In which type of decontamination does the contaminant adhere to the surface of an added material?

The correct answer is Adsorption because this process involves the adherence of contaminants to the surface of a material, creating a layer of the contaminant on that surface. In adsorption, the molecules of the contaminant stick to the surface of a solid or liquid without being absorbed into the material itself, which is essential in various decontamination scenarios. This principle is frequently utilized in the design of materials for cleaning hazardous substances, where the goal is to remove contaminants from surfaces effectively without allowing them to penetrate deeply into the medium.

Absorption, on the other hand, involves the entire volume of a material being penetrated by the contaminant. Here, the contaminant would be taken in and distributed throughout the absorbing material, which is not what is described in the question. Desorption refers to the process of a substance releasing and departing from a surface or phase back into the environment, indicating a reversal of adsorption, and is not the focus of this question. Filtration is a physical separation process that removes particles from a fluid by passing it through a barrier, rather than relying on the adherence of contaminants to a surface material.