Optimization Of Three-dimensional Electrochemical Reactor And Application In Wastewater Treatment

Three-dimensional electrochemical reactor(3DER)is a effective electrochemical oxidation technology,with the advantages of excellent treatment performance,environmental compatibility and easy operability.The current efficiency and mass transfer of the reactor can be greatly improved by packing particle electrodes between the main electrodes.3DER has been successfully applied in the treatment of dyes,petrochemicals and other refractory organic wastewater with high concentration,exhibiting unique superiorities.However,there are some problems that limit the practical application of 3DER,such as high energy consumption for operation and high cost of particle electrode catalysts.To solve these problems,two works were carried out in this thesis.On the one hand,multiple response optimization method was used to optimize the 3DER operation parameters to improve the contaminants removal efficiency as well as reducing energy consumption of 3DER.On the other hand,granular sludge carbon catalysts were prepared using sewage sludge as raw material and further applied in the 3DER as cheap and efficient particle electrode.The main research contents include:1.The degradation of high-concentration rhodamine B(RhB)wastewater was investigated in a 3DER packed with granular activated carbon(GAC)particle electrodes.Response surface methodology(RSM)coupled with grey relational analysis(GRA)was used to evaluate the effects of voltage,initial pH,aeration rate and NaCl dosage on RhB removal and energy consumption of the 3DER.The optimal conditions were determined as voltage 7.25 V,pH 5.99,aeration rate 151.13 mL/min,and NaCl concentration 0.11 mol/L.After 30 min electrolysis,COD removal rate could arrive at 60.13% with an relatively low energy consumption of 6.22 kWh/kg COD.The voltage and NaCl were demonstrated to be the most significant factors affecting the COD removal and energy consumption of 3DER.The intermediates generated during the treatment process were identified and the possible degradation pathway of RhB was proposed.It is worth noting that 3DER also showed an excellent performance in total nitrogen(TN)removal under the optimal condition.The activated chlorine generated from chloride had great contributions to eliminate carbon and nitrogen of RhB wastewater.The treatment effluent had a good biodegradability,which was suitable for subsequent biological treatment.2.We developed a one-step facile synthesis method of converting iron-rich sewage sludge into granular sludge carbon(GSC),further applying as particle electrodes in 3DER for wastewater treatment.The prepared GSC under different pyrolysis temperature were characterized to investigate the physical,chemical and electrochemical properties.The treatment performances of GSC as particle electrodes were evaluated by degrading bisphenol A(BPA)and RhB in a continuous-flow 3DER and the stability of the GSC were also estimated.Possible reaction mechanism were explored by detecting the hydroxyl radical(·OH)generated in 3DER with electron spin resonance(ESR)technique.Results indicated that GSC fabricated were typical macroporous material,exhibiting good electrocatalytic activity due to the co-existence of iron oxide and zinc oxide.The 500°C/GSC packed 3DER showed the best performances in contaminants removal attributed to its superior adsorption and electrochemical properties.The 500°C/GSC prepared were proved to be suitable for utilizing as cheap and efficient particle electrodes in 3DER.