Influence of chemical compositions and molecular weights of humic acids on Cr(VI) photo-reduction

JOURNAL OF HAZARDOUS MATERIALS

卷:197

Article

Chen, S. Y.¹  Huang, S. W.¹  Chiang, P. N.²  Liu, J. C.³  Kuan, W. H.⁴  Huang, J. H.¹  Hung, J. T.⁵  Tzou, Y. M.¹  Chen, C. C.⁶  Wang, M. K.⁷ 

[1] Natl Chung Hsing Univ, Dept Soil & Environm Sci, Taichung 40227, Taiwan

[2] Natl Taiwan Univ, Nantou 55743, Taiwan

[3] Agr Res Inst, Wufong 41301, Taichung County, Taiwan

[4] Ming Chi Univ Technol, Dept Safety Hlth & Environm Engn, Taipei 24301, Taiwan

[5] Natl Taitung Jr Coll, Dept Hort, Taitung 95045, Taiwan

[6] Natl Taiwan Normal Univ, Dept Life Sci, Taipei 116, Taiwan

[7] Natl Taiwan Univ, Dept Agr Chem, Taipei 10617, Taiwan

关键词: Humic acid;    Molecular weight;    Chromate;    Photo-reduction;    Fractionation;   

DOI  :  10.1016/j.jhazmat.2011.09.091

来源: Elsevier

【 摘 要 】

Humic acids (HA) strongly affect the fate of trace metals in soils and aquatic environments. One of the remarkable properties of HA is its ability to reduce Cr(VI), an extremely toxic anion. However, it is unclear which HA components are involved in Cr(VI) reduction and possess the photo-induced properties. In this study, an ultrafiltration technique was used to fractionate HAs into four fractions of different nominal molecular weights (M-w): >100.50-100, 10-50 and <10 kDa. Each HA fraction was characterized by spectroscopic analyses followed by examining Cr(VI) removal on each fraction of HA at pH 1-5. Spectroscopic results indicated that low-M-w HA was enriched with polar and aromatic domains. These polar, including polar C in aliphatic region, and aromatic groups were the major sites for Cr(VI) reduction because they disappeared rapidly upon interaction with Cr(VI). As a result, low M-w of HA exhibited greater efficiency of Cr(VI) reduction. Light induced the rapid transfer of electrons between chromate-phenol/carboxyl ester, or the formation of peroxide radicals or H2O2 through the ready decay of peroxy radicals associated with polar substituents, explained the rapid scavenging of Cr(VI) on polar and aromatic groups of HAs under illumination. (C) 2011 Elsevier B.V. All rights reserved.

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