EXAFS Studies on Adsorption Microscopic Structures of Zn at Manganite-Water Interaface and δ-MnO2-Water Interaface

  • Microscopic structures of Zn(Ⅱ) surface complexes adsorbed at the manganite-water interface and δ-MnO2 water interface (in a 0.1M NaNO3 solution at 25°C )were studied using extended X-ray absorption fine structure (EXAFS) spectroscopy.Quantitative analysis of the EXAFS spectra showed that Zn(Ⅱ) was adsorbed onto the solid surface by sharing the oxygen atom in the hydrous Zn2+ ions and in the structural unit MnO6 on the manganite surface at pH7.5. Most of the adsorbed Zn(Ⅱ) was in the form of octahedral Zn(H2O)62+,but part of Zn(Ⅱ) was adsorbed as tetrahedral Zn(OH)2 or Zn(OH)42-.The average Zn-O bond length was 2.00±0.01A.EXAFS analysis of the second sphere indicated that Zn(Ⅱ) adsorbed on the manganite resulted in two Zn-Mn atomic distances of 3.08±0.02A and 3.54±0.02A,corresponding to the edge-linkage(stronger adsorption site) and corner-linkage(weaker adsorption site),respectively.The ZnO polyhedron was linked to the octahedron MnO6 of the manganite in these two modes by sharing two O atoms on the edges of the polyhedral and/or one O atom on the corners of the polyhedral.At pH 5.50,Zn(Ⅱ) was adsorbed onto δ-MnO2 surface in the form of octahedral hydrous Zn2+ ions.The octahedral Zn2+ was linked to the structural unit of octahedral MnO6 of the δ-MnO2 surface by sharing the O atoms.The average bond length of RZn-O was 2.07±0.01A and the Zn-Mn atomic distance was 3.53±0.01A,which corresponded to a corner-sharing linkage adsorption mode(weaker adsorption).Macroscopic adsorption-desorption isotherm experiments showed that,in contrast to that of Zn manganite,adsorption of Zn(Ⅱ) on δ-MnO2 was highly reversible and no apparent adsorption hysteresis was observed.EXAFS results indicated that the adsorption reversibility was corresponded to the corner sharing linkage mode or edge sgaring linkage mode between the adsorbate and adsorbent polyhedra.
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  • [1] Comans R N J, Van Dijik C P J. Nature, 1988, 336: 151-1542 PAN G , Krom M D, Hert B. Environ. Sci. Technol. , 2002, 36: 3519-25243 PAN G, Liss P S. J. Colloid Interface Sci. , 1998 ,201 : 77-854 PAN Gang, QIN Yan-Wen, LI Xian-Liang et al. Chinese Journal of Environmental Science, 2003 , 24 (3 ) : 1-7 ( in Chinese) (潘纲,秦延文.李贤良等.环境科学,2003 , 24 ( 3 ) ; 1-7 )5 PAN Gang, LI Xian-Liang, QIN Yan-Wen et al. Chinese Journal of Environmental Science, 2003, 24 (4) :54-59 ( in Chinese) (潘纲,李贤良,秦延文等.环境科学,2003, 24(4):54-59 )6 PAN G,QIN Y W,LI X L et al. J. Colloid Tnterface Sci. (in press)7 LI X T.,PAN G, QIN Y W et al. J. Colloid Tnterface Sci. (in press)8 PAN G, Liss P S. J. Colloid lnterface Sci. ,1998,201 : 71-779 Pavlov M, Sieghahn P E M, Sandstronm M. J. Phys. Chem. A,1998, 102: 219-22810 Bochatay L, Persson P. J. Colloid Interface Sci. , 2000, 229 :593-59911 Munoa-Paez A, Diaa S, Perez P J el al. Physica B , 1995,208209: 395-39712 Mokili B, Charreire Y, Corks R el al. Thin Solid Films, 1996,288:21-2813 Bochatay L, Persson P, Sjoherg S. J. Colloid Inlerlace Sci. , 2000,229: 584-59214 Manceau A, Schlegel M L, Musso M el al. Geochim. Cosniochim.Acta, 2000, 64(21) : 3643-366115 Manceau A, Nagy K L, Spadini L. et al. J. Colloid lnterface Sci. ,2000,228 : 306-31616 Baes C F, Mesmer R E. The Hydrolysis of Cations. Wiley, New York , 1976. 287-29317 Trainor T P, Jr Brown C E, Parks C A. J. Colloid Inlerlace Sci. ,2000, 231 : 359-37218 Sarrel G, Manceau A, Haaemann J L el al. J. Phys. IV France,1997, 7 :799-80219 Giovanoli R, Stahli E, Feilknecht W. Helv. Chim. Acta, 1970,53 :209-22020 Post J E, Vehlen D R. Am. Miner. , 1990,75: 477-48921 ChristopherJ M , Evert J E , Donald L S. Environ. Sci. Technol. ,2001, 35 ( 14 ) : 2967-297222 Hayes K F,Roe A L,Brown G E et al. Science, 1987,238:783-786
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LI Xian-Liang, PAN Gang, QIN Yan-Wen, HU Tian-Dou, WU Zi-Yu, XIE Ya-Ning, CHEN Hao and DU Yong-Hua. EXAFS Studies on Adsorption Microscopic Structures of Zn at Manganite-Water Interaface and δ-MnO2-Water Interaface[J]. Chinese Physics C, 2003, 27(S1): 23-27.
LI Xian-Liang, PAN Gang, QIN Yan-Wen, HU Tian-Dou, WU Zi-Yu, XIE Ya-Ning, CHEN Hao and DU Yong-Hua. EXAFS Studies on Adsorption Microscopic Structures of Zn at Manganite-Water Interaface and δ-MnO2-Water Interaface[J]. Chinese Physics C, 2003, 27(S1): 23-27. shu
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EXAFS Studies on Adsorption Microscopic Structures of Zn at Manganite-Water Interaface and δ-MnO2-Water Interaface

    Corresponding author: LI Xian-Liang,
  • state Key Laboratory of Environmental Aquatic Chemistry,Research center for Eco-Environmental Sciences,CAS,Beijing 100085,China2 Qingdao University of Science and Technology,Qingdao 266042,China3 Institute of High Energy Physics,CAS,Beijing 100039,China

Abstract: Microscopic structures of Zn(Ⅱ) surface complexes adsorbed at the manganite-water interface and δ-MnO2 water interface (in a 0.1M NaNO3 solution at 25°C )were studied using extended X-ray absorption fine structure (EXAFS) spectroscopy.Quantitative analysis of the EXAFS spectra showed that Zn(Ⅱ) was adsorbed onto the solid surface by sharing the oxygen atom in the hydrous Zn2+ ions and in the structural unit MnO6 on the manganite surface at pH7.5. Most of the adsorbed Zn(Ⅱ) was in the form of octahedral Zn(H2O)62+,but part of Zn(Ⅱ) was adsorbed as tetrahedral Zn(OH)2 or Zn(OH)42-.The average Zn-O bond length was 2.00±0.01A.EXAFS analysis of the second sphere indicated that Zn(Ⅱ) adsorbed on the manganite resulted in two Zn-Mn atomic distances of 3.08±0.02A and 3.54±0.02A,corresponding to the edge-linkage(stronger adsorption site) and corner-linkage(weaker adsorption site),respectively.The ZnO polyhedron was linked to the octahedron MnO6 of the manganite in these two modes by sharing two O atoms on the edges of the polyhedral and/or one O atom on the corners of the polyhedral.At pH 5.50,Zn(Ⅱ) was adsorbed onto δ-MnO2 surface in the form of octahedral hydrous Zn2+ ions.The octahedral Zn2+ was linked to the structural unit of octahedral MnO6 of the δ-MnO2 surface by sharing the O atoms.The average bond length of RZn-O was 2.07±0.01A and the Zn-Mn atomic distance was 3.53±0.01A,which corresponded to a corner-sharing linkage adsorption mode(weaker adsorption).Macroscopic adsorption-desorption isotherm experiments showed that,in contrast to that of Zn manganite,adsorption of Zn(Ⅱ) on δ-MnO2 was highly reversible and no apparent adsorption hysteresis was observed.EXAFS results indicated that the adsorption reversibility was corresponded to the corner sharing linkage mode or edge sgaring linkage mode between the adsorbate and adsorbent polyhedra.

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