Chemical Separation and Purification Techniques

Chemical separation and purification techniques are the family of physical and physicochemical methods used to divide a mixture into its component substances or to remove impurities from a target product, so the desired material can be isolated, measured, or used at the purity an application requires. Members of this class range from thermally driven methods such as distillation, which exploits differences in boiling point, through membrane-based methods such as ultrafiltration, nanofiltration, reverse osmosis, pervaporation, and electrodialysis, which exploit differences in molecular size, charge, or vapor pressure across a semi-permeable barrier, to sorption and phase-transfer methods such as ion exchange, liquid-liquid solvent extraction, supercritical fluid extraction, and Soxhlet extraction, which exploit differences in chemical affinity between two phases. These techniques underlie water treatment, industrial chemical manufacturing, food and pharmaceutical processing, and analytical laboratory work, and a real process plant or laboratory workflow typically combines several of them in sequence to reach a required purity or yield.