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Evaluation of Poly (Ethylene Glycol) Grafting as a Tool for Improving Membrane Performance

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2010, Doctor of Philosophy in Engineering, University of Toledo, Chemical Engineering.
Although commercially available cellulose acetate membranes are characterized by having high fluxes during filtration as compared to other membrane materials, they are more prone to microbial attack and organic fouling because of their natural cellulose acetate backbone structures. Fouling, or the accumulation of foreign substances on the membrane surface, occurs mostly due to hydrophobic interactions between the membrane and the foreign substances, especially natural organic matter (NOM). In order to reduce the hydrophobic interactions and thereby fouling due to NOM, flexible hydrophilic poly(ethylene glycol) (PEG) monomer chains were grafted to the cellulose acetate membrane to increase its hydrophilicity. Two methods were used to achieve PEG grafting on the membrane surface. In Method I, grafting was achieved by the action of an oxidizing agent for free radical development, followed by monomer for polymerization, and a chain transfer agent (CTA) for termination of the polymerization. Two different techniques of introducing the chemicals to the membrane were investigated. These were a bulk approach, where membranes were immersed in the chemical solutions, and drop approach, where chemicals were added drop wise to the surface of the membrane to avoid polymerization within the pores. Both techniques led to improvements in membrane performance, as observed by lower fouling, lower flux declines and lower rates of flux decline, when compared to unmodified membranes. While the drop approach displayed slightly higher initial flux values, the bulk method was preferred for its ease of modification and replication. Method II was characterized by a greener solvent-free enzymatic polycondensation to graft PEG to the membrane surface. NOM feed solutions were used to compare organic fouling between the modified and unmodified membranes. Modification led to higher fluxes, lower flux declines, and a more reversible fouling layer easily removed by backwashing during operation. Method I and II led to 16 and 17% increase in the pure water flux of the cellulose acetate membrane, respectively. Both the methods resulted in improved membrane fouling resistance when using NOM as the feed content.
Isabel Escobar, PhD (Advisor)
Sasidhar Varanasi, PhD (Committee Member)
Maria Coleman, PhD (Committee Member)
Dong-Shik Kim, PhD (Committee Member)
Jared Anderson, PhD (Committee Member)
155 p.

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Citations

  • Gullinkala, T. (2010). Evaluation of Poly (Ethylene Glycol) Grafting as a Tool for Improving Membrane Performance [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1271440380

    APA Style (7th edition)

  • Gullinkala, Tilak. Evaluation of Poly (Ethylene Glycol) Grafting as a Tool for Improving Membrane Performance. 2010. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1271440380.

    MLA Style (8th edition)

  • Gullinkala, Tilak. "Evaluation of Poly (Ethylene Glycol) Grafting as a Tool for Improving Membrane Performance." Doctoral dissertation, University of Toledo, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1271440380

    Chicago Manual of Style (17th edition)