Related Experiment Video
Updated: Jun 26, 2026
11:03
An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
A dynamic force balance model for colloidal expansion and its DLVO-based application.
Longcheng Liu1, Luis Moreno, Ivars Neretnieks
1Department of Chemical Engineering and Technology, Royal Institute of Technology, S-100 44 Stockholm, Sweden. lliu@ket.kth.se
Langmuir : the ACS Journal of Surfaces and Colloids
|December 25, 2008
Summary
This study presents a force balance model for colloidal bentonite gels/sols, revealing how ion and particle concentration influence expansion dynamics. The model predicts variable diffusivity, crucial for understanding bentonite behavior.
Area of Science:
- Colloid and Surface Science
- Materials Science
- Rheology
Background:
- Bentonite gels/sols exhibit complex dynamic expansion behavior.
- Understanding this expansion is critical for applications in various fields.
Purpose of the Study:
- To develop a force balance model for dynamic expansion of colloidal bentonite.
- To investigate the influence of ionic and particle concentration on expansion dynamics.
Main Methods:
- A force balance model incorporating van der Waals, double layer, thermal, gravitational, and friction forces.
- Mathematical formulation resulting in a variable diffusivity equation.
- Simulation and analysis of bentonite tablet expansion under varying conditions.
Main Results:
- The model yields an equation similar to unsteady diffusion but with highly variable diffusivity.
- Diffusivity is significantly affected by counterion and particle concentrations.
- Model accurately describes upward expansion of compacted bentonite.
Conclusions:
- The developed model provides a framework for understanding bentonite gel/sol expansion.
- Concentration of ions and particles are key factors governing bentonite's dynamic expansion.
- The model's variable diffusivity captures the complex behavior observed in experiments.
Related Concept Videos
01:17Colloids and Suspensions
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles visible to the naked eye or seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. The suspended particles in a suspension settle out after some time of mixing. The separation of particles from a suspension is...
01:20Stokes' Law
Viscous forces, like friction, are intermolecular forces that resist the relative motion of molecules over each other. When a solid body moves through a liquid, viscous forces drag it in the opposite direction. The force's magnitude depends on the solid's shape and size, as well as its speed and the liquid's coefficient of viscosity, density and temperature.
The expression for the force on a solid spherical object in a fluid is called Stokes' law. Stokes' law is valid only for low Reynolds...
The expression for the force on a solid spherical object in a fluid is called Stokes' law. Stokes' law is valid only for low Reynolds...
01:09Theories of Dissolution: The Danckwerts' Model and Interfacial Barrier Model
Various dissolution theories provide insight into the factors that influence the dissolution rate. Danckwerts' Model suggests that turbulence, rather than a stagnant layer, characterizes the dissolution medium at the solid-liquid interface. In this model, the agitated solvent contains macroscopic packets that move to the interface via eddy currents, facilitating the absorption and delivery of the drug to the bulk solution. The regular replenishment of solvent packets maintains the concentration...
01:19Viscosity of Fluid
Viscosity measures the resistance a fluid offers to flow and deformation. It results from internal friction between layers of fluid moving relative to one another. Dynamic viscosity, denoted by the Greek letter mu (μ), quantifies the force needed to move one fluid layer over another. For Newtonian fluids like water and air, the relationship between the shearing stress and the rate of shearing strain is linear, meaning their viscosity remains constant regardless of the applied stress.
01:18Newtonian Fluid: Problem Solving
Newtonian fluids exhibit a constant viscosity, meaning their shear stress and shear strain rate are directly proportional. This property ensures a predictable and stable response to applied forces, maintaining a linear relationship between force and flow. Examples include water, air, and light oils, consistently demonstrating this proportional behavior regardless of external conditions.
A velocity gradient forms within the fluid when a Newtonian fluid is placed between two parallel plates, with...
A velocity gradient forms within the fluid when a Newtonian fluid is placed between two parallel plates, with...
01:15Application of the Linear Momentum Equation
The application of the linear momentum equation can be used to analyze the forces needed to hold a 180-degree pipe bend in place with flowing water. In this case, water flows through the bend with a constant cross-sectional area of 0.01 square meters and a flow velocity of 15 meters per second. The pressure at the entrance is 0.2 Megapascals and the pressure at the exit is 0.16 Megapascals.
The goal is to determine the force components in the x and y directions to hold the pipe in place. Since...
The goal is to determine the force components in the x and y directions to hold the pipe in place. Since...