Rejection of organic micropollutants (disinfection by-products, endocrine disrupting compounds, and pharmaceutically active compounds) by NF/RO membranes
“…In laboratory-scale cross-flow tests with NF-90 membranes rejections of ketoprofen and diclofenac were reported to be greater than 90% Xu et al, 2005). In another study with RO membranes the retention of negatively charged diclofenac was 95 % (Kimura et al, 2003). Some studies reported higher removal efficiencies of polar and charged compounds in NF/RO processes due to interactions with membrane surfaces (Ozaki and Li, 2002;Bellona et al, 2004;Amy et al, 2005;Braeken et al, 2005).…”
“…In laboratory-scale cross-flow tests with NF-90 membranes rejections of ketoprofen and diclofenac were reported to be greater than 90% Xu et al, 2005). In another study with RO membranes the retention of negatively charged diclofenac was 95 % (Kimura et al, 2003). Some studies reported higher removal efficiencies of polar and charged compounds in NF/RO processes due to interactions with membrane surfaces (Ozaki and Li, 2002;Bellona et al, 2004;Amy et al, 2005;Braeken et al, 2005).…”
“…This adsorption causes lower retentions than expected for membranes with smaller pores than the compound [64] due to diffusion of the xenobiotic through the membrane. The main difference between estrone and BPA is in their molecular structure.…”
Section: Adsorptionmentioning
confidence: 83%
“…In general it increases with increase of compound MW [14,35,64] and retentions are usually higher than 90% [112,111,138,62,69] for compounds with MW higher than the MWCO of the membrane [14,136,70] (see Figure 4A). MW has been shown to be a good indicator of the retention trend obtained by NF and RO membranes compared to other molecular sizes, e.g.…”
Section: Size Exclusionmentioning
confidence: 96%
“…Adsorptions of pesticides, steroid hormones, volatile organic carbon (VOCs) and pharmaceuticals of up to 100% are obtained [24,35,66,96,64,119,65,87,148,93,106,151,70,97].…”
Section: Adsorptionmentioning
confidence: 99%
“…Until saturation of the membrane sites is achieved the real retention is overestimated [63,64,91]. While adsorption occurs, the apparent retention is often >90% but once the membrane becomes saturated this latter decreases drastically, sometimes to <10% [63,64,55,56,80].…”
Small molecular weight xenobiotics are compounds of extreme concern in potable water applications due to their adverse human health and environmental effects. However, conventional water treatment processes cannot fully and systematically remove them due to their low concentrations in natural waters and wastewaters. Biological limitation to degrade such compounds is another cause for inefficient removal.Physical barriers like membranes possessing pore sizes smaller than the compounds to be removed emerged as a good solution. Nanofiltration and reverse osmosis proved to be quite effective for xenobiotics removal in potable water production in the Paris purification plant of Méry-sur-Oise. However, even these very narrow pore membrane processes may result in incomplete removal: xenobiotics retention is high but factors such as adsorption, size exclusion and charge repulsion affect unpredictably their retention. The water solutions complexity to be treated renders xenobiotics removal predictions even more difficult due to interactions between xenobiotics and compounds in water.Removal of xenobiotics by microfiltration and ultrafiltration is very low because adsorption on the membrane is the main retention mechanism. Combining those with other processes (e.g. activated carbon) can considerably improve xenobiotics removal.The least studied processes in xenobiotics removal are electrodialysis, membrane distillation and pervaporation. Electrodialysis removal of organic xenobiotics shows a breakthrough through the membrane possibly due to adsorption followed by diffusion. Membrane distillation presents high removal rates of xenobiotics due to the compounds low vapour pressure. For volatile organic xenobiotics or solutions of trace amounts both membrane distillation and pervaporation can be used, xenobiotics interaction with the membrane being the key factor.In this book chapter a thorough synopsis of current knowledge on xenobiotics removal is presented and balanced with recent fundamental studies of underlying mechanisms, informing both the practitioner regarding membrane capabilities for xenobiotics removal and the researcher with the current state-of-art.
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