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Adsorption Characteristics of Zinc (Zn2+) from Aqueous Solution by Natural Bentonite and Kaolin Clay Minerals: A Comparative Study  [PDF]
Tushar Kanti Sen, Chi Khoo
Computational Water, Energy, and Environmental Engineering (CWEEE) , 2013, DOI: 10.4236/cweee.2013.23B001

Clay minerals are one of the potential good adsorbent alternatives to activated carbon because of their large surface area and high cation exchange capacity. In this work the adsorptive properties of natural bentonite and kaolin clay minerals in the removal of zinc (Zn2+) from aqueous solution have been studied by laboratory batch adsorption kinetic and equi- librium experiments. The result shows that the amount of adsorption of zinc metal ion increases with initial metal ion concentration, contact time, but decreases with the amount of adsorbent and temperature of the system for both the ad- sorbents. Kinetic experiments clearly indicate that adsorption of zinc metal ion (Zn2+) on bentonite and kaolin is a two-step process: a very rapid adsorption of zinc metal ion to the external surface is followed by possible slow decreas- ing intraparticle diffusion in the interior of the adsorbent. This has also been confirmed by an intraparticle diffusion model. The equilibrium adsorption results are fitted better with the Langmuir isotherm compared to the Freundlich model. The value of separation factor, RL from Langmuir equation give an indication of favourable adsorption. Finally from thermodynamic studies, it has been found that the adsorption process is exothermic due to negative ?H0 accompa- nied by decrease in entropy change and Gibbs free energy change (?G0). Overall bentonite is a better adsorbent than kaolin in the the removal of Zn2+ from its aqueous solution.

Removal of Phosphate from Aqueous Solution with Modified Bentonite
TANG Yan-kui,TONG Zhang-fa,WEI Guang-tao,LI Zhong-min,LIANG Da-wen,

过程工程学报 , 2006,
Abstract: Bentonite combined with sawdust and other metallic compounds was used to remove phosphate from aqueous solutions in this study. The adsorption characteristics of phosphate on the modified bentonite were investigated, including the effects of temperature, adsorbent dosage, initial concentration of phosphate and pH on removal of phosphate by conducting a series of batch adsorption experiments. The results showed that 98% of phosphate removal rate was obtained since sawdust and bentonite used in this investigation were abundantly and locally available. It is concluded that modified bentonite is a relatively efficient, low cost and easily available adsorbent for the removal of phosphate from aqueous solutions.
Physico-chemical characterization of bentonite and its application for Mn2+ removal from water
Ran?elovi? Marjan S.,Purenovi? Milovan M.,Zarubica Aleksandra R.,Mladenovi? Igor D.
Hemijska Industrija , 2011, DOI: 10.2298/hemind110322029r
Abstract: Bentonite is mainly composed of clay minerals from smectite group, therefore it has a well developed and chemically active surface area and high cation exchange capacity. Moreover, an interlayer space of smectite has unusual hydration properties, which manifest as swelling of bentonite in water. These properties make bentonite as a commonly used raw material in chemistry and industry, and it is very important in environmental protection and water treatment as an effective sorbent of heavy metals. The results of X-ray diffraction, a cationic exchange capacity, specific surface area, acid-base properties of the surface and the swelling index showed that the bentonite sample contains mostly montmorillonite. The aim of this study was to test the efficacy of bentonite in the removal of Mn2+ from aqueous systems. The experimental results of Mn2+ adsorption on the bentonite were interpreted by Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherms. The adsorption isotherm studies indicate that the adsorption of Mn2+ follows Langmuir isotherm very well. Theoretical monolayer saturation capacity according to Langmuir model was 12.41 mg/g. The removal of Mn2+ is achieved by ion exchange mechanism with naturally occurring cations in bentonite, as well as by forming the inner- and outer-sphere complexes with bentonite surface.
A kinetic and equilibrium study of zinc removal by Brazilian bentonite clay
Araujo, Ana Lucia Pereira de;Gimenes, Marcelino Luiz;Barros, Maria Angelica Sim?es Dornellas de;Silva, Meuris Gurgel Carlos da;
Materials Research , 2013, DOI: 10.1590/S1516-14392012005000148
Abstract: this paper aimed to study the removal of zinc using bentonite clay from the northeastern brazil, as an adsorbent. a study of the clay subjected to thermal and chemical treatment was performed in order to evaluate the optimization of the adsorption capacity of this material. for the evaluation of the kinetic equilibrium of the process, experimental tests were carried out in a finite bath system. the maximum amount of metal adsorbed was 0.151 meq of metal per gram of calcined clay and 0.257 meq of metal per gram of sodium saturated clay. the kinetic models of pseudo-first order, pseudo-second order and intraparticle diffusion were fitted to experimental data, and the pseudo-second order model provided the best result. the langmuir and freundlich models were used for the adsorption equilibrium analysis, and the langmuir model provided the best fit for sorption isotherms. the physicochemical characterization of clay involved x-ray diffraction, scanning electron microscopy, chemical analysis by energy-dispersive x-ray spectroscopy, helium pyconometry and thermogravimetric analysis. the modified clay has potential use for removing zn2+ ions replacing more expensive adsorbents, since good adsorption properties will be also associated with great availability and low cost.
Surface cellulose modification with 2-aminomethylpyridine for copper, cobalt, nickel and zinc removal from aqueous solution
Silva Filho, Edson Cavalcanti;Santos Júnior, Luiz Sousa;Silva, Marcia Maria Fernandes;Fonseca, Maria Gardênnia;Santana, Sirlane Aparecida Abreu;Airoldi, Claudio;
Materials Research , 2013, DOI: 10.1590/S1516-14392012005000147
Abstract: cellulose was first modified with thionyl chloride, followed by reaction with 2-aminomethylpyridine to yield 6-(2'-aminomethylpyridine)-6-deoxycellulose. the resulting chemically-immobilized surface was characterized by elemental analysis, ftir, 13c nmr and thermogravimetry. from 0.28% of nitrogen incorporated in the polysaccharide backbone, the amount of 0.10 ± 0.01 mmol of the proposed molecule was anchored per gram of the chemically modified cellulose. the available basic nitrogen centers attached to the covalent pendant chain bonded to the biopolymer skeleton were investigated for copper, cobalt, nickel and zinc adsorption from aqueous solution at room temperature. the newly synthesized biopolymer gave maximum sorption capacities of 0.100 ± 0.012, 0.093 ± 0.021, 0.074 ± 0.011 and 0.071 ± 0.019 mmol.g-1 for copper, cobalt, nickel and zinc cations, respectively, using the batchwise method, whose data was fitted to different sorption models, the best fit being obtained with the langmuir model. the results suggested the use of this anchored biopolymer for cation removal from the environment.
Removal of Cadmium(II) and Lead(II) ions from aqueous phase on sodic bentonite
Galindo, Luz Stella Gaona;Almeida Neto, Ambrósio Florêncio de;Silva, Meuris Gurgel Carlos da;Vieira, Melissa Gurgel Adeodato;
Materials Research , 2013, DOI: 10.1590/S1516-14392013005000007
Abstract: this paper describes the adsorption of cd2+and pb2+ions using sodic bentonite clay type fluidgel modified. the fluidgelbefore and after chemical modification and thermal activation was characterized by different techniques including x-ray diffraction, thermal analysis, fourier transform infrared, surface area, helium pycnometry, cation exchange capacity and scanning electron microscopy. pseudo-first order, pseudo-second order and intra-particle diffusion models were used to analyze the kinetic curves. equilibrium data were analyzed using langmuir and freundlich models. the thermodynamic study indicated that lead adsorption process is endothermic and interactions between clays and solutions of lead occurred spontaneously, while cadmium adsorption revealed an exothermic and spontaneous nature. the maximum removal efficiencies were 97.62% for cd(ii) using fluidgelmodified chemically and 91.08% for lead by fluidgel modified chemical and thermally.
Adsorption characteristics of humic acid-immobilized amine modified polyacrylamide/bentonite composite for cationic dyes in aqueous solutions

T S Anirudhan,P S Suchithra,

环境科学学报(英文版) , 2009,
Abstract: Humic acid-immobilized amine modified polyacrylamide/bentonite composite (HA-Am-PAA-B) was prepared and used as an adsorbent for the adsorption of cationic dyes (Malachite Green (MG), Methylene Blue (MB) and Crystal Violet (CV)) from aqueous solutions. The polyacrylamide/bentonite composite (PAA-B) was prepared by intercalative polymerization of acrylamide with Na-bentonite in the presence of N,N'-methylenebisacrylamide as a crosslinking agent and hexamethylenediammine as propagater. PAA-B was subsequently treated with ethylenediammine to increase its loading capacity for HA. The surface characterizations of the adsorbent were investigated. The adsorbent behaved like a cation exchanger and more than 99.0% removal of dyes was detected at pH range 6.0-8.0. The capacity of HA-Am-PAA-B was found to decrease in the following order: MG > MB > CV. The kinetic and isotherm data were interpreted by pseudo-second order rate equation and Freundlich isotherm model, respectively. Experiments were carried out using binary solute systems to assess the competitive adsorption phenomenon. The experimental isotherm data for each binary solute combination of MG, MB and CV were analyzed using Sheindrof-Rebhun-Sheintuch (SRS) (multicomponent Freundlich type) equation.
Simultaneous removal of chromotrope 2B and radionuclides from mixed radioactive process wastewater using organo-bentonite  [cached]
Kamal Shakir,Hussein Fouad Ghoneimy,Ibtisam Tadros Hennawy,Ahmed Faouzy Elkafrawy
European Journal of Chemistry , 2011, DOI: 10.5155/eurjchem.2.1.83-93.191
Abstract: The simultaneous removal of cationic radionuclides, 137Cs(I), 60Co(II) and 152+154Eu(III), and a chemically toxic anionic pollutant, the analytical reagent chromotrope 2B (C2B), from simulated mixed radioactive process wastewater (MRPWW) has been investigated using bentonite modified with cetyltrimethylammonium bromide. Modification was confirmed by elemental analysis, X-ray diffraction and infrared spectroscopy. Bentonite partially modified to 78% of the cation exchange capacity (PMB) was found capable to adsorb adequately both C2B and the radionuclides from aqueous solutions. Detailed batch kinetics and isotherm studies for removal of C2B singly and the radionuclides simultaneously were performed. The C2B and radionuclides kinetics conform to pseudo-first-order rate equation and the adsorption isotherms are treated with Freundlich and Langmuir models. Thermodynamic parameters were evaluated. Results suggest physisorption and ion-exchange as the principal uptake mechanism for C2B and the radionuclides, respectively. High simultaneous removal was obtained for C2B (≈ 100%) and each of the test radionuclides (>99%) from the simulated MRPWW.
Efficiency of Removal of Lead, Cadmium, Copper and Zinc from Aqueous Solutions Using Six Common Types of Plant Leaves  [PDF]
Rajab Abu-El-Halawa,Rami Quora,Radi Salim
Journal of Applied Sciences , 2003,
Abstract: Dry plant leaves of thyme, sage, banana, mint, anise and oleander plants have been used for removing lead, cadmium, cooper and zinc ions for aqueous solutions. The most efficient types of plant leaves for the removal process have been found to be oleander leaves for removing lead and copper and sage leaves for removing dmium and zinc. The maximum efficiency of removal of the studied metal ions by plant leaves was equal to that obtained by activated carbon. The concentration of metal ion in solution has been found to have only slight effect on the efficiency of the removal process. Oven-dried leaves have a little higher efficiency removal of metal ions than naturally dried leaves.
Application of Algerian Bentonite in the Removal of Cadmium (II) and Chromium (VI) from Aqueous Solutions  [PDF]
Mahfoud Barkat, Salah Chegrouche, Abdelhamid Mellah, Belgacem Bensmain, Djamel Nibou, Makhlouf Boufatit
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2014, DOI: 10.4236/jsemat.2014.44024

The aim of this study is to report batch adsorption results of Cd (II) and Cr (VI) onto Algerian bentonite. The equilibrium adsorption process was achieved at about 120 min contact time. The kinetic and isotherms aspects of Cr (VI) and Cd (II) adsorption were investigated by varying operation parameters such as pH (0.5 - 6), initial Cd (II) and Cr (VI) concentrations (50 - 200 mg/l) and temperature (293.15 K - 343.15 K). The optimum conditions obtained were: pH = 6.0 and 4.0 for Cd (II) and Cr (VI) respectively, initial concentrations of Cd (II) and Cr (VI) = 50 mg/L and T = 293.15 K. The kinetic of the adsorption process was studied by application of the most important kinetic models namely the pseudo-first order, the pseudo-second order and Elovich equations. The results showed that the pseudo-second order model fitted well the adsorption data of Cr (VI) whereas, and the Cd (II) adsorption data fitted best the Elovich equation. The equilibrium data fitted best the Langmuir isotherm, and the maximum adsorption capacity was determined through this model and was found to be 13.17 and 12.61 mg/g for Cd (II) and Cr (VI) respectively. The temperature had a reverse effect on the Cd (II) and Cr (VI) adsorption; our results showed that the removal efficiency increased to82.4% and 55.70% for Cd (II) and Cr (VI)when the temperature decreasedto 293.15 K.The negative figures of the Gibbs free energy ΔG°ads values range from 15.23 kJ/mol to 14.37 kJ/mol for Cd (II) and from 9.70 kJ/mol to 9.64 kJ/mol for Cr(VI) at 293.15 K to 343.15 K showed that the adsorption process is spontaneous and favourable. These results confirmed the ability of the low-cost Algerian natural bentonite to efficiently and competitively adsorb the two toxic elements investigated: cadmium (II) and chromium (VI).

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