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Abstract Nitrate reduction by zero valent iron (Fe0) has been gained increasing attention. However, two key issues, that is, the reduction is efficient only at acidic condition; and the major… Click to show full abstract
Abstract Nitrate reduction by zero valent iron (Fe0) has been gained increasing attention. However, two key issues, that is, the reduction is efficient only at acidic condition; and the major reduction product is ammonium, which limited the application of Fe0 for the nitrate removal. In this study, to address these issues, a novel system of Fe0@Cu0 bimetal with formate/Fe3+ under UV irradiation was developed for the nitrate reduction. The results showed that 100% nitrate removal efficiency and 98% N2 selectivity were achieved at initial pH of 6.47 by a two-step reduction process: (1) the nitrate was firstly reduced to nitrite, while ammonium was negligible in the Fe0@Cu0/formate/UV system; (2) the accumulated nitrite in the effluent from the first-step reduction could be further reduced to nitrogen by CO2•− radical generated by the reaction of formic acid, Fe3+ and UV radiation. Almost no formate residual was found in the effluent due to the action of photo-induced electron transfer of Fe3+. The optimization of operation conditions and the combination mode of Fe0@Cu0 with formate/formic acid, Fe3+ and UV were investigated. The chemical denitrification mechanism of the Fe0@Cu0 particles was proposed.