KINETICS OF ZINC SORPTION BY SOILS

The rate of zinc (Zn) sorption from solution onto solid surfaces is a dynamic factor that directly or indirectly regulates the amount of Zn in solution at any given time. To understand the pattern of Zn sorptio n and the soil characteristics affecting it, the kinetics of Zn sorpti on by twelve Alabama soils were studied using five equations (Elovich, zero-, first-, second-, third-order, and parabolic diffusion). The ti me required to reach the equilibrium state was 24 h. The Elovich equat ion was superior in fitting the data. The choice of the Elovich equati on over the others was based on the higher coefficient of determinatio n (R(2)), lower standard error of estimate (SE) over the whole isother m, and the close values for both the measured and predicted Zn sorbed at different time intervals. Elovich parameters were regressed against some soil properties to identify soil properties that were related to Zn sorption. The regression equations indicated that cation exchange capacity, organic matter, and clay content were the main soil properti es contributing to the Zn sorption process in these soils.