Water Science & Technology Vol 65 No 10 pp 1729–1737 © IWA Publishing 2012 doi:10.2166/wst.2012.183

The sorption of lead, cadmium, copper and zinc ions from aqueous solutions on a raw diatomite from Algeria

Messaouda Safa, Mohammed Larouci, Boumediene Meddah and Pierre Valemens

The adsorption of Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ ions from aqueous solution by Algerian raw diatomite was studied. The influences of different sorption parameters such as contact pH solution, contact time and initial metal ions concentration were studied to optimize the reaction conditions. The metals ions adsorption was strictly pH dependent. The maximum adsorption capacities towards Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ were 0.319, 0.311, 0.18 and 0.096 mmol g⁻¹, respectively. The kinetic data were modelled using the pseudo-first-order and pseudo-second-order kinetic equations. Among the kinetic models studied, the pseudo-second-order equation was the best applicable model to describe the sorption process. Equilibrium isotherm data were analysed using the Langmuir and the Freundlich isotherms; the results showed that the adsorption equilibrium was well described by both model isotherms. The negative value of free energy change ΔG indicates feasible and spontaneous adsorption of four metal ions on raw diatomite. According to these results, the high exchange capacities of different metal ions at high and low concentration levels, and given the low cost of the investigated adsorbent in this work, Algerian diatomite was considered to be an excellent adsorbent.

Keywords: adsorption; diatomite; heavy metals; kinetics

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