Conventional asymmetric or thin-film composite forward osmosis (FO) membranes suffer from severe internal concentration polarization, which significantly hinders process performance and practical applications. Here we report the synthesis of the COOH-derived polyoxadiazole copolymer for the fabrication of a self-standing selective thin film without a support layer. The thickness of the membrane was controlled at merely a few micrometers to achieve a high rate of rejection of the Na₂SO₄ draw solution, while maintaining acceptable water permeability. Because of the symmetric architecture, the membrane exhibited excellent and identical FO performance at both of its sides. The structural parameter of the fabricated membranes was zero because of the absence of internal concentration polarization in the symmetric FO membranes. Our results highlight the potential of support-free membranes for the further development of FO technology.

中文翻译：

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自立，无支撑的正渗透膜，无内部浓度极化

常规的不对称或薄膜复合正向渗透（FO）膜遭受严重的内部浓度极化，这严重阻碍了工艺性能和实际应用。在这里，我们报告了合成COOH衍生的聚恶二唑共聚物的过程，用于制造不带支撑层的自立式选择性薄膜。将膜的厚度控制在仅几微米，以实现较高的Na ₂ SO ₄排斥率。吸取溶液，同时保持可接受的透水性。由于对称结构，该膜在其两侧均表现出出色且相同的FO性能。由于在对称的FO膜中没有内部浓度极化，所以制成的膜的结构参数为零。我们的结果凸显了无支撑膜在FO技术的进一步发展中的潜力。