טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentNoi Dalit
SubjectStudy of Magnetic Surfaces as a Platform for
Controlling Biofouling in Water Systems
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Emeritus Carlos Dosoretz
Full Thesis textFull thesis text - English Version


Abstract

Biofilm is a phenomenon which occurs when bacteria attach and grow on a surface in water environment.  Biofouling occurs when the biofilm limits or prevents the proper function of the surface. For example, in membrane process system the permeate flux is decreased as a result of the biofouling.

A number of approaches for biofouling prevention are accepted, such as physical removal or metabolic inactivation. A third method, which is currently under research, is creating 'anti-bacterial' surfaces from materials with reduced bacterial affinity or even reject the attachment of bacteria.

The proposed concept for biofouling reduction presented in this research, which is example of the third method, is based on a composite surface (polymer-magnetic particles) with a permanent magnetic field. The magnetic surface will be designed to attach metallic nanoparticles from the water flow by magnetic forces. The nanoparticles can be linked to antibacterial ligands (such as quaternary ammonium).

The proposed surface can be recharged and reused by applying an external magnetic field without major influence to the operation of the process.

The study was divided into theoretical calculations and experimental work. The theoretical calculation includes an analysis of the involving forces between the magnetic surface and the metallic nanoparticles in the solution in order to determine the feasibility of the process. The experimental work comprised the synthesis of a composite surface with embedded nanoparticles with constant magnetic force and testing the attraction between metallic nanoparticles and the composite surface under flow conditions.

The force analysis shows that the magnetic attractive force is over 30 orders higher than all other forces at a distance of nanometers (10-9m), becoming only slightly higher than the drag force at distance of millimeters (10-3m). Therefore, the magnetic force is the dominant attractive force at particle-surface distance lower than 10-3m, and especially at the nanometer scale, which is the viable distance for such interactions.

The experimental result supports the theoretical analysis. The magnetic attraction was high enough to attract the magnetite nanoparticles to the magnetic film. It is shown that the nanoparticles were attracted to the magnetic surface; till it was saturated with nanoparticles and even the drag force didn’t diminish the attraction.

The experiments of preparing magnetic nanoparticles in a polymer matrix result in high homogeneous surfaces but with very low magnetism property.