REMOVAL OF HEAVY METALS FROM WASTE WATER BY ADSORPTION ON EXHAUSTED COFFEE GROUNDS
C. N. Mbah1 and C. I. Nwoye2
In this study, exhausted coffee grounds, a waste product of coffee processing, was used as adsorbent for the removal of lead, cadmium, zinc and copper from waste water. The experiments were performed using synthetic wastewater prepared by dissolving the respective metal nitrates in deionized water. The process variables considered were coffee ground dosage, pH of solution and metal ion concentration. The solution-adsorbent contact time was 24 hours within which equilibrium must have been attained. Spectrometric analysis was used to obtain the residual metal ion concentration. Results show that all the metal ions are highly adsorbed by the exhausted coffee grounds and in the following order: Pb2+ > Zn2+ > Cu2+ > Cd2+. At a coffee ground dosage of 10g/l, and pH of 5, 80.2% 80%, 75% and 60.6% of the respective metal ions were adsorbed. Adsorption was best at intermediate pH characteristic of industrial waste waters.