Adsorption op cadmium and chromium from wastewater by flyash

Abstract
The removal of cadmium and chromium from wastewater by adsorption on fly ash was investigated to determine the effects of contact time, pH, and temperature. Removals of cadmium and chromium attained an equilibrium in three hours. The alkaline (pH 7 to 8) aqueous medium favoured the removal of cadmium by fly ash, while chromium removal was maximum in the pH range of 2.0 to 3.0. Batch adsorption experiments conducted at 5°C, 10°C, and 21°C showed that adsorption capacity of fly ash with respect to cadmium and chromium decreased with an increase in temperature. The data for the adsorption of cadmium by fly ash fitted well the Langmuir isotherm while the removal of chromium by fly ash followed generally the Freundlich isotherm. The maximum removals of cadmium and chromium by fly ash were 93% and 44% respectively.