Abstract:Printing and dyeing wastewater is characterized by large discharge volume and complex components, and contains toxic aniline or carcinogens with azo moieties, thus it can hardly reach the national discharge standard. Cost-effective tertiary treatment technologies are required to meet the industrial reuse standards. The heterogeneous photo-Fenton oxidation with natural ferrous mineral catalysts was exploited to treat the biological effluent of printing and dyeing wastewater. The present work focused on comparison of the catalytic activity of natural ferrous minerals in heterogeneous photo-Fenton under different light sources including high-pressure mercury lamps, xenon lamps and metal halide lamps. Catalytic mechanisms were investigated in terms of organic pollutant removal and variation of iron ion concentrations. The result showed that UV-Vis light could remarkably improve the treatment effect of the biological effluent of printing and dyeing wastewater, and COD removal increased by 40% at an initial pH 3~7. Chalcopyrite, magnetite and pyrrhotite as catalysts in heterogeneous photo-Fenton oxidation could remove 58.83%, 54.07% and 55.64% COD, respectively. Minerals exhibited excellent reusability and could maintain over 50% COD removal after reuse of 5 cycles. When H2O2 was taken as oxidant, the order of treatment efficiencies was following: pyrrhotite > chalcopyrite > magnetite > FeSO4, and low-pressure mercury lamp > high-pressure mercury lamp > metal halide lamp > xenon lamp. The pathway of oxidative species ·OH generation included H2O2 photolysis, H2O2 decomposition catalyzed by Fe2+ and Fe(II) on minerals surface, photo-induced charge separation of catalyst and two-electron oxygen reduction reaction. At pH >3, the catalysis of Fe(II) on the mineral surface played a major role in ·OH generation, whereas the contribution of Fe2+ homogeneous catalysis was negligible. Key words:mineral catalysts/ catalytic mechanism/ heterogeneous photo-Fenton oxidation/ printing and dyeing wastewater/ tertiary treatment.
图1催化剂用量对COD去除率的影响 Figure1.Effect of catalyst dosage on COD removal
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1.School of Environment Science and Engineering, Donghua University, Shanghai 201620, China 2.Shanghai Institution of Pollution Control and Ecological Security, Shanghai 200092, China Received Date: 2020-11-18 Accepted Date: 2021-01-29 Available Online: 2021-05-23 Keywords:mineral catalysts/ catalytic mechanism/ heterogeneous photo-Fenton oxidation/ printing and dyeing wastewater/ tertiary treatment Abstract:Printing and dyeing wastewater is characterized by large discharge volume and complex components, and contains toxic aniline or carcinogens with azo moieties, thus it can hardly reach the national discharge standard. Cost-effective tertiary treatment technologies are required to meet the industrial reuse standards. The heterogeneous photo-Fenton oxidation with natural ferrous mineral catalysts was exploited to treat the biological effluent of printing and dyeing wastewater. The present work focused on comparison of the catalytic activity of natural ferrous minerals in heterogeneous photo-Fenton under different light sources including high-pressure mercury lamps, xenon lamps and metal halide lamps. Catalytic mechanisms were investigated in terms of organic pollutant removal and variation of iron ion concentrations. The result showed that UV-Vis light could remarkably improve the treatment effect of the biological effluent of printing and dyeing wastewater, and COD removal increased by 40% at an initial pH 3~7. Chalcopyrite, magnetite and pyrrhotite as catalysts in heterogeneous photo-Fenton oxidation could remove 58.83%, 54.07% and 55.64% COD, respectively. Minerals exhibited excellent reusability and could maintain over 50% COD removal after reuse of 5 cycles. When H2O2 was taken as oxidant, the order of treatment efficiencies was following: pyrrhotite > chalcopyrite > magnetite > FeSO4, and low-pressure mercury lamp > high-pressure mercury lamp > metal halide lamp > xenon lamp. The pathway of oxidative species ·OH generation included H2O2 photolysis, H2O2 decomposition catalyzed by Fe2+ and Fe(II) on minerals surface, photo-induced charge separation of catalyst and two-electron oxygen reduction reaction. At pH >3, the catalysis of Fe(II) on the mineral surface played a major role in ·OH generation, whereas the contribution of Fe2+ homogeneous catalysis was negligible.