title: [Competitive adsorption kinetics of aqueous Pb2+ and Cu2+ on nano-HAP surfaces].
abstract: Competitive adsorption kinetics of aqueous Pb2+ and Cu2+ on Nano-HAP surfaces were investigated by performing the adsorption kinetic experiments and comparing the change of zeta potentials and XRD-map before and after metal adsorption. The results showed that the adsorption quantity of Pb2+ on Nano-HAP was higher than that of Cu2+ in the single system. However, the competitive adsorption of Pb2+ and Cu2+ occurred in the co-existence system of Pb2+ and Cu2+. The adsorption quantity of Cu2+ on Nano-HAP increased, while that of Pb2+ decreased. The X-ray diffraction (XRD) and adsorption quantities of Ca2+ surface analysis indicated that dissolution-precipitation is the primary immobilization mechanism for Pb2+, while surface complexation and electrostatic adsorption account for Cu2+ sequestration. The adsorption quantities of Pb2+ and Cu2+ on Nano-HAP had marked linear relationship with Ca2+ release from Nano-HAP (R2 0.861-0.954). The adsorption kinetics were fitted with the equations of first-order, second-order, parabola, Elovich, double constant equation and LJ function, respectively, in which the second-order and power function kinetics equation fitted the results best. According to above results, the adsorption kinetics of Pb2+ and Cu2+ on Nano-HAP is a complex adsorption processes with both chemical reaction and physical adsorption.
authors.affiliation: College of Resources and Environmental Sciences, Anhui Agricultural University, Hefei 230036, China. hutt871225@hotmail.com
authors.forename: Tian-tian
authors.initials: TT
authors.lastname: Hu
authors.forename: Long
authors.initials: L
authors.lastname: Cang
authors.forename: Yu-jun
authors.initials: YJ
authors.lastname: Wang
authors.forename: You-bin
authors.initials: YB
authors.lastname: Si
authors.forename: Dong-mei
authors.initials: DM
authors.lastname: Zhou
mesh_terms: D000327:Adsorption; D003300:Copper / Q000302:isolation & purification*; D017886:Durapatite / Q000737:chemistry*; D007700:Kinetics; D007854:Lead / Q000302:isolation & purification*; D053758:Nanoparticles / Q000737:chemistry*; D013499:Surface Properties; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*
chemical_list: D014874:Water Pollutants, Chemical; D007854:Lead; D003300:Copper; D017886:Durapatite