title: Co-sequestration of Zn(II) and phosphate by γ-Al2O3: From macroscopic to microscopic investigation.
abstract: Little information is available concerning co-sorbing oxyanion and metal contaminants in the environment, yet in most metal-contaminated areas, co-contamination by phosphate is common. In this study, the mutual effects of phosphate and Zn(II) on their interaction with γ-Al2O3 are investigated by batch experiments and X-ray absorption fine structure spectroscopy (XAFS) technique. The results show that the co-sorption of phosphate on γ-Al2O3 modifies both the extent of Zn(II) sorption and the local atomic structures of sorbed Zn(II) ions. Multiple mechanisms are involved in Zn(II) retention in the presence of phosphate, including electrostatic interaction, binary and ternary surface complexation, and the formation of Zn(II)-phosphate polynuclear complexes. At pH 6.5, type III ternary surface complexation occurs concurrently with binary Zn-alumina surface complexation at low phosphate concentrations, whereas the formation of type III ternary surface complexes is promoted as the phosphate concentration increases. With further increasing phosphate concentration, Zn(II)-phosphate polynuclear complexes are formed. At pH 8.0, Zn dominantly forms type III ternary surface complexes in the presence of phosphate. The results of this study indicate the variability of Zn complexation on oxide surface and the importance of combining macroscopic observations with XAFS capable of determining metal complex formation mechanism for ternary system.
authors.affiliation: School of Environment and Chemical Engineering, North China Electric Power University, Beijing 102206, PR China; Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, 230031, Hefei, PR China.
authors.forename: Xuemei
authors.initials: X
authors.lastname: Ren
authors.affiliation: Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, 230031, Hefei, PR China.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Tan
authors.affiliation: Department of Mathematics, Quaid-I-Azam University, Islamabad 44000, Pakistan; NAAM Research Group, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
authors.forename: Tasawar
authors.initials: T
authors.lastname: Hayat
authors.affiliation: NAAM Research Group, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Alsaedi
authors.affiliation: School of Environment and Chemical Engineering, North China Electric Power University, Beijing 102206, PR China; NAAM Research Group, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia; Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, PR China. Electronic address: xkwang@ipp.ac.cn.
authors.forename: Xiangke
authors.initials: X
authors.lastname: Wang
mesh_terms: D000327:Adsorption; D000537:Aluminum Oxide / Q000737:chemistry*; D004785:Environmental Pollutants / Q000737:chemistry* / Q000302:isolation & purification; D006863:Hydrogen-Ion Concentration; D008962:Models, Theoretical; D010710:Phosphates / Q000737:chemistry* / Q000302:isolation & purification; D012996:Solutions; D055672:Static Electricity; D013499:Surface Properties; D056928:X-Ray Absorption Spectroscopy; D017967:Zinc Compounds / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D004785:Environmental Pollutants; D010710:Phosphates; D012996:Solutions; D017967:Zinc Compounds; D000537:Aluminum Oxide
keywords: Addition sequences; Co-sorption mechanism; Phosphate; XAFS; Zn(II)