Nitrate Removal From Groundwater By Electrochemical Process Using TiO₂ Nano Electrode

Nitrate contamination of water resources has become an increasingly problem for all over the world. The increase of nitrate content in groundwater is has brought not only some potential safe problem to residents’ drinking water safety, but also a threat to people’s health. Compared with other nitrate processing technologies, electrochemical denitrification has the advantages of high efficiency, easy operation and environmental friendliness, attracting increasing research interests. However, this electrochemical method also has some disadvantages such as low current efficiency and high energy consumption. Owing to electrode materials play an important role in nitrate removal in electrochemical denitrification, thus, it is needed to develop new kinds of electrodes materials to improve the performance of nitrate reduction and reduce the operating costs.The objective of this study was to produce a novel TiO₂ nano cathode electrochemical for electrochemical denitrification of groundwater, in order to improve the current reduction efficiency, reduce the formation of by-products, increase nitrogen selectivity and nitrate reduction efficiency. TiO₂ nano electrode was fabricated by anodic oxidation. Using response surface methodology optimized the factors that influence the production of TiO₂ nano electrodes, determined the best conditions for preparation of the TiO₂ nano electrode. Through the characterization of TiO₂ nano electrode, we found that the surface of the titanium nano electrode showed tubular structures with relatively uniform pore diameter and wall thickness and the the main component was TiO₂.In this electrochemistry system, TiO₂ nano electrode and Ti/Pt electrode were used as the cathode and the anode, respectively. The reaction mechanisms and performance of nitrate reduction were studied using synthetic groundwater. Results are as follows（1） at current densities in the range of 12⁶2 mA/cm², the nitrate reduction rate increased with the increase of current density. At the current density of 50 mA/cm², the nitrate reduction efficiency reached 82.9% which was 286.2% higher than that from a Ti electrode;（2） the initial concentration of nitrate had little effect on nitrate reduction. When the initial nitrate concentration at the range of 20¹00 mg/L, the nitrate reduction efficiency remained 70.0% after 90 min electrolysis; The temperature had a great effect on nitrate reduction. Increasing temperature in the range of 0⁶0oC, the removal efficiency reached 86.7% at 60oC;（3） NaCl addition was found to have a positive effect on the removal of ammonia and other by products. At the current density of 50 mA/cm², NaCl concentration of 1.0 g/L, the concentration of nitrate decreased from 50 mg/L to 8.15 mg/L after 180 min electrolysis and no ammonia and nitrite were detected. The results showed that electrochemical method is a promising approach for the treatment of nitrate groundwater.