Adsorption – Types & Isotherms

This chapter discusses the adsorption phenomenon, its types, theoretical models, and the importance of adsorption in industries. Adsorption may be described as the sticking of molecules in a fluid phase on the surface of a solid and is used in catalysis, separation process and also in environmental applications. The chapter distinguishes between the physical adsorption (physisorption) that is formed due to weak Van der Waals forces, and the chemical adsorption (chemisorption) formed due to strong chemical bonds. It uses isotherms of adsorption that comprise the Langmuir and the Freundlich models to describe the dependence of the concentration of adsorbates and the quantity of adsorbates that was adsorbed at the equilibrium. The chapter describes the factors that affect adsorption, including the temperature, pressure, the surface area, and the nature of the adsorbent. Its use in industrial processes is stated, including gas purification, water treatment, heterogeneous catalysis, chromatography and activated carbon filters. The chapter also describes the other problems of adsorbent regeneration, the maximization of efficiency, and the scale-up of the adsorption processes. With theory, mathematical modeling and practice, students can learn not only how to design industrial processes based on adsorption, but they also learn how to approach the surface on a molecular scale. Adsorption is also a subject in the engineering and biotechnology degrees of chemical engineering, environmental science, catalysis, and materials technology.