Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06520-8286, United States.
Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment (NEWT), Yale University, New Haven, Connecticut 06520-8286, United States.
Environ Sci Technol. 2020 Mar 17;54(6):3663-3677. doi: 10.1021/acs.est.9b07482. Epub 2020 Mar 6.
Electro-driven technologies are viewed as a potential alternative to the current state-of-the-art technology, reverse osmosis, for the desalination of brackish waters. Capacitive deionization (CDI), based on the principle of electrosorption, has been intensively researched under the premise of being energy efficient. However, electrodialysis (ED), despite being a more mature electro-driven technology, has yet to be extensively compared to CDI in terms of energetic performance. In this study, we utilize Nernst-Planck based models for continuous flow ED and constant-current membrane capacitive deionization (MCDI) to systematically evaluate the energy consumption of the two processes. By ensuring equivalently sized ED and MCDI systems-in addition to using the same feed salinity, salt removal, water recovery, and productivity across the two technologies-energy consumption is appropriately compared. We find that ED consumes less energy (has higher energy efficiency) than MCDI for all investigated conditions. Notably, our results indicate that the performance gap between ED and MCDI is substantial for typical brackish water desalination conditions (e.g., 3 g L feed salinity, 0.5 g L product water, 80% water recovery, and 15 L m h productivity), with the energy efficiency of ED often exceeding 30% and being nearly an order of magnitude greater than MCDI. We provide further insights into the inherent limitations of each technology by comparing their respective components of energy consumption, and explain why MCDI is unable to attain the performance of ED, even with ideal and optimized operation.
电驱动技术被视为一种替代当前最先进的反渗透技术的潜在方法，用于淡化咸水。基于电吸附原理的电容去离子（CDI）在节能的前提下得到了广泛研究。然而，尽管电渗析（ED）是一种更为成熟的电驱动技术，但在能量性能方面，它尚未与 CDI 进行广泛比较。在这项研究中，我们利用基于 Nernst-Planck 的模型，对连续流电渗析和恒流膜电容去离子（MCDI）进行了系统评估，以评估这两个过程的能耗。通过确保 ED 和 MCDI 系统具有相同的尺寸-除了在两种技术中使用相同的进料盐度、盐去除率、水回收率和产率-适当比较了能耗。我们发现，对于所有研究的条件，ED 的能耗（能量效率更高）都低于 MCDI。值得注意的是，我们的结果表明，ED 和 MCDI 之间的性能差距在典型的咸水淡化条件下很大（例如，进料盐度为 3 g L、产品水为 0.5 g L、水回收率为 80%、产率为 15 L m h），ED 的能量效率通常超过 30%，几乎比 MCDI 高出一个数量级。我们通过比较各自的能耗组成部分，进一步深入了解了每种技术的固有局限性，并解释了为什么即使在理想和优化的操作条件下，MCDI 也无法达到 ED 的性能。
