Toward concurrent organics removal and potential hydrogen production in wastewater treatment: Photoelectrochemical decolorization of methylene blue over hematite electrode in the presence of Mn(II)

A sustainable system capable of simultaneous removal of organic contaminants and hydrogen generation in wastewater treatment operation was studied using hematite electrode in the presence of Mn(II), PEC-Mn(II), as a proof of concept. The photoelectrochemical (PEC) system exhibited methylene blue (MB) decolorization threefold faster than that of photo-Fenton processes and yielded comparable photocurrent density to relative to the control system, i.e., PEC water splitting in the absence of MB at otherwise identical operation conditions. Furthermore, the advantages of PEC-Mn(II) system were no H2O2 addition, hydrogen production potential, and ease in Mn(II) separation via the formation of MnO2 precipitates during wastewater treatment operations. The PEC-Mn(II) process is a promising and sustainable approach toward wastewater treatment with the capability of concurrent photochemical energy generation. Moreover, the PEC-Mn(II) process can be an emerging energy from -wastewater alternative in addition to other systems such as microbial fuel cell and anaerobic digestion.