Electrochemical Catalytic Degradation Of Organic Wastewater By Metal-oxide Electrode

Organic wastewater is usually greatly harmful to water resource with the development of agriculture and industry, and moreover, water pollution greatly affects human health and ecological balance. Therefore, searching a high efficiency, convenient and low cost method to treat wastewater is very important. Electrochemical oxidation has been received widespread attention, due to high efficiency, easy control and low cost. Electrode materials will greatly influence the effect of wastewater treatment in electrochemical degradation process.In this paper, Ti/PbO₂-Sm₂O₃, Ti/PbO₂-AC, titanium sub-oxide ?Ti₅O₉/Ti₄O₇? and Ti/RuO₂ mesh electrodes with high catalytic performance were prepared successfully and used in degrading alizarin yellow R, phenylhydrazine, p-nitrobenzoic acid and 2,4,6-trinitrophenol wastewater. The main research contents are as follows:Ti/PbO₂ and Ti/PbO₂-Sm₂O₃ electrodes were prepared by electrodeposition method. The results showed that after doping Sm₂O₃ to PbO₂, the diffraction peak intensity of PbO₂ increased and the grain size of Ti/PbO₂-Sm₂O₃ was smaller than that of Ti/PbO₂-Moreover, compared with Ti/PbO₂ electrode, Ti/PbO₂-Sm₂O₃ had higher oxygen evolution potential, smller impedance and more excellent electrocatalytic performance to oxidation of alizarin yellow R. Electrolyte concentration, plate spacing, pH and electrolysis voltage were chosen as influencing factors to discuss the effect of degrading alizarin yellow R wastewater on Ti/PbO₂-Sm₂O₃ electrode. Under the optimum condition of 9.0 g·L-1 Na2SO4 electrolyte concentration,3.0 V electrolysis voltage, pH 3 and plate spacing of 3 cm, after electrolysis for 180 min, the removal efficiency of COD and degradation efficiency of alizarin yellow R were 89.1% and 88.9%, respectively.Ti/PbO₂ and Ti/PbO₂-AC electrodes were prepared by electrodeposition method. The results showed that after doping AC to PbO₂, the diffraction peak intensity of PbO₂ was increased, and furthermore, the grain size of Ti/PbO₂-AC was smaller and more tightly than that of Ti/PbO₂. Moreover, compared with Ti/PbO₂ electrode, Ti/PbO₂-AC had higher oxygen evolution potential, smller impedance and more excellent electrocatalytic performance in degrading phenylhydrazine, indicating that AC assist PbO₂ electrode enhanced electrocatalytic performance to oxidation of phenylhydrazine. Some influencing factors were used to discuss better processing conditions on Ti/PbO₂-AC electrode, including electrolyte concentration, current density, pH and electrolysis temperature. The removal efficiency of COD and degradation efficiency of phenylhydrazine were 80.59% and 81.9%, respectively, after electrolysis for 150 min under the optimum condition of 5.0 g·L-1 Na2SO4 electrolyte concentration,3.75 mA·cm-2 current density, pH 5 and 30? electrolysis temperature.Ti/RuO₂ mesh electrode was prepared by brush coating method. RuO₂ was rutile structure and its microstructure presented "mud crack" Ti/RuO₂ mesh electrode was used in degrading p-nitrobenzoic acid wastewater and four influencing factors were discussed, inculding electrolysis voltage, pH, electrolysis temperature and electrolysis time. Orthogonal experiment showed that the four factors affecting in a descending order as:pH, electrolysis temperature, electrolysis time, electrolysis voltage. Single-factor experiment showed that the removal efficiency of COD and degradation rate of p-nitrobenzoic acid were 79.5% and 77.2%, respectively, under the optimum condition of 2.0 V electrolysis voltage, pH 3,30? electrolysis temperature and 180 min electrolysis time.Ti₅O₉/Ti₄O₇ electrode was prepared by pelleting-sintering method. The main component of the electrode was Ti₅O₉, before using, the particle size of Ti₅O₉/Ti₄O₇ was small. However, the particle size of Ti₅O₉/Ti₄O₇ gathered to form waxberry spheres after using. Polarization curve demonstrated that oxygen evolution potential of Ti₅O₉/Ti₄O₇ electrode was about 2.0 V?vs. SCE? and had relatively wide electrochemical window. The electrocatalytic degradation of 2,4,6-trinitrophenol was investigated by using Ti₅O₉/Ti₄O₇ electrode. The results showed that the removal efficiency of COD and degradation rate of 2,4,6-trinitrophenol were 90.6% and 93.9%, respectively, under the optimum condition of 180 min electrolysis time,20 mA·cm-2 current density,6.0 g·L-1 Na2SO4 electrolyte concentration, pH 7 and electrolytic temperature of 30?.This study showed that Ti/PbO₂-Sm₂O₃, Ti/PbO₂-AC, Ti₅O₉/Ti₄O₇ and Ti/RuO₂ mesh electrodes had the characteristics of high catalytic performance and non-pollution in treating of organic wastewater, which had preferable application foreground in organic wastewater treatment.