Mechanism Research Of Enhanced Chlorine Evolution And Ammonia Transformation By RuO₂/TiO₂ Array Electrode

In recent decades,Ammonia nitrogen removal from wastewaters has gained much attention as a result of the environmental problems associated with discharge of excessive amounts of this critical nutrient including eutrophication of receiving waters,generation of offensive odours as a result of organism decay and complications associated with the disinfection of water supplies.Electrochemical oxidation,as a potentially effective alternative method for removing ammonia nitrogen from wastewater,has unique advantages including less secondary pollution,easy automation,versatility and safety for ammonia nitrogen from high salt industrial wastewater that is difficult to treat biochemically,and has now gradually escaped the""promising technology""designation in this field,becoming an increasingly used technology in actual productionElectrochemical oxidation methods are mainly divided into direct oxidation method and indirect oxidation method.Electrochemical indirect oxidation method is widely used due to the faster,more efficient and cost-effective removal of ammonia-n.It mainly oxidizes ammonia nitrogen to nitrogen indirectly through reactive chlorine action by in situ generation of reactive chlorine on the anode.So the key of electrochemical indirect oxidation process of ammonia nitrogen is how to improve the efficiency of the electrode for chlorine production and thus enhance the ability to remove ammonia nitrogen.In this paper,mainly,the chlorine evolution performance as well as the strengthening of the performance of indirect ammonia-N oxidation by titanium ruthenium nanoarray electrode was investigated,and the optimal reaction conditions for the removal of ammonia-N were confirmed after condition optimization,the reaction mechanism and path of electrochemical indirect ammonia-N oxidation were speculated,and the main contents are as follows:（1）The RuO₂/TiO₂ nanoarray electrode with nanorod,nanoparticle and plate architectures have been fabricated by combining anodization method with magnetron sputtering process and characterized as available,and the ruthenium metal coating obtained by magnetron sputtering method is uniformly and densely coated on the surface of titanium substrate.The overpotential of RuO₂/TiO₂ NRA electrode at a current density of 100 m A/cm² is only 120 m V,with a Tafel slope of 36.4 m V/dec,and the current grows rapidly,which is proved to have an extremely high electron transport efficiency by EIS characterization.Apart from that,the electrode has a faradaic efficiency of up to 90%with a high stability.（2）The effect of different influencing factors on the degradation of ammonia nitrogen was investigated,and it was found that the current density and Cl^-addition were the main influencing factors on the electrochemical indirect oxidation of ammonia nitrogen,which was more favorable under neutral or basic conditions for ammonia nitrogen removal.The raising of the initial concentration of ammonia nitrogen would affect the degradation efficiency of the electrode.The stability of the electrode was investigated by cyclic use,and it was found that cyclic use for four times,could still completely degrade ammonia nitrogen within 35 min,indicating that the RuO₂/TiO₂ NRA electrode is an efficient and reliable electrocatalyst for the degradation of ammonia nitrogen.（3）It is studied by ESR analysis that the radical responsible for the indirect oxidation of ammonia nitrogen is·Cl;and in the process of activating Cl^-to produce·Cl at the RuO₂/TiO₂ NRA electrode,so the electrochemical indirect oxidation of ammonia nitrogen is different from the point of folding chloride method.At the beginning of the reaction,ammonia nitrogen can be directly degraded to monochloramine,after which oxidation to N₂ is removed from solution.