Kinetics and Diffusion Analysis for the Removal of Cadmium Ion from Aqueous Solutions Using Chitosan-iso-Vanillin Sorbent

Kinetic and diffusion analysis of the process of cadmium ion removal from water via sorption has been explored. The experimental kinetics data were approximated with pseudo-first and pseudo-second-order equations, Elovich equation, and Ritchie modified second-order models. Diffusion analysis is performed using homogeneous particle diffusion model and Weber-Morris kinetics. Kinetic results reveal that chemisorption is the sole-controlling step representing high sorption rate during the first 2 h of agitation with 50.90% removal. Activation energy is also calculated (26.57 kJ mol(-1)) disclosing chemical interaction among solute-adsorbent phase. Weber-Morris plots show the sorption process is controlled by two or more simultaneous mechanisms with higher K-id values at higher initial concentrations. The study demonstrates that rate values of pore and film diffusion are improved with increase of initial ion concentration and the effect of diffusion resistance is not efficiently removed or minimized by sufficient agitation time.