| With increasingly serious problems of water resoures shortage, sewage recyling has gradually attracted more attention, making the desalination technology study and application a hot spot. Recently, Membrane capacitive desalination(MCDI), a new desalination technology, with high desalination efficiency, low energy comsuption and non-pollution, particularly with better desalination performance than capacitive desalination(CDI), has been widely concerned. This paper studied on MCDI desalination performance by focusing on periodicdesalination characteristicsof MCDI, different desalination performances between MCDI and CDI, and the influence factors of MCDI desalination performance, including membrane parameters, operation parameters and ionic properties, which would lay the foundation for the application of MCDI. The main achievements of this study are as follows:(1) During the adsorption process, the efflune nt concentration decreased rapidly and dramatically followed by relatively slow and slight increasing; good positive correlation was recovered between the desalination rate and the residual adsorption capacity. It showed that significantly higher current efficiency, enery efficiency and desalination efficiency was observed by MCDI than by CDI under the voltage of 0~1.2 V, indicating that better desalination performance of MCDI than CDI. Generally, significantly higher removel ra te by MCDI was recovered under both smaller menbrane resistance and larger ion exchange capacity.(2) The effect of operation parameters, including voltage, efflunent rate, temperature and efflunent concentration and regeneration form, on desalination perfermance was studied by both the control variable method and orthogonal test method. The results indicated that the desalination efficiency increased with the increase of voltage and temperature; whereas, decreased with the increase of efflunent rate and concentration. The optimal desalination performance in terms of the removal rate and energy efficiency was found under individual parameter, respectively, with the voltage of 1.2 V, the flow rate of 5.0~7.5 m L/min, the temperature of 20~25℃ and the concentration of 50~250 mg/L.To evaluate the index of salt removal rate, salt removal amount, energy consumption(E/V) and energy efficiency(E/M), respectively, it indicated that the dominant influencing factor was the flow rate,influent concentration, voltage and voltage.During regeneration, the regeneration efficiency reached the highest with reverse voltage, while this required extra energy. It is also observed that there was nearly no any regeneration efficiency in an open-circuit way. Results also showed that the short-circuit way yielded the best regeneration efficiency with no energy consumption. It implied that the short-circuit way is the most promising solution by considering regeneration performance and energy consumption.(3) The study on removel efficinecy of 10 kinds of ions by MCDI, including Ca2+,Mg2+,Na+,K+,SO42-,Cl-,NO3-,F-,Br-and PO43-, showed that the adsorption capacity of MCDI was negatively correlated with the ion valence, and positively correlated withion mass. It also indicated that the adsorption capacity of MCDI was negatively correlated with hydration radius of ion for ion with small hydration radius, and with crystal radius of ion for ionwith highhydration radius. The MCDI adsorption kinetics of 8 kinds of ions were more consistent with the first order reaction than the second order reaction, which was showed by the fitting results based on pseudo-first-order kinetic equation and pseudo-second-order kinetic equation, suggesting that the adsorption rate of the ion was proportional to the adsorption capacity of MCDI. |
