Gaseous toluene, ethylbenzene, and xylene mixture removal in a microbial fuel cell: Performance, biofilm characteristics, and mechanisms

Microbial fuel cells (MFCs) are regarded as promising alternatives to anaerobic benzene, toluene, ethylbenzene, and xylene (BTEX) mineralization due to the enhancement of microbial degradation rate caused by bioanodes. In this research, a dual-chambered MFC was employed to evaluate the removal efficiency and power generation of single TE(o-X) or of dual or ternary TE(o-X) mixtures. Individually, TE(o-X) was readily biodegradable with a removal efficiency of 94.8%, 86.3%, and 71.6%, respectively, but the presence of toluene and o-xylene exhibited an adverse influence on the degradation of other mixed components. The o-xylene has the greatest inhibitory effect on microbial activity, as evidenced by laser scanning confocal microscope images. Microbial community analysis revealed that exoelectrogens prevailed in the absence of the o-xylene. Shifting the feeding gas from toluene to another individual gas or mixture caused the quantities of the exoelectrogens to gradually decrease. Moreover, the o-xylene degrader of Alicycliphilus sp. were prevailed from ~17.7% to ~60.3% in presence of the o-xylene. In addition, the observation of the nanowire/pili using scanning electron microscope images and cyclic voltammetry analysis revealed that the electrons produced were transferred to the anode directly.