Sélectivité des écailles de cacao pour l'enlèvement des métaux des effluents de décontamination de sols

Washing using inorganic acids is a common method for treatment of metal-polluted soils. Metals solubilized during soil washing have to be removed from washing solutions (leachates). The purpose of this research was to evaluate the efficiency and the selectivity of cocoa shells to adsorb metals contained in acid leachates of soil decontamination. Shake flask experiments were done using 15 g/L of cocoa shells and a doped (addition of 100 and 300 mg metal/L) acid leachate (pHi = 2.4) using 1 or 10 metal salts. These tests have revealed that this natural sorbent is particularly efficient to remove lead and, to a lesser degree, copper from solution. A maximal lead concentration of 17 900 mg/kg, corresponding to 75 % of lead removal, has been adsorbed on cocoa shells during tests using a soil leachate doped with 300 mg Pb/L. This research also showed that cocoa shell selectivity generally follows this order: Pb >> Cu >> Fe > Al > Cr >> Co > Zn > Mn > Cd > Ni. Kinetic studies over a 24-h period have indicated th...