Singapore Membrane Technology Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, Singapore 637141, Singapore.
Singapore Membrane Technology Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, Singapore 637141, Singapore; School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
Water Res. 2022 Aug 1;221:118768. doi: 10.1016/j.watres.2022.118768. Epub 2022 Jun 16.
Recently, thermo-responsive nonionic amphiphilic copolymers have shown a great potential as forward osmosis (FO) draw solutes for high-salinity water desalination and zero-liquid discharge (ZLD). However, the relationship between the copolymer structural properties and key characteristics as draw solutes, as well as copolymer's chemical stability after regeneration have not been much studied. In this work, we systematically investigated poly (ethylene oxide)-block-poly (propylene oxide)-block-poly (ethylene oxide) (PEO-PPO-PEO) copolymers as draw solute. The results showed that the PEO segments significantly influenced the viscosity, osmotic pressure and lowest phase separation temperature of the copolymer aqueous solutions. Among four commercial copolymers studied, Pluronic® L35 with moderate molecular weight (Mn 1,900 Da), 50% PEO, and relatively high hydrophilic-lipophilic balance (HLB) showed the best draw solution (DS) performance. It also showed great stability in physiochemical properties and draw capacity after more than ten cycles of regeneration. On the other hand, despite the fact that membrane fouling was observed due to the use of copolymer DS, the FO flux (∼1.2 L m h, as similar with the virgin membrane) was not affected when high-salinity feedwater such as seawater RO brine was applied. Overall, our study has provided a more comprehensive understanding on the characteristics of nonionic amphiphilic copolymer DS and showcased the promise of copolymer-driven FO process in high-salinity water desalination and ZLD.
最近，温敏型非离子两亲嵌段共聚物作为正向渗透（FO）汲取剂在高盐度水淡化和零液体排放（ZLD）方面显示出巨大的潜力。然而，共聚物结构特性与作为汲取剂的关键特性之间的关系，以及共聚物再生后的化学稳定性还没有得到太多研究。在这项工作中，我们系统地研究了聚（环氧乙烷）-嵌段-聚（环氧丙烷）-嵌段-聚（环氧乙烷）（PEO-PPO-PEO）共聚物作为汲取剂。结果表明，PEO 链段显著影响共聚物水溶液的粘度、渗透压和最低相分离温度。在所研究的四种商业共聚物中，具有中等分子量（Mn1900 Da）、50%PEO 和相对较高亲水-亲油平衡值（HLB）的 Pluronic® L35 表现出最佳的汲取液（DS）性能。它在经过十多次再生循环后，在物理化学性质和汲取能力方面也表现出很好的稳定性。另一方面，尽管由于使用共聚物 DS 而观察到膜污染，但当使用高盐度原水（如海水 RO 浓水）时，FO 通量（约 1.2 L m h，与原始膜相似）不受影响。总的来说，我们的研究更全面地了解了非离子两亲嵌段共聚物 DS 的特性，并展示了共聚物驱动的 FO 工艺在高盐度水淡化和 ZLD 方面的应用前景。
