Recent advances in application of iron-manganese oxide nanomaterials for removal of heavy metals in the aquatic environment

Heavy metal pollution has a serious negative impact on the ecological environment and human health due to its toxicity, persistence, and non-biodegradable properties. Among the technologies applied in heavy metals removal, adsorption has been widely used as the most promising method because of its simple operation, high removal efficiency, strong applicability, and low cost. Iron-manganese oxide nanomaterials, as an effective absorbent, have attracted wide attention due to their simple preparation, wide material sources, and lower ecological impact. So far, no quantitative investigation has been conducted on the preparation and application of iron‑manganese oxide nanomaterials in heavy metals removal. This review discussed the preparation methods and characteristics of iron‑manganese oxide nanomaterials over the past decade and provided some basic information for the improvement of preparation methods. The physicochemical properties of iron‑manganese oxide nanomaterials and environmental conditions are regarded as important factors that affect the removal efficiency of heavy metals. In addition, the removal mechanisms of heavy metals in aqueous solution with iron‑manganese oxide nanomaterials were mainly included redox, complex precipitation, electrostatic attraction, and ion exchange. The reusability and practicability in actual wastewater treatment of 3nganese oxide nanomaterials were further discussed. Several key problems still need to be solved in the existing progress, such as improving the ability and stability of the iron‑manganese oxide nanomaterials to remove heavy metals from actual wastewater. In conclusion, this review provides a future direction for the application of iron‑manganese oxide nanomaterials for heavy metals removal and even in the large-scale treatment of actual wastewater. • Synthesis methods and characteristics of iron-manganese oxide nanomaterials are discussed. • Application and influencing factors of heavy metals removal by iron-manganese oxide nanomaterials are reviewed. • Mechanisms of interaction between heavy metal ions and iron-manganese oxide nanomaterials are discussed. • Regeneration and utility of iron-manganese oxide nanomaterials for actual wastewater are summarized.