Comparative Study of the Bioadsorbtion of Cadmium and Lead from Industrial Waste Water Using Melon (Citrullus colocynthis) Husk Activated with Sulphuric Acid

Abstract

Melon (Citrullus colocynthis) husk (Lloyd, 1898), a readily available agricultural waste product was used as a low-cost potential adsorbent to remove cadmium and Lead from industrial effluents. Adsorption studies were carried out on melon husks activated with sulphuric acid as a function of parameters such as contact time, adsorbent dosage and adsorbate concentration. Cadmium removal was found to be dependent on the three parameters with maximum removal attained at 70min with 0.6g for sulphuric acid (H2SO4) activated melon husk. Both metals were mostly removed at low adsorbate concentration. Lead removal did not show strict dependency on these parameters with maximum removal attained within the first minute with H2SO4 activated melon husks with records of 100% adsorption. Adsorption isotherms correlated well with both Langmuir and Freundlich isotherm models and their R2 values ranges from 0.911- 1. Experimental data were also evaluated to find out kinetic characteristics of the adsorption process. Adsorption process for the two target heavy metal ions were found to follow pseudo-second order adsorption kinetics while their r2 values ranges from 0.797- 0.999. The r2 values and the pairwise t- test showed that lead is better adsorbed than cadmium. Activated melon husk, a readily available adsorbent was found to be efficient in the uptake of Cd(II) and Pb(II) ions in industrial effluents, thus, predisposing it as an excellent alternative for the removal of heavy metals from water and waste water.