Sulfonated Polysulfone Membranes water

Transport of Ions and Water in Sulfonated Polysulfone Membranes... 

A sulfonated polysulfone membrane with commercial potential has been developed in the form of a hollow fiber by workers at Albany International Corporation.86 87 In a 5,000-hour test on 3,500 ppm brackish water at 400 psi, this membrane exhibited 98% salt rejection at 1 gfd. Flux and salt rejection remained constant even with addition of 100 ppm chlorine. In a 12,000-hour test on seawater at the Wrightsville Beach Test Facility, this membrane exhibited 98+% salt rejection and an average flux of 1.5 gfd at 1,000 psi operating pressure. Thus, it is possible to make a high rejection membrane from sulfonated polysulfone. Flux was rather low in this particular case, but suitable for hollow fiber membrane use. 

Siracusano, S., Bagbo, V., Lufrano, F., Staiti, R, Aric6, A.S., Electrochemical characterization of a PEM water electrolyzer based on a sulfonated polysulfone membrane, J. Membr. ScL, 2013, 448, 209-214. 

Loeb-Sourirajan membranes based on sulfonated polysulfone and substituted poly(vinyl alcohol) produced by Hydranautics (Nitto) have also found a commercial market as high-flux, low-rejection membranes in water softening applications because their divalent ion rejection is high. These membranes are also chlorine-resistant and have been able to withstand up to 40 000 ppm h of chlorine exposure without degradation.1 The structures of the polymers used by Hydranautics are shown in Figure 5.8. 

After the initial work on asymmetric sulfonated polyphenylene oxide membranes, sulfonated polysulfone was subsequently examined by several research groups. However, the appearance of patents in 1973 and 1977 by Rhone-PoulencM 8S covering asymmetric membranes of sulfonated polysulfones appeared to dampen such research efforts. Also, a basic problem with sulfonated polysulfone was the fact that salt rejections fell rapidly when a critical level of sulfonation was exceeded, but water fluxes were too low until this sulfonation level was exceeded. 

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). 

For preparation of acid-base membranes of this type, the used polyacids include polycar-boxylic acids, polyphosphonic acid, polysulfonic acid, as well as perfluorinated sulfonic acid membranes. Carboxylic acids and phosphoric acid are weak acids with pK ranging from 2 to 5 (see Fig. 3.1), showing a low proton conductivity of 10 S cm level in its crystalline state. When blended with a stronger base than water, e.g., benzimidazole, a high conductivity of 4 X 10 S cm was reported at 130 °C [78]. Bozkurt et al. [79] prepared polyacrylic... 

The initial weight loss at around 100°C is caused by evaporation of water molecules bound in the hydrophilic sulfonated polysulfone (SPSU) membrane (Eigure 4.14) [29]. The secondary weight loss between 200°C and 400°C is mainly due to the thermally activated decomposition of the sulfonic acid groups in the polymer chains, which is confirmed by the evolution of SO and SO2 gases detected in the mass spectra. Above 550°C, it was found that the production of characteristic pyrolyzate with a hydroxyl end gronp snch as phenol as well as benzene occurs. 

Sulfonated polysulfones of degrees of sulfonation (D.S.) 0.16, 0.34, 0.42, 0.53, 0.68, 1.00 were synthesized as the sodium and potassium salts. Dense membranes were prepared by casting from a solution of DMF or DMSO the details of dense membrane preparation are given elsewhere. Typically 0.599 M (3.5%) NaCl(aq) solutions were prepared. Additional electrolytes studied were solutions of NaC103, KCl, MgCl2 and choline chloride. Glass-distilled water was used as the solvent. 

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