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The Colloidal State

The Colloidal State

The formation of a colloidal system is exemplified by an aqueous solution containing Cl− ions is introduced to another containing Ag+ ions, resulting in the precipitation of solid AgCl as extremely tiny crystals. Instead of settling out as a filterable precipitate, these crystals remain suspended in the liquid, showcasing a colloidal system.A colloidal system involves colloidal particles within the approximate range of 1 to 1000 nm in at least one dimension, dispersed in a medium called the...

Colloidal precipitates

Colloidal precipitates

The high insolubility of some precipitates can result in an unfavorable relative supersaturation. This can lead to colloidal particles with a large surface-to-mass ratio, where adsorption is promoted. For instance, in the precipitation of silver chloride, silver ions are adsorbed on the surface of the colloidal particles, forming a primary layer. This layer attracts ions of opposite charge (such as nitrate ions), forming a diffuse secondary layer of adsorbed ions. This electric double layer...

Colloids

Colloids

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 that are visible to the naked eye or can be seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. On the other hand, a solution is a homogeneous mixture in which no settling occurs and in which the dissolved...

Colloids and Suspensions

Colloids and Suspensions

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Coagulation

Coagulation

Colloidal solids are solid particles suspended in solution. They are usually negatively charged, attracting a compact primary layer of positively charged ions, which attract more counterions to form an electrical double layer. Electrostatic repulsion between the charged double layers prevents the particles from colliding, stabilizing the colloids. These solids are often undesirable because they can contain toxins that are difficult to remove. Coagulation is a technique that helps aggregate and...

Solubility

Solubility

Solution, Solubility, and Solubility Equilibrium
A solution is a homogeneous mixture composed of a solvent, the major component, and a solute, the minor component. The physical state of a solution—solid, liquid, or gas—is typically the same as that of the solvent. Solute concentrations are often described with qualitative terms such as dilute (of relatively low concentration) and concentrated (of relatively high concentration).
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Related Experiment Video

Updated: Jun 14, 2026

Diffuse Reflectance Infrared Spectroscopic Identification of Dispersant/Particle Bonding Mechanisms in Functional Inks

Diffuse Reflectance Infrared Spectroscopic Identification of Dispersant/Particle Bonding Mechanisms in Functional Inks

Published on: May 8, 2015

Polymeric dispersants delay sedimentation in colloidal asphaltene suspensions.

Sara M Hashmi¹, Leah A Quintiliano, Abbas Firoozabadi

¹Department of Chemical Engineering, Yale University, New Haven, Connecticut 06510, USA.

Langmuir : the ACS Journal of Surfaces and Colloids

|March 26, 2010

Summary

Adding dispersants to asphaltene particle suspensions in heptane improves stability and alters sedimentation dynamics. Beyond a critical concentration, dispersants significantly delay sedimentation, likely by reducing particle size and polydispersity.

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Published on: September 16, 2016

Area of Science:

Colloid and Surface Science
Petroleum Chemistry
Materials Science

Background:

Asphaltenes, complex heavy organic molecules in crude oil, are prone to instability and precipitation.
Asphaltene precipitation can cause operational issues in oil production and refining.

Purpose of the Study:

To investigate the effect of dispersants on the sedimentation behavior of asphaltene particles in heptane.
To understand the mechanism by which dispersants stabilize asphaltene suspensions.

Main Methods:

Sedimentation measurements of colloidal scale asphaltene particles in heptane.
Dynamic light scattering (DLS) to analyze particle size and polydispersity.

Main Results:

Dispersants alter the sedimentation front dynamics, transitioning from power-law collapse to a rising front.
An optimal dispersant concentration leads to improved suspension stability.
Excess dispersant beyond a crossover concentration significantly delays sedimentation dynamics.

Conclusions:

Dispersants enhance the stability of asphaltene suspensions in heptane.
Stabilization is attributed to dispersant-induced reduction in asphaltene particle size and polydispersity.
Understanding these effects is crucial for managing asphaltene-related issues in the petroleum industry.