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   作者單位： 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： 重慶大學(xué)學(xué)報(bào)（英文版）  英文刊名： JOURNAL OF CHONGQING UNIVERSITY(ENGLISH EDITION)  年，卷(期)： 2008 7(3)  分類(lèi)號(hào)： X703  關(guān)鍵詞： wastewater treatment   azo dyes   microwave   chromium   Fenton-like   decolorization   persistent organic pollutant  

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