How can absorption be defined in the context of air filtration?

In the context of air filtration, absorption refers to the process where a liquid or gas is taken into a porous substance. This process is essential in air filtration systems that utilize materials designed to capture and hold contaminants, such as odors, gases, or particulate matter, within their structure. This is distinct from simply adhering to a surface, as absorption involves the internalization of the substance into the material, which enhances the filter's ability to purify the air.

In contrast, the other options address different phenomena that do not align with the concept of absorption as it applies to filtration. Gas adherence to a surface describes adsorption, where molecules stick to a surface without penetrating it. The separation of solids from liquids pertains to filtration in a broader sense but does not specifically relate to the absorption of gases or vapors. Lastly, the evaporation of moisture describes a physical change of state and does not pertain to the capture or internalization of gases or liquids by a filter medium. Understanding this distinction is vital for grasping the various processes involved in air filtration technologies.