Kinetic studies on the removal of some metal ions from aqueous solution using modified orange mesocarp extract

Abstract

This study examines the kinetics of the removal of zinc, copper, nickel and cobalt ions from aqueous solutions by Carboxylated-Toluene Di-isocyanate Orange Mesocarp Extract Resin (CTOR) and Sulphonated-Toluene Di-isocyanate Orange Mesocarp Extract Resin (STOR). Results from contact time experiments indicate that the rate of ion exchange was initially rapid and equilibrium was attained within 40 to 45 min. It was found that the uptake of Zn2+, Cu2+, Ni2+ and Co2+ ions by CTOR and STOR is related to the dissociation power of the exchangeable hydrogen and in sequence similar to the ionic radii of the metal ions. The Vermeulen’s particle diffusion model best described the ion exchange process. The fraction attainment of equilibrium (α) values increase with time and reaching constant value at about 40 to 45 min for the resins, indicating the time for saturation of the active sites. The rate constants for CTOR and STOR decreased with increase in temperature from 29 to 70°C. The negative values of the activation energy calculated using the Arrhenius equation showed that low temperatures favoured the exchange process. Key words: Kinetics, orange mesocarp, ion exchange, metal ions, resin, diffusion.