School of Civil and Environmental Engineering, Nanyang Technological University, 639798, Singapore; Singapore Membrane Technology Centre, Nanyang Environment & Water Research Institute, Nanyang Technological University, 637141, Singapore.
School of Civil and Environmental Engineering, Nanyang Technological University, 639798, Singapore; Singapore Membrane Technology Centre, Nanyang Environment & Water Research Institute, Nanyang Technological University, 637141, Singapore.
Water Res. 2024 Feb 1;249:120982. doi: 10.1016/j.watres.2023.120982. Epub 2023 Dec 6.
Two-pass reverse osmosis (RO) process is prevailing in seawater desalination, but each process must consume considerable amounts of chemicals to secure product water quality. Caustic soda is used to raise the pH of the first-pass RO permeate (also the second-pass RO feed) to ensure adequate removal of boron in the subsequent second-pass RO, while antiscalants and disinfectants such as hypochlorite are added in the feed seawater for scaling and biofouling control of the first-pass RO membranes. Here, we report for the first time a flow-through electrochemically assisted reverse osmosis (FT-EARO) module system used in the first-pass RO, aiming to dramatically reduce or even eliminate chemical usage for the current RO desalination. This novel system integrated an electroconductive permeate carrier as cathode and an electroconductive feed spacer as anode on each side of the first-pass RO membrane. Upon applying an extremely low-energy (< 0.005 kWh/m) electrical field, the FT-EARO module could (1) produce a permeate with pH >10 with no alkali dosage, ensuring sufficient boron removal in the second-pass RO, and (2) generate protons and low-concentration free chlorine near the membrane surface, potentially discouraging membrane scaling and biofouling while maintaining satisfactory desalination performance. The current study further elucidated the high scalability of this novel electrified high-pressure RO module design. The low-chemical manner of FT-EARO presents an attractive practical option towards green and sustainable seawater desalination.
两段式反渗透（RO）工艺在海水淡化中占主导地位，但每个工艺都必须消耗大量的化学品来确保产品水的质量。氢氧化钠用于提高第一段 RO 渗透物的 pH 值（也是第二段 RO 的进料），以确保在后段第二段 RO 中充分去除硼，而阻垢剂和次氯酸盐等消毒剂则添加到进料海水中，以控制第一段 RO 膜的结垢和生物污染。在这里，我们首次报告了一种用于第一段 RO 的流通式电化学辅助反渗透（FT-EARO）模块系统，旨在大幅减少甚至消除当前 RO 脱盐过程中的化学品使用。该新型系统在第一段 RO 膜的每一侧集成了一个作为阴极的导电渗透物载体和一个作为阳极的导电进料间隔物。在施加极低能量（<0.005 kWh/m）电场的情况下，FT-EARO 模块可以：1）产生 pH 值>10 的渗透物，无需加碱，确保在第二段 RO 中充分去除硼；2）在膜表面附近生成质子和低浓度游离氯，可能抑制膜结垢和生物污染，同时保持令人满意的脱盐性能。本研究进一步阐明了这种新型带电高压 RO 模块设计的高可扩展性。FT-EARO 的低化学方法为绿色可持续海水淡化提供了有吸引力的实用选择。
