Influence of natural organic matter on nanoscale zero-valent iron for contaminants removal in water: A critical review

Nanoscale zero-valent iron (nZVI) is attracting a great deal of attention for its widely study in the fields of groundwater remediation and wastewater treatment. Natural organic matter (NOM) widely exists in nature, and its complexity and specificity inevitably affect the process of nZVI removing contaminants. In this review, how NOM influences nZVI performance in contamination remediation is well summarized. Firstly, the influence of NOM on properties of nZVI is consolidated. This includes overcoming its tendency to easily aggregate and sediment, improving its transport in groundwater, affecting its structural transformation, and decreasing its toxicity. Furthermore, the latest viewpoints about possible influence mechanisms of NOM on various contaminants removal by nZVI are sorted out. The effect of NOM is changed with different situations and composed of multiple synergies, such as competing reactive sites, being as an electron shuttle, supporting nZVI dispersion, and so on. Finally, the challenge and future development of nZVI environmental application in the presence of NOM are summarized from theoretical and practical perspectives. Overall, this review aims at providing a reference specifically for the environmental application of nZVI and the prediction of products fate with NOM existence.