Recent development and application of mixed metal oxides in wastewater treatment: A review

Mixed metal oxides (MMO) containing more than one type of metal, have shown great application potential to be adsorbents and catalysts due to their unique structural changes in water. Therefore, they have great potential in wastewater treatment. In this paper, the preparation methods of MMO are described, including solid-phase sintering, polymeric precursor calcination, layered double hydroxides precursor calcination, chemical coprecipitation and hydrothermal methods, and control methods of the element composition, element proportion, and structure of MMO to regulate their properties by changing these synthesis methods and conditions are introduced in detail. The main mechanisms of MMO in the removal of heavy metals, metalloids, organic pollutants and anionic are comprehensively analyzed which can be summarized as: in the process of structural reorganization of MMO, adsorption, catalysis and their synergy are accompanied. MMO can not only remove single pollutants efficiently, but also remove multiple pollutants simultaneously due to these three effects, so MMO have significant effects in effluent treatment, but at present most of the research is still at the experimental stage, and there are few studies on effluent treatment and engineering applications.