title: Removal of aqueous lead ions by hydroxyapatites: equilibria and kinetic processes.
abstract: The capacity of hydroxyapatite (HAp) to remove lead from aqueous solution was investigated under different conditions, namely initial metal ion concentration and reaction time. The sorption of lead from solutions containing initial concentrations from 0 to 8000 mg/L was studied for three different HAp powders. Soluble Pb and Ca monitoring during the experiment allows characterizing the mechanism of lead uptake. Dissolution of calcium is followed by the formation of a solid solution, Pb(x)Ca(10-x)(PO4)6(OH)2, with a Ca/P ratio decreasing continuously. Langmuir-Freundlich classical adsorption isotherms modeled adsorption data. The adsorption capacities calculated from this equation vary from 330 to 450 mg Pb/g HAp for the different solids. Modeling of the sorption process allows to determine theoretical saturation times and residual lead concentrations at equilibrium.
authors.affiliation: Laboratoire de Génie des Procédés des Solides Divisés, UMR 2392, Ecole des Mines d'Albi-Carmaux, Campus Jarlard, Route de Teillet, 81 013 Albi CT Cedex 09, France.
authors.forename: Baillez
authors.initials: B
authors.lastname: Sandrine
authors.forename: Nzihou
authors.initials: N
authors.lastname: Ange
authors.forename: Bernache-Assolant
authors.initials: BA
authors.lastname: Didier
authors.forename: Champion
authors.initials: C
authors.lastname: Eric
authors.forename: Sharrock
authors.initials: S
authors.lastname: Patrick
mesh_terms: D006882:Hydroxyapatites / Q000737:chemistry*; D007700:Kinetics; D007854:Lead / Q000737:chemistry*
chemical_list: D006882:Hydroxyapatites; D007854:Lead