Processing of steel rinse waters through coextraction and selective stripping



Recovery of iron(III), HNO3, and HF from stainless steel rinse waters by liquid–liquid extraction using Cyanex-923 extractant was studied. The influence of equilibration time, temperature, Vaq/Vorg phase ratios, and extractant concentrations on the extraction of iron(III) was investigated. Furthermore, the separate extraction of HNO3 and HF by Cyanex-923 was also studied. Conditions for the coextraction of iron(III), HNO3, and HF were established as: 30 min of contact, 20°C, Vaq/Vorg phase ratio of 1 and using undiluted Cyanex-923 (water presaturated) as extractant. Under the appropriate experimental conditions, water is effective for the selective stripping of the three extracted solutes. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1150–1155, 2004