The effects of microbial fuel cells coupled with solar cells under intermittent illumination on sediment remediation

Comparative study of the removal of sulfate by UASB in light and dark environment

At present, the application of sewage treatment technologies is restricted by high sulfate concentrations. In the present work, the sulfate removal was biologically treated using an upflow anaerobic sludge blanket (UASB) in the absence/presence of light. First, the start-up of UASB for the sulfate removal was studied in terms of COD degradation, sulfate removal, and effluent pH. Second, the impacts of different operation parameters (i.e., COD/SO42- ratio, temperature and illumination time) on the UASB performance were explored. Third, the properties of sludge derived from the UASB at different time were analyzed. Results show that after 28 days of start-up, the COD removal efficiencies in both the photoreactor and non-photoreactor could reach a range of 85-90% while such reactors could achieve > 90% of sulfate being removed. Besides, higher illumination time could facilitate the removal of pollutants in the photoreactor. To sum up, the present study can provide technical support for the clean removal of sulfate from wastewater using photoreactors.

In situ degradation of organic pollutants by novel solar cell equipped soil microbial fuel cell

The soil microbial fuel cell (SMFC) has been widely used for soil remediation for its low cost and being eco-friendly. But low degradation efficiency and high mass transfer resistance limit its performance. This study constructed a solar cell-soil microbial fuel cell (SC-SMFC) with different voltages, which use clean energy to improve system performance. At different voltages, 2.0-V system showed the best performance and the maximum output power increased by 330% compared with SMFC. Moreover, 2.0-V SC-SMFC showed the fastest phenol degradation rate of 14 μg·mL^-1·d^-1 at the concentration of 80 μg/mL, which was twice of SMFC. Further increasing the concentration to 320 μg/mL, the system showed extremely high concentration limit and degraded 90% within 19 days. Under this condition, SC-SMFC still showed excellent cycle stability, with the third-round degrading 90% phenol in 13 days. Finally, electrochemical impedance spectroscopy (EIS) mechanism study showed that solar cells can accelerate microbial metabolic process and reduce the internal resistance, in which the 2.0-V system was only 87% of SMFC. In conclusion, SC-SMFC provides a green, low-cost, and convenient method for in situ soil remediation in the future.

Performance Study on Methanol Steam Reforming Rib Micro-Reactor with Waste Heat Recovery

Automobile exhaust heat recovery is considered to be an effective means to enhance fuel utilization. The catalytic production of hydrogen by methanol steam reforming is an attractive option for onboard mobile applications, due to its many advantages. However, the reformers of conventional packed bed type suffer from axial temperature gradients and cold spots resulting from severe limitations of mass and heat transfer. These disadvantages limit reformers to a low efficiency of catalyst utilization. A novel rib microreactor was designed for the hydrogen production from methanol steam reforming heated by automobile exhaust, and the effect of inlet exhaust and methanol steam on reactor performance was numerically analyzed in detail, with computational fluid dynamics. The results showed that the best operating parameters were the counter flow, water-to-alcohol (W/A) of 1.3, exhaust inlet velocity of 1.1 m/s, and exhaust inlet temperature of 773 K, when the inlet velocity and inlet temperature of the reactant were 0.1 m/s and 493 K, respectively. At this condition, a methanol conversion of 99.4% and thermal efficiency of 28% were achieved, together with a hydrogen content of 69.6%.