| Microbial capacity desalination cells (MCDCs) recently emerged as a promisingtechnology to simultaneously treat wastewater, desalinate saline water, and producerenewable energy such as electricity or hydrogen gas.MCDCs share the same principle ofbioelectrochemical reactions with microbial desalination cells (MDC). Waterfront ofsewage treatment plant effluent containing high salt concentration, generally traditionaldesalination process need relatively high energy consumption. But the new technologyhas several key problems need to breakthrough. This paper has carried out contrastMCDC reactor structure and desalting efficiency and mechanism research.Three types of ACC assemblies-bases MCDCs system were built. The first reactorE-MCDC with the exchanged situation of AEM and CEM in traditional MDC. TheA-MCDC used two piece of AEM to separate three chambers. The C-MCDC utilized twopieces of CEM to separate three chambers. The conductivity reductions of salt solutionfor the three MCDCs were47.71%、43.32%and51.61%. The total adsorbtion capacityfor the three chambers were31.25、26.63and29.1mg TDS/gACC. The ACC capacityelectrodes have physical adsorption and electro-adsorption effects. Electric adsorption inthe total removed salt accounted for28.95%,16.62%and23.7%respectively. For the firstdesalination cycle to remove most of salt and the amount of removed salt was reducedwith the increase of the desalination cycle. The A-MCDC system got the most stableperformance during5months operation.The conductivity of salt water for all the MCDCs decreased at the beginning of timeand then increased slowly, when treating5g/L of NaCl solution. The salt removalefficiency of E-MCDC reached the highest of47.83%. The conductivity reductions ofanolyte and catholyte in MCDC were14.46%and5.32%after desalinated150min. Withthe increase of NaCl concentration, the salt removal efficiency decreased and theadsorbing capacity increased. According to the equation liner fittings of the Langmuirand Freundlich，the maximum adsorption capacity of E-MCDC was72.99mg/g and thecapacity adsorption was complex bilayer adsorption. When the flow rate is less than50mL/min, the desalination ratio increases with the flow rate, continue to increase the flowrate, desalting efficiency lower. The salt removal efficiency of E-MCDC increased 37.37%, when the electrode number increased from1to4pairs. The capacity can beregenerated within1h through exchange the connection of electrode and activated carboncloth assemblies.The ionic composition and transport behavior of multiple ions in MCDCs had a greateinfluence on system performance and membrane scaling and fouling. The presence ofsparingly soluble cations such as Ca2+、Mg2+in saltwater negatively affected MCDCpower generation and desalination. Anions such as Br and SO42with Na+as counter-iondid not show significant effects on system performance. In the C-MCDC, calcium andmagnesium hydroxide could be formed on the CEM membrane during the desalination ofCa2+or Mg2+then cause the desalination performance decrease.The saline wastewater was demonstrated as inflow for the three chambers.Thedesalination ratio for the MCDCs under the function of physical adsorption andelectro-adsorption were1.43ms/(cm·h),1.25ms/(cm·h) and1.51ms/(cm·h), which wasgreater than the MDC system for0.1275ms/cm h). The saline water in middle chamberofr the MCDCs was decomposed under low voltage system, pH change rate higher thanthat of the MDC. The COD change rate in middle chamber for MCDCs was about17times than the MDC system. The COD removal rate in middle chamber was about3.6times than the anolyte for MCDCs. |
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