Mass transfer and reaction simultaneously enhanced airlift microbial electrolytic cell system with high gaseous o-xylene removal capacity

To overcome the limitation of mass transfer and reaction rate involved in the biodegradation of gaseous o-xylene, the airlift reactor and microbial electrolysis cell were integrated to construct an airlift microbial electrolysis cell (AL-MEC) system for the first time, in which the bioanode was modified by polypyrrole to further improve biofilm attachment. The developed AL-MEC system achieved 95.4% o-xylene removal efficiency at optimized conditions, and maintained around 75% removal efficiency even while the inlet o-xylene load was as high as 684 g m(- 3) h(-1). The existence of O-2 exhibited a competition in electrons with the bioanode but a positive effect on ring-opening process in the o-xylene oxidation. The limitation of mass transfer had been overcome as the empty bed resistance time in the range of 20-80 s did not influence the system performance significantly. The microbial community analysis confirmed the o-xylene degradation microbes and electroactive bacteria were the dominant, which could be further enriched at 0.3 V against standard hydrogen electrode. This work revealed the feasibility of the AL-MEC system for the degradation of o-xylene and similar compounds, and provided insights into bioelectrochemical system design with high gaseous pollution removal capacity.

Automated summary

The integration of an airlift reactor and a microbial electrolysis cell in the development of an airlift microbial electrolysis cell system has successfully addressed the limitations in mass transfer and reaction rate in the biodegradation of gaseous o-xylene. The system achieved a high removal efficiency of 95.4% under optimized conditions, and maintained a removal efficiency of approximately 75% even at high inlet o-xylene loads. The presence of O-2 had a positive effect on the ring-opening process in the o-xylene oxidation. The study also confirmed the dominant microbial communities involved in o-xylene degradation and electroactivity.