Application of thin-film composite hollow fiber membrane to submerged nanofiltration of anionic dye aqueous solutions

Submerged nanofiltration of anionic dye aqueous solution by laboratory-fabricated sodium carboxymethyl cellulose (CMCNa)/polypropylene (PP) thin-film composite hollow fiber membrane was investigated in this paper. The CMCNa/PP thin-film composite membranes were prepared through dip-coating CMCNa skin layer on the outer surface of polypropylene microporous hollow fibers followed by cross-linking with FeCl3. The molecular weight cut-off (MWCO) and surface zeta potential of the tailor fabricated membrane were estimated through permeation tests using different PEG solutions and measurements of surface steaming potential, respectively. Submerged nanofiltration tests were then performed with anionic dye solutions under different conditions. It was found that, at neutral pH, the negatively charged CMCNa/PP composite hollow fiber membrane with a MWCO of about 700 Da could effectively remove anionic dyes (Congo red and Methyl blue) from aqueous solution with good long-term performance stability and anti-fouling property through submerged nanofiltration. The dye retention and water permeability was affected by the trans-membrane pressure, the dye concentration as well as the presence of salt in the solution. The dye retention, water permeability and salt rejection rate to aqueous solution containing 2000 mg/l Congo red and 10,000 mg/l NaCl were 99.8%, 7.01/m(2) h bar, and lower than 2.0%, respectively. (C) 2011 Elsevier B.V. All rights reserved.