El Tohamy, S. A. ; Shreen S. Ahmed and Mervat A. Hamed( 2012). Removal of lead ions from aqueous solutions using modified clay mineralsEgypt . J. of Appl. Sci., 27 (3) 2012 , 251-266
Abstract: Lead contamination is known as one of the most pervasive and elusive environmental health threats, as considered by the fact that exposure lead (II) ions has been associated with death and disease in humans, birds, and animals. The present research aims to increase the efficiency of the modified clay as an adsorbent that it can be used in the removal of lead (II) ions by adsorption. Modified Clay was prepared from bentonite or zeolite and different types of amino acids,(cystein and serine) as aliphatic amino acid, while phenylalanine as aromatic or heterocyclic structures. Ten different lead solutions (2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 mgL-1) were used. At the same time, an accurately weighed amount of modified clay was added to the lead solution. The effect of different pH values (2, 4, 6, and 8) on the adsorption of lead (II) ions onto modified clay with different amino acids was determined. The final concentrations of Pb (II) were measured. Adsorption was assessed by determining the concentration of metal ion remaining in an aliquot. Data showed that all modified clays under investigation with different pH values were decreased strongly lead metal concentration. Adsorption percentage of lead ions reached 99.9% when phenylalanine was used as a modified of zeolite and bentonite clay. The efficacy of all amino acids as modified was different. It is evident that the removal of Pb using different modified zeolite was in the following order: Zeo-phy > Zeo-cys > Zeo-ser, while the removal of Pb using modified bentonite was in the following order: Ben-phy > Ben-ser > Ben-cys. Sorption of Pb (II) for modified zeolite and bentonite respectively at different pH. The equilibrium sorption data were fitted to the linear form of the Langmuir equation. It could be seen that, the sorption of Pb(II) is markedly pH-dependent. It was obvious that the amount of the metal ions adsorbed on the solid phase (q) was low at low pH values.
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