Suspended anode-type microbial fuel cells for enhanced electricity generation

Abstract

Electricity generation in microbial fuel cells can be restricted by a few factors, such as the effective area of the anode for biofilm attachment, diffusion limitation of substrates and internal resistance. In this paper, a suspended anode (carbon-based felt granule)-type microbial fuel cell was developed to make full use of the volume of the anode chamber and provide a larger surface area of the anode for the growth of exoelectrogenic bacteria. The current collector was rotated in the anodic chamber to contact with the suspended granules intermittently and achieve better mixing. The open-circuit voltage reached steady state at around 0.83 V. The maximum power density obtained from each scenario increased steadily with the increase in mixing rate. The internal resistance decreased when the rotational rate and the content of the carbon granules were increased. The maximum power density reached 951 AE 14 mW m À3 with a corresponding minimum internal resistance of 162.9 AE 3.5 U when the mass of carbon granules was 50 g and the rotational rate was 300 rpm. The suspended microbes made negligible contribution to the power density. The microbial fuel cell with a higher content of carbon granules had lower coulombic efficiency and lower relative abundance of exoelectrogenic bacteria.rsc.li/rsc-advances 9868 | RSC Adv., 2020, 10, 9868-9877This journal is

Moving bed capacitive bioanodes

“…The implementation of capacitive bioanodes has followed two directions [100]: a bioanode with an internal or external capacitor [84][85][86][87][88]101,128,147,148,[187][188][189][190][191][192][193][194], or fluidized capacitive granules [96,[104][105][106][107]114,115,150,[195][196][197]. The main difference between the two is that the bioanode with a capacitor is used with intermittent control, which requires a period without producing an electrical current in the circuit [85], whereas the fluidized granules are in intermittent contact, where the capacitive granules only discharge when they are in contact with the current collector [96].…”

“…The fluidized bed bioanode continuously produces a capacitive current on top of the faradaic current as charged particles pass the discharge cell. The fluidization also improves access to substrate [196] and promises to decrease clogging issues related to wastewater treatment since it allows for physical separation of the charging and discharging process [107].…”

“…Several types of fluidized bed bioanode reactors have been developed [116]. Mechanical stirring [104,196], liquid [105][106][107]114,127,150,[195][196][197] and gas [96,107] have been used to move the charged granules to induce intermittent contact with the discharge anode, which generated an electrical current. A moving granular bed reactor has been developed, in which the granules were fluidized in a gas lift and recirculated through settling on top of a moving granular bed.…”

“…To be able to use large amounts of activated carbon granules, and thus a large specific surface area of electrode surface, as capacitive bioanodes, fluidized bed bioanode reactors have been developed [96,[104][105][106][107][108]114,127,196,197,203]. The granules function as charge carrier as well as biofilm carrier, and are discharged at a current collector to produce a continuous current [108].…”

“…The granules function as charge carrier as well as biofilm carrier, and are discharged at a current collector to produce a continuous current [108]. These granules are fluidized to make intermittent contact with a current collector, by stirring [104,196], liquid [105,106,114,127,196,197,203] and gas [96,107,108]. The reactors make use of intermittent charge storage of the capacitive bioanode granules by using the large ratio of external surface area per volume of granules for the biofilm to produce charge.…”