Quinoid Redox Mediators and Their Involvement in Environmental Pollution Treatment

In recent years, quinoid redox mediators (QRMs) have attracted increasing attention because of their key role in wastewater biotreatment. Previous studies have shown that the anaerobic respiration of many bacteria could be coupled to the reduction and reoxidation of quinone groups. Thus, QRMs are widely involved in the microbial transformation of various organic and inorganic substances. To date, few reviews have focused on the involvement of quinoid compounds in environmental pollution biotreatment processes. In this paper, we review the different types of QRMs that interact closely with microorganisms, the characteristics of those QRMs, the involvement of QRMs during the biotransformation of recalcitrant organic pollutants, heavy metal ions and metallic oxides, and their enhancement on microbial fuel cells. Finally, the future research focus and application prospects with regard to different types of QRMs are proposed. This study can improve our understanding of QRM-mediated environmental pollution biotreatment processes and provide fundamental guidance on what kinds of QRMs are practical for engineering applications.