Nanofiltration of textile wastewater for water reuse

Nanofiltration of textile wastewater for water reuse

MembSept.qxd 09/09/2002 12:33 Page 16 RESEARCH TRENDS different V. cholerae strains are partly distinguished by their fractogram profiles. P. Resc...

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RESEARCH TRENDS different V. cholerae strains are partly distinguished by their fractogram profiles. P. Reschiglian, B. Roda, A. Zattoni, B. Ryul Min, M. Hee Moon: J. of Separation Science 25(8) 490–498 (June 2002).

Separation of conjugated linoleic acid isomers and parinaric fatty acid isomers Separation of two types of fatty acid isomers – parinaric acid and conjugated linoleic acid – by capillary electrophoresis has been investigated. The performance of a number of different buffer systems was investigated. The use of SDS micelles combined with an organic modifier made it possible to dissolve and separate parinaric acid isomers. For the separation of conjugated linoleic acids a buffer system containing a chiral surfactant (R)-N-dodecoxycarbonylvaline ((R)-N-DOCV), and a mixture of two cyclodextrins, heptakis(2,3dimethyl-6-sulfo)-β-CD (HDMSβ-CD) and β-CD, and an organic modifier were utilized. M. Öhman, H. Wan, M. Hamberg, L.G. Blomberg: J. of Separation Science 25(8) 499–506 (June 2002).

Analyses of organic foulants in membranes Fouling of membranes is a serious problem in membrane technology. By characterizing the foulants it is possible to understand the fouling process and reduce it. However, the characterization of foulants, especially organic ones, is difficult. The purpose of this study was to find out whether there are any organic foulants such as extractives in the membranes, and if it is possible to identify them. Membranes of different materials and hydrophilicity were used in filtration of ground wood mill (GWM) circulation water during one month in an integrated pulp and paper mill. Solid– liquid extraction was employed to remove the extractives from the membranes and their characterization was carried out with a gas chromatograph. According to the results, there are extractives in the membranes and it is possible to characterize them. It seems that the fouling by extractives mainly comes from resin and fatty acids. In addi-


tion, some traces of lignans were found in the membranes. Moreover, the hydrophobic membranes contained more of these acids and lignans than the hydrophilic membranes. L. Puro, J. Tanninen, M. Nyström: Desalination 143(1) 1–9 (10 May 2002).

Nanofiltration of textile wastewater for water reuse The textile industry produces a large amount of wastewater that is highly coloured with high loading of inorganic salt. Crossflow nanofiltration, using a thin film composite polysulphone membrane, was used to recover the electrolyte solution and reject the colour. Using a synthetic textile effluent of reactive dye and NaCl solution, this study focused on the mechanism controlling flux and rejection by varying four main parameters – crossflow velocity, initial dye concentration, feed pressure and electrolyte concentration. Results show that flux was dominated by the osmotic pressure created from the presence of NaCl, and that dye concentration did not significantly effect the flux or rejection. Working at low pressures of up to 500 kPa, relatively high fluxes were obtained, with an average dye rejection of 98%, and NaCl rejections of less than 14%. Thus high quality reuse water could be recovered. Even after a number of cycles, the membrane did not foul irreversibly, with an overall mean waterflux recovery of 99%. C. Tang, V. Chen: Desalination 143(1), 11–20 (10 May 2002).

Desalting of subsurface water using spiral-wound RO Subsurface water rise is a major problem in Kuwait. The impact of this problem is manifested in surface water ponds, cracks in buildings, flooded basements and damaged roads. Dewatering this water of moderate salinity is necessary. Being in an arid area with very limited water resources, treatment and recycling of the subsurface water could be very important to a country like Kuwait. For this purpose, a pilot study was carried out to desalinate the subsurface water using the reverse osmosis (RO) technique.

The main aim of this study is to assess the viability and economic feasibility of using RO technology. This paper outlines the results of over 8000 operating hours of performance data for an RO plant that utilizes spiral-wound membranes which are used to desalinate subsurface water with TDS of about 11 000 mg/1, and an economic feasibility evaluation. Results indicate that the RO system is a feasible technique to desalinate this type of water. The improvements in TDS, COD and BOD were 99%, 96% and 42%, respectively. The economic feasibility evaluation indicates that the unit cost of desalting subsurface water by RO is 0.235 KD/m3 (0.776 US$/m3), which is considered to be economically feasible for a small-scale plant. Y. Al-Wazzan, M. Safar, S. Ebrahim, N. Burney, A. Mesri: Desalination 143(1) 21–28 (10 May 2002).

Candidates for new proton exchange membranes Novel biphenol-based, wholly aromatic poly(arylene ether sulphone) containing up to two pendant sulphonate groups per repeat unit were prepared by potassium carbonate mediated direct aromatic nucleophilic substitution polycondensation of disodium 3,3´disulphonate-4,4´-dichlorodiphenylsulphone (SDCDPS), 4,4´-dichlorodiphenylsulphone (DCDPS) and 4,4´-biphenol. Copolymerization proceeded quantitatively to high molecular weight in N-methyl-2-pyrrolidinone at 190°C. Tough membranes with a SDCDPS/DCDPS molar ratio up to 60:40 were successfully cast using N,N-dimethylactamide. An increase of sulphonate groups in the copolymer resulted in increased glass transition temperature, enhanced membrane hydrophilicity, and intrinsic viscosity. The 100% SDCDPS homopolymer was water soluble. The acid form membranes were successfully obtained by treating the sodium form of the membranes with dilute sulphuric acid solution. Thermogravimetric analysis shows that the sodium form materials have enhanced thermal stability relative to the acid form, as expected. Atomic force microscopy (AFM) phase

images of the acid-form membranes clearly showing the hydrophilic domains, with sizes increasing from 10 to 25 nm as a function of the degree of sulphonation. A phase inversion could be observed for the 60% SDCDPS copolymer, which was consistent with a rapid increase in water absorption. Short-term ageing (30 min) indicates that the desired acid-form membranes are stable to 220°C in air and conductivity values at 30°C of 0.11 S/cm (SDCDPS/DCDPS = 0.4) and 0.17 S/cm (SDCDPS/ DCDPS = 0.6) were measured, which are comparable to or higher than fluorinated copolymer Nafion 1135 control (0.12 S/cm). The new copolymers, which contain ion conductivity sites on the deactivated positions of the aryl backbone rings, are potential candidates as electrolyte materials for proton exchange membrane fuel cells. F. Wang, M. Hickner, Y.S. Kim, T.A. Zawodzinski, J.E. McGrath: J. of Membrane Science 197(1–2) 231–242 (15 March 2002).

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Membrane Technology September 2002