טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentAberman Israel
SubjectSurface Tension and Properties of Protein Solutions
DepartmentDepartment of Chemical Engineering
Supervisor Professor Emeritus Abraham Marmur


Abstract

This objective of this research is to develop the understanding of the kinetic processes that affect the surface tensions of aqueous bio-materials solutions, using the “pendant drop” method  while working with small volumes.

Interfacial tension is a function of the chemical composition of the interface between two phases. Changes in interfacial composition occur due to adsorption/desorption of dissolved materials in a solution.

The quantities of the materials of interest were small, so ability to work with small amounts of low molar concentrations and small volumes was required. Moreover, it was concluded from preliminary experiments and from the literature that, when working with bio-materials, the processes which control the adsorption to the interface and cause changes in surface tension, take longer time. It was also concluded from the literature that for bio-material solutions, especially for proteins, there are some additional processes, which control the adsorption, and do not exist in simple solutions.

The following objectives and conclusions were achieved:

1.      An instrument that measures static and dynamic surface tension was built, based on the pendant drop method.

2.      A computer program was developed that imports digital pictures, analyzes them, calibrates them, and calculates surface tension using an algorithm which is based on fitting a 10th order polynomial to a series of points that define an experimental drop profile:

3.      The correlation between surface tension and the coefficients of 6th and 8th order polynomials were found.

4.      The diffusion-dependent mechanism of the adsorption process was investigated. Simulations and measurements showed that solutions with low molecular concentration and small volumes do not have enough molecules to adsorb to the surface and keep the bulk concentration at its nominal value. Therefore, the dynamic and static surface tensions in this case depend on the relationship between the surface area and volume of the drop.