The Construction Of Electrocatalytic Membrane-biocathode Series Reactor And The Mechanism Of Dye Wastewater Treatment

Dye wastewater with large emissions,high chroma and strong toxicity is hard to be degraded.The most critical challenge is to develop an efficient method with a low energy cost to treat dye wastewater.This paper proposed to couple the electrochemical oxidation with the bioelectrochemical technology to build an electrocatalytic membrane?ECM?-bio sequential reactor?BSR?system so as to achieve the highly efficient and low cost treatment of dye wastewater via the electrochemical detoxification-biomineralization mechanism.A nano-Mn O_x loading Ti-based electrocatalytic membrane electrode?Mn O_x/Ti?was prepared using a microporous Ti membrane as a substrate by a sol-gel method.According to the pricinple of hydrodynamics,the residence time?RT?of fluids is the key parameter in both anode and cathode systems in a sequential reactor.Several reactor systems with the anode RT of 5?20 min and cathode RT of 8?32 h as well as a number of membrane electrodes was designed and fabricated.Besides,a two-chamber electrocatalytic membrane-bio sequential reactor?ECM-BSR?system?100×101×184mm?was successfully constructed using the Mn O_x/Ti electrocatalytic membrane as the anode,carbon felts as the cathode fillers and microbial carriers,and cation exchange membrane as the separator between the anode and cathode.The ECM-BSR system was started by using two power supply modes,i.e.,constant current and constant voltage with no current.The results showed that the mode of constant voltage with no current was not able to start up the ECM-BSR system.The reactor could not simultaneously achieve the removal of organic matter by both the anode and cathode.Interestingly,using the mode of constant current operating with 2m A,the ECM-BSR system was successfully started up to treat methylene blue waster water?100 mg/L??COD 120 mg/L?with 15 g/L Na₂SO₄ as electrolyte for 18 days.The COD removal rate was up to 40%.The BOD₅/COD ratios obtained in the anode system increased from 0.295 to 0.65.Simultaneously,when the effluent of anode system was used as the influent of cathode system,the COD removal rate obtained from cathode system was 60%.It impled that the ECM-BSR system exhibites the synergistic reaction meachanism for the COD removal.The ECM-BSR system was further employed to treat dye wastewater.The effects of the amount of electrocatalytic membrane electrodes,the concentration of methylene blue and the operating current on the removal efficiency as well as the energy consumption of the ECM-BSR were investigated.When the concentration of methylene blue was 100 mg/L,15 g/L Na₂SO₄ was used as eletrolyte and the operating current was2 m A,the COD removal rate obtained from the anode and cathode system was 28.8%and 15.9%,respectively.That was to say,the total of COD removal rate was 44.7%.At the same time,it was found that the number of electrocatalytic membranes in ECM-BSR had little effect on the removal of COD.Further,when the concentration of methylene blue was 700 mg/L,the total of COD removal rate was up to 69%.And the energy consumption was 0.12 k Wh/kg COD,which was much lower than that obtained from other electrochemical oxidation technologies in the literature.Similarly,the COD removal rate obtained from the anode system increased with the increae of the operating current in the ECM-BSR system and the COD removal rate obtained from the cathode system was basically unchanged.Under this stage,the total of COD removal rate increased,and energy consumption increased.Moreover,the reaction kinetics analysis of ECR-BSR system showed that the degradation of methylene blue by anodic system fited the first-order kinetic model.Thereaction rate constant obtained from the ECR-BSR system at the operating currents of 3.5 m A and 6.5 m A were 0.00615/h and0.02112/h,respectively.