Utilization of coconut shell carbon in the anode compartment of microbial desalination cell (MDC) for enhanced desalination and bio-electricity production

• Utilization of granular coconut shell carbon in a MDC and its influence on desalination efficiency was investigated.
• The performance of MDC was better in terms of desalination and current production in the case of carbon loaded MDC.
• Highest sodium removal efficiency was seen to be 84.2% in granular carbon loaded MDC with 20,000 mg L−1 initial NaCl concentration.
• SEM analysis of the anode bio-film showed meager coverage of rod shaped microorganisms and molecular pili (nanowires) structure.

Microbial desalination cell (MDC) is an emerging bio-electrochemical system. This is considered as one of the promising technologies for clean water and energy production. MDC technology is a derivative of the microbial fuel cell (MFC). This study reports bench-scale laboratory desalination using MDC loaded with granular coconut shell carbon, as a new electrode material in the anode compartment. Control experiments were performed without granular coconut shell carbon to evaluate the effect of carbon. Two different initial salt concentrations (20,000 and 30,000 mg L−1) were investigated. The experimental MDC (with carbon) for an initial concentration of 20,000 mg L−1 NaCl, produced the highest voltage of 461 ±9 mV at the same time removing about 84.2% of sodium and 58.25% of chloride in a single desalination cycle. The control MDC (without carbon) at the same time produced 261 mV and 68.2% removal of sodium and 50.7% removal of chloride. The SEM analysis of the bio-film showed meager coverage of rod shaped microorganisms and molecular pili (nanowires) structure. In the current study, nanowires as observed in SEM may be the potential electron transfer pathways. These results demonstrate for the first time the possibility of using activated carbon from a biomass waste, as electrode material for enhanced water desalination and power production in a MDC.

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