Interdisciplinary Graduate School, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore; Residues and Resource Reclamation Centre (R3C), Nanyang Environment and Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, CleanTech One, Singapore 637141, Singapore.
Division of Environmental and Water Resources, School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore; Singapore-Berkeley Building Efficiency and Sustainability in the Tropics (SinBerBEST) Program, Berkeley Education Alliance for Research in Singapore (BEARS) Center, Singapore.
Water Res. 2017 Mar 1;110:332-341. doi: 10.1016/j.watres.2016.11.040. Epub 2016 Nov 14.
We investigated the removal of haloacetic acids (HAAs) from swimming pool waters (SPWs) by two nanofiltration membranes NF270 and NF90. The strong matrix effect (particularly by Ca) on membrane rejection prompts us to systematically investigate the mechanistic role of Ca in HAA rejection. At typical SPW pH of 7.5, NF90 maintained consistently high rejection of HAAs (>95%) with little influence by Ca, thanks to the dominance of size exclusion effect for this tight membrane (pore radius ∼ 0.31 nm). In contrast, the rejections of both inorganic ions (e.g., Na and Cl) and HAA anions were decreased at higher Ca concentration for NF270 (pore radius ∼ 0.40 nm). Further tests show that the rejection of neutral hydrophilic molecular probes and the membrane pore size were not affected by Ca. Although Ca is unable to form strong complex with HAAs, we observed the binding of Ca to NF270 together with a reduction in its surface charge. Therefore, the formation of membrane-Ca complex, which weakens charge interaction effect, was responsible for the reduced HAA rejection. The current study reveals important mechanistic insights of the matrix effect on trace contaminant rejection, which is critical for a better understanding of their fate and removal in membrane-based treatment.
我们研究了两种纳滤膜 NF270 和 NF90 从游泳池水中去除卤乙酸 (HAAs) 的效果。强基质效应（特别是 Ca 对膜排斥的影响）促使我们系统地研究 Ca 在 HAA 排斥中的机械作用。在典型的 SPW pH 值为 7.5 时，NF90 对 HAA 的排斥率始终保持在较高水平（>95%），受 Ca 的影响较小，这得益于这种紧密膜（孔径约为 0.31nm）对尺寸排除效应的主导作用。相比之下，对于 NF270（孔径约为 0.40nm），在较高的 Ca 浓度下，无机离子（例如 Na 和 Cl）和 HAA 阴离子的排斥率都降低了。进一步的测试表明，中性亲水分子探针的排斥率和膜孔径不受 Ca 的影响。尽管 Ca 不能与 HAAs 形成强配合物，但我们观察到 Ca 与 NF270 的结合以及其表面电荷的减少。因此，形成的膜-Ca 复合物削弱了电荷相互作用效应，这是导致 HAA 排斥率降低的原因。本研究揭示了基质效应对痕量污染物排斥的重要机理见解，这对于更好地理解它们在膜基处理中的命运和去除至关重要。
