Aqueous Cadmium Removal by Adsorption on Barley Hull and Barley Hull Ash

Abstract

Adsorbents prepared from barley hull and barley hull ash, an agricultural waste product, were used to remove cadmium from an aqueous solution in batch mode as a function of appropriate equilibrium time, amount of adsorbent, concentration of adsorbate, pH and particle size. Studies showed that pH of aqueous solutions affected cadmium removal as a result of removal efficiency increased with increasing solution pH. The maximum adsorption was about 95.8 and 99.2 % for barley hull and barley hull ash, respectively, at pH 9, contact time 180 min and initial concentration of 30 mg L^-1. Desorption of cadmium was 8 % at pH 9. The cadmium sorption obeyed both the Langmuir and Fraundlich isotherms. The sorption kinetics are well described by the pseudosecond- order kinetic model. The studies showed barley hull ash was more favourable than barley hull in removing cadmium and thus was a better adsorbent as low-cost alternatives in wastewater treatment for cadmium removal.