Chromium removal on chitosan-based sorbents - An EXAFS/XANES investigation of mechanism
Chromium removal on chitosan-based sorbents - An EXAFS/XANES investigation of mechanism
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DOI：
10.1016/j.matchemphys.2014.03.046
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发表时间：
2014-08
影响因子：
4.6
通讯作者：
R. Vieira;E. Meneghetti;P. Baroni;E. Guibal;V. Cruz;A. Caballero;E. Rodriguez-castellon;M. Beppu
中科院分区：
文献类型：
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作者：
R. Vieira;E. Meneghetti;P. Baroni;E. Guibal;V. Cruz;A. Caballero;E. Rodriguez-castellon;M. Beppu
已知壳聚糖是含金属离子的良好吸附剂，因为氨基和羟基官能团的存在充当有效结合位点。它的交联，采用戊二醛或环氧氯丙烷，可能会改变这种生物聚合物的吸附性能（吸附容量或扩散性能），因为可用的官能团在每种情况下是不同的。利用X射线吸收光谱（XAS），包括扩展X射线吸收精细结构（EXAFS）和X射线吸收近边结构（XANES），傅立叶变换红外光谱衰减全反射装置（FTIR-ATR），沿着形态图，研究了土壤对铬酸盐的吸附机理。在原始壳聚糖和表氯醇交联壳聚糖膜中，氨基最有可能负责吸附，尽管不能排除羟基的贡献（特别是对于金属吸附剂稳定）。在这种情况下，当被吸附时，约70%的铬酸根离子保持在Cr（VI）氧化态。在戊二醛交联膜的情况下，所涉及的官能团是不同的。由交联剂和氨基反应产生的羰基和亚氨基键可能参与吸附机制。此外，较高分数的铬酸根阴离子，约44%，在负载的吸附剂中还原为Cr（III）氧化态。游离醛基的存在可以解释这种部分还原。
Chitosan is known to be a good sorbent for metal-containing ions as the presence of amino groups and hydroxyl functions act as effective binding sites. Its crosslinking, employing glutaraldehyde or epichlorohydrin, may change the sorption properties (sorption capacity or diffusion properties) of this biopolymer, since the available functional groups are different in each case. X-ray absorption spectroscopy (XAS), including extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES), Fourier-transformed infrared spectroscopy with attenuated total reflectance device (FTIR-ATR) was used along with speciation diagrams, in order to identify the binding groups involved in chromate sorption and its mechanisms. In pristine chitosan and epichlorohydrin-crosslinked chitosan membranes, amino groups are most likely responsible for adsorption, although the contribution of hydroxyl groups cannot be excluded (especially for metal-sorbent stabilization). In this case, when adsorbed about 70% of chromate ions remain in the Cr(VI) oxidation state. In the case of glutaraldehyde-crosslinked membranes, the functional groups involved are different. Carbonyl groups and imino bonds – resulting from the reaction of the crosslinking agent and amino groups – may be involved in the adsorption mechanism. Additionally, a higher fraction of chromate anions, around 44% are reduced to Cr(III) oxidation state in loaded sorbent. The presence of free aldehyde groups may explain this partial reduction.