摘要
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 o 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 particula importance to controlling the water quality of the Three Gorges Reservoir.
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.
基金
the Natural Science Foundation of Chongqing (CSTC2007BB6155)
the Key Lab Visiting Scholar Foundation of Chongqing University (KLVF-2006-5)
