膜电容去离子（Membrane capacitive deionization, MCDI）是一种低能耗脱盐技术，通过在电极两端施加一定电压，溶液中阴阳离子在电场作用下分别向正负极迁移，并储存在电极表面的双电层上，实现了盐的去除。在MCDI的基础上，当电极可流动时称为流动电极电容去离子（Flow electrode capacitive deionization, FCDI）。驱动力是影响MCDI脱盐性能的重要因素之一。本论文主要研究在不同电压下MCDI的脱盐性能，以及FCDI脱盐性能影响因素，并通过在FCDI电极液中添加导电剂实现对FCDI脱盐性能的优化。以活性炭布作为电极构建MCDI装置研究电压对其脱盐性能的影响。在吸附阶段，当电压为4.8 V时，MCDI脱盐速度为1.2 V时的7.4倍，而动态电荷效率维持稳定(>93%)的时长随电压升高而减少。在解吸阶段，电压为4.8 V时，MCDI的解吸速度为1.2 V时的3.4倍，当电压小于3.6 V时，MCDI动态电荷效率维持稳定，在电压为4.8 V运行135 s后，电荷效率开始下降。采用三种不同加电模式（1.2 V/20 min，4.8 V/90 s，4.8 V/20 min）运行50周期后，4.8 V /90 s的加电方式实现了MCDI快速稳定的脱盐。采用FCDI装置研究多种因素对其脱盐性能的影响。FCDI采用整体循环的运行模式，其脱盐速度较分别循环提升74%。在整体循环模式运行时，FCDI的脱盐速度随电压与活性炭电极浓度的增加而增大，其电荷效率在电压超过1.2 V时开始下降。当电极液盐浓度由0.65 g/L增大到30 g/L时，在电压大于0.6 V时FCDI的脱盐速度加快，但是电极室与脱盐室之间盐离子的浓差扩散加强，FCDI的电荷效率大幅下降，在2.4 V时达到最大也仅为59.3%。通过在FCDI电极液中添加导电剂优化FCDI的脱盐性能。添加炭黑对FCDI脱盐性能提升优于石墨，是由于炭黑的导电性强于石墨。当1 wt%的炭黑加入20 wt%活性炭电极中，在0.9 V时FCDI的脱盐速度提升67%。FCDI电荷效率随炭黑添加量的增加而增大，当炭黑添加量为1.5 wt%时，FCDI的电荷效率高达96.5%。这是由于炭黑的添加减少了流动电极的欧姆内阻与界面接触阻力，使流动电极内电子传递加快，实现了FCDI脱盐性能的优化。但是添加炭黑并不能阻止离子的浓差扩散，在电极液盐浓度为30 g/L时，添加炭黑没能提升FCDI脱盐性能。

Membrane capacitive deionization (MCDI) is an energy-efficient desalination technology. When the voltage is applied across the anode and cathode, ions are driven to migrate to the electrodes and stored in the electric double layers (EDL) formed on the electrode surface. Flow-electrode capacitive deionization (FCDI) uses suspended carbon materials as electrodes in an MCDI. Driving force is one of the main factors that greatly impact MCDI’s desalination performance. In this study, the desalination performance of MCDI and FCDI were investigated at different applied voltages. For FCDI, the conductive additives were added into flow-electrode electrolyte to enhance the desalination performance.The flow-by MCDI device employed carbon cloth as electrode in this study. The desalination rate of MCDI at 4.8 V applied voltage was 7.4 times than that at 1.2 V during adsorption stage. While the dynamic charge efficiency remained stable at first and then decreased regardless of applied voltages. During desorption phase, the MCDI’s desalination rate at 4.8 V was 3.4 times than that at 1.2 V. The dynamic charge efficiency remained stable when the voltage was below 3.6 V, but it began to decrease after 135 s at 4.8 V. The high desalination rate and good stability were realized when the desalination time was 90 s at 4.8 V after 50 cycles at three applied voltage modes (1.2 V/20 min, 4.8 V/90 s, 4.8 V/20 min). Factors that influence FCDI’s desalination performance were investigated, including operation modes, applied voltages, concentration of flow-electrode and flow-electrode electrolyte. FCDI operated under short-circuited closed cycle mode, which ensured sufficient desorption of flow-electrode, delivered better performance than that under isolated closed cycle mode. Meanwhile, the desalination rate increased with the applied voltage, but the charge efficiency began to decrease when the voltage exceeded 1.2 V. Higher desalination rate was gained when the flow-electrode electrolyte increased from 0.65 to 30 g/L and the applied voltage overtop 0.6 V, but the charge efficiency decreased greatly, which was attributed to the concentration diffusion between middle chamber and electrode compartments. The desalination performance of FCDI with additional carbon black (CB) was better than that with graphite because of the better conductivity of CB. With 1 wt% CB added, the desalination performance increased nearly 67% at 0.9 V, and the charge efficiency increased with CB concentration. The highest charge efficiency (96.5%) was obtained in FCDI with 1.5 wt% CB. The addition of CB reduced the ohmic resistance and interfacial charge transfer resistance of a flow-electrode, which facilitated the electronic charge transfer and strengthened the FCDI’s desalination performance. However, the addition of CB couldn’t restrain the concentration diffusion, thus it was invalid to promote the performance of FCDI when the flow-electrode electrolyte was 30 g/L.