Electron shuttles mediated bioelectrochemical degradation of volatile chlorinated hydrocarbons: A review

Persistent contamination and rapid spread of volatile chlorinated hydrocarbons (VCHs) seriously threaten human health and ecosystems. Utilizing a bioelectrochemical system (BES) to treat VCHs is a promising strategy while inefficient extracellular electron transfer between cathode and VCHs is a bottleneck in improving VCHs removal effects of BES. Thus, electron shuttles (ESs) which facilitate extracellular electron transfer have been extensively involved in BES over the last two decades. In this review, the studies of VCHs degradation in BES with ESs were summarized and the structural characteristics of different ESs were classified. Besides, the mechanisms of ESmediated extracellular electron transfer were clarified and the influencing factors to this process were explored. Finally, the outlooks and challenges of BES application in VCHs degradation were discussed. In all, this review provided the theoretical guidance for VCHs degradation in BES with the assistance of ESs and offered technical support for BES application in VCHs removal from wastewater and groundwater.