Abstract Nanofiltration (NF) is seen as a very promising technology to remove micropollutants (MPs) from wastewater. Unfortunately this process tends to produce a highly saline concentrate stream, as commercial NF membranes retain both the MPs and most of the ions. The high salinity makes subsequent degradation of the MPs in a bio-reactor very difficult. The main goal of this study is to prepare and study a NF membrane that combines a low salt rejection with a high MPs rejection for the treatment of secondary-treated municipal wastewater. This membrane was prepared using layer by layer (LbL) deposition of the weak polycation poly(allylamine hydrochloride) (PAH), and the weak polyanion poly(acrylic acid) (PAA), on the surface of a hollow fiber dense ultrafiltration (UF) membrane. The ionic strength of the coating solutions was varied and properties of the formed polyelectrolyte multilayers (PEMs), such as hydration, hydrophilicity, hydraulic resistance and ions retention were studied. Subsequently we tested the apparent and steady state rejection of MPs from synthetic wastewater under cross-flow conditions. The synthetic wastewater contained the MPs Diclofenac, Naproxen, Ibuprofen and 4n-Nonylphenol, all under relevant concentrations (0.5–40 µg/L, depending on the MP). PEMs prepared at lower ionic strength showed a lower hydration and consequently a better retention of MPs than PEMs prepared at higher ionic strengths. A strong relationship between the apparent rejection of MPs and their hydrophobicity was observed, likely due to adsorption of the more hydrophobic MPs to the membrane surface. Once saturated (steady state), the molecular size of the MPs showed the best correlation with their rejection, indicating rejection on the basis of size exclusion. In contrast to available commercial NF membranes with both high salt and MP rejection, we have prepared an unique membrane with a very low NaCl retention (around 17%) combined with a very promising removal of MPs, with Diclofenac, Naproxen, Ibuprofen and 4n-Nonylphenol being removed up to 77%, 56%, 44% and 70% respectively. This membrane would allow the treatment of secondary treated municipal wastewater, strongly reducing the load of MPs, without producing a highly saline concentrate stream.

中文翻译：

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使用弱聚电解质多层纳滤膜去除二级处理城市废水中的微污染物

摘要 纳滤（NF）被视为一种非常有前景的去除废水中微污染物（MPs）的技术。不幸的是，这个过程往往会产生高盐浓度的浓缩液，因为商业 NF 膜保留了 MP 和大部分离子。高盐度使得 MPs 在生物反应器中的后续降解变得非常困难。本研究的主要目标是制备和研究一种结合了低盐截留率和高 MPs 截留率的 NF 膜，用于处理二级处理的城市废水。该膜是使用弱聚阳离子聚（烯丙胺盐酸盐）（PAH）和弱聚阴离子聚（丙烯酸）（PAA）在中空纤维致密超滤（UF）表面逐层（LbL）沉积制备的膜。涂层溶液的离子强度是变化的，并且研​​究了所形成的聚电解质多层膜 (PEM) 的性能，例如水合作用、亲水性、耐水压性和离子保持力。随后，我们测试了在错流条件下合成废水中 MP 的表观和稳态排斥。合成废水中含有 MPs 双氯芬酸、萘普生、布洛芬和 4n-壬基酚，均处于相关浓度（0.5–40 µg/L，取决于 MP）。与在较高离子强度下制备的 PEM 相比，在较低离子强度下制备的 PEM 显示出较低的水合作用，因此对 MP 的保留更好。观察到 MP 的表观排斥与其疏水性之间存在很强的关系，这可能是由于更疏水的 MP 吸附到膜表面。一旦饱和（稳态），MPs 的分子大小与它们的排斥反应最好，表明基于大小排阻的排斥反应。与具有高盐分和 MP 截留率的市售 NF 膜相比，我们制备了一种独特的膜，其 NaCl 截留率非常低（约 17%），并且具有非常有希望的 MPs 去除效果，包括双氯芬酸、萘普生、布洛芬和 4n-壬基酚的去除率分别高达 77%、56%、44% 和 70%。这种膜可以处理二级处理的城市废水，大大减少 MP 的负荷，而不会产生高盐浓度的浓缩液。我们已经制备了一种独特的膜，其 NaCl 保留率非常低（约 17%），并且对 MPs 的去除效果非常好，双氯芬酸、萘普生、布洛芬和 4n-壬基酚的去除率高达 77%、56%、44% 和 70 ％ 分别。这种膜可以处理二级处理的城市废水，大大减少 MP 的负荷，而不会产生高盐浓度的浓缩液。我们已经制备了一种独特的膜，其 NaCl 保留率非常低（约 17%），并且对 MPs 的去除效果非常好，双氯芬酸、萘普生、布洛芬和 4n-壬基酚的去除率高达 77%、56%、44% 和 70 ％ 分别。这种膜可以处理二级处理的城市废水，大大减少 MP 的负荷，而不会产生高盐浓度的浓缩液。