Chinese Acad Sci, State Key Lab Environm Aquat Chem, Ecoenvironm Sci Res Ctr, Beijing 100085, Peoples R China
; Chinese Acad Sci, Inst High Energy Phys, Beijing Synchrotron Radiat Facil, Beijing 100039, Peoples R China
Mechanisms of adsorption and precipitation of Zn (II) on gamma-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 0.202nm, 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, Zn 21 was adsorbed on (110) or (001) plane of gamma-MnOOH by edge linkage mode, which corresponded a Zn-Mn distance of similar to 0.300 nm. At pH 7.50 and 8.00, most Zn(11) 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.