Removal Nitrite From Wastewater With Electric-catalytic Reduction

Nitrite pollution can induce human disease, such as cancer and even for children it may cause High-speed Rail hemoglobin disorders, called hypertension. Therefore, it is necessary to treat nitrate in groundwater by effective means. As Pd-Me bimetallic catalytic reduction was based on the mechanism of NO3--N reduction and advantages of electrochemical water treatment technology are multiple functions, wide applications, no double-pollution, good controllability and economic advantages. Here we used PdCl2 as the anodes to depose of nitrite nitrogen in water by electrochemical catalytic.This paper was to achieve harmless for the removal of NO2--N with Pd coated and Cu coated electrode coated series. The electrode was focused on the ways of the preparation of Pd and Cu cathode respectively coating by using impregnation method and thermal decomposition. The factors affecting nitrate contaminants removal of the neutral condition were also investigated. The electrode used in water treatment must meet the "green" requirements and cannot be corroded in the reaction process, which may produce harmful substances to release into the water. Therefore, during the electro-catalysis experiment, choosing suitable electrode was a key step. On the other hand, the catalyst not only increased the reaction speed to improve the reaction efficiency, but also raised the ideal choice of ratio of reactants.Different anodes affected the removal experiment. This experiment selected Ti/Ir-Ru, uncoated titanium and graphite as anodes. According to the assay in the preliminary studies, our experiments were carried out by the selection of Ti/Ir-Ru anode as electrode. According to the study the optimum reaction conditions were as the following:the current density is 4mA/cm2, plate distance is 3mm, stirring intensity is 600rad/min and the reaction temperature is 30℃, under which the nitrate removal rate reached more than 90%; namely, the removal amount of NO2--N was 9.6mg/L, and TN removal rate can reach 86.32%, which means it could realize the harmless targeted process to remove NO2--N.Through the result analysis of the DSA anode and Pd cathode coating catalytic reduction of NO2--N we studied the mechanism of NO2--N reduction. The results showed that the catalytic electrolysis system tended to form a new bond, with solution by Pd cathode coating surface adsorption fixed in NO2--N, which was active in reducing the electronic cloud on the realization of NO2--N attack and O-O-H in the Pd desorption, NO2--N was reduced to NO-N, with the formation of N2 phase.Electro-catalytic reduction removing nitrate in water is considered as an efficient and applicable denitrification method in the future, especially for the small-scale application in the rural areas. Finally, we discussed existing problems and methods dealing with these problems, pointing out the final developing directions.