Filtration is a commonly used separation process in various industries, including chemical engineering. It involves the removal of solid particles from a liquid or gas by passing it through a porous medium. One of the actions of filtration is sedimentation, which is the correct answer in this case.

- Sedimentation as an Action of Filtration:

Sedimentation is the process by which particles settle down under the influence of gravity. In the context of filtration, sedimentation refers to the settling of solid particles that are larger and denser than the liquid or gas medium. This settling action allows for the removal of these particles from the fluid stream.

- Mechanism of Sedimentation Filtration:

When a fluid containing colloidal particles is subjected to sedimentation filtration, the particles gradually settle down due to gravity. The settling rate of particles is influenced by their size, shape, and density, as well as the viscosity of the fluid. As the particles settle, they accumulate at the bottom of the filtration medium, forming a sediment layer.

- Filtration Medium:

The filtration medium used in sedimentation filtration is typically a porous material that allows the fluid to pass through while retaining the solid particles. Common filtration media include sand, gravel, activated carbon, and filter paper. The choice of filtration medium depends on the specific application and the size of particles to be removed.

- Efficiency of Sedimentation Filtration:

Sedimentation filtration is particularly effective in removing colloidal particles from a fluid stream. Colloidal particles are small and have a tendency to remain suspended in the fluid due to their low settling velocity. However, under the influence of gravity in sedimentation filtration, these particles settle and are trapped by the filtration medium, resulting in their removal from the fluid.

- Advantages of Sedimentation Filtration:

Sedimentation filtration offers several advantages in terms of particle removal:

1. High efficiency: Colloidal particles, which are typically difficult to remove by other methods, can be effectively removed through sedimentation filtration.

2. Simple operation: Sedimentation filtration is relatively simple and does not require complex equipment or processes.

3. Cost-effective: Compared to other separation techniques, sedimentation filtration is often a cost-effective solution for particle removal.

In conclusion, sedimentation is an important action of filtration where colloidal particles are removed from a fluid stream. By allowing the particles to settle under the influence of gravity, sedimentation filtration effectively separates the solids from the liquid or gas medium.