Which process involves the formation of a separable substance from a solution?

The process that involves the formation of a separable substance from a solution is chemical precipitation. In chemical precipitation, certain chemicals are added to a solution, which react with dissolved substances to form solid particles. These solid particles often have a lower solubility than the original dissolved species, leading to their separation from the liquid phase. This process is commonly used in wastewater treatment to remove contaminants, such as heavy metals or phosphates, through the formation of solid precipitates that can be easily filtered or settled out.

Coagulation and sedimentation are related processes but do not specifically result in the direct formation of a separate substance from a solution in the same manner. Coagulation involves the neutralization of charges on particles in suspension to allow them to clump together, while sedimentation is the process where these larger clumps or particles settle to the bottom of a container due to gravity. Evaporation, on the other hand, is a physical change that involves the transition of water from a liquid to a gas, and does not form a new substance in the solution. This context highlights the uniqueness of chemical precipitation as the correct answer.