铝污泥吸附六价铬的特征和机理

Characteristic and mechanisms of chromium(Ⅵ) adsorption on alum sludge

铝污泥是给水处理过程中不可避免的副产物,为了解其资源化利用作为吸附剂对Cr(Ⅵ)的吸附行为和吸附特征,本研究通过静态实验研究了铝污泥的水解特征、Cr(Ⅵ)在铝污泥上的吸附机理和影响因素。结果表明,(1)铝污泥表面的主要官能团为羟基、SO24-和Cl-;(2)铝污泥与Cr(Ⅵ)的吸附过程中,液相中Cr(Ⅵ)的浓度随吸附时间延长而降低(由20 mg/L降为15.42 mg/L),同时,液相中pH由6.01升高为7.06、SO24-由8.79 mg/L升高为11.40 mg/L、Cl-由10.54 mg/L升高为11.88 mg/L,这一结果表明,HCrO4-与铝污泥表面的羟基、SO24-、Cl-等官能团交换,其吸附机理为配体交换;(3)pH是影响Cr(Ⅵ)在铝污泥上的吸附量的主要因素,当pH由4.0升高至10.0时,吸附容量由7.63 mg/g下降为0.70 mg/g。实验表明,铝污泥作为一种新型的Cr(Ⅵ)吸附剂具有较高吸附能力和应用前景,并为优化吸附工艺提供了技术支撑。

Aluminum sludge was an inevitable by-product from the processing of drinking water in water treatment works. Batch studies were performed to investigate the influences of experimental parameters such as pH of solution, contact time, and Cr （Ⅵ） concentration. The results showed that： （ 1 ） the main functional groups of the surface of aluminum sludge were-OH, SO42- , Cl- ; （2） in the adsorption process, as the concentra- tion of Cr varied from 20 mg/L to 15.42 mg/L, pH increased from 6.01 to 7.06, both of SO42- and Cl- concen- tration increased （from 8.79 mg/L to 11.40 mg/L for SO42-and from 10.54 mg/L to 11. 88 mg/L for Cl-）, which demonstrated that HCrO4- exchanged with the functional groups of aluminum sludge such as-OH, SO42- , Cl- and the adsorption mechanism was ligand exchange ; （3） pH played a major role in the adsorption capacity. The adsorption capacity decreased from 7.63 mg/g to 0.70 mg/g with an increas of pH from 4.0 to 10. O. It in- dicated that alum sludge was a promising material for the removal of phosphate from wastewater, and also could be helpful to optimize the absorption process.