Experimental Study On Nitrate Removal In Ground Water By Catalytic Reduction And Electrolysis Chlorina Oxide Based On Ti/Fe Substrate Cathode

Groundwater serves as an important source of drinking water in various parts of the world. However, nitrate pollution in ground water, recently, has become a severe problem worldwide due to the agricultural and industrial development. Awareness of nitrate contamination leads to an increasing interest in the removal of nitrates from raw water. Numerous efforts have been reported so far on the removal of nitrate through biological methods and physico-chemical methods. However, these approaches are proved inappropriate and ineffective for gound water. Further, the catalysts used in the previous study mainly rely on noble metal, such as Pd, which affects their wide use. Electrochemical reduction has been proposed as a promising technology for removal of nitrates, but the reaction mechanism with various catalysts needs to be future studied. In addition, the study of simultaneous removal of ammonia is rare. The aim of the program is complete removal of nitrates from the contaminated groundwater in cost-effectively way, associated with the drinking water chlorine disinfection.The preparation and characterization of Ferrum coated titanium electrodes play essential role in this project. Fe coated Ti cathode was the principal determinant of catalytic reduction performance which affects the reduction efficiency of nitrate. The optimal technological parameters in term of nitrate reduction efficiency were:no annealing treatment for Ti substrate, precursor liquid concentration2mol-Fe/L, calcination temperature500℃, the brushing times4, and calcination time60mins.Based on mechanism analysis of the supported bimetallic palladium catalysts for water-phase nitrate reduction, an innovative method which reduces nitrate to ammonia nitrogen by Ti/Fe cathode was proposed. By exploring electrochemical reduction regularity, the reasonable parameters for the reaction condition were: current density10mA/cm2, electrode distance6cm, stirring intensity450rad/min, electrolysis time60mins. Under this condition, the reduction rate of NO3--N was up to51.8%.Supported by the mechanism of ammonia nitrogen reduction by chlorination, the study focused on reaction condition optimization. The main reactions include cathodic reduction of nitrate and anodic oxidation of the produced ammonia. Through orthogonal experimentation, the optimum condition in terms of low energy consumption and the high TN removal rate were obtained:concentration of chloride ion200mg/L, current density10mA/cm2, electrode distance6cm, stirring intensity450rad/min. When the reaction, under this condition, sustained for90minutes, TN removal rate was up to74.9%, with concentrations of nitrate, nitrite and ammonia meeting the drinking water standard.According to the above research results and theoretical analysis, the mechanism of nitrate-N reduction on cathode may be related with Fe chemical adsorbing O in nitrogen-oxides ion to fix N-O, then reductant produced by electrolysis attacking N-O to form new chemical bond N-O.In conclusion, the new technology, based on Ferrum coated titanium cathode, was effective and efficient to reduce nitrate from ground water.