Advanced redox processes for sustainable water treatment

Oxidation and reduction reactions govern a wide range of biotic and abiotic processes. Among these are advanced oxidation processes (AOPs) and advanced reduction processes (ARPs) that have been developed to remove contaminants and pathogens from water. While these AOPs and ARPs can be very effective, they do not take full advantage of the synergy between oxidation and reduction. In this Review we summarize the chemistry of state-of-the-art UV-based AOPs and ARPs and compare them with a novel alternative process that involves UV activation of low-molecular-weight diketones. Contaminant removal by this process involves a synergistic combination of oxidation and reduction, the benefits of which could lead to a shift in water treatment technologies from discrete AOPs and ARPs to combined oxidation–reduction processes. Beyond applications for water treatment, the proposed advanced oxidation–reduction processes may also be helpful for the design and application of electron transfer in a range of other fields.