2021 Fiscal Year Annual Research Report
Dynamics of polyelectrolyte adsorption and colloidal flocculation studied using model colloids
| Project/Area Number |
20F20388
|
|---|
| Research Institution | University of Tsukuba |
|---|
Principal Investigator |
小林 幹佳 筑波大学, 生命環境系, 准教授 (20400179)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
GEONZON LESTER 筑波大学, 生命環境科学研究科(系), 外国人特別研究員
|
|---|
| Project Period (FY) |
2020-11-13 – 2023-03-31
|
| Keywords | Water-soluble polymer / kinetics of adsorption / optical tweezers / microfluidics / hydrodynamic flow |
|---|
| Outline of Annual Research Achievements |
The kinetics of water-soluble polymer onto a single colloidal particle was investigated from a single particle viewpoint. The effect of hydrodynamic drag on the spherical particle at different locations near-wall was also studied using optical tweezers and microfluidics. Optical tweezers were used to trap silica particles and probe the fluid shear stress on the particle. The friction coefficients with and without shear flow were obtained by combining optical tweezers and microfluidic.
We developed novel techniques using microfluidics and optical tweezers to investigate polymer adsorption onto a single colloidal particle. Methodologies to investigate the adsorption/desorption kinetics of water-soluble polymer to colloidal particles using optical tweezers and microfluidics were used. The polymer layer thickness was monitored directly by exploiting the balance of the trapping force and the hydrodynamic drag force of the flowing solution past the particle. Different parameters affecting the layer thickness were evaluated using the methodology. This presents a novel perspective in understanding polymer adsorption kinetics by directly evaluating the layer thickness on a single particle viewpoint that is not accessible to the bulk measurements.
|
| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The project aimed to understand the adsorption kinetics of the water-soluble polymer onto colloidal particles from the viewpoint of the single-particle level. We have successfully developed a novel technology to investigate the kinetics of polymer adsorption onto a single colloidal particle using an optical tweezer and microfluidics. The kinetics were evaluated using different parameters such as polymer concentration, volumetric flow rate, pH, particle size, and molecular weight. Moreover, the dynamics of particle aggregation with adsorbed PEO were studied using force measurement via optical tweezers.
The effect of water-soluble, nonionic polymer on electric double-layer (EDL) was investigated in terms of the long-range interaction forces between silica particles of different sizes using optical tweezers. Different molecular weights of polyethylene oxide (PEO) with higher silica affinity were used. Based on the force measurements using optical tweezers, we emphasize that the adsorption of nonionic polymer onto the surface of the silica particles does not affect the EDL surrounding the particles. These are important pieces of information to understand the flocculation dynamics of colloidal particles with adsorbed polymer layer.
The kinetics adsorption of similar and oppositely charged polyelectrolytes was also investigated using single-particle adsorption studies and electrophoretic mobility analysis. The effect of homopolymer and copolymer on the flocculation and stabilization of colloidal silica was also studied. This is an ongoing experiment.
|
| Strategy for Future Research Activity |
Based on the developed methodology, we will investigate in detail the kinetics of polyelectrolyte adsorption onto the silica particle from a single particle viewpoint. The effect of salt, polymer concentration, and types of polyelectrolytes on the kinetics of adsorption to colloidal particles will be investigated using optical tweezers, microfluidic and electrophoretic mobility analysis. Adsorption of polyelectrolytes with opposite and similar charge properties with the colloidal particles will be explored. The dynamics of aggregation of colloidal particles with adsorbed polyelectrolyte will be investigated using the force measurements between two different size particles, which is crucial for the fate of wastewater particulates.
The utilization of biopolymers with different functional properties as novel natural-based polymeric flocculants will be evaluated. Different biopolymers, i.e., carrageenans, pectin, etc., will be used. The adsorption kinetics of biopolymers on the surface of the colloidal particles will be analyzed using optical tweezers, microfluidics, and electrophoretic mobility analysis. The effect of the molecular weight will also be studied by controlling the molecular weight of biopolymers using physical and chemical depolymerization procedures.
|
