Augmenting microbial fuel cell power by coupling with supported liquid membrane permeation for zinc recovery

Simultaneous removal of organic and zinc contamination in parallel effluent streams using a Microbial Fuel Cell (MFC) would deliver a means of reducing environmental pollution whilst also recovering energy. A Microbial Fuel Cell system has been integrated with Supported Liquid Membrane (SLM) technology to simultaneously treat organic- and heavy metal containing wastewaters. The MFC anode was fed with synthetic wastewater containing 10mM acetate, the MFC cathode chambers were fed with 400mgL^-1 Zn²⁺ and this then acted as a feed phase for SLM extraction. The MFC/SLM combination produces a synergistic effect which enhances the power performance of the MFC significantly; 0.233mW compared to 0.094mW in the control. It is shown that the 165±7mV difference between the MFC/SLM system and the MFC control is attributable to the lower cathode pH in the integrated system experiment, the consequent lower activation overpotential and higher oxygen reduction potential. The change in the substrate removal efficiency and Coulombic Efficiency (CE) compared to controls is small. Apart from the electrolyte conductivity, the conductivities of the bipolar and liquid membrane were also found to increase during operation. The diffusion coefficient of Zn²⁺ through the liquid membrane in the MFC/SLM (4.26*10^-10m²s^-1) is comparable to the SLM control (5.41*10^-10m²s^-1). The system demonstrates that within 72h, 93±4% of the zinc ions are removed from the feed phase, hence the Zn²⁺ removal rate is not significantly affected and is comparable to the SLM control (96±1%), while MFC power output is significantly increased.