Chlorobenzene (CB) is typically emitted during industry
and waste
incineration, posing hazards to the safety of humans and the ecosystem.
Successful CB elimination has been achieved in microbial electrolysis
cells (MECs), whereas little is known about elimination effectiveness
in response to the structural and functional characteristics of biofilms.
Herein, the bacterial viability and functional gene abundance of biofilms
in MECs with carbon cloth (CC), reticulated vitreous carbon (RVC),
and nickel foam (NF) as cathodes are emphasized. Experimental results
reveal that bacterial viability on RVC is 62 and 92% higher than that
of CC and NF, respectively, achieving 30 and 65% superior CB removal
efficiency. Notably, the MEC with RVC outperforms that with the highly
conductive NF due to low electron loss, causing a twice as much increase
in coulombic efficiency. Metagenomic analysis indicates that the CB
degrader (i.e., Pandoraea), electrochemically
active bacteria (i.e., Chryseobacterium), and genes responsible for CB metabolism (i.e., todD and clcB) in RVC biofilms increase by over 30%,
fourfold, and 10%, respectively, compared to CC and NF. Moreover,
CB degradation is found to occur via two possible pathways: (1) thorough
elimination by dechlorination, hydrolysis, and oxidation after conversion
to 3-chlorocatechol, and (2) conversion into phenol and benzoate for
complete degradation.