Reaction mechanism of hexavalent chromium with cellulose, hemicellulose, chitin and lignin

• Main Authors: Yu-Chi Lin, 林郁錡
• Other Authors: Shan-Li Wang
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/35574396001622202844

碩士 === 國立中興大學 === 土壤環境科學系所 === 98 === Biomaterials and their degraded derivatives in nature (i.e., natural organic matter, NOM) play a critical role in reducing toxic Cr(VI) to less toxic Cr(III) in the environment. Because of the complicated compositions of these materials, the mechanism of Cr(VI) reaction with these materials have not been fully understood. Therefore, the aims of this work were to investigate the reaction mechanisms of Cr(VI) with cellulose, hemicellulose, chitin and lignin, which are the major components of NOM and biomaterials. The materials before and after Cr(VI) reaction were analyzed using FTIR and Cr K-edge XAS to identify the functional groups governing Cr(VI) reduction and the oxidation state and local structure of Cr bound to the materials, respectively. The results showed that the Cr(VI) was sorbed and reduced to Cr(III) on the surfaces of hemicellulose, chitin and lignin, while sorption and reduction of Cr(VI) on cellulose were not noticeable. The Cr K-edge XAS results indicated that Cr(III) resulting from Cr(VI) reduction is bound to the surfaces through surface complexation and precipitation. The reaction of the materials with Cr(VI) resulted in the formation of carbonyl and carboxyl groups on the surfaces of these materials, which subsequently provide binding sites for the resultant Cr(III). The results of this work will be helpful in clarifying the mechanisms of Cr(VI) reactions with NOM and biomaterials and understanding the roles of these materials in the fate of Cr(VI) in the environment.