Preparation Of Titanium Based DSA Electrode And Performance And Mechanism Of Electrochemical Oxidation Of Aniline Wastewater

Aniline containing wastewater discharged by printing and dyeing,leather making,pharmacy and other industries always has a high concentration of COD and inorganic salt with biotoxicity,which is difficult for traditional biological process to degrade.However,electrochemical process has great advantages in the treatment of refractory organic wastewater and has been widely concerned.Dimensional stable anode?DSA?with electrochemical catalytic oxidation ability is the key factor in dealing with the refractory organic wastewater.Although there are many types of DSA electrodes can degrade refractory organic compounds in water through direct oxidation or indirect oxidation of active chlorine,there are still many problems such as lower oxygen evolution potential,lower direct oxidation ability and unstable for the coating material.In this study,performance of traditional Ti/RuO₂ electrode in aniline degradation and the degradation mechanism under different conditions has been investigated.And on the basis,modified polymetallic DSA anodes doped SnO₂ and IrO₂ were prepared by thermal decomposition process.LSV,SEM and XRD analytical methods were utilized to analyze the catalytic oxidation ability,surface morphology,stability,and the electrochemical degradation behavior.Mechanism of aniline degradation was explored under different electrolyte and current density,and the degradation efficiency was compared between different electrodes.Electrochemical oxidation of aniline in different electrolyte,current density,pH and plate distance using Ti/RuO₂ as anode were conducted.The results showed that when the current density was 20 mA/cm²,pH was 10.0,plate distance was 1 cm,the removal rate of aniline and COD in NaCl solution were 29.2 and 10.0 times higher than that of Na₂SO₄ solution respectively.In addition,the increase of NaCl concentration not only improve the degradation rate of aniline and COD,but also the current efficiency,and an acidic condition conductive to COD removal,It was found that the current efficiency was the highest?14.6%?when NaCl was 1.00 g/L,the COD removal efficiency was the highest?80.5%?when pH was 3.0,while the amino group could be effectively removed by electrochemical REDOX during the reaction process.Moreover,using Na₂SO₄ as background electrolyte,a small amount of Cl^-or Fe²⁺could enhance the action of hydroxyl radical?·OH?,which would improve the mineralization efficiency and reduce the energy consumption while ensuring the efficient degradation of aniline.When a low-concentration of NaCl was added,the maximum TOC removal efficiency of 71.1%was got at 40 mA/cm²,while the average energy consumption reduced by 6.4%,when a small amount of Fe²⁺was added,the TOC removal rate increased by 43.6%and the average energy consumption reduced by 73.5%.It was found that when the concentration of Cl^-was low and the current density was high,the inhibition of Cl^-on·OH was wake,TOC was mineralized through electrochemical transformation by the anode itself cooperated with electrochemical combustion and active chlorine indirect oxidation.While in the presence of a small amount of Fe²⁺,fenton reaction would occur at lower current density to promote the removal of TOC.Ti/Sb-SnO₂-Ta₂O₅ electrode was fabricated by thermal oxidation method.SEM image showed that the electrode coating was dense with few cracks.XRD pattern indicated that Ti-Sn,Ti-Ta,Sn-Sb and Sn-Ta solid solution were generated in the coating,which could maintain the stability of the electrode.LSV analysis showed that the oxygen evolution potential of Ti/Sb-SnO₂-Ta₂O₅ electrode was 2.254 V?vs.SCE?,higher than that of Ti/RuO₂?1.040 V?,which was in favor of reducing energy consumption.Moreover,when the current density was 20 mA/cm²,the removal efficiency of TOC by Ti/Sb-SnO₂-Ta₂O₅ was higher than that of Ti/RuO₂,and the average power consumption was 73.6%lower than Ti/RuO₂?in Na₂SO₄ electrolyte?or89.1%lower than Ti/RuO₂?in NaCl electrolyte?.Ti/RuO₂-SnO₂ and Ti/RuO₂-IrO₂ electrodes were prepared by thermal oxidation method.Characterization analysis showed that the coatings on both electrodes were dense,rough and had less cracks,and Ru-Sn,Ti-Sn and Ru-Ir solid solution were generated,which could effectively enhance the stability of the electrodes.The oxygen evolution potentials of Ti/RuO₂-SnO₂ and Ti/RuO₂-IrO₂ electrodes were 1.295 and1.255 V?vs.SCE?,respectively,which were both higher than Ti/RuO₂.With Na₂SO₄as the electrolyte,Ti/RuO₂-SnO₂ had the capability of electrochemical transformation and electrochemical combustion at lower and higher current density.The removal efficiency of aniline and TOC was higher than other electrodes,and it was not easy to be passivated.in addition,with NaCl as the electrolyte,when the current density was low,removal rate of aniline and TOC by Ti/RuO₂-SnO₂ and Ti/RuO₂-IrO₂ were lower than Ti/RuO₂ and Ti/Sb-SnO₂-Ta₂O₅,but Ti/RuO₂-SnO₂ got the maximum removal efficiency?47.5%?,and Ti/RuO₂-IrO₂ was not easy to be passive under high current density,with the highest removal rate of TOC?63.1%?.After a small amount of Fe²⁺added,the removal efficiency and current efficiency of Ti/RuO₂-SnO₂ on TOC at lower current density were higher compared with those of other electrodes,and the power consumption was 38.5%lower than that in a single Na₂SO₄ electrolyte.The results of this study showed that all the traditional Ti/RuO₂ electrode and the fabricated Ti/Sb-SnO₂-Ta₂O₅,Ti/RuO₂-SnO₂ and Ti/RuO₂-IrO₂ electrodes performed good in the degradation of aniline wastewater,while the electrodes fabricated were superior to Ti/RuO₂ in the degradation of TOC under certain conditions and consumed less electricity.Therefore,this study provides theoretical and technical support for the selection of electrodes and optimization of operation conditions in electrochemical treatment of aniline wastewater.