Thermodynamics Study on Extraction of Silver in Hydrophobic Room-Temperature Ionic Liquid

Silver is widely used in electronics, aerospace technology, medical equipment, and other fields because of its excellent physical and chemical properties. Solvent extraction is a common method for silver extraction, and the organic solvent used in this method does not accord with the concept of green chemistry. Based on this, the ionic liquid extraction system was constructed, and the ionic liquid 1-pentyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide ([C5mim][NTf2]) was selected as a diluent of the organic phase. The effects of temperature, ionic strength, and extractant concentration on the extraction effect were studied, and the optimum extraction conditions were obtained; that is, the extraction rate could reach 98.79% at 25 °C and I = 0.2 mol·kg–1. The experimental data of the extraction process were analyzed in detail, and the standard equilibrium constants at each temperature were calculated. Other thermodynamic values were calculated by the method of polynomial fitting, such as enthalpy change, entropy change, and Gibbs free energy change. This relationship between enthalpy change, entropy change, Gibbs free energy change, and temperature was discussed deeply, which lays a solid theoretical foundation for the industrial production of silver extraction in the future.