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

Abstract

The removal of copper (II) and cadmium (II) ions from aqueous solutions, by adsorption on activated carbon prepared from rice hulls (ACRH); was investigated depending on pH, activated carbon dosage, contact time, initial metal concentration and solution temperature. The optimum values of pH, ACRH dosage 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. From the initial concentrations, the constants for the Freundlich and Langmuir isotherm were calculated at 293 K and 313 K. The adsorption of Cu (II) and Cd (II) ions from aqueous solutions was found to be exothermic [Delta H degrees=-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 Delta S degrees, were also calculated at 293 K and 313 K.