Improved filtration membranes through self-organizing amphiphilic comb copolymers

The operating cost of a membrane filtration system is generally determined by two major factors: the permeability of the membrane to water, and the lifetime of the membrane. Both of these are strongly affected by the chemical structure and surface properties of the membrane. Hence, the development of novel membrane materials that improve these two properties would make membrane treatment of water streams cheaper. One of the most important reasons for low permeability and short membrane life is fouling, which makes it one of the most important challenges faced in membrane operations, especially in processes where the feed has high concentrations of biomolecules, such as wastewater treatment, and in food and biochemical industries. In this thesis, the self-organization of amphiphilic comb copolymers is employed to develop improved membranes for aqueous filtration. The use of self-assembling copolymers leads to the desired properties (surface chemistry, selectivity) without additional processing steps. One aspect of this thesis focuses on the development of size-selective nanofiltration (NF) membranes that can fractionate small molecules by size through the microphase separation of the amphiphilic comb copolymers. This size scale corresponds to a "missing link" in the separations currently offered by commercial membranes. Such membranes formed by coating a porous support membrane with the comb copolymer poly(vinylidene fluoride)-graft-poly(ethylene oxide methacrylate) (PVDF-g-POEM) were first introduced by Akthakul et al. (Macromolecules 37 (2004) 7663-7668). The microphase separation of the comb copolymer results in the formation of interconnected effective "nanochannels" of the hydrophilic poly(ethylene oxide) (PEO) side-chains, which allow water permeability and size selectivity. This thesis includes work that characterizes the fouling resistance of these membranes in more detail, including their performance in the presence of various foulants as well as in the context of membrane bioreactor (MBR) operation for wastewater treatment.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2009

Author dc:creator

• Asatekin Alexiou, Ayse

Advisor dc:contributor.advisor

• Anne M. Mayes and Michael F. Rubner.

• Chemical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/46611

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/46611