UNSW Centre for Transformational Environmental Technologies, Yixing, Jiangsu 214206, PR China; School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052, Australia.
UNSW Centre for Transformational Environmental Technologies, Yixing, Jiangsu 214206, PR China.
Water Res. 2021 Oct 1;204:117646. doi: 10.1016/j.watres.2021.117646. Epub 2021 Sep 9.
Membrane capacitive deionization (MCDI) is an emerging electric field-driven technology for brackish water desalination involving the removal of charged ions from saline source waters. While the desalination performance of MCDI under different operational modes has been widely investigated, most studies have concentrated on different charging conditions without considering discharging conditions. In this study, we investigate the effects of different discharging conditions on the desalination performance of MCDI electrode. Our study demonstrates that low-current discharge (1.0 mA/cm) can increase salt removal by 20% and decrease volumetric energy consumption by 40% by improving electrode regeneration and increasing energy recovery, respectively, while high-current discharge (3.0 mA/cm) can improve productivity by 70% at the expense of electrode regeneration and energy recovery. Whether discharging electrodes at the low current or high current is optimal depends on a trade-off between productivity and energy consumption. We also reveal that stopped flow discharge (85%) can achieve higher water recovery than continuous flow discharge (35-59%). However, stopped flow discharge caused a 20-30% decrease in concentration reduction and a 25-50% increase in molar energy consumption, possibly due to the higher ion concentration in the macropores at the end of discharging step. These results reveal that an optimal discharging operation should be obtained from achieving a balance among productivity, water recovery and energy consumption by varying discharging current and flow rate.
膜电容去离子（MCDI）是一种新兴的电场驱动技术，用于咸水淡化，涉及从盐水源水中去除带电离子。虽然 MCDI 在不同操作模式下的脱盐性能已经得到了广泛的研究，但大多数研究都集中在不同的充电条件上，而没有考虑放电条件。在本研究中，我们研究了不同放电条件对 MCDI 电极脱盐性能的影响。我们的研究表明，低电流放电（1.0 mA/cm）可以通过分别提高电极再生和增加能量回收来提高脱盐率 20%和降低体积能耗 40%，而高电流放电（3.0 mA/cm）可以提高 70%的产率，但代价是电极再生和能量回收的降低。无论是以低电流还是高电流放电，其是否为最优取决于产率和能耗之间的权衡。我们还发现，停流放电（85%）可以实现比连续流放电（35-59%）更高的水回收率。然而，停流放电导致浓缩率降低 20-30%，摩尔能量消耗增加 25-50%，可能是由于放电步骤结束时大孔中离子浓度较高所致。这些结果表明，通过改变放电电流和流速，可以在产率、水回收率和能耗之间取得平衡，从而获得最佳的放电操作。
