Microwave-assisted Fenton-like decolorization of methyl orange solution using chromium compounds
Azo dyes discharged in the environment are persistent organic pollutants (POPs), which are very difficult to remove. We developed a microwave-assisted Fenton-like process to degrade methyl orange (MO), an azo dye, with hydrogen peroxide (H2O2) catalyzed by chromium compounds coexisting with MO in the solution. Comparison between the Cr(III)-H2O2 and Cr(VI)-H2O2 systems shows that Cr(VI) has a stronger and more stable catalytical activity than Cr(III), and Cr(III) is more susceptible to a change in the acidity or alkalinity of the reaction system. With a Cr(VI) concentration of 10 mmol L-1 or a Cr(III) concentration of 12 mmol L-1 in the solution under the microwave irradiation of a power larger than 300 W for 3 min, 10 mmol L-1 H2O2 can degrade more than 95% of 1 000 mg L-1 methyl orange; when the microwave power is increased to 700 W, the same amount of H2O2 can degrade all methyl orange in the solution with the same amount of Cr(VI) catalyst. Ultraviolet-visible spectrography indicates the cleavage of the azo bond in methyl orange after treatment, suggesting the potential of this Fenton-like process to degrade azo dye POPs. Reusing waste chromium compounds coexisting with dyestuff in wastewater to catalyze the degradation of azo dyes could be a cost-effective technique for azo dyes and chromate manufacturers and/or users to treat their wastewater and prevent POPs from endangering the environment. This is of particular importance to controlling the water quality of the Three Gorges Reservoir.
作 者： LIU Zuo-hua TAO Chang-yuan DU Jun SUN Da-gui LI Bai-zhan 作者单位： LIU Zuo-hua(College of Chemistry & Chemical Engineering, Chongqing University, Chongqing 400030, P. R. China;Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment Under the Ministry of Education, Chongqing University, Chongqing 400030, P. R. China)TAO Chang-yuan,DU Jun,SUN Da-gui(College of Chemistry & Chemical Engineering, Chongqing University, Chongqing 400030, P. R. China)
LI Bai-zhan(Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment Under the Ministry of Education, Chongqing University, Chongqing 400030, P. R. China)
刊 名： 重庆大学学报（英文版） 英文刊名： JOURNAL OF CHONGQING UNIVERSITY(ENGLISH EDITION) 年，卷(期)： 2008 7(3) 分类号： X703 关键词： wastewater treatment azo dyes microwave chromium Fenton-like decolorization persistent organic pollutant