Abstract

With rapid global economic, population growth and accelerated industrialization, heavy metal pollution has become increasingly severe, with the heavy metal content in many rivers and groundwater exceeding safety standards. The aim of this study is to evaluate the kinetic models of heavy metal adsorption from water using cactus ash adsorbent. Three kinetic models i.e., pseudo-first-order, pseudo-second-order and power function were applied to study the reaction pathways and potential rate determining steps of the adsorption of Cr, Ni, Pb and Cd onto Cactus ash residue. The pseudo-first-order model did not provide a good fit to the experimental data, rather the adsorption of Cr, Ni, Pb and Cd by cactus ash residue followed the pseudo-second-order kinetics. Suitability of pseudo-second-order model suggests chemisorptions as the rate limiting step. The study therefore shows that the adsorption of Cr, Ni, Pb and Cd ions onto cactus ash residue adsorbent was best fitted in the pseudo second order model for the evaluation of kinetic parameters of the adsorption process, which R2 values of the ions tends towards 1.