Abstract
Desilicated fly ash (DFA), the residue from leaching of silica from fly ash, was used as an adsorbent for metals from acid mine drainage (AMD). DFA was found to be an impure phillipsite K zeolite. Batch adsorption experiments were carried out using a thermoshaker. A 0.6% m/v solid loading of DFA removed over 95% of Mn, Al and Cu from AMD. The adsorption process followed the Langmuir adsorption isotherm model and pseudo second order kinetics. The maximum adsorption capacities for Mn, Al and Cu were 14.3, 7.1 and 7.6 mg/g respectively at 25°C. The adsorption of Mn, Al and Cu onto DFA was found to be endothermic and with a positive entropy energy. The Gibbs free energy for the adsorption was found to be -1.7, -7.0 and -11.2 kJ/mol for Mn, Al and Cu. The preference for adsorption was found to be Cu>Al>Mn.