Tang Chuyang Y, Fu Q Shiang, Criddle Craig S, Leckie James O
Environmental Engineering and Science, Department of Civil and Environmental Engineering, Stanford University, Stanford, California 94305-4020, USA.
Environ Sci Technol. 2007 Mar 15;41(6):2008-14. doi: 10.1021/es062052f.
Perfluorooctane sulfonate (PFOS) is an emergent contaminant of substantial environmental concerns. In this study, reverse osmosis (RO) and nanofiltration (NF) membranes were used to remove this toxic and persistent compound from PFOS-containing wastewater. Five RO membranes and three NF membranes were tested at a feed concentration of 10 ppm PFOS over 4 days, and the PFOS rejection and permeate flux performances were systematically investigated. PFOS rejection was well correlated to sodium chloride rejection. The rejection efficiencies for the RO membranes were > 99%, and those for the NF membranes ranged from 90-99%. Improvement in PFOS rejection, together with mild flux reduction (< 16%), was observed at longer filtration time. Such shifts in rejection and flux performance were probably due to the increased PFOS accumulation at longer duration, as shown by X-ray photoelectron spectroscopy and liquid chromatograph and tandem mass spectrometry results. A fraction of PFOS molecules might be entrapped in the polyamide layer of the composite membranes, which hindered the further passage of both water and other PFOS molecules. In a similar fashion, PFOS rejection and fouling were enhanced for greater initial flux and/or applied pressure, where PFOS accumulation was promoted probably due to increased hydrodynamic permeate drag. Flux reduction was also shown to correlate to membrane roughness, with the rougher membranes tend to experience more flux reduction than the smoother ones.
全氟辛烷磺酸（PFOS）是一种引发大量环境问题的新兴污染物。在本研究中，采用反渗透（RO）和纳滤（NF）膜从含PFOS的废水中去除这种有毒且持久的化合物。在进水PFOS浓度为10 ppm的条件下，对5种RO膜和3种NF膜进行了为期4天的测试，并系统研究了PFOS截留率和渗透通量性能。PFOS截留率与氯化钠截留率密切相关。RO膜的截留效率>99%，NF膜的截留效率在90 - 99%之间。在较长的过滤时间内，观察到PFOS截留率有所提高，同时通量略有下降（<16%）。截留率和通量性能的这种变化可能是由于在较长时间内PFOS积累增加所致，X射线光电子能谱以及液相色谱和串联质谱结果表明了这一点。一部分PFOS分子可能被困在复合膜的聚酰胺层中，这阻碍了水和其他PFOS分子的进一步通过。同样，对于更高的初始通量和/或施加压力，PFOS截留率和污染加剧，这可能是由于流体动力渗透拖曳增加促进了PFOS积累。通量下降还显示与膜粗糙度相关，较粗糙的膜比较光滑的膜往往通量下降更多。
