Adsorption of cadmium(II) ions from aqueous solution onto kaolinite and metakaolinite

Abstract

The removal of cadmium(II) ions from aqueous solution by adsorption on kaolinite (KAO.1) and metakaolinite (MKB) was investigated depending on the initial concentration, adsorbents dosage, initial pH of solution, and contact time.The influences of those factors have been experimentally verified by a batch method at (27±3 °C).These results have showed that the amount of cadmium(II) ions adsorbed increases with increased contact time and that equilibrium adsorption is reached in 10 minutes, the optimum value of pH was 8.0 and the effect of absorbent dose for the uptake of cadmium(II) ions by kaolinite and metakaolinite was found to decrease by increasing the adsorbent dose.The experimental results obtained are described by Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich (D-K-R) isotherm models.The Langmuir and D-K-R adsorption isotherms described the adsorption data very well.The maximum adsorption capacity; Q max , determined from the Langmuir adsorption isotherm studies was found to be 7.407 and 9.174 mg/g for KAO.1 and MKB respectively.Pseudo-first order, pseudo-second order, Elovich and the intraparticular diffusion kinetic models were used to describe the kinetic data obtained.The experimental data fitted well to the pseudo-second order kinetic model, which indicates that 12 Jean Serge ESSOMBA et al.chemical adsorption is the rate-limiting step.The results indicate that kaolinite and metakaolinite adsorb cadmium(II) ions efficiently and could be employed as a low-cost alternative in waste water treatment for the elimination of cadmium(II) ions.