A microbial fuel cell driven capacitive deionization technology for removal of low level dissolved ions

The microbial fuel cell (MFC) is an emerging technology, which uses exoelectrogenic microorganisms to oxidize organic matter in the wastewater to produce electricity. However, the low energy output limits its application in practice. Capacitive deionization (CDI), an electrochemically controlled method for deionization by the adsorption of ions in the electrical double layer region at an electrode–solution interface, requires a low external power supply. Therefore, in this study, we investigated the MFC driven CDI (MFC–CDI) technology to integrate deionization with wastewater treatment and electricity production. Taking advantage of the low potential requirement of CDI, voltage generated from a continuous flow MFC could be used to drive the CDI to achieve removal of the electrolyte to a stable status. The results indicated that among the three connection types of MFCs including single-, series-, and parallel-configuration, the parallel connection of two MFCs resulted in the highest potential (0.63 V) applied to CDI and the conductivity removal of NaCl solution was more than 60%. The electrosorption capacities under different electrolyte concentrations of 50, 100 and 150 mg L−1 were 150, 346 and 295 μg g−1, respectively. These results suggest that the new MFC–CDI technology, which utilizes energy recovery from the wastewater, has great potential to be an energy saving technology to remove low level dissolved ions from aqueous solutions for the water and wastewater treatment processes.

► Continuous flow MFCs driven CDI for removal of dissolved ions was developed.
► Parallel connection of two MFCs to drive CDI displayed better deionization effect.
► Conductivity removal efficiency above 50% was observed for 50 and 100 mg L−1 NaCl.