and treat olive mill wastewater (OMW). The efficacy of the plant-based coagulants (PBCs) in the coagulation–flocculation–decantation process (CFD) was evaluated through the removal of turbidity, total suspended solids (TSS), total polyphenols (TPh), and dissolved organic carbon (DOC). The CFD process was demonstrated to be effective in turbidity and TSS reduction in OMW. Using cherry stems (CSs), these reductions were 65.2% of turbidity and 58.0% of TSS, while cherry pits (CPs) achieved higher reductions, 78.6% of turbidity and 68.2% of TSS. To improve the effectiveness of OMW treatment, mainly regarding the removal of TPh and DOC, the CFD process was complemented with the adsorption process (using bentonite clay). The adsorption capacity of bentonite was higher in acidic conditions (pH 3.0) and, with a dosage of 3.0 g L−1, reached 17.3 mg of DOC and 13.8 mg of TPh per gram of bentonite. Several adsorption isothermal models were assessed, and the Langmuir (r2 = 0.985), SIPS (r2 = 0.992), and Jovanovic models (r2 = 0.994) provided the best fittings. According to the optimal operational conditions defined throughout the present work, the combination of CFD and adsorption removals were as follows: (1) 98.0 and 91.3% of turbidity, (2) 80.8 and 81.2% of TSS, (3) 98.1 and 97.6% of TPh and (4) 57.9 and 62.2% of DOC, for CSs and CPs, correspondingly. Overall, the results suggest that cherry by-products can be used as low-cost natural coagulants and, when combined with another natural, abundant, and cheap material, such as bentonite clay, can be a sustainable alternative for treating OMW.

Adsorption thermodynamics and kinetics of hydrochloric-acid-modified bentonite for Zn(II) in wastewater

In order to study the Zn(II) adsorption characteristics of hydrochloric-acid-modified bentonite in wastewater, physical characterization of hydrochloric-acid-modified bentonite was carried out, the effects of the initial concentration, reaction time, and temperature on the Zn(II) adsorption were investigated, and the adsorption kinetics and thermodynamic mechanism of the hydrochloric-acid- modified bentonite adsorption of Zn(II) were examined. The results showed that hydrochloric acid modification increased the interlayer spacing of the bentonite, and the structure of the binding between slices became looser. Hydrochloric acid modification altered the hydroxyl groups on the bentonite surface, and the hydrophilicity was enhanced. The Zn(II) adsorption capacities of bentonite and hydrochloric-acid-modified bentonite increased with the increase in the initial Zn(II) concentration, and the adsorption followed the Langmuir and Freundlich equations. The thermodynamic parameters suggested that the adsorption of Zn(II) was an endothermic, spontaneous, and entropy-increasing process. The adsorption basically reached equilibrium within 120 min, and the adsorption followed the quasi-second-order adsorption kinetic equation. The adsorption process was mainly chemical adsorption, and the intra-particle diffusion process was not the only step controlling the adsorption rate. This study provides a theoretical basis for the remediation of toxic metal wastewater and contaminated soil.

The efficacy of Acorus calamus L. crude extract formulated in bentonite nanoparticles against Crocidolomia pavonana (Lepidoptera:Pyralidae)

The prospect of A. calamus extract to be botanical insecticides to control the insect pests is very promising. The insect control properties of the A. calamus are predominantly to have β-asarone, saponin and flavonoid. However, there are some factors limiting their efficacy. Short release rate at the point contact, the inherent volatility and vulnerability to oxidation and ultra-violet light are causing phytochemical changes during the application. Thus developing nanotechnology to increase their efficacy studied in this research. To develop the plant extract in nanoformulation, experiment on adsorption and desoption capacity were carried out with Acorus extract treated bentonite substrate analysed by GC techniques. In addition, to investigate the effectiveness of the plant extract treated bentonite were evaluated on Crocidolomia pavonana. Third instar larvae were used in the evaluation of antifeedant effect by using no choice methods. The results showed that Bentonite nanoparticles was effective in controlling the release of a bioactive element. Purifed clay bentonite for getting Na-bentonite increased the specific surface area of material therefore increased the adsorption site on the clay layer of the material. Crude extract of A.calamus can dissolve well in combination of water and organic solvents. Desorption experiments proved that Na-bentonite released more slowly than raw clay bentonite. Purification of bentonite to Na-bentonite resulted the changing of phytochemical properties bentonite which lead to an increase in the adsorption capacity of bentonite. In term of antifeedant evaluation based on damage to cabbage leaves seedling, the least damage was observed on leaves with nanoparticle plant extract formulation. The antifeedant index of A. calamus in nanoparticles formulation showed 25% higher that untreated cabbage plant seedling. The glasshouse trial was conducted to evaluate their efficacy on cabbage seedling. However, the brown leaves or phytotoxic effect has been found by the time the extracts nano formulation has been sprayed.

Adsorption of Methylene Blue by Bentonite Supported Nano Zero Valent Iron (B-nZVI)

Dyes used in textiles, foods, cosmetics, and chemicals have become a major environmental pollution issue around the world. To address this issue, a number of technologies have been created to remove these pollutants from the environment. Due to their superior properties at nanoscale, numerous nanomaterials have been applied to remove dyes from polluted waters. This research presents the findings of the development of bentonite nano zero-valent iron (B-nZVI) for the treatment of synthetic cationic dyes. This study has three objectives: (i) to produce bentonite nano zero-valence iron (B-nZVI), (ii) to characterize its adsorbents (B-nZVI), (iii) to characterize its adsorption capacity. Four main tests were used for this purpose: (i) a physical test (Brunauer–Emmett–Teller (BET) surface area), (ii) a chemical test (cation exchange capacity (CEC) and X-ray fluorescence (XRF)), (iii) morphology (field emission scanning electron microscopy (FESEM) and (iv) mineralogy (Fourier transform infrared spectroscopy (FTIR). The five factors for the batch equilibrium test are adsorbent dose, concentration, kinetic, pH, and temperature. The batch test showed that the optimum dose for all adsorbents is 0.5 g. For the concentration factor, B-nZVI exhibits larger adsorption capacity (KL = 30,314.0536 L/g; R2 = 1) compared to bentonite (Kd = 0.0219 L/g; R2 = 0.8892). The kinetic factor showed that the adsorption capacity by pseudo-second-order model was the best for both adsorbents (qe = 1.2038 mg/g, R2 = 0.9993 for bentonite and qe = 6.9979 mg/g, R2 = 1 for B-nZVI). For B-nZVI, the interparticle diffusion model (Kf = 0.8645 m2 g−1 min L−1; R2 = 0.9) and intraparticle diffusion model (Kd = 2.3829 m2 g−1 min L−1; R2 = 0.9189) showed a good correlation with the adsorption data, while bentonite showed a lower correlation with the interparticle diffusion model (Kf = 0.0002 m2 g−1 min L−1; R2 = 0.6253) and intraparticle diffusion model (Kd = 0.2886 m2 g−1 min L−1; R2 = 0.6026), respectively. The pH factor showed that the adsorption capacity of bentonite (qe = 0.5674 mg/g) and B-nZVI (qe = 5.3284 mg/g) was highest in acidic conditions (pH 2). As for the temperature factor, there was no significant effect on bentonite and B-nZVI. Therefore, tests can be conducted at room temperature, saving energy. It was also concluded that B-nZVI is the best material for removing MB compared to bentonite and can be considered for the treatment materials of contaminated water.

Elimination of orthophosphate from synthetic leachate using adsorption on bentonite clay

The composition of leachates is very variable and rich in toxic compounds, which requires treatment before discharge into the natural environment in order to avoid their impact on the environment and/or human health and to comply with the requirements of regulatory discharge standards in the natural environment. Among the parameters indicating pollution by leachates, we have COD, BOD5, conductivity, pH, the presence of ammonium ions, nitrite, nitrate, chloride, orthophosphate, etc. This study presents the results of synthetic leachate orthophosphate adsorption tests on bentonite clays. For the determination of the orthophosphate concentration in the synthetic leachate, before and after adsorption, we applied the method of Ultra-Violet adsorption spectroscopy. The adsorption capacity of bentonite, the amount needed and the removal efficiency were determined. The orthophosphate adsorption yield on bentonite reaches up to 32.6 % for 5 g/L of bentonite stirred for 4 hours and exceeds 39,19 % after 24 hours of stirring.

Sorption Studies of Cesium on Kunipia-F Bentonite and Silicon Dioxide

Adsorption is one of the effective methods used for the removal of contaminants from radioactive wastewater. In this research, removal efficiency of Cs from the prepared low-concentration Cs solution (100 μg/L) was studied using two different adsorbents namely high purity Kunipia-F bentonite and Silicon dioxide (SiO2). After performing the adsorption tests, the Cs ions in liquid and solid phases were analyzed using the inductively coupled plasma mass spectrometry (ICP-MS) technique. The adsorption capacities of both materials were then compared. It was found that the Cs adsorption capacity of bentonite was higher than that of SiO2. The distribution coefficient of Cs in the bentonite was 1.0 L-sol/g-solid, which was 100 times greater than that of SiO2. The highest sorption of Cs on bentonite could be attributed to its smaller particle size (0.362 μm), compared to the SiO2 particle size (0.625 μm). Bentonite is natural clay and is generally used as a buffer material in geological disposal systems for high-level nuclear waste. The results of this research indicate that bentonite could be an effective absorbent for decontaminating low concentration Cs in radioactive wastewater.

Removal of tetracycline from aqueous solutions by adsorption on raw Ca-bentonite. Effect of operating conditions and adsorption mechanism

• Bentonite had the highest capacity for adsorbing tetracycline (TC) than other clays. • Bentonite presented a maximum adsorption capacity towards TC of 283.5 mg/g. • Adsorption capacity of bentonite was comparable to those of carbon-based materials. • TC adsorbed on the external surface and in the interlayer space of bentonite. • Adsorption of TC was due to cation exchange and electrostatic attraction. This study aims to investigate the adsorption of tetracycline (TC) from water onto several clays with different structural characteristics such as bentonite, sepiolite, vermiculite, halloysite, phlogopite and kaolinite. Among these, raw bentonite (Bent) presented the highest adsorption capacity due to its swelling characteristic, interlayer cations nature, and TC molecular size. The Bent and Bent equilibrated with TC were characterized by SEM, XRD, FT-IR, TGA, N 2 physisorption and Zeta potential techniques. The importance of the pH, ionic strength and temperature upon Bent adsorption capacity towards TC was studied thoroughly, and the reversibility of TC adsorption onto Bent was also analyzed. The results showed that the TC adsorption occurred on the external surface and in the interlayer space of Bent, and both physical and chemical mechanisms governed the adsorption. The basal space (0 0 1) at pH = 7 increased from 1.50 to 1.62 nm, while raised from 1.50 to 1.89 nm at pH = 3. The TC maximum uptake was 283.5 mg/g at pH = 3, relating to cationic exchange between interlaminar cations of Bent and the cationic TC species (TCH 3 + ), and electrostatic attraction among the negative surface of Bent and TCH 3 + . At pH = 7, there are weak electrostatic attractions between the Bent cationic sites and the positively charged dimethylamino group of the zwitterionic TC species (TCH 2 ± ) and the formation of outer-sphere coordination complexes between the TC negative species (TCH - ) and the internal hydration sphere of the interlayer Ca 2+ cation. Additionally, the TC adsorption on Bent was partially reversible and endothermic.

U(VI) adsorption by one-step hydrothermally synthesized cetyltrimethylammonium bromide modified hydroxyapatite-bentonite composites from phosphate‑carbonate coexisted solution

Cetyltrimethylammonium bromide modified hydroxyapatite-bentonite composites (CTAB-HAp-Bent) were first synthesized by one-step hydrothermal method to test its U(VI) adsorption behaviors from phosphate‑carbonate coexisted solution. When pH = 8.0, U(VI) = 50 mg/L, [CO3]T = 2 mmol/L, and [P] = 1.5 μmol/L, CTAB-HAp-Bent achieved the maximum qe values ~108.19 mg/g compared to HAp-Bent (~40.62 mg/g), CTAB-Bent (~81.70 mg/g) and HAp (93.90 mg/g). High alkalinity and ionic strength were unfavorable for U(VI) adsorption. Specifically, qe values increased with an increase of [P] up to 500 μmol/L and then changed little in the ranges from 500 μmol/L to 2000 μmol/L, whereas carbonate suppressed U(VI) adsorption in the whole studied [CO3]T. Pseudo-second-order model, Langmuir isotherm and the thermodynamics deduced a spontaneous endothermic monolayer surface chemical adsorption process. Besides, characterization results suggested that the adsorption mechanisms were involved in the Br− anion exchange and -OH group coordination. Our present work optimized the U(VI) adsorption capacity of bentonite in eutrophic carbonate water, benefiting the research and design of potential modified clay or clay minerals materials for uranium recovery from eutrophic natural uranium-containing water.

Brazilian bentonite and a new modified bentonite material, BAC302, reduce zearalenone-induced cell death

Bentonite clays exhibit high adsorptive capacity for contaminants and is frequently used as a feed additive to reduce the bioavailability and thus the toxicity of several mycotoxins. Zearalenone (ZEN) is a secondaryFusarium toxic metabolite that can contaminate a wide range of food- and feedstuff. Since organophilic treatments is known to increase the adsorption capacity of bentonites, the aim of study was to evaluate and compare the ability of natural bentonite and bentonite treated with BAC302 to protect against ZEN-induced cytotoxicity in the epithelial colorectal adenocarcinoma (Caco-2) and human leukemia monocytic (THP-1) cell lines. The two materials were not toxic to the cell lines at lower concentrations. Furthermore, the results indicate that the two materials protect the Caco-2 and THP-1 cells against ZEN-induced cytotoxicity, probably by extracellular adsorption of ZEN. The tested natural bentonite shows potential forin vivo testing to evaluate if it is suitable for intoxication in ZEN contaminated animal feeds.

Improved recovery of cadmium from aqueous medium by alginate composite beads filled by bentonite and phosphate washing sludge

Alginate (AL)-based composite beads filled with bentonite (BE) and phosphate washing sludge (PS) have been prepared and used as low-cost adsorbents for removal of cadmium (Cd) from aqueous solution. Such composite beads were prepared by solvent mixing technique followed by a crosslinking reaction. The obtained humid beads were dried using two approaches, namely air drying (AD) and freeze-drying (FD) and then separately used as adsorbents. All the materials investigated in this study were analyzed in terms of their structural, textural, morphological, thermal properties as well as their chemical composition and size distribution. The adsorption capacities of the as-prepared freeze-dried and air-dried composite beads toward Cd ions were evaluated in batch experiments. To optimize the adsorption conditions, the effect of adsorbent dosage, equilibrium time, Cd concentration, initial pH and temperature was evaluated and compared. It was found that the adsorption capacities of BE- and PS-filled composite beads are higher than those determined with BE and PS. The performed adsorption studies showed that the adsorption equilibrium was reached within 180 min. The pseudo-second order model can be effectively used to evaluate the adsorption kinetics and the adsorption isotherms can also be well described by the Langmuir isotherm model with a maximum adsorption capacity of 54.27 and 53.24 mg/g for PS- and BE-filled composites, respectively. Moreover, Cadmium recovery was enhanced with temperature increase and the thermodynamics studies revealed that the adsorption processes were spontaneous and endothermic in nature.

Comparative study of the effect of structural arrangement of clays in the thermal activation: Evaluation of their adsorption capacity to remove Cd(II)

In this work, comparison of the effect of thermal activation on the physicochemical properties of laminar clays bentonite and vermiculite and sepiolite as fibrous clay and their adsorption capacity of Cd(II) from aqueous solution, were studied. The physicochemical characterization demonstrated that the elimination of superficial, interlaminar and crystalline water resulted in materials with reduced specific surface area, increased negative superficial charges and cation exchange capacity depends of crystalline structure. With an increase in the activation temperatures of 100–300 °C, 300–600 °C, and 600–900 °C, the Cd(II) adsorption capacity of bentonite was reduced by 32, 30, and 55 %, respectively. Increasing the thermal activation temperature of sepiolite from 300 to 800 °C, encourage the capacity of sepiolite to adsorb metallic ions by 40 %. Raw vermiculite always presented a better capacity to adsorb Cd(II) than thermally activated vermiculite; sample activated at 300 °C adsorbed 50 % less than natural vermiculite. The relation between the chemical and textural properties of the activated clays and their capacity to adsorb Cd(II) demonstrated that the adsorption capacity of the thermally activated clays was strongly dependent on the quantity of negative charge surface and their cation exchange capacity, inferred that the main mechanisms was due to two mechanism, electrostatic interactions of attractive forces between negative superficial charge and cationic specie of Cd(II) and cation exchange between interlaminar cations, OH− in silanols and aluminols groups with Cd(II).

Removal Performance and Mechanism for Treating Phosphorus in Agricultural Wastewater by Three Adsorbents

To screen the optimal absorbents for P removal from agricultural wastewater, the P adsorption capacity of bentonite, red soil, and slag was studied using synthetic wastewater. Combing the properties of three adsorbents measured by SEM, XDS, and BET methods, the isothermal adsorption, adsorption kinetics, and Ca2+ release capacity were analyzed to elucidate the mechanisms of P adsorption. The results showed that the P adsorption capacity of slag was higher than that of bentonite and red soil, and the Langmuir isotherm model was able to better fit the adsorption data (R2>0.96). The P theoretical saturation sorption capacity of slag was higher (16.87 mg·g-1) than that of bentonite (1.21 mg·g-1) and red soil (0.92 mg·g-1) (P<0.05). The results for adsorption kinetics indicated that slag rapidly removed 95.6% of P from 10 mg·L-1 solution, and the Elovich equation fit the data well (R2=0.812). The adsorption kinetics of P on bentonite and red soil were better described by the pseudo-second-order kinetic equation (R2=0.982 and 0.959, respectively). The Ca2+ release capacity of slag (10.46 mg·g-1) was significantly higher compared to bentonite (0.31 mg·g-1) and red soil (0.03 mg·g-1) (P<0.05). The P adsorption capacity of red soil was 0.26 mg·g-1 when the pH value was 3, and it decreased as the pH values increased. At the initial pH of 7.0, the P adsorption capacity of bentonite was about 0.01 mg·g-1, lower than 0.04 mg·g-1 at pH 3, and 0.05 mg·g-1 at pH 11. The initial pH value had little effect on the P adsorption capacity of slag. The P-loaded bentonite, red soil, and slag were effectively regenerated by using CaCl2 solution, and bentonite was easier to reuse compared to red soil and slag. The key factors affecting the P adsorption capacity of the three adsorbents were physical and chemical properties, such as crystal structure and the content of metal ions, Ca2+ release capacity, and initial pH. These findings demonstrated that slag was a better choice for P removal compared to bentonite and red soil and could be used as an effective P adsorbent for agricultural wastewater treatment.

Optimization of humic acid removal by adsorption onto bentonite and montmorillonite nanoparticles

Nanoclays are low cost and non-toxic materials with high adsorption capacity for the removal of various contaminants from water. In this study the efficiency of two nanoclays was examined for the adsorption of humic acid under batch conditions. The effect of various parameters such as pHzpc, pH, contact time, humic acid initial concentration and adsorbent dosage was studied. The adsorption data regarding compliance with pseudo first and pseudo second order kinetics was studied. The thermodynamically aspects of adsorption was also investigated. Characterization of the adsorbents was determined by the analytical methods including Field Emission-Scanning Electron Microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray Diffraction (XRD).The results of this study showed that the nanoparticles examined were proven most effective in removing humic acid from aqueous solutions at pH=3. Adsorption capacity increased by increasing the humic acid concentrations so adsorption capacity of bentonite and montmorillonite nanoparticles at humic acid concentration of 40mg/L, reached to 58.21 and 48.20mg/g, respectively. The results showed that adsorption process follows the Freundlich isotherm as well as pseudo-second order kinetics. The results of temperature and thermodynamic process showed that ΔS° values were positive for both absorbents and ΔH° values were negative, but the values of ΔG° became more negative with temperature decrease. The results lead to the conclusion that nanoclays are appropriate adsorbents for removing humic acid from aqueous solutions.

γ-radiation induced corrosion of copper in bentonite-water systems under anaerobic conditions

In this work we have experimentally studied the impact of bentonite clay on the process of radiation-induced copper corrosion in anoxic water. The motivation for this is to further develop our understanding of radiation-driven processes occurring in deep geological repositories for spent nuclear fuel where copper canisters containing the spent nuclear fuel will be embedded in compacted bentonite. Experiments on radiation-induced corrosion in the presence and absence of bentonite were performed along with experiments elucidating the impact irradiation on the Cu2+ adsorption capacity of bentonite. The experiments presented in this work show that the presence of bentonite clay has no or very little effect on the magnitude of radiation-induced corrosion of copper in anoxic aqueous systems. The absence of a protective effect similar to that observed for radiation-induced dissolution of UO2 is attributed to differences in the corrosion mechanism. This provides further support for the previously proposed mechanism where the hydroxyl radical is the key radiolytic oxidant responsible for the corrosion of copper. The radiation effect on the bentonite sorption capacity of Cu2+ (reduced capacity) is in line with what has previously been reported for other cations. The reduced cation sorption capacity is partly attributed to a loss of Al-OH sites upon irradiation.

Adsorption performance of modified bentonite granular (MBG) on sediment phosphorus in all fractions in the West Lake, Hangzhou, China

Modified bentonite granulars (MBGs) were prepared by acidification, natrification, calcination, and combined modification methods, and evaluated as effective in-situ adsorption materials to remove sediment phosphorus (P) in all fractions. The morphology and microstructure of MBG were characterized by scanning electron microscope (SEM), X-ray fluorescence (XRF), fourier transform infrared (FTIR) and X-ray diffraction (XRD). Results showed that the P removal capacity of CMBG-Na10-450 treated with 10% (g/g) Na2CO3 and calcined at 450°C exhibited the highest P removal capacity. Under the optimal conditions of stirring tests, the removal rates of sediment TP, OP, IP, Fe/Al-P and Ca-P by CMBG-Na10-450 were 35.5%, 29.1%, 54.5%, 44.6% and 10.7%, respectively. The adsorption mechanism analysis found that MBG adsorbed sediment P mainly by anionic coordination exchange adsorption. These results indicated that modification enhanced the P adsorption capacity of bentonite, and the MBG can be further applied to control and reduce sediment P in eutrophication remediation.

Attenuation of metal species in acidic solutions using bentonite clay: implications for acid mine drainage remediation

A laboratory batch experimental study has been carried out to evaluate the adsorption capacity of selected metal species in acid mine drainage (AMD) by bentonite clay. Bentonite clay was mixed with simulated AMD at specific solid–liquid (S/L) ratios and agitated in a reciprocating shaker and adsorption of selected toxic metals assessed over time. Cation exchange capacity varied from 1140 to 1290 meq kg−1. Contact of AMD with bentonite leads to increase in pH and a possible reduction in electrical conductivity and total dissolved solids. At constant agitation time of 60 min, the pH increased with dosage of bentonite. Removal of Mn2+, Al 3+, and Fe3+ was observed to be greatest at 60 min of agitation. Bentonite clay exhibits high adsorption for Al3+ and Fe3+ at concentration less than 300 mg L−1, while the capacity for Mn2+ was observed to be lower. Adsorption capacity for SO42− was low with a great percentage of the SO42− remaining in solution. Adsorption capacity of bentonite with more complex formulated AMD and gold tailing leachates was low for Fe3+, Al3+, and Mn2+. This indicates that optimum adsorption of bentonite clay is dependent on the chemistry of the AMD and its application might be site specific.

Equilibrium and kinetic study on the adsorption of basic dye (BY28) onto raw Ca-bentonite

AbstractThe adsorption of Basic Yellow 28 (BY28) onto bentonite in a batch system was carried out at temperatures of 20 and 40°C. The initial dye concentrations were in the range of 100 and 300 mg/L based on the total organic carbon (TOC) content of the dye solution. The effects of contact time, initial pH, and initial dye concentration on BY28 adsorption by the bentonite have been studied. BY28 removal was observed to increase until equilibrium, with increasing contact time and initial dye concentration, and the adsorption capacity of bentonite was seen to increase with increasing pH from 3 to 8. Adsorption efficiencies up to about 98.1% were obtained based on the TOC at various adsorption conditions. The adsorption process was determined to follow the pseudo-second-order adsorption kinetics. Kinetic parameters, rate constants, equilibrium adsorption capacities, and correlation coefficients of the adsorption kinetic models were calculated and discussed. The experimental isotherm data were analyzed using ...

Formation and Characteristics of Bentonite/Cationic Starch Composite as Adsorbent for Acid Red G Dye

In order to increase the adsorption capacity of bentonite, a novel and cost-effective cationic starch (CS) intercalated raw bentonite (RB) composite matrix was prepared by controlling the weight ratio of RB and CS. The intercalated microstructure of the RB/CS composite was then characterized by Fourier transform infrared spectroscopy (FTIR), X-ray-diffraction (XRD), respectively. The acid red G adsorption from aqueous solution on RB/CS composite was studied using batch technique and compared with the adsorption onto RB under various parameters such as weight ratio of RB to CS, initial dye concentration, contact time, pH, and adsorbent dosage. It was found that more than 90% of the dye from 100 ml L-1 solution was removed by RB/CS composite under the optimal conditions and it had a higher color removal efficiency and a shorter adsorption equilibrium time compared with the RB as the adsorbent for acid red G dye. In summary, the result showed that RB/CS could be as a kind of low-cost material for the removal of acid red G from aqueous solution.

KINETICS AND EQUILIBRIUM ADSORPTION STUDY OF LEAD (II) ONTO LOW COST CLAYS

The performance of four low cost Iraqi clays, bentonite (BT), kaolinite (KT), attapalgite (AT) and flint (FT) to remove lead ions from aqueous solutions by adsorption was investigated. Batch experiments were carried out at pre determined equilibration time, adsorbent dosage, solution pH, particle sizes, ionic strength, initial lead ions concentration and temperature. Adsorption of Pb2+ ions was strongly affected by pH and best adsorption is achieved at pH 4.5. The systems were investigated at 10, 25, 35 and 50 oC using Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. At pH 4.5, the maximum lead adsorption capacity of BT, KT, AT and FT estimated with the Langmuir model at 25 oC and pH 4.5 was 24.814, 35.710, 30.488 and 7.692 mg g-1, respectively. Dubinin-Radushkevich (D-R) isotherm model was also applied to equilibrium data. The mean free energy of adsorption (8.404, 7.305, 8.588 and 7.322 kJ/mole) onto BT, KT, AT and FT, respectively, indicates adsorption process may be carried out via physisorption mechanism. Pseudo first-order and pseudo second-order were used to fit the adsorption kinetics data. In comparison to first-order kinetic model, pseudo-second-order model described well the adsorption kinetics of Pb(II) onto four clays from aqueous solution. Thermodynamic parameters such as Gibbs free energy .G , enthalpy change .H and entropy .S were evaluated. The thermodynamics of Pb(II) on these clays indicates the spontaneous and exothermic nature of adsorption.