Nitrate Reduction Using Iron and Copper Bimetallic Nanoparticles Supported by Chelating Resin: Effect of Solution Chemistry, Mechanism, and Regeneration

Abstract

Nanoscale zero-valent iron/copper supported on chelating resin (D-Fe/Cu) was prepared for removing nitrate from water. Batch experiments were carried out to investigate the effect of solution chemistry, including the initial pH of the solution, initial dissolved oxygen (DO), coexisting anions, and humic acid on the removal of nitrate. Results showed that the initial pH and DO had a significant effect on the removal of nitrate. Coexisting anions, including Cl−, SO42−, PO43−, and HCO3−, inhibited nitrate reduction. The removal efficiency of nitrate was 95.51%, and the selectivity of N2 was 52.49% at the end of the reaction. The results of X-ray photoelectron spectroscopy (XPS) analysis before and after the reduction showed that Fe(0) was directly involved in the nitrate reduction reactions. After the reaction with nitrate, Fe(0) was oxidized to Fe(II) or Fe(III), the content of Fe(II) increased, and the amount of Fe(III) decreased. The Fe(II)/Fe(III) cycle existed on the surface of Fe(0) during the reduction process with nitrate. Cu only provided active sites to adsorb hydrogen, without direct participation. The results demonstrated that D-Fe/Cu can be reused, and the removal efficiency of nitrate was 97.41% in the fifth recycle.