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365433 
Journal Article 
Adsorption characteristics of some heavy metals by some soil minerals 
Wahba, MM; Zaghloul, AM 
2007 
June 
421-426 
The objective of this study was to compare three different soil minerals (montmorillonite, kaolonite and calcite) for their ability to remove heavy metals (HM). These minerals were applied in chloride form dissolved in aqueous solutions of these metals at two concentrations i.e. 2000 and 6000 ppm. The effect of contact time, initial metal concentration and type of natural soil minerals on the adsorption process at 20±2°C was studied using kinetic approach. Data gathered from Electrical Stirred Flow Unit (ESFU) used for kinetic study indicated that almost steady state adsorption conditions were reached after 2-4 h of unit working for the adsorption of Pb (II), Cd (II) and Zn (II). At 2000 ppm metal concentration and 2 h reaction time, for example, the maximum Pb metal removed from the solution was found in calcite by about 74.2%, followed by montmorillonite and kaolonite by about 66% and 58% respectively. With an increase in the concentrations of these metals, the same trend of HM retention was detected. Six kinetic models were tested to select the best fitted once. Results indicated that power function or modified Freundlich MFE, Elovich and parabolic diffusion equations were the best models. The constants rate represented capacity and intensity factors of the best fitted equations showed that the increasing trend of adsorption capacity have the order: calcite > montmorillonite > kaolonite in their tendency to retain HM. Moreover, results of distribution coefficient Kd represent the HM tendency to retain to specific soil minerals, showed that in all cases the higher values of this parameter take the order Pb > Cd > Zn regardless the type of clay mineral or solution concentration of the studied HM. Different mechanisms of HM reaction with the selected soil minerals were discussed. 
adsorption; cadmium; calcite; chlorides; clay minerals; heavy metals; kaolinite; lead; montmorillonite; pollutants; polluted soils; removal; soil pollution; soil types; zinc; Soil Chemistry and Mineralogy (JJ200); Pollution and Degradation (PP600); Industrial Wastes and Effluents (XX400)