Frontier review on metal removal in bioelectrochemical systems: mechanisms, performance, and perspectives
Zixuan Wang, Zhen He
Abstract
Bioelectrochemical systems (BESs) have been investigated for metal removal and potential recovery from wastewaters. To better understand BES-based metal removal, in this paper we conducted a deeper literature analysis of BES-based metal removal, explored the removal mechanisms, and discussed the challenges of this approach. Four mechanisms are involved to achieve metal removal in BESs: direct redox reaction (DRO), indirect byproduct precipitation (IBP), ion migration, and biological removal. Most removals were via DRO or IBP mechanisms. IBP showed the highest median removal rate at 0.062 kg m−3 d-1 and biological removal had the lowest at 0.0034 kg m−3 d-1. More than 60% of the studies could achieve >95% removal efficiency. Cathode efficiency is affected by the competition from co-existing electron acceptors. More energy consumption data should be reported to better understand the energy advantages of BESs in metal removal. Kinetic analysis demonstrates that IBP may lead to a higher removal rate when the metal concentration is low, while DRO would be more advantageous at a higher initial concentration. The future of metal removal is to recover the removed metal and the recovering methods must consider the minimal interruption of BES operation.