In general, drying refers to the removal of moisture from solids, gases or liquids.
In the context of thermal process engineering, evaporation is understood to be the separation of a solvent from a solution.
Absorption is used to remove one or more gaseous components from a gas flow using a solvent.
Adsorption is used to remove individual components from a gas or liquid mixture. The component to be removed is physically or chemically bonded to a solid surface.
Distillation is a unit operation that can be used to fractionate liquid mixtures. It utilises the different volatility of the components of the mixture to be separated.
Rectification is an application of distillation and its uses include fractionation of crude oil. In practice, this multi-stage distillation process is carried out in the form of countercurrent distillation (rectification) in a column.
Crystallisation is a unit operation in thermal process engineering, and is mainly used for separation and cleaning but also for shaping substances.
Compared to filtration, membrane separation processes remove much smaller substances, such as viruses and dissolved ions, from the water. The driving forces of the separation process are differences in concentration or pressure between the two sides of the membrane.
Liquid-liquid extraction involves using a liquid solvent to remove a liquid component from a liquid mixture.
Solid-liquid extraction allows soluble components to be removed from solids using a solvent.