TY - JOUR
T1 - Partitioning of organic solutes between water and polyamide layer of RO and NF membranes
T2 - Correlation to rejection
AU - Ben-David, Adi
AU - Bason, Sarit
AU - Jopp, Juergen
AU - Oren, Yoram
AU - Freger, Viatcheslav
N1 - Funding Information:
The authors are indebted to Ms. Rosalia Fainstein and Dr. Sophia Belfer for their excellent technical assistance in preparing the membranes and performing ATR-FTIR spectroscopy and to Prof. Ora Kedem for stimulating discussions. The authors wish to thank Dr. Mark Wilf at Hydranautics and Dr. Jean-Paul DeWitte at Liquid Separations, Dow Deutschland for kindly supplying membrane samples. Financial support from the German-Israeli Foundation (Young Scientists Grant no. 1-2035.1102.05/2001) and the Ministry of Science of the State of Israel (Project no. 01-01-01496, the Program for Scientific and Technological Development for the Quality of the Environment and Water) is gratefully acknowledged.
PY - 2006/9/15
Y1 - 2006/9/15
N2 - The presence of organic compounds such as pesticides, herbicides, hormones and other toxic substances in raw surface and ground water is one of the emerging problems in the drinking water production. Membrane processes such as reverse osmosis (RO) and nanofiltration (NF) are considered promising candidates for removal of organics from water, however, recent reports indicate that many organic compounds, such as amines, phenols and amides, pass the membranes. Sorption in the membrane was assumed to be one of the factors that govern the selectivity of membranes towards small organic molecules and quantitative sorption data are crucial for understanding this effect. In this paper we report results of sorption measurements in the polyamide active layer (skin) of thin film composite membranes (SWC1, ESPA1 and NF200) of a group of organic compounds that pass these membranes significantly. The method is based on the analysis of attenuated total reflection FTIR spectra of the isolated active layer and is thus free of possible artifacts related to sorption by the support. Knowledge of the skin thickness allowed us to calculate the partition coefficient of the organic solute between the polyamide and water. Comparison of the sorption and rejection data for different membranes and solutes reveals that partitioning may significantly modify and even reverse the general rejection-size trend, as was demonstrated for a homologous series of alcohols. For some solutes, different rejection was found for similar values of both partitioning coefficient and size, suggesting that yet unclear effects related to molecular friction could be involved.
AB - The presence of organic compounds such as pesticides, herbicides, hormones and other toxic substances in raw surface and ground water is one of the emerging problems in the drinking water production. Membrane processes such as reverse osmosis (RO) and nanofiltration (NF) are considered promising candidates for removal of organics from water, however, recent reports indicate that many organic compounds, such as amines, phenols and amides, pass the membranes. Sorption in the membrane was assumed to be one of the factors that govern the selectivity of membranes towards small organic molecules and quantitative sorption data are crucial for understanding this effect. In this paper we report results of sorption measurements in the polyamide active layer (skin) of thin film composite membranes (SWC1, ESPA1 and NF200) of a group of organic compounds that pass these membranes significantly. The method is based on the analysis of attenuated total reflection FTIR spectra of the isolated active layer and is thus free of possible artifacts related to sorption by the support. Knowledge of the skin thickness allowed us to calculate the partition coefficient of the organic solute between the polyamide and water. Comparison of the sorption and rejection data for different membranes and solutes reveals that partitioning may significantly modify and even reverse the general rejection-size trend, as was demonstrated for a homologous series of alcohols. For some solutes, different rejection was found for similar values of both partitioning coefficient and size, suggesting that yet unclear effects related to molecular friction could be involved.
KW - Attenuated total reflection FTIR spectroscopy
KW - Nanofiltration
KW - Organics removal
KW - Polyamide layer
KW - Reverse osmosis
KW - Solute partitioning
UR - http://www.scopus.com/inward/record.url?scp=33746706938&partnerID=8YFLogxK
U2 - 10.1016/j.memsci.2006.04.017
DO - 10.1016/j.memsci.2006.04.017
M3 - Article
AN - SCOPUS:33746706938
VL - 281
SP - 480
EP - 490
JO - Journal of Membrane Science
JF - Journal of Membrane Science
SN - 0376-7388
IS - 1-2
ER -