Articles Effect of Temperature on the Transport of Water and Neutral Solutes across Nanofiltration Membranes N. Ben Amar, †,‡ H. Saidani, †,‡ A. Deratani, ‡ and J. Palmeri* ,‡ Laboratoire de Mode ´ lisation Mathe ´ matique et Nume ´ rique dans les Sciences de l’Inge ´ nieur, ENIT, Campus UniVersitaire, B.P 37 Le belVe ´ de ` re 1002, Tunis, Tunisia, and Institut Europe ´ en des Membranes, cc047, UMR5635 CNRS-ENSCM-UniVersite ´ Montpellier II, 2 Place Euge ` ne Bataillon, 34095 Montpellier Cedex 5, France ReceiVed January 27, 2006. In Final Form: December 22, 2006 We carry out a detailed experimental and theoretical study of the influence of temperature on nanofiltration performance using the Desal5DK membrane. Experimental results for the permeate volume flux density and rejection of four neutral solutes (glycerin, arabinose, glucose, and sucrose) are presented for temperatures between 22 and 50 °C. Solute rejection is modeled using a hindered transport theory that allows us to unveil the crucial role played by changes in the membrane structural parameters (effective pore radius and membrane thickness) due to changes in temperature. Introduction Besides important uses in the desalination of geothermal brackish water (2-4 g/L, 50 to 55 °C), nanofiltration (NF) membranes also have a large number of other industrial applications (paper, sugar, food, textile, etc.) in which the temperature can be high and may even reach 90 °C (bleaching and dyeing applications). Moreover, nanofiltration may be used in hybrid systems for seawater desalination coupled with thermal desalination processes, such as NF-MSF (multistage flash) 1 and NF-MSF-RO (reverse osmosis). 2 It is also used, for example, as the final stage in the Mery-sur-Oise river water treatment plant to make drinking water. 3,4 In these surface water applications, the temperature of the feed (sea or river water) varies with the season, and it has been observed that the temperature plays a significant role on nanofiltration membrane performance. For a better mastery of all the applications described above, it is essential to obtain a detailed understanding of the influence of temperature on nanofiltration performance (permeate volume flux density and solute rejection). In spite of the increasingly widespread industrial use of NF and RO membranes, much remains to be learned about the physicochemical mechanisms governing solvent and solute transport at the molecular level. The acquisition of such knowledge, which depends on simultaneous advances in preparation and modeling methods, would have a potentially large payoff in terms of the elaboration of cost-effective tailor- made nanoporous membranes for specific industrial applications (such as low-cost seawater desalination). Membrane manufacturers have only treated the effect of temperature on water flux and give in their product literature correlations which correct the water flux compared to that given at a reference temperature (20 or 25 °C). 5 In this way, plant operators can estimate the conversion factor corresponding to the real feed temperature. The effect of temperature on flux and rejection of solutes (neutral and charged) has already been touched upon in the areas of microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO). Perhaps the earliest investigation of temperature effects was a study of the sodium chloride-water- cellulose acetate system. 6 More recent work can be found in studies of MF, 7 UF, 8 NF, 3,4,9-11 and RO. 12,13 All of the above-mentioned studies show an increase of permeate volume flux with increasing temperature. There are, however, variable results for solute rejection. Although the usual trend for NF is a decrease in rejection with increasing temperature, Schaep et al. 11 find an increase of the rejection of divalent ions * Corresponding author. Current address: Laboratoire de Physique The ´orique, IRSAMC UMR CNRS-UPS 5152, Universite ´ Paul Sabatier, 118 route de Narbonne, 31062 Toulouse CEDEX 4, France. Tel: +33 (0)5.61.55.61.77. Fax: +33 (0)5.61.55.60.65. E-mail: john.palmeri@ irsamc.ups-tlse.fr. † ENIT. ‡ CNRS. (1) Al-Sofi, M. A. K.; Hassan, A. M.; Mustafa, G. M.; Dalvi, A. G. I.; Kither, M. N. M. Desalination 1998 118, 123-129. (2) Hassan, A. M.; Al-Sofi, M. A. K.; AL-Amoudi, A. S.; Jamaluddin, A. T. M.; Farooque, A. M.; Rowaili, A.; Dalvi, A. G. I.; Kither, N. M.; Mustafa, G. M.; Al- Tisan, I. A. R. Desalination 1998, 118, 35-51. (3) Wittman, E. La Nanofiltration dans le domaine du traitement des eaux: conditions d’application et mode ´lisation. Ph.D. Thesis, University of Montpellier II, France, 1998. (4) Ventresque, C.; Gisclon, V.; Bablon, G.; Chagneau, G. Desalination 2000, 131,1-16. (5) Desal Pure Water, Membrane Technology & Applications; GE-Osmonics; 2003. (6) Londsdale, H. K.; Merten, U.; Riley, R. L. J. Appl. Polym. Sci. 1965, 9, 1341. (7) Mohammadi, T.; Pak, A.; Karbassian, M.; Golshan, M. Desalination 2004, 168, 201-205. (8) Huisman, I. H.; Dutre ´, B.; Persson, K. M.; Tra ¨gardh, G. Desalination 1997, 113, 95-103. (9) Tsuru, T.; Izumi, S.; Yoshiota, T.; Asaeda, M. AIChE J. 2000, 46, 565- 574. (10) Sharma, R. R.; Agrawal, R.; Chellam, S. J. Membr. Sci. 2003, 223, 69- 87. (11) Schaep, J.; Van der Bruggen, B.; Uytterhoeven, S.; Croux, R.; Vande- casteele, C.; Wilms, D.; Van Houtte, E.; Vanlerberghe, F. Desalination 1998, 119, 295-302. (12) Goosen, M. F. A.; Sablani, S. S.; Al-Maskari, S. S.; Albelushi, R. H.; Wilf, M. Desalination 2002, 144, 367-372. (13) Kilduff, J. E.; Mattaraj, S.; Wigton, A.; M. Kitis, M.; Karanfil, T. Water Res. 2004, 38, 1026-1036. 2937 Langmuir 2007, 23, 2937-2952 10.1021/la060268p CCC: $37.00 © 2007 American Chemical Society Published on Web 02/17/2007