Study On Photoelectric Synergistic Degradation Of Azo Dye Wastewater By Modified TiO₂/AC

The dyeing performance of azo dyes is excellent and azo dyes are widely used in the textile,printing and dyeing industries,but their wastewater may lead to carcinogenesis,teratogenesis or mutagenesis.Direct discharge into rivers will cause serious damage to the surrounding natural environment.The biodegradability of azo dye wastewater is poor,and traditional biological methods are difficult to achieve good degradation effect.Therefore,it is necessary to seek an efficient and convenient treatment method.In this study,the activated carbon three-dimensional electrode electrocatalysis method is combined with TiO₂ photocatalysis method.The Ti/Ir O₂-Ta₂O₅ plate is used as the anode,the Ti plate is used as the cathode,the modified TiO₂/AC composite material prepared by the sol-gel method is used as the particle electrode,and the long-arc xenon lamp is in order to simulate the sunlight.The simulated methyl orange wastewater is used as the representative of azo dye wastewater.The material preparation conditions and reaction conditions of the modified TiO₂/AC photoelectric synergistic method were optimized.Through the reaction kinetics analysis and free radical quenching experiments to explore its degradation mechanism,data and theoretical reference were provided for the practical application of this method in azo dye wastewater treatment.X-N-TiO₂/AC（X=Fe or Cu or Mn）composites were prepared by the sol-gel method.In the experiment of photoelectric synergistic degradation of 20 mg/L methyl orange wastewater,Fe-N-TiO₂/AC compared with Cu-N-TiO₂/AC and Mn-N-TiO₂/AC exhibits higher catalytic efficiency.The optimized material preparation conditions are acetic acid addition of 12.6 m L,Fe doping amount of 0.6%,N doping amount of 10%（molar ratio）,and the degradation rate of methyl orange is 66.59%when the reaction time of the photoelectric catalysis is 180 min.The characterization results of SEM and XRD show that the modified anatase TiO₂ is successfully loaded on the granular activated carbon.The reaction conditions of Fe-N-TiO₂/AC photoelectric synergistic degradation of methyl orange wastewater were optimized by single factor experiment and orthogonal test.The voltage between the plates is 14 V,the electrolyte sodium sulfate concentration is 1.5 g/L,the initial p H is 3,the composite material is 35 g/L,aeration rate is 600 m L/min,the reaction time is 60 min,the degradation rate of methyl orange wastewater is 86.5%,and the COD removal rate is73.54%.The degradation rate of methyl orange by Fe-N-TiO₂/AC photoelectric synergistic method is higher than the sum of photocatalysis（26.75%）and three-dimensional electrode electrocatalysis（47.8%）,and the synergy factor is 1.16.In addition,the energy consumption of the Fe-N-TiO₂/AC photoelectric synergistic method is 18.36 W·min/mg,which is lower than that of the traditional activated carbon three-dimensional electrode electrocatalysis.The reusable experiments show that the Fe-N-TiO₂/AC composite has excellent reusable performance.After 10 times of reuses,the degradation rate of methyl orange is 74.13%.The material reused 10 times is loading by the sol-gel method again,and the degradation rate of methyl orange is 89.64%.The results of reaction kinetics fitting show that the degradation reaction of Fe-N-TiO₂/AC photoelectric synergy on methyl orange wastewater is an apparent first-order reaction with a first-order kinetic constant k=3.26×10^-2 min^-1.The results of free radical quenching experiments indicates that hydroxyl radical（·OH）plays a major role in the degradation of methyl orange.