Comparison of the removal of monovalent and divalent cations in the microbial desalination cell

Abstract

Microbial desalination cell (MDC) is a promising technology to desalinate water and generate electrical power simultaneously. The objectives of this study were to investigate the desalination performance of monovalent and divalent cations in the MDC, and discuss the effect of ion characteristics, ion concentrations, and electrical characteristics. Mixed salt solutions of NaCl, MgCl 2 , KCl, and CaCl 2 with the same concentration were used in the desalination chamber to study removal of cations. Results showed that in the mixed salt solutions, the electrodialysis desalination rates of cations were: Ca 2+ > Mg 2+ > Na + > K + . Higher ionic charges and smaller hydrated ionic radii resulted in higher desalination rates of the cations, in which the ionic charge was more important than the hydrated ionic radius. Mixed solutions of NaCl and MgCl 2 with different concentrations were used in the desalination chamber to study the effect of ion concentrations. Results showed that when ion concentrations of Na + were one-fifth to five times of Mg 2+ , ion concentration influenced the dialysis more profoundly than electrodialysis. With the current densities below a certain value, charge transfer efficiencies became very low and the dialysis was the main process responsible for the desalination. And the phosphate transfer from the anode chamber and potassium transfer from the cathode chamber could balance 1%-3% of the charge transfer in the MDC.

Simultaneous Removal of Phenol and Dissolved Solids from Wastewater Using Multichambered Microbial Desalination Cell

“…It might be due to the non-ideal characteristics of AEM near cathode, which might have diffused back the Na + ions from concentrate chamber toward cathodic chamber. Chen et al [32] reported that the ions may back diffuse through membrane due to concentration gradient and decreased electric field force with low current developed by the MDCs. Generally, when the substrate depletes, the current density of the system starts decreasing with increase in internal resistance.…”

Microbial desalination cells as a versatile technology: Functions, optimization and prospective

“…It was reported that the decrease of conductivity in saline solution increased the IR and thus decreased the overall cell potential of the MDC [8]. The IR was also affected by the intermembrane distance [56]. With inter-membrane distance of 0.30 cm, 1 cm and 1.50 cm, the corresponding IR was 342 Ω, 222 Ω and 214 Ω, respectively.…”

“…At lower ER values, the electrical current in theory is higher and thus can increase the desalination rate. Researchers demonstrated that when ER reduced from 1000 Ω to 10 Ω, the maximum current density and columbic efficiency increased by 680% and 275% respectively [56]. A continuously operated UMDC with 2 d of HRT showed that at an ER of 0.1 Ω, the UMDC achieved a maximum current of 143 mA and 86 mA, and TDS removal of 60.10 ± 6.50% and 42.50 ± 1.40% for saltwater and artificial seawater, respectively.…”

New insights into the application of microbial desalination cells for desalination and bioelectricity generation

“…Therefore, the effects of proton accumulation in the anolyte was diminished by setting back Rext to low external resistance at 1  to facilitate an easy flow of electrons from the anode to the cathode. Such higher flow of electrons enhanced the migration of ions from the desalination chamber to anode and cathode chambers, which ultimately increased the EC decrement (Chen et al, 2013). The migrated Clions neutralized the accumulated proton in the anolyte and reduced the effect of pH drop.…”

“…This is mainly due to the precipitations of ions on the membrane leading to membrane scaling. Such precipitation of ions could decrease the whole reactor performance over time (Chen et al, 2013;Ma et al, 2015;Ebrahimi et al, 2018). Moreover, the rate of ions transportation through IEMs depends on the membrane microstructures.…”