ADSORPTION STUDIES ON THE REMOVAL OF HEXAVALENT CHROMIUM AND LEAD FROM CONTAMINATED WASTEWATER USING LEAVES OF WATER HYACINTH AS AN ADSORBENT

Present of heavy metals in the aquatic system has become a serious problem. As a result, there has a great deal of attention give to new technologies for removal of heavy metal ions from contaminated waters. Biosorption is one such emerging technology which utilized naturally occurring waste materials to sequester heavy metals from industrial wastewater. The wastewater containing hexavalent chromium and lead was treated with biomass prepared from water hyacinth leaves. It was found that a time of 2 hrs was sufficient for sorption to attain equilibrium. The equilibrium sorption capacity after 2 hrs was 18 mg/L and 15 mg/L for lead and chromium, respectively. The optimum pH was 5 for lead and 2 for chromium. Temperature has strong influence on biosorption process. The removal of lead decreased with increase in temperature. On the other hand, chromium removal increased with increasing in temperature up to 400C and then started decreasing. Ion exchange was the major removal mechanism along with physical sorption and precipitation. Equilibrium data were analyzed by Langmuir and Freundlich isotherm models and the biosorption data were well fitted to Freundlich isotherm model. It was concluded that adsorbent prepared from water hyacinth leaves can be utilized for the treatment of lead and chromium in wastewater. The water hyacinth leaves can be possible recycled by washes with 0.5 N NaOH solution then with tap water several times to get rid of metals. These results introduce applicable technique for removal heavy metal ions from contaminated waters resulted from industrial activities and