| The challenge of nitrate pollution in ground water has become severe. For the NO3--N Pollution Control Technology of groundwater, it is widely recognized that the electrochemical catalytic reduction technology is the most promising one. However, the catalysts used in the current study all rely on noble metal, which affects their widely use. The objective of this study is to explore a new electrochemical method to remove nitrate from ground water, based on the cheap transition metal Co as the catalytist.The performance of electrode catalytic is directly related to its facial features, of which the precursor liquid concentration, baking time, the brushing frequency of liquid coating precursor and burned time are determinants. For these three factors, research concerning the catalytic effect of the cathode in different conditions was carried out. The experimental results showed that the optimal conditions were: precursor liquid concentration2mol-Co/L, calcination temperature500℃, the brushing times6, and calcination time60minutes.With Ti coated Co electrode, the NO3--N in water could be catalytic deoxygenated. And the reduction production was mainly ammonia, and the nitrite was excluded. The optimal treatment conditions in terms of catalytic reduction rate were: current density6mA/cm2, electrode distance9mm, stirring intensity450rad/min. Adding Cl-to the pretreated groundwater contaminated by nitrate, Cl" can react with HClO which has high oxidation activity under the electric field. Then HClO could convert NH4+-N to N2, so that it could really achieve the harmless treatment of NO3--N. Based on the above experimental studies, the optimal reaction conditions were:concentration of Cl-200mg/L, current density14mA/cm2, electrode distance 9mm, stirring intensity300rad/min, electrolysis time120mins. Under this condition, the reduction rate of TN was up to90.0%and the concentrations of nitrate, nitrite and ammonia met the national drinking water standard.Based on the research above, this study proposed a mechanism model of the catalytic reduction that NO3-was adsorbed on the cataylist and reducted. The mechanism of NH4+-N removal is that HClO, which is the product of electrolysis, oxidates NH4+-N to N2. |
