Mass Transfer: Basic Concepts

Mass transfer refers to the net movement of a component (species) in an inhomogeneous system from one location to another in the same or different phase with the aim of making it homogenous and bringing the system closer to equilibrium. Chemical potential difference is the main driving force for mass transfer and depends on various factors like concentration, temperature, pressure, and molecular interactions. Mass transfer occurs by molecular diffusion and bulk flow and does not include movements of materials such as pneumatic conveying of powders, carrying of fruit boxes, or pumping of liquids through pipes. Mass transfer is an important molecular phenomenon that occurs extensively in gases, liquids, and solids in the natural environment as well as in processing and manufacturing industries. It is the basis for numerous biological and chemical processes of direct interest to us, ranging from cooking, digestion, and absorption of foods to separation and purification of products from their matrices.