Elaboration of copper hydroxide phase modified diatomite and their application in lead ions immobilization

A new kind of composite material made of diatomite and deviline (CaCu4(SO4)2OH6[middle dot]3H2O) has been prepared by mixing diatomite and aqueous solutions of copper(ii) sulfate at room temperature for 8 h. X-Ray powder diffraction shows evidence for the contribution of calcium carbonate initially present in the diatomite in the formation of deviline. The formation of deviline onto diatomite surface, as observed by EDX and SEM analysis, is suggested to occur by the formation of hydrogen bonds between the surface silanol groups and cupric species. Two mechanisms of formation of deviline are suggested. Remediation properties of diatom-Cu towards Pb(ii) cations in aqueous solution were investigated. The materials have a noticeably higher Pb(ii) sorption capacity (130 mg g-1) than the native diatomite (25 mg g-1). Such a performance is attributed to the mechanism of Pb(ii) immobilization, characterized by the precipitation of the stable caledonite phase (Cu2Pb5(SO4)3(OH)6CO3) from the dissolution of deviline.