Suksabye Parinda, Nakajima Akira, Thiravetyan Paitip, Baba Yoshinari, Nakbanpote Woranan
The Joint Graduate School of Energy and Environment, King Mongkut's University of Technology Thonburi, 91 Pracha-Utit Road, Bangmod, Thungkru, Bangkok 10140, Thailand.
J Hazard Mater. 2009 Jan 30;161(2-3):1103-8. doi: 10.1016/j.jhazmat.2008.04.064. Epub 2008 Apr 23.
The oxidation state of chromium in coir pith after Cr(VI) adsorption from aqueous solution was investigated using electron spin resonance (ESR). To elucidate the mechanism of chromium adsorption on coir pith, the adsorption studies of Cr(VI) onto lignin, alpha-cellulose and holocellulose extracted from coir pith were also studied. ESR signals of Cr(V) and Cr(III) were observed in coir pith adsorbed Cr(VI) at solution pH 2, while ESR spectra of lignin extracted from coir pith revealed only the Cr(III) signal. In addition, ESR signal of Cr(V) was observed in alpha-cellulose and holocellulose extracted from coir pith adsorbed Cr(VI). These results confirmed that lignin in coir pith reduced Cr(VI) to Cr(III) while alpha-cellulose and holocellulose extracted from coir pith reduced Cr(VI) to Cr(V). The Cr(V) signal exhibited in ESR of alpha-cellulose and holocellulose might be bound with glucose in cellulose part of coir pith. In addition, xylose which is main in pentosan part of coir pith, indicated that it is involved in form complex with Cr(V) on coir pith. The adsorption kinetic of Cr(VI) from aqueous solution on coir pith was also investigated and described well with pseudo second order model. ESR and desorption experiments confirmed that Cr(VI), Cr(V) and Cr(III), exist in coir pith after Cr(VI) adsorption. The desorption data indicated that the percentage of Cr(VI), Cr(V) and Cr(III) in coir pith were 15.63%, 12.89% and 71.48%, respectively.
利用电子自旋共振（ESR）研究了椰壳髓吸附水溶液中Cr(VI)后铬的氧化态。为阐明椰壳髓对铬的吸附机制，还研究了从椰壳髓中提取的木质素、α-纤维素和全纤维素对Cr(VI)的吸附。在溶液pH值为2时，椰壳髓吸附Cr(VI)中观察到了Cr(V)和Cr(III)的ESR信号，而从椰壳髓中提取的木质素的ESR光谱仅显示Cr(III)信号。此外，在从椰壳髓中提取的吸附了Cr(VI)的α-纤维素和全纤维素中观察到了Cr(V)的ESR信号。这些结果证实，椰壳髓中的木质素将Cr(VI)还原为Cr(III)，而从椰壳髓中提取的α-纤维素和全纤维素将Cr(VI)还原为Cr(V)。α-纤维素和全纤维素的ESR中显示的Cr(V)信号可能与椰壳髓纤维素部分的葡萄糖结合。此外，椰壳髓戊聚糖部分中的主要成分木糖表明它参与了在椰壳髓上与Cr(V)形成络合物。还研究了水溶液中Cr(VI)在椰壳髓上的吸附动力学，并用伪二级模型很好地进行了描述。ESR和解吸实验证实，吸附Cr(VI)后椰壳髓中存在Cr(VI)、Cr(V)和Cr(III)。解吸数据表明，椰壳髓中Cr(VI)、Cr(V)和Cr(III)的百分比分别为15.63%、12.89%和71.48%。
