Sorption of cadmium, zinc, copper and lead by soils developed on alum shales and other materials.

摘要

A laboratory experiment was conducted to study the adsorption of cadmium, zinc, copper and lead by four different soils (alum shale, sandy loam, organic soil and peat soil) developed on alum shale and other mineral materials. Equilibration time wasdetermined and half an hour shaking time was sufficient for near complete equilibration. The adsorption data were well fitted to the nonlinear Freundlich equation, the R2 value ranging from 0.966 to 0.999. The Freundlich adsorption isotherms showed thatthe curves are steep at low concentrations and became less steep when the concentration of metals in equilibrium solution increased. For all soils, with the exception of sandy loam, the adsorption capacity was high and the order of adsorption capacity was alum shale > peat soil > organic soil > sandy loam. The desorption of adsorbed amount of metals by 0.005M CaCl2 was low from all soils except for sandy loam. The order of desorption of metals was Cu < Pb < Zn < Cd. Desorption of all metals was least from alum shale, which indicated that metals were strongly adsorbed by this soil. The desorption of metals increased significantly when the concentration of desorbing solution (CaCl2) was increased from 0.005M to 0.5M.