טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentVainrot Nataly
SubjectMembranes for Nano and Ultra Filtration: Synthesis and
Performance
DepartmentDepartment of Chemistry
Supervisors Professor Moris Eisen
Professor Emeritus Raphael Semiat


Abstract

             Nanofiltration is a membrane liquid separation technology which displays separation characteristics in the intermediate range between reverse osmosis (RO) and ultrafiltration (UF). Reverse osmosis is capable of producing very clean water and high concentrate retentate. Ultrafiltration, may be used for removal of suspended solids and large organic molecules. Nanofiltration, a lower-pressure operation is capable of removing hardness elements such as calcium or magnesium and also capable of removing bacteria, viruses, pesticides and other organic contaminants from surface and ground waters to help ensure the safety of public drinking water supplies.

            Industrial applications of NF membranes are common in food and dairy, chemical process, pulp and paper, electronic and textile industries. The primary application of NF membranes continues to be in water treatment.

            Various methods can be used to prepare NF/RO membranes: phase inversion by immersion precipitation, dip-coating, gas phase deposition by plasma polymerization, interfacial polymerization, etc. The main disadvantage of these methods is the inability to control the pore size distribution.

            Most membranes are prepared from organic polymeric materials. Cellulose ester, polysulfone, cellulose, polyamide, polyimide, and poly(acrylonitrile) comprise the most common membrane materials for the preparation RO/NF membranes.

Insertion of functional groups such as hydrophilic/hydrophobic, charged or reactive groups can influence membrane performance such as: mechanical strength, separation properties, rejection to dissolved particles, membrane permeability and other physical properties.

             The synthesis of new polymers is presented here, with different functional groups on the skeleton polymer chain to improve membrane performance.  These groups include: ethylene glycol, buthylene glycol, chloroethane, chlorooctane, 2,3:5,6-Di-O-isopropylidenemannofuranose, β-D-galactopyranosylamine, boronic acid, phosphonic acid, neomycin and carboxylic acid groups. Two kinds of polymers with different functional groups within the polymer backbone were also synthesized to establish the influence of these groups on membrane properties.

            Two novel techniques were applied to produce the membranes with uniform pore size distribution. These techniques includes: nano-iron particles etching by a strong acid, and base hydrolysis of ester bonds in cross-linked polymers. Later, base hydrolysis of ester anhydride groups in two component polymer mixtures.

            The membranes produced here shares the common properties of UF-NF membranes with different membrane performance and functions depend on polymer type, functional groups attached to polymer backbone, and the manufacture methods that were involved. It was shown that membranes with different functional groups can be successfully synthesized, which enable high flux and low operating pressure work. In addition some of new methods were applied for homogeneous pore creation.