Research progress in efficient nitrogen generation <italic>via</italic> nitrate wastewater degradation by nanoscale zero-valent iron

Nanoscale zero-valent iron （nZVI） is used for the reductive degradation of nitrate wastewater due to its advantages， such as abundant elemental content， strong reducibility， and easy recoverability. However， its surface is prone to passivation， making efficient reactions difficult to sustain. The reaction is highly dependent on an acidic environment and has poor selectivity toward target reactants. The products of its reaction with nitrate wastewater are often dominated by toxic ammonia nitrogen. For this reason， numerous researchers have conducted studies focusing on the efficient reaction between nZVI and nitrate wastewater to generate pollution-free nitrogen gas. This paper first elaborates on the mechanism of nitrate wastewater degradation by nZVI alone and highlights its limitations. It then summarizes the enhancement measures to improve the nitrate-degradation efficiency and nitrogen-generation rate of nZVI. The summary shows that the key to improving the nitrate degradation efficiency of nZVI lies in providing sufficient protons and reducing the negative impact of oxides. The main measures to increase the nitrogen yield include three aspects. First is the modification of the chemical properties or structure of nZVI itself. Second is the addition of reducing additives. Third is the coupling with other processes. Finally， this paper comments on and prospects various measures for enhancing the efficient degradation of nitrate wastewater by nZVI.