טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentBussi Yonit
SubjectFunctionalized Polystyrene Based Membranes
DepartmentDepartment of Chemistry
Supervisor Professor Moris Eisen
Full Thesis textFull thesis text - English Version


Abstract

Reverse osmosis (RO) technology for water filtration still has a major shortcoming in fouling of the membrane. Water passes through the membrane containing environmental contaminants with based gram negative bacteria such as E-coli, Pseudomonas putida, Salmonella, and many other infections bacteria. The solid-liquid interface between a surface and an aqueous medium provides an ideal environment for the attachment and growth of these microorganisms which develops biofilm. The disruption of bacterial membrane function appears to be a common feature of the action of phenolic compounds and certain other antibacterial agents, which in turn is relatable to their antibacterial behavior action. Moreover, hydrophobic membranes are more prone to fouling in an aqueous medium.

Therefore, in this thesis, we gathered this information and developed membranes incorporated with hydrophilic groups which possess a kind of poisoning affect against bacteria. The idea is that in order to kill the bacteria, it is sufficient to disrupt the bacterial membrane functions, and in that way it is easy to maintain the antibacterial action.  The strategy was to use stereoregular polystyrene as a polymer based membrane due to its good properties and especially to incorporate hydroxyl groups in order to mimic the phenol bactericidal groups. However, as known, the permeability of water through a polystyrene membrane is low due to the lack of hydrophilic character. By post functionalization using conventional, known reactions, there was a possibility to incorporate hydrophilic groups on the polystyrene in order to improve the water permeability. Furthermore, it was found that halobenzenes also exhibit biological activities towards gram negative bacteria, as well as towards gram-positive bacteria and fungus. Therefore, in this research we incorporated halogens and other hydrophilic groups to the polystyrene side chains; this functionalization was characterized by physical methods and their effects on the water fluxes as membranes were tested. The functionalized atactic polystyrene membranes were analyzed based on thermodynamics (solubility parameter difference) and kinetics (mass exchange) effects. As for the semi-crystalline polystyrene membranes the analysis was based only on the kinetic effects.

In order to evaluate the efficiency of the antifouling effect of these membranes, both static and flowing system has been tested. Moreover, the results from the cross flow assay in combination with scanning electron microscopy have successfully exhibit that the functionalized polystyrene with the hydroxyl groups were much more effective against biofouling than the pristine polymer.