Enhanced boron removal by electricity generation in a microbial fuel cell

Abstract

Boron needs to be removed during desalination, because excessive boron in the product water for irrigation can deteriorate plant growth. In this study, a microbial fuel cell (MFC) equipped with anion exchange membrane (AEM) was proposed and investigated to remove boron via two successive steps: boric acid is ionized to borate ions in the presence of high pH as a result of cathode reaction, and borate ions are transported across AEM driven by electricity generation. Two scenarios were examined, the MFC as a pretreatment process and the MFC as a post-treatment step in connection with conventional desalination. In the pretreatment mode, the MFC achieved 40–50% boron removal and the high pH condition could benefit downstream desalination or other methods for further boron removal. In the post-treatment mode, the MFC removed 80–90% of boron and decreased the boron concentration from 20 to 2 mg L− 1 or from 5 to 1 mg L− 1, which meets the irrigation water requirement. The removal rate in this MFC was much higher than that of a previously reported microbial desalination cell coupled with Donnan Dialysis system. Those results have demonstrated the potential of using MFCs for boron removal with benefits of conductivity reduction and electricity generation.NPRP grant # 6-289-2-125 from the Qatar National Research Fund (a member of Qatar Foundation).Scopu