Research On The Process Of Reducing And Removing Nitrate By Iron-based Metal Composites

The content of nitrate in wastewater has gradually increased,the content of nitrogen elements has far exceeded the national discharge standard.The pollution of nitrate in groundwater has become a quite important environmental problem,and the pollution has a worsening trend,which has attracted widespread attention.At present,the main technologies used in nitrate removal in groundwater are biological denitrification,ion exchange technology,membrane separation and chemical reduction repair,among which biological treatment is efficient and low consumption but must be followed up;ion exchange and membrane separation only concentrate or transfer nitrate pollutants,and not completely remove them;H₂ is used as reducing agent in the process of catalytic reduction by chemical reduction method,and H₂ is easy to explode,which is not convenient for engineering application,Fe⁰ is widely used to reduce nitrate in groundwater because of its cheap and easy to obtain,however,its product is mainly NH₄⁺-N,only a very small part of nitrate may be converted to N₂.To solve the above problems,the Fe-Cu?Fe-Ag and Fe-Ni bimetallic composites were prepared by liquid phase reduction method.The surface morphology and structure characteristics of the materials were analyzed by XRD and SEM,and the materials were used to simulate the reduction and removal of nitrate nitrogen wastewater in laboratory,to change the amount of p H?and reaction temperature of wastewater,to obtain the better process conditions in the reduction process,and to speculate the possible nitrate nitrogen reduction mechanism of the denitrification method.The results show that the type and loading amount of the second metal deposited on the Fe0 will affect the composition of the reduction products of denitrification reaction.Ag the Fe-Ag alloy with a loading rate of 3%has the highest reduction activity,the reaction 60 can remove 91%nitrate nitrogen,and the nitrogen selectivity is close to 20%,but the ammonia nitrogen production rate is larger.Under the condition of no buffer to control the change of solution pH,both Fe-Cu and Fe-Ag composite metal materials have high removal rate in acid solution,and the nitrogen efficiency of denitrate decreases with the increase of pH value,which indicates that the removal of nitrate from iron alloy is an acid-driven reaction.100mL nitrate solution with an initial concentration of 22.58mg-N/L,the nitrate removal rate can reach 92%after 60 min of reaction when the dosage of Fe-Ag metal composite is 0.3 g and the pH is 2.In addition,the experiment speculated that the mechanism of nitrate nitrogen reduction catalyzed by bimetallic catalyst is a typical heterogeneous catalytic reaction,which is catalytic activity or related to the formation of bimetallic active sites on the surface.Considering the practical application of the materials in the future,a suitable process for denitration of wastewater was designed and its main equipment was designed with the plant wastewater contaminated by nitrate as the treatment object of denitration reaction.