title: [Advanced treatment of coking wastewater with a novel heterogeneous electro-Fenton technology].
abstract: A novel electro-catalytic reactor, with oxygen-reduction cathode (PAQ/GF), dimensionally stable anode (IrO2-RuO2 -TiO2/ Ti) and heterogeneous catalysts, is developed for advanced treatment of coking wastewater after biological process, integrating cathodic and anodic simultaneous oxidation processes. A PAQ/GF electrode was synthesized by the electro-polymerization of 2-ethyl anthraquinone on graphite felt, which was characterized with cyclic voltametry measurements; the results indicated that the PAQ/GF electrode showed high reversibility for oxidation-reduction reaction of anthraquinone and catalytic activity for O2 reduction to H2O2; 13.5 mmol/L H2O2 was obtained after electrolysis for 6 h at -0.7 V (vs. SCE) and pH 6 with a current efficiency of 50% in a membrane reactor. Fe-Cu/Y350 catalysts, prepared by impregnation method, could catalyze the production of hydroxyl radicals (*OH) from H2O2, which was confirmed both by fading reaction of crystal violet and oxidation of *OH-probe compound (p-chlorobenzoic acid); Fe-Cu/Y350 also showed high catalytic-activity for the oxidation of organics by hypochlorous sodium, because COD removal of coking wastewater reached 26% in the catalytic process while only 11% of COD removal was obtained in the absence of Fe-Cu/Y350. COD removal of coking wastewater reached 49.4% (26.0% and 23.4% in cathodic system and anodic system, respectively) in the developed electrolytic-reactor, which was higher than that of conventional cathodic-anodic-oxidation process (29.8%). At optimal reaction condition of initial COD = 192 mg/L, I = 10A x m(-2) and pH 4-5, more than 50% COD were removed after electrolysis for 1 h. The mechanism might be as follows: in cathodic system, H2O2 is generated from reduction of O2 on PAQ/GF cathode, and catalyzed by Fe-Cu/Y350 for production of *OH, which causes mineralization and degradation of organic pollutants; in anodic system, Cl2 and HClO are generated from Cl- oxidation on IrO2-RuO2-TiO2/Ti anode and the organic pollutants are oxidized by Cl2, and HClO with Fe-Cu/Y350 catalysts or by direct anodic oxidation.
authors.affiliation: School of Chemical Engineering & Technology, Tianjin University, Tianjin 300072, China. lihaitao103904@126.com
authors.forename: Hai-Tao
authors.initials: HT
authors.lastname: Li
authors.forename: Yu-Ping
authors.initials: YP
authors.lastname: Li
authors.forename: An-Yang
authors.initials: AY
authors.lastname: Zhang
authors.forename: Hong-Bin
authors.initials: HB
authors.lastname: Cao
authors.forename: Xin-Gang
authors.initials: XG
authors.lastname: Li
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D003077:Coke; D004563:Electrochemistry; D006861:Hydrogen Peroxide; D007220:Industrial Waste; D007501:Iron; D014865:Waste Disposal, Fluid / Q000379:methods*; D018508:Water Purification / Q000379:methods*
chemical_list: D003077:Coke; C045076:Fenton's reagent; D007220:Industrial Waste; D006861:Hydrogen Peroxide; D007501:Iron