Title: Membrane-Colloidal Interactions: Comparison of Extended DLVO predictions with AFM Force Measurements.
Journal: Environmental Engineering Science
Authors: Jonathan A., Brant and Amy E. Childress*
Department of Civil Engineering, Universitu of Navada, Reno, Reno, NV 89557-0152
The original and creativity of paper: The paper aimed to examine interactions between membrane and colloids. The results qualified and demonstrated significance of the polar interactions in membrane-colloid interactions. Moreover, the comparison of DLVO and XDLVO prediction using AFM direct force measurement was assessed to investigate its significance.
Summary:
- Surface characterization
o Both CD (heat-treated cellulose triacetate/diacetate blend membrane) and SG (thin-film composite membrane) have weak negative zeta potential (-2.5 and -6.6. mV, respectively) at pH 5.4.
o According to the free energy of cohesion per unit area for each membrane, CD membrane is strongly hydrophilic; the SG membrane is strongly hydrophilic. It is important to know that the free energy of cohesion may provide some quantitative assessment of the adhesive energy between the two surfaces.
- Quality of AFM forces curves and determination of surface contact
o Fig. 3 (a) showed the attractive force, which created and obvious minimum that makes the contact point is easily to define.
o Fig. 3 (b) revealed the repulsive force profile; the point of contact can be determined by looking for a pseudocompliance region where the short-range interaction between the colloid probe and membrane is strongly repulsive. The contact point is the point that separates the linear compliance region from the almost linear psudocompliance region.
Fig. 1 Method for determining the point of contact between the colloid probe and membrane surface for (a) attractive and (b) repulsive interaction.
- Surface roughness considerations
o Previous studies found that surface roughness extends the range and depth of the secondary minimum and in the same time decreases the magnitude of the potential energy barrier.
o Also, the repulsive interactions of flat surface were greater than rough surface. This is possible due to the rough surface may reveal longer-range attraction compared to the value which expected from the theory.
Application & further study:
The results of these interactions are critical in determining the fouling propensity of membrane. Also the results may provide the optimum operating conditions which reduce the contact between membrane and foulants. Thus, the maximum critical flux for membrane process can be obtained.
By Monruedee Moonkhum
Email: moon@gist.ac.kr
Journal: Environmental Engineering Science
Authors: Jonathan A., Brant and Amy E. Childress*
Department of Civil Engineering, Universitu of Navada, Reno, Reno, NV 89557-0152
The original and creativity of paper: The paper aimed to examine interactions between membrane and colloids. The results qualified and demonstrated significance of the polar interactions in membrane-colloid interactions. Moreover, the comparison of DLVO and XDLVO prediction using AFM direct force measurement was assessed to investigate its significance.
Summary:
- Surface characterization
o Both CD (heat-treated cellulose triacetate/diacetate blend membrane) and SG (thin-film composite membrane) have weak negative zeta potential (-2.5 and -6.6. mV, respectively) at pH 5.4.
o According to the free energy of cohesion per unit area for each membrane, CD membrane is strongly hydrophilic; the SG membrane is strongly hydrophilic. It is important to know that the free energy of cohesion may provide some quantitative assessment of the adhesive energy between the two surfaces.
- Quality of AFM forces curves and determination of surface contact
o Fig. 3 (a) showed the attractive force, which created and obvious minimum that makes the contact point is easily to define.
o Fig. 3 (b) revealed the repulsive force profile; the point of contact can be determined by looking for a pseudocompliance region where the short-range interaction between the colloid probe and membrane is strongly repulsive. The contact point is the point that separates the linear compliance region from the almost linear psudocompliance region.
Fig. 1 Method for determining the point of contact between the colloid probe and membrane surface for (a) attractive and (b) repulsive interaction.
- Surface roughness considerations
o Previous studies found that surface roughness extends the range and depth of the secondary minimum and in the same time decreases the magnitude of the potential energy barrier.
o Also, the repulsive interactions of flat surface were greater than rough surface. This is possible due to the rough surface may reveal longer-range attraction compared to the value which expected from the theory.
Application & further study:
The results of these interactions are critical in determining the fouling propensity of membrane. Also the results may provide the optimum operating conditions which reduce the contact between membrane and foulants. Thus, the maximum critical flux for membrane process can be obtained.
By Monruedee Moonkhum
Email: moon@gist.ac.kr