Abstract Membrane distillation (MD) has great potentials to treat produced water in energy industries. However, volatile organic compounds (VOCs) existing in the produced water added in the fracking process can hinder the treatment process regarding two aspects: permeate quality and MD flux performance. To address this challenge, this study aims to systematically study the effects of the VOCs on the MD permeation performance and permeate quality, and the mechanism of its penetration. Acetic acid, ethylene glycol, isopropyl alcohol (IPA), and 2-Butoxyethanol (2-BE), which are commonly found in the produced water, were extensively investigated and their impacts were reviewed and compared. Among all the VOCs, 2-BE had the highest mass transfer despite its low vapour pressure and large molecule weight. Some of the VOCs had surfactant properties, which meant they could penetrate the membrane pores easily during MD process. In long-term operation, pore wetting started to appear as the salt rejection was dropping in the MD process, and flux was also decreasing. Based on the results, this study suggested that the strength of surfactant properties and intra-molecular hydrogen bonds between water molecules and VOCs are as significant as vapour pressure for the VOCs in terms of mass transfer efficiency in MD system.

中文翻译：

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挥发性有机物对真空膜蒸馏采出水中水的影响

摘要 膜蒸馏（MD）在处理能源工业产出水方面具有巨大潜力。然而，在压裂过程中添加的采出水中存在的挥发性有机化合物（VOCs）会在两个方面阻碍处理过程：渗透质量和MD通量性能。为了应对这一挑战，本研究旨在系统地研究 VOCs 对 MD 渗透性能和渗透质量的影响及其渗透机制。广泛研究了产出水中常见的乙酸、乙二醇、异丙醇 (IPA) 和 2-丁氧基乙醇 (2-BE)，并对它们的影响进行了审查和比较。在所有 VOC 中，2-BE 尽管蒸气压低且分子量大，但具有最高的传质能力。一些 VOC 具有表面活性剂特性，这意味着它们可以在 MD 过程中轻松穿透膜孔。在长期运行中，随着MD过程中脱盐率的下降，孔隙润湿开始出现，通量也随之下降。基于这些结果，该研究表明，就 MD 系统中的传质效率而言，表面活性剂的强度和水分子与 VOC 之间的分子内氢键与 VOC 的蒸气压一样重要。