THERE are many environmental factors that influence the mobility …. and bioavailability behavior of some heavy metals in soils. One of these factors is the content and form of calcium carbonate in soils.
Experimental work has been carried out applying 1 and 3 mmole (mM) of Pb, Cd and Ni (in chloride forms) on 5 different calcareous soils from the north coast area, Egypt. The adsorption of these elements at interval times from 1 to 168 hours was measured. Four kinetic models were applied: Elovich, Modified Frendlich, Horels and Diffusion equation.
The obtained results indicate that the adsorption process takes three stages, a rapid rate from the starting time to about 2 hr, intermediate stage until about 100 hours and slow or steady rate until the end of the reaction (168 hr). Comparing the adsorption process through the five soil samples can be arranged as follows; S5>S3>S4>S2>S1. The retention of heavy metals depends on the amount of active calcium carbonate, clay content and surface area of the soil. The values of adsorbed three heavy metals on the five soil samples can be arranged as; Cd > Pb >Ni.
The constants of the four kinetic equations (a, b and r2) were compared for the two concentrations of each metal (Elovich, Modified Frendlich Equation "MFE", Horels and Diffusion). The correlation coefficient between soil criteria and the constants of the applied kinetic models reveals that highly positive correlation between active calcium carbonate, surface area and clay content with a and b constants in Elovich and Diffusion equations.