Acta Chimica Sinica ›› 2012, Vol. 70 ›› Issue (07): 929-937 .DOI: 10.6023/A1108242 Previous Articles     Next Articles

Full Papers


李克斌a, 王勤勤a, 党艳a, 魏红b, 罗倩a, 赵锋a   

  1. a 西北大学化学与材料科学学院/合成与天然功能分子化学教育部重点实验室 西安 710069;
    b 西安理工大学市政与环境工程系 西安 710048
  • 投稿日期:2011-08-24 修回日期:2011-11-28 发布日期:2011-12-27
  • 通讯作者: 李克斌
  • 基金资助:

    陕西省教育厅科学研究计划项目(No. 09JK757)、西北大学科研实验类项目(No. 10YSY07)和国家自然科学基金项目(No. 51009115)资助项目.

Characteristic and Mechanism of Cr(VI) Biosorption by Buckwheat Hull from Aqueous Solutions

Li Kebina, Wang Qinqina, Dang Yana, Wei Hongb, Luo Qiana, Zhao Fenga   

  1. a Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, School of Chemistry and Materials Science, Northwest University, Xi'an 710069;
    b Department of Municipal and Environmental Engineering, Xi'an University of Technology, Xi'an 710048
  • Received:2011-08-24 Revised:2011-11-28 Published:2011-12-27
  • Supported by:

    Project supported by the Scientific Research Plan Projects of Education Department of Shaanxi Province (No. 09JK757), the Experiment Project of Scientific Research of Northwestern University (10YSY07), and the National Natural Science Foundation of China (51009115).

Buckwheat hull, an agricultural industry waste, was used as a novel biosorbent to remove hexavalent chromium from water. The absorption kinetics was investigated by measuring the change of Cr(VI) and total chromium concentration with time. It showed that the removal of Cr(VI) by buckwheat hull followed the pseudo-second-order adsorption kinetics. Effects of pH, biosorbent dosage and initial concentration of Cr(VI) on its adsorption removal were also examined in the batch mode. The results showed that the buckwheat hull was very effective for removing Cr(VI) from water. At pH 2.0, load of 5.0 g·L-1, buckwheat hull could almost completely remove Cr(VI) (99.87% of 100 mg·L-1) from water. The removal of Cr(VI) increased with the decrease of solution pH values, and the maximum percentage removal was attained at pH 2.0. Increase of adsorbent dosage would raise the removal efficiency, while it would simultaneously reduce the adsorption capacity. Moreover, the removal of Cr(VI) was found to decrease with rising the initial concentration of Cr(VI). Whereas, the Cr(VI) uptake capacity increased with the rise of Cr(VI) concentration until reaching saturation, which was found to be about 36.4 mg·g-1 at pH 2.0, temperature of 20 ℃ and adsorbent dose of 5.0 g·L-1. In addition, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX) analyses were employed to characterize buckwheat hull, and further to elucidate the mechanisms involved at the molecular level. SEM revealed that the buckwheat hull is a porous material, while FT-IR and XPS displayed that the biomass possess many active groups such as hydroxyl, carboxyl, and amino groups. The removal of Cr(VI) by the buckwheat hull was found to be a adsorption-coupled reduction process based on XPS analysis and batch experiments. Finally, the mechanisms of chromate anions removal from water by the buckwheat hull were proposed, which included adsorption of Cr(VI) onto buckwheat hull followed by the partial reduction to Cr(III). The reduced Cr(III) was rebound to the biomass mainly through the complexation and ion-exchange mechanisms.

Key words: buckwheat hull, biosorption, Cr(VI), adsorption mechanism, XPS