Acta Phys. -Chim. Sin. ›› 2005, Vol. 21 ›› Issue (10): 1169-1173.doi: 10.3866/PKU.WHXB20051022

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EXAFS Study of Zn (II) Adsorption and Precipitation on γ-MnOOH Surface under Different pH Conditions

ZHU Meng-qiang; PAN Gang; LI Xian-liang; LIU Tao; YANG Yu-huan   

  1. State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco- Environmental Sciences, Chinese Academy of Sciences, Beijing 100085; Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039
  • Received:2005-03-03 Revised:2005-04-19 Published:2005-10-15
  • Contact: PAN Gang

Abstract: Mechanisms of adsorption and precipitation of Zn(II) onγ-MnOOH-water interfaces at pH 7.00, 7.50 and 8.00 were studied using EXAFS (extended X-ray absorption fine structure). The Zn—O distance for adsorbed Zn(II) was 0.202 nm, which did not change when pH increased from 7.00 to 8.00. This result implied that Zn2+ was adsorbed as a mixture of tetrahedron and octahedron. At pH 7.00, Zn2+ was adsorbed on (110) or (001) plane of γ-MnOOH by edge linkage mode, which corresponded a Zn—Mn distance of ~0.300 nm. At pH 7.50 and 8.00, most Zn(II) was precipitated as multinuclear hydroxo-complexes with similar structures where the Zn—Zn distances were 0.353 nm (tetrahedron-octahedron linkage) and 0.311 nm (octahedron-octahedron linkage), respectively.

Key words: Zn(II), Adsorption, Precipitation, γ-MnOOH, EXAFS