Membranes for Nanofiltration

While reverse osmosis and ultrafiltration were being established in several applications, there was a lack of available membranes with cutoffs between 400 and 4000 g/mol. Increasing interest in NF membranes developed in the last decade. An extensive review on principles and applications of nanofiltration has been published recently [38]. Nanofiltration is important for water softening [39] and removal of organic contaminants. In the food industry, nanofiltration can be applied for concentration and demineralization of whey, concentration of sugar and juice. Nanofiltration also finds application in the pulp and paper industry, in the concentration of textile dye effluents and in landfill leachate treatment. The improvement of solvent stabihty of available NF membranes opens a wide range of potential applications in the chemical and pharmaceutical industry as weU as in metal and acid recovery. 

The membrane is very hydrophilic and when applied to paper-mill waters in typical pH range above 4, its surface is negatively charged leading to the repulsion also of negatively charged solutes. 

GE-Osmonics (part of GE Water Technologies) commercializes the Desal 5 nanofiltration membranes, used for removal of hardness and other contaminants, alcohol recovery from aqueous solution and removal of salt from salt whey. The membrane has 4 layers, a polyester nonwoven, an asymmetric micro-porous polysulfone and two proprietary thin films, which might be based on sulfonated polysulfone and polypiperazineamide [34]. A comparison between DesaF 5 and NF270 for nanofiltration has been reported by [44] (Tab. 4.3). 

Nanofiltration membranes can also be obtained by coating ultrafiltration membranes with different polymer solutions. Nitto Denko commercializes NTR-729 HF, a low-pressure spiral element also suitable for nanofiltration of salt and low molecular weight organic compounds. The membrane has a polysulfone porous support coated with a thin layer of polyvinyl alcohol. Analogous procedures have been reported in the Hterature. Membranes with cutoffs between 800 and 4500 g/mol and water permeabihties of up to 10 1/h m bar 

Although the composihons of the MPS-44 and -50 membranes are not completely open, two patents of Kiryat Weizmann describe interesting procedures 

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More work is urgently needed if membranes are to be used in conditions of very large or very small pH values or in steam. This holds even more for the thermal stability for microporous membranes and for both chemical and thermal stability of membranes for nanofiltration. 

G. Grund, C.W. Robinson and B.R. Glick, Protein type effects on steady-state crossflow membrane ultrafiltration fluxes and protein transmission. /. Membr. Sci., 70 (1992) 177. J.L. Negrel, G.M. Rios and J.L. Cuq, Design and performance of new formed-in-place proteinic membranes for nanofiltration. Presented at ISMMP 94, 5-10 April 1994, Hangzhou, P.R. China. 

S. Sarrade, C. Bardot, M. Carles, R. Soria, S. Cominotti and R. Gillot, Elaboration of new multilayer membrane for nanofiltration. Proceedings of the 6th World Filtration Congress, 18-21 May 1993, Nagoya, Japan. 

S.Sarrade, G.M. Rios and M.Carles, Dynamic characterisation and transport mechanisms of two inorganic membranes for nanofiltration. J. Membr. Sci., 114 (1996) 81. 

Sekuli J, ten Elshof JE, Blank DHA. A microporous titania membrane for nanofiltration and pervaporation. Adv Mater. 2004 16(17) 1546-50. 

Liu, M., Yao, G., Cheng, Q., Ma, M., Yu, S., and Gao, C. 2012. Acid stable thin-fihn composite membrane for nanofiltration prepared from naphthalene-1,3,6-trisulfonylchloride (NTSC) and piperazine (PIP). Journal of Membrane Science 415-416 122-131. 

Van Gestel T, Kruidhof H, Blank DHA, and Bouwmeester HIM. Zr02 and Ti02 membranes for nanofiltration and per-vaporation. Part 1. Preparation and characterization of a corrosion-resistant Zr02 nano filtration membrane with a MWCO < 300. J. Membr. Set 2006 284 128-136. 

Van Gestel T, Sebold D, Kruidhof H, and Bouwmeester HJM. ZrOj and Ti02 membranes for nanofiltration and pervaporation. Part 2. Development of Zr02 and TiOj toplayers for pervaporation. J. Membr. Set 2008 318 413 21. 

Table 4.3 Comparison between Desaf 5 and NF270 membranes for nanofiltration [44].

Zhang et al. prepared TFC membranes for nanofiltration by interfacial polymerization of piperazine and trimesoyl chloride on top of polysulfone UF membranes with molecular weight cutoff (MWCO) values of 60 000 Da and water permeabilities of 100-150 Lm h bar [28]. Figure 4.12 shows the SEM picture of the sur-... 

Verssimo, S., Peinemann, K.V. and Bordado, J. 2005. New composite hollow fiber membrane for nanofiltration. Desalination 184 1—11. 

Sarrade S., Rios G., Carles M. Dymamic characterization and transport mechanisms of two inorganic membranes for nanofiltration. J. Membr. Sci. 1994 97 155-166 Sastre A.M., Kumar A., Shukla J.P., Singh R.K. Improved techniques in hquid membrane separations an overview. Separ. Purif. Methods 1998 27(2) 213-298 Schaefer D.W. Engineered porous materials. MRS Bull. 1994 19(4) 14—17... 

A commercial composite polyamide/polysulfone membrane for nanofiltration... 

Van Gestel, T., Vandecasteele, C., Buekenhoudt, A. et al. (2002) Alumina and titania multilayer membranes for nanofiltration Preparation, characterization and chemical stability. Journal of Membrane Science, 207, 73-89. 

Yu, S., Zheng, Y, Zhou, Q., Shuai, S., Lu, Z., and Gao, C. 2012b. Facile modification of polypropylene hollow fiber microfiltration membranes for nanofiltration. Desalination 298 49-58. 

S.P. Sun, K.Y. Wang, N. Peng, T.A. Hatton, T.-S. Chung, Novel polyamide-imide/cellu-lose acetate dual-layer hollow fiber membranes for nanofiltration. Journal of Membrane Science, 363 (2010) 232-242. 

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