流动电极电容去离子是一种低能耗的脱盐和离子富集技术。本论文通过活性炭流动电极，成功实现了Cu2+的有效去除和高效回收；并利用炭黑电极的强导电性和电极液pH值调控特性，提升了脱盐效果和铜沉积质量；在此基础上对该技术的选择性效果和热力学效率进行了分析，以评价不同因素对能耗的影响，并通过不同技术的能耗对比阐述了该技术的节能特点。以活性炭作为电极研究不同因素对铜去除和回收的影响。电极混合循环模式下电极腔室中Na+得到解吸，并主要存在于电极液中（97.9%），而去除的Cu2+完全迁移至活性炭上，两种物质在电极腔室内实现了选择性分离。随着加电电压的上升，脱盐速率得到加快，但脱盐能耗也同时提高。电极中加入酸性试剂后，活性炭上铜可由二价形态优化为单质形态。连续运行12 h，出水铜浓度均低于2 mg/L，但同离子效应使得后期出水Cu2+浓度缓慢上升；24 h后电极上铜含量为4.2 mg/g 活性炭。以炭黑作为流动电极材料，优化脱盐效果和铜回收品质。与2.5 wt%和10 wt%活性炭相比，1.2 V电压下2.5 wt%炭黑的离子去除率更高。3.6 V电压下2.5 wt%炭黑的脱盐效果即可接近4.8 V电压下10 wt%活性炭的脱盐效果。由于炭黑的碳氧化作用，电极pH值逐渐下降，无需加入酸性试剂即实现了单质铜的产生。连续运行18 h，出水铜浓度均低于2 mg/L；24 h后电极铜含量为19 mg/g 炭黑。相比较离子过膜的选择性，电极富集作用下的选择性分离效果更明显，选择比达到20以上。电压和电流的上升会导致离子过膜选择比的下降，进而引发除铜能耗的上升；电极混合循环时选择比上升，储存的电容性能量得以释放，除铜能耗下降；连续运行时，选择比逐渐下降，同离子的进一步泄露导致除铜能耗逐渐上升。随着运行时间的延长，脱盐的能量利用效率（热力学效率）得到提高；炭黑流动电极用于脱盐的能量利用效率高于活性炭流动电极。由于有效的离子富集机制，流动电极电容去离子技术的能量消耗控制在30 kWh/kg Cu以下，与其他水处理电化学技术相比优势明显。
Flow electrode capacitive deionization (FCDI) is recognized as an energy-efficient technology for desalination and ion accumulation. In this study, effective removal and selective recovery of copper was achieved by FCDI using activated carbon electrode (AC-FCDI). The desalination and recovery performance were enhanced by FCDI using carbon black electrode (CB-FCDI), since carbon black was a strong conductive agent and could be oxidized with protons release. Selective separation and thermodynamic parameters were analyzed to evaluate the effects of different factors on energy consumption. The comparsion of energy consumption by various electrochemical wastewater treatments was also constructed to authenticate FCDI’s energy conservation.Factors affecting the desalination and copper recovery were investigated by AC-FCDI system. In short-circuited closed mode, 97.91% sodium ions were desorbed into the electrolyte and 100% copper ions were adsorbed on the AC particles. Therefore, selective separation was realized in the flow electrode chamber. Desalination process was accelerated by the increase of applied voltage, which was also accompanied with the rise of energy consumption. Divalent copper was transformed into elementary copper after the addition of acid in the electrolyte. The effluent concentration of copper ions was lower than 2 mg/L in the first 12 hours and gradually increased due to co-ion effect. The loading content reached 4.2 mg/g AC after 24-hour continuous operation. Better desalination and recovery performance were attained by substituting CB for AC as the flow electrode. Compared with that by 2.5 wt% AC and 10 wt% AC, higher ion removal efficiency was achieved by 2.5 wt% CB. The desalination performance by 2.5 wt% AC (3.6 V) was close to that by 10 wt% AC (4.8 V). The pH decrease of flow electrode, which was caused by oxidation of CB, resulted in the production of elementary copper. The effluent concentration of copper ions was lower than 2 mg/L in the first 18 hours and the loading content reached 19 mg/g CB after 24-hour continuous operation.Selective separation was more clear under the force of electrode-assisted accumulation than that by migration through cation exchange membrane; the value of selectivity could be over 20. The enhancement of voltage/current could result in decrease of trans-membrane selectivity and further increase of energy consumption used for copper removal. Electrode-assisted selectivity was raised in short-circuited closed mode, which led to the release of capacitive energy and decrease of energy consumption. In continuous operations, electrode-assisted selectivity slowly decreased, which triggered more co-ion leakage and then higher energy consumption. In continuous operations, thermodynamic energy efficiency (TEE) gradually increased. TEE values by CB-FCDI were higher than that by AC-FCDI. Compared with other electrochemical wastewater treatments, FCDI showed its advantage in being more energy-efficient with lower energy consumption (< 30 kWh/kg), which was attributed to its effective ion enrichment.
