| Dye wastewater is a typical refractory industry sewage, which is characterized with high chroma, complication of organic components, high value of CODcr and poor biochemical quality. As a domain producer of dye stuff, discharge of dye wastewater has become a threat to China’s water environment security. Therefore, it is time to effectively and efficiently treat dye wastewater to safety disposal.In recent years, microbial fuel cell(MFC) is a rapidly developing biological treatment technology that could harvest electricity while degradating organic compounds. Most researches focus on elevation of MFC output power density and degradation of certain pollutants, while few research is related to utilization of MFC’s electricity. As one of advanced oxidation processes, Ti O2 photocatalytic technology(PC) has been widely used in waterwater treatment for its high efficiency and clean character. The main problem lies in low light utilization and high recombination efficiency of photo-generated electron and holes.In this work, MFC and PC technology was applied to treat dye wastewater respectively. Then a combination of MFC and PC technology was imposed using MFC output voltage to assist PC process and PC pre-treatment product as fuel for MFC. The main contents and results are stated as follows:1、Preparation and optimization of Ti O2/Ti film electrode: Ti O2/Ti film electrode was prepared by sol-gel method. The best preparation condition is 500 centigrade calcinations for 2 hrs and 3 layers coating. X-ray diffraction(XRD) characteriazation indicated that the main crystal form was anatase, I-V response suggested Ti O2/Ti film electrode had excellent ultraviolet light response.2、Degradation of wastewater using aqueous thin-film photocatalytic technology: Dual slant-placed aqueous thin-film reactor was assembled using Ti O2/Ti film electrode as anode and Cu as cathode and applied to treat Amaranth solution. The best reaction condition was: circulation flux 100 m L/min, p H 2.52, Na2SO4 concentration 1.5g/L,Amaranth initial concentration 40mg/L. Under such condition, after 90 min treatment,Amaranth decolourization efficiency reached 88.1%. UV-vis analysis indicated that the mechanism of Amaranth degradation was to break azo bond and naphthalene nucleus and to form small molecular organics.3 、 Mechanism of high efficiency for aqueous thin-film photocatalytic technology:Respective degradation and H2O2 concentration of cathodic and anodic chamber was investigated. Result indicated that under ultraviolet irradiation, as schottky barrier existed between Ti O2 and Ti, photo-generated electron was traffered form Ti O2 surface to Ti substrate and then to Cu electrode after connecting Ti O2/Ti electrode with Cu electrode through a Cu wire. High degradation efficiency, namely double effect was obtained due to dual electrodes degradation, namely direct photooxidation on the photoanode as well asdirect reduction and additional degradation on the cathode, which was speculated via hydrogen peroxide(H2O2) generated by dissolved oxygen on aqueous thin-film.4 、 Degradation and simultaneous electricy generation using MFC: Self-made dual chamber MFC was assembled using active sludge of sewage treatment plant as inoculation source. Factors of Amaranth concentration, initial p H, circuit resistance and co-substrate concentration were investigated after MFC stabilized. Result showed microbial catalytic activity was the ensurance of MFC performance. The best degradation condition was Amaranth concentration 20mg/L, p H 9.00, circuit resistance 2k?, Na Ac concentration1.68g/L. Under best condition, 90% decolourization efficiency was achieved in 72 h treatment, and highest 721.38 m W·m-2 power density was obtained. UV-vis analysis indicated that primary mechanism of MFC degradation of Amaranth was not mineralization but breakage of azo bonds and to form kinds of low molecular compounds.5、MFC assisted PC(MFC-PC) to treat Amarath: MFC series or parallel connection output electricity was applied to assist dual aqueous PC precess, which used MFC electicity as PC additional electric field and enhanced separation efficiency of photo-generated electron and hole. And a higher photocatalytic degradation efficiency was obtained. Factors of MFC connection, circuit flux, initial p H, electrolyte concentration and Amaranth concentration were investigated. Result showed the best MFC-PC reaction condition was: Under two series connected MFC, circulation flux 120 m L/min, p H 2.52,Na2SO4 2.0g/L, Amaranth initial concentration 20mg/L. Under best condition, Amaranth decolourization efficiency reached 100% in 120 min. UV-vis analysis indicated MFC-PC degradation of Amaranth was to break azo bonds, naphthalene nucleus and cyclobenzene to form low molecular organics, and partly mineralized.6、MFC degradation of PC pre-treatment dye wastewater: PC pre-treatment Amaranth solution was added to MFC for deep degradation, thus high efficiency of PC and economical of MFC was combined. Factors of PC Amaranth initial concentration and PC decolourization efficiency, MFC circuit resistance, co-substrate concentration and initial p H was investigaged. Result showed the best degradation condition was Amaranth concentration 20mg/L, decolourization efficiency 20%, Na Ac concentration 3.36g/L, p H9.00, circuit resistance 2k?. PC pre-treatment could enhance bio-degradation of Amaranth.100% color removal efficiency was achieved in 48 h for PC pre-treament 20% 20mg/L Amaranth. UV-vis analysis and COD removal efficiency indicated that MFC degradation of Amaranth intermidates was the breakage of azo bonds and to form quantity of low molecular organics, and 67.1% COD removal efficiency was obtained.In this work, dual aqueous thin-film photocatalytic technology(PC) was imposed, and MFC was combined with PC to realize both efficient and economical goals on this system.This research provides a good reference to development of high efficiency photocatalytic reactor and combination of MFC and PC technology. |
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