Chapter 6: Adsorption

Only one letter separates Absorption from Adsorption, yet these two methods to capture carbon dioxide differ in important ways. Adsorption is the process by which the surface of a solid holds on to small molecules in solution or in the gas phase. In other words, the molecules reside on the surface of the material. In absorption, the molecules actually enter into the material. One way these differences play out is in the development of strategies for increasing the capacity of the capture material. With absorption, increasing the capacity of the technology usually involves increasing the amount of capture material. In contrast, with adsorbents, increasing capacity involves increasing the exposed surface area of the material.