What Exactly is Liquid-Liquid Extraction

Welcome to a chemical engineering lesson presented by the KMN student.

Understanding Liquid-Liquid Extraction Process Liquid-liquid extraction is a process to separate two liquids by transferring them into an immiscible solvent where equilibrium favors the transfer of solute. Understanding the mechanics helps in selecting the best solvent and determining equilibrium position. Examples include extracting penicillin from fermentation mixtures and fatty acids from vegetable oils using different solvents like ethyl acetate or liquid propane.

Operational Aspects of Liquid-Liquid Extraction In liquid-liquid extraction, two immiscible solvents are used for interfacial mass transfer of solute between phases resulting in extract and raffinate products. The operation involves nomenclature such as feed (solution to be extracted), solvent (contacting with feed), extract (solvent-rich product), and raffinate (residual liquid). The process requires feasible separation for successful operation, aiming at easier purification than original mixture through selective solvent choice.

Efficient Liquid-Liquid Extraction Process Setup Liquid-liquid extraction is a process used for separating components in a mixture efficiently. The setup involves feed containing acetic acid and water, ethyl acetate as the solvent, and mass balances are crucial for monitoring flow rates. Trays in the extraction column facilitate efficient contact between solvents and solutes to enhance mass transfer.

Optimizing Mass Transfer in Liquid-Liquid Extraction Liquid-liquid extraction is preferred over other separation methods when distillation or chromatography are not feasible. It allows near-complete separation of components by manipulating mass transfer between solute and solvent. Maximizing surface area through trays or spray systems enhances mass transfer rate, although some diffusion reactions may also occur before significant interfacial reactions take place.

Selecting the appropriate solvent is crucial for efficient liquid-liquid extraction. The key considerations include high selectivity for solute over carrier, high solute dissolving capacity to minimize solvent usage, minimal solubility in carrier to prevent unwanted reactions, low volatility for easy recovery without extreme conditions, chemical stability for prolonged use and inertness to allow construction with common materials.