Adsorption & Absorption The words adsorption and absorption may sound similar but they are fundamentally different in the functions they represent. Adsorption describes how clay is able to attach to other substances. The clay molecule can perhaps be pictured as a stack of business cards with space between them. Around the edge of these cards is a negative electrical charge of unsatisfied ionic bonds. These ions naturally seek to be satisfied and therefore when in contact with substances that carry the opposite (positive) electrical charge an ion exchange takes place. Absorption is the when clay swells and is stretched open like a highly porous sponge, drawing pollutants and toxins etc. into its internal structure, literally locking them away. The greater the surface area the greater the power to pick up positively charged particles.