Adsorption of copper and cadmium ions by activated carbon from rice hulls

The removal of copper (II) and cadmium (II) ions from aqueous solutions, by adsorption on activated carbon prepared from rice hulls (ACRH); was invest igated depending on pH, activated carbon dosage, contact time, initial meta l concentration and solution temperature. The optimum values of pH, ACRH do sage and contact time were determined to be 5-8, 0.5 g ACRH/25 mt solution an 60 minutes respectively for the adsorption of Cu (II) ions and 5-8, 1.5 g ACRH/25 mt solution and 60 minutes for the adsorption of Cd (II) ions. Fr om the initial concentrations, the constants for the Freundlich and Langmui r isotherm were calculated at 293 K and 313 K. The adsorption of Cu (II) an d Cd (II) ions from aqueous solutions was found to be exothermic [Delta H d egrees=-13.474 KJ/mol for Cu (II) and Delta H degrees=-2.302 KJ/mol for Cd (II)]. Furthermore, the other thermodynamic data for Delta G degrees and De lta S degrees, were also calculated at 293 K and 313 K.