Comparison of cadmium and copper removal by maize cobs and mixed adsorbent from industrial effluents

Abstract

The adsorbent studies with agricultural adsorbent (maize) and commercially purchased activated charcoal and bone charcoal (1:1 ratio) were carried out for the removal of copper and cadmium. The Mixed adsorbent was prepared by mixing activated charcoal and bone charcoal in 1:1 ratio for the batch studies. The activated charcoal prepared from maize cob was used as an adsorbent in order to evaluate its potential for the removal of copper and cadmium from electroplating industries. The characterization studies were performed which includes BET analysis, XRD analysis, Proximate and Ultimate analysis, pore size distribution, evaluation of particle size of the mixed adsorbent and maize cob. Adsorption studies were performed by batch experiments as a function of process parameters such as pH varying from 2, 4, 6 and 8, metal ion concentration of 50 ppm, adsorbent dosage of 0.5–5 g/L, equilibrium time varying from 150 to 180 min, and at fixed agitation rate of 180 rpm. Comparison studies were made for the mixed adsorbent and maize cobs for the removal of copper and cadmium in terms of % removal, and adsorption capacity for the process parameters pH, adsorbent dosage and contact time. In comparison with the maize cobs, the highest % removal was obtained for mixed adsorbent (Activated Charcoal + Bone Charcoal) due to the high surface area of the activated charcoal as well as negative charge from the bone charcoal which induces the synergistic effect (of the mixed adsorbent) as well as less particle size and more pore volume that enhances the % removal for three parameters that were studied in this paper. The adsorption parameters such as metal ion concentration of copper and cadmium was fixed at 50 ppm, constant agitation rate of 180 rpm, and constant temperature of 25 °C were maintained throughout study. All the findings and experimental results were discussed in detailed and presented in this paper.