Electrochemistry/Catalytic Hydrogenation Coupling Process To Remove Nitrate From Wtaer

Nitrate(NO3--N) in potable water is an important issue because of its effects onwater safety. In recent years, due to the agricultural production of nitrogen fertilizerexcessive use, loss of contaminated soil, industrial wastewater and domestic sewagedischarge and other reasons, drinking water pollution of NO3--N is getting worse,and its governance is imminent. Currently, NO3--N in water removal methodbecause of technical and economic reasons limits its application in water treatment.Therefore, this paper presents a new technology of electrochemical/catalytichydrogenation coupling process for removing NO3--N from water.Nano Pd-Cu/γ-Al2O3catalyst was prepared by excessive impregnation methodwith palladium chloride (PdCl2) and copper nitrate (Cu (NO3)2) as the activeingredient, γ-phase nano-alumina (γ-Al2O3) as the carrier. The actual load of thecatalyst was determined by plasma atomic emission spectroscopy (ICP-AES); thecatalyst specific surface area, pore volume and average pore size characterizationwas analyzed by specific surface area analyzer (BET); the activity metal particlemorphology, size and distribution of nano Pd-Cu/γ-Al2O3catalyst was observed bytransmission electron microscopy (TEM); and analysis of catalyst activecomponents and phase crystal structure by X-ray diffraction (XRD). Researchresults showed that, the different load rate catalysts active metal of Pd and Cu canbe well supported on the γ-Al2O3carrier; the catalyst’s specific surface area is125m2/g with average pore diameter between15nm and18nm, is mesoporous; themorphology of active metal particles of catalyst is spherical and dispersion wellwith no significant agglomeration occurs, the average particle diameter is about6nm and its crystal structure is Pd0(111). Study of nano Pd-Cu/γ-Al2O3catalystperformance showed that with the increase of load factor, also a correspondingincrease in the activity of the catalyst, but its selectivity to N2decreases, when theload rate of5%, the catalyst exhibits excellent catalytic activity and goodselectivity.Denitrification performance, selectivity and current efficiency ofelectrochemical and electrochemical/catalytic hydrogenation process using smallelectrochemical test device was investigated. The results showed that low performance of electrochemical system with poor N2selectivity of only about25%,and low current efficiency(20%),when the5%Pd-Cu/γ-Al2O3catalysts wasadded to the reactor constitute an electrochemical/catalytic hydrogenation systemcan effectively improve the performance of the process, selectivity (82%) andcurrent efficiency (over50%); kinetics of the reaction indicates that theelectrochemical denitrification reaction is zero order reaction, as the same time, theelectrochemical/catalytic hydrogenation denitrification reaction is second-orderreaction,and the reaction kinetic constant k1=0.247(mg L-1min-1)and k2=0.00551(cm2mA-1min-1),respectively.Mechanism of electrochemical/catalytic hydrogenation denitrificationreaction was investigated by analyze intermediate products(NO2--N) and byproducts(NH4+-N), research results showed that the reaction mechanism is theaggregation of electrochemical denitrification and catalytic hydrogenationdenitrification: two simultaneously and independently reaction coupling by thereaction of brine electrolysis; the whole denitrification process is step-wise withmain degradation process of NO3--Nâ†'NO2--Nâ†'N2â†'NH4+-N.