Working and Principle of Colloidal Mill : Pharmaguideline

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Working and Principle of Colloidal Mill

Colloidal mill is used to make the colloidal solution or reduce the particles size of the pharmaceutical ingredients in pharmaceutical manufacturing.
Pharmaceutical companies work with small compound particles. They seek to separate chemical compounds to get to the smallest state of the compounds. That is why the colloidal mill is important in the pharmaceutical manufacturing industries. 

This is a machine that is used to reduce the size of particles of solids that are suspended in a liquid. When a liquid is suspended in another liquid, meaning that they are immiscible, this machine is used alternatively to reduce the size of this droplet.

Simply put the colloidal mill is used to solids present in suspensions and emulsions or even the suspensions size. It is used in the reduction of almost all types of materials. 

The end result of this type of mix is a very stable mix which is able to resist contamination by water or bleed. In fact, this is the method used in mixing cement based grout. The colloidal mill uses a method known as shearing.

Principle of the Colloidal Mill

The basic principle used in the colloidal mill is known as rotor-stator which is placed in a cylindrical vessel. The rotor and stator are placed close enough to create a narrow passage where the material to be reduced in size are passed through. That is why the process is known as shearing, because of you literary shear the material into smaller particles.

The solid is first fed into a compartment known as a hopper which guides the product to the gap that is between the rotor and the stator. The rotor and stator surface is covered with two metal toothed coverings which cut and shear the solid.

The rotor rotates at a speed of between 3,000 and 20,000 RPM. This, in turn, distorts the fluid or solid structure as it rubs between these two rough-edged surfaces. The resultant product is then passed through to the discharge area. The drain pipe then removes the final product from the colloidal mill. If the final product has not been sheared to the desired size, it can be re-circulated back to the machine for further shearing.

Related: Working and Principle of Rapid Mixer Granulator (RMG)

Working of the Colloidal Mill

The product to be shared is passed through the inlet which is on top of the mill known as a hopper. It is then passed through to the narrow gap between the rotor and stator. The rugged edges shear the material into the tiniest particles depending on the rotation speed. This mill uses a hydraulic system to shear the material into the final product. It mainly works on the material that will be suspended on the liquid or emulsion. 

As you continue to add the heavier liquid, the suspension floats to the narrow gap and the shearing process continues. As the process continues, the two viscous elements continue to mix. There are models where both the stator and rotor rotate together and there are other models where only the rotor rotates and the stator remains still.

This mechanism is used for various purposes in the pharmaceutical field like dispersing of solid particles in an emulsion, emulsification, milling, homogenization, and improving the stability of emulsions.

Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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