| The three-dimensional electrocatalytic technology has been recently paid more attention owning to its high removal efficiency, rapid degradation and no secondary pollution production, providing a new technology for treatment of refractory organic wastewater. In this study, the three-dimensional electrocatalytic system with DIY Fe/Fe2O3/Fe3O4/AC particle electrodes was used to degrade the benzothiazole. Structure parameters including electrode type, electrode distance, impressed voltage, filling proportion of the particle electrodes and operating parameters including p H of inflow,electrolyte species, electrolyte concentration, injection time and electrocatalytic reaction time of the sequencing batch reactor were investigated. In addition, the degradation mechanism of benzothiazole was discussed and the results could be a theoretical direction for practical engineering projects.Fe/Fe2O3/Fe3O4/AC particle electrodes were prepared by wetness impregnation with Fe(NO3)3 solution. The conditions of impregnation were optimized, and results show the optimum impregnation conditions: impregnation time of 18 h, impregnation concentration of 0.74mol/L. The corresponding TOC removal and iron ion dissolution concentration are 66.7% and 99μg/L, respectively.Adsorption and electrocatalytic degradation of the Fe/Fe2O3/Fe3O4/AC particle electrodes were analyzed, and compared with the pure AC. The static adsorption capacities of AC and Fe/Fe2O3/Fe3O4/AC particle electrodes are 4.68mg/g and 5.89mg/g respectively for 100mg/L BTH in volume of 2L at room temperature. The TOC removal of Fe/Fe2O3/Fe3O4/AC particle electrodes of electrocatalytic degradation carried out with 100mg/L concentration of BTH, 0.1 mol/L Na Cl electrolyte, 60% particle electrodes in volume, electrode distance of 4cm under the constant voltage of 10 V in500m L reactor for 2h is 66.7%, which is 54.4% higher than pure AC. The improvement of adsorption is determined by variation in porous structure and surface chemical property. According to the adsorption rate constant of kinetics, the chemisortion plays the major role in the progress of BTH adsorption. The improvement of electrocatalytic degradation is determined by the Fe-containing catalysts. The activation energy of Fe/Fe2O3/Fe3O4/AC particle electrodes is 261KJ/mol, decreased by 32% in comparison with AC, so as to more easily take degradation reaction.A sequencing batch bipolar three-dimensional electrocatalytic reactor wasconstructed and applied on benzothiazole degradation. By measuring BTH removal,mineralization, current efficiency and energy consumption, the results show the optimal structure parameters: electrode type of cathode surrounding anode, electrode distance of4.24 cm, impressed voltage of 9.9V, particle electrodes proportion in volume of 60%.The corresponding TOC removal is 98.1787%. The optimal operating conditions of reactor are follows: electrolyte of 0.1 mol/L Na Cl solution, p H of 7, inflow duration for30 min, up-flow velocity of 8.333 m L/min and electrocatalytic reaction time for 3 h.When operated at such conditions, the reactor achieved the completely degradation of BTH with initial concentration of 100 mg/L and 92% removal of mineralization with low energy consumption of 13.00 KW·h/kg COD. Moreover, the open circuit potential(OCPT), oxygen-evolution potential and impedance of Fe/Fe2O3/Fe3O4/AC system are all higher than AC system, suggesting Fe/Fe2O3/Fe3O4/AC system has higher resistance to corrosion, less by-reactions and short-circuit current.The degradation mechanism of BTH was analyzed and the results show the major intermediate products are 2-methylphosphitesulfonylaniline and2-methylsulfonylaniline. According to the analysis of LC-MS, there are two pathways in the progress of degradation. The major gaseous product is CO2, in volume of about 90%.The major ion products are SO42- and NO3-, whose concentration are 20mg/L and10mg/L, respectively. According to the law of conservation of chemical, BTH was nearly mineralized. |
PDF Full Text Request