Forward osmosis (FO) has recently emerged as a new separation platform for a range of applications that are currently not possible for other membrane processes. This review paper covers key aspects of FO development with a specific emphasis on current technical challenges for practical applications. Main hurdles in the transition of FO from a lab-scale process to large scale applications include low-performance membranes, development of suitable draw solute, inherent transport phenomena (e.g. concentration polarization and reverse solute flux), membrane fouling and subsequent membrane cleaning. Several new FO membranes have been developed with some improved performances but no membrane has yet been found convincing in all of the key performance indicators. Draw solutes have been broadly investigated but mainly at the lab-scale. There have only been very few pilot-scale studies, most of them using inorganic salts as draw solutes. Development of thermo-responsive draw solutes and TFC membranes have been reported to be most effective in reducing reverse solute flux while altering the hydrodynamic conditions and the use of ultrasonication along with exploring other viable options have been suggested to tackle external and internal concentration polarization respectively. Although membrane fouling types and mitigation strategies have been extensively explored, this review also highlights the need for further research in biofouling for long-term FO operation.

中文翻译：

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从实验室到正向渗透的大规模应用：研究挑战和机遇

正渗透（FO）最近已成为一种新的分离平台，可用于目前其他膜工艺无法实现的一系列应用。这篇综述文章涵盖了FO开发的关键方面，特别强调了实际应用中当前的技术挑战。FO从实验室规模的过程过渡到大规模应用的主要障碍包括低性能膜，合适的牵引溶质的开发，固有的传输现象（例如浓差极化和反向溶质通量），膜结垢和随后的膜清洁。已经开发了几种具有改进性能的新型FO膜，但尚未发现在所有关键性能指标中令人信服的膜。抽提溶质已得到广泛研究，但主要是在实验室范围内。只有很少的中试规模研究，其中大多数使用无机盐作为提取溶质。据报道，开发热响应性拉伸溶质和TFC膜在降低反向溶质通量的同时改变流体力学条件最为有效，并且已建议使用超声波技术以及探索其他可行方案分别解决内部和内部浓度极化问题。尽管膜结垢的类型和缓解策略已得到广泛研究，但本综述还强调了对于长期FO操作在生物结垢方面需要进一步研究。据报道，开发热响应性拉伸溶质和TFC膜在减少反向溶质通量的同时改变流体力学条件最为有效，并且已建议使用超声波技术以及探索其他可行方案分别解决内部和内部浓度极化问题。尽管膜结垢的类型和缓解策略已得到广泛研究，但本综述还强调了对于长期FO操作在生物结垢方面需要进一步研究。据报道，开发热响应性拉伸溶质和TFC膜在降低反向溶质通量的同时改变流体力学条件最为有效，并且已建议使用超声波技术以及探索其他可行方案分别解决内部和内部浓度极化问题。尽管膜结垢的类型和缓解策略已得到广泛研究，但本综述还强调了对于长期FO操作在生物结垢方面需要进一步研究。