Research And Application Of Electrocatalytic Oxidation For Treating Ammonia Nitrogen Contaminated Groundwater

Ammonia nitrogen pollution in groundwater has the characteristics of persistence,concealment and refractory degradation,which poses a serious threat to the water ecological environment and human drinking water safety.Electrocatalytic oxidation water treatment technology is a promising method for remediating ammonia nitrogen polluted groundwater due to its easy operation,high efficiency,and wide applicability.However,traditional electrochemical reactions mostly use submerged reactors,which have disadvantages such as low mass transfer utilization efficiency and high energy consumption.Therefore,optimizing electrochemical reactors to enhance mass transfer efficiency,while concurrently developing combination processes based on electrocatalytic oxidation technology,holds significant significance for the research and design of efficient ammonia removal water treatment technologies that are suitable for industrial applications.This study takes the groundwater from a solid waste landfill in a steel industrial area in Shanghai as the research object,and designs a flow-by cell and a flow-through cell suitable for engineering applications based on electrocatalytic oxidation.The removal efficiency of ammonia nitrogen by individual electrocatalytic oxidation and combined electrocatalytic oxidation processes was investigated.The main contents and conclusions are as follows:（1）The surface morphology and electrochemical properties of three commercially available porous electrodes,including titanium ruthenium iridium foam（Ti Ru Ir-F）,titanium ruthenium iridium mesh（Ti Ru Ir-M）,and carbon felt（CF）,were tested and analyzed.The experiments showed that Ti Ru Ir-F electrode possesses optimal surface structure,maximum double-layer capacitance(72.25 m F cm^-2)and minimum Tafel slope(20.81 m V dec^-1).Three corresponding flow-through cells were constructed using these three electrodes as anodes.The cells can stably remove ammonia nitrogen in continuous flow,and the Ti Ru Ir-F system has the best removal effect.The optimal operating conditions are as follows:HRT=10 min,p H=10,U=5 V,the target pollutant ammonia nitrogen can be degraded by 93.73%in a single pass-through,which is higher than CF and Ti Ru Ir-M systems by 67.52%and 5.89%,respectively.（2）A flow-by cell was constructed to investigate the effectiveness of electrocatalytic oxidation coupled with ultraviolet（UV）technology in removing ammonia.The study found that the active chlorine and·HO generated on the surface of the anode were found to be the main factors in converting ammonia nitrogen to N₂,and the degradation of ammonia nitrogen followed zero-order kinetic reaction.After electrolysis for 30 minutes at a current density of 73.46 A·m^-2,the removal rate of ammonia nitrogen was found to be 19.43%higher in the single electrochemical oxidation compared to the photoelectrocatalytic oxidation method.The by-product NO₃^-was reduced by 5.299 mg·L^-1 and active chlorine was increased by 10.8 mg·L^-1.The introduction of UV light changed the composition and proportion of strong oxidizing groups in the system.Cl O·was only produced by the catalysis of UV light from·HO and active chlorine.The consumption of strong oxidizing substances such as·HO and active chlorine led to a decrease in the removal rate of ammonia nitrogen in the system with added UV light.（3）A coupled process of stripping ammonia as a pretreatment was integrated with electrocatalytic oxidation to develop a stable and efficient stripping-electrocatalytic oxidation combination process.Under the optimal operating conditions,the removal rates of COD,TN,and NH₄⁺-N were 88.51%,90.23%,and 97.62%,respectively,achieving a good decarbonization and denitrification effect.