Mass-transfer operations are physical processes in chemical engineering that involve the movement of chemical species from one phase to another or within a single phase, primarily driven by a or chemical potential [1.1, 1.4, 4]. These operations are essential for the purification of raw materials and the final separation of products in industries like petroleum, pharmaceuticals, and environmental engineering [3, 8, 32]. Fundamental Principles
: Scrubbers and absorbers are used to remove pollutants from industrial discharge streams [5, 8]. Mass-transfer operations
Mass-transfer operations are categorized by the phases involved and the method of separation [8, 32]. Phases Involved Basis of Separation Industrial Example Liquid-Vapour Differences in boiling points/volatility Petroleum refining, alcohol recovery Gas Absorption Gas-Liquid Solubility of a gas in a liquid solvent SO2cap S cap O sub 2 from flue gases Extraction Liquid-Liquid Solubility in an immiscible solvent Recovery of aromatics or edible oils Leaching Solid-Liquid Solubility of a solid solute in a solvent Extracting sugar from sugar beets Adsorption Fluid-Solid Selective adherence to a solid surface Air purification using activated carbon Drying Solid/Liquid-Gas Removal of moisture via evaporation Removing water from PVC or food products Membrane Separation Fluid-Fluid Selective permeability through a barrier Desalination (Reverse Osmosis) Design and Calculation Methods and environmental engineering [3
: Used for continuous contact equipment (like packed towers). It involves differential mass balances and transfer units, such as the Height of a Transfer Unit (HTU) and Number of Transfer Units (NTU) [4, 12, 32]. Industrial and Biological Applications Mass-transfer operations
: Techniques like freeze-drying, microencapsulation, and controlled-atmosphere packaging rely heavily on mass-transfer rates to maintain quality [25].
Mass transfer is fundamentally analogous to heat and momentum transfer, often referred to as the "triple analogy".