An Electrochemical Process Intensified By Metallic Particles For Nitrate Removal

Groundwater plays an important role in the planet’s hydrological cycle, and itserves as an important source of drinking water in various parts of the world.However, due to the increased use of fertilizers in intensive agriculture, industrial andmunicipal effluent discharge, nitrate contamination in groundwater is now widespread.The worldwide pollution represents a risk on human health. For this reason, effectivetreatment measures should be taken to tackle the problem of nitrate contamination.Electrochemical reduction of nitrate is receiving more and more attention due to itshigh efficiency, low investment cost, easy operation and environmental friendliness,compared to the traditional physicochemical and biological methods. However, thiselectrochemical method is limited in use due to its high energy consumption, lowcurrent efficiency and fouling problems. Thus optimization and modification of theprocess is needed to reduce the energy consumption and lower the operating costs.The objective of this study was to develop an electrochemical process intensifiedby metallic particles for nitrate reduction from groundwater. Iron, steel and copperparticles were evaluated as bipolar electrode materials for the reduction of nitrate inthe developed system. Among the three metallic particles studied, iron apparent to bethe optimal choice since it is none toxic, readily available and highly efficient.Electrolysis experiments confirmed the efficiency of the developed system.In the developed system, Ti/IrO2-Pt and Cu-Zn were employed as the anode andthe cathode, respectively. The performance and reaction mechanisms of nitratereduction were evaluated using synthetic groundwater. Results showed that highernitrate conversion yield of6.7%-17.7%along with29.4%-34.8%less energyconsumption were obtained in the electrochemical process intensified by iron particlesat current densities in the range of5-30mA/cm2with sodium chloride (NaCl),compared with those in the control experiment under similar conditions without iron.Sodium chloride addition was found to have a positive effect on the systemperformance. No nitrite-N was detected during the electrolysis in the presence ofsodium chloride. The concentration of total iron ion in the solutions was found to be less than0.25mg/L after100min electrolysis, which was lower than the maximumlimit recommended by the WHO（0.3mg/L），thus no post treatment was required. Thedeveloped system has been proved to promote electrochemical nitrate reduction andgreatly improve the electrical energy efficiency under various pH conditions. It is apromising approach for the treatment of nitrate-contaminated groundwater.