The extraction of Fe(III) using cation-exchange carboxylic resins

Six commercial cation-exchange carboxylic resins were evaluated with respect to their ability to extract Fe(III) ions from acid sulphate media. It was found that these resins exhibit strikingly different characteristics, which depend on the matrix morphology and the acidity of the –COOH group. Gel-type resins do not extract large amounts of Fe(III), and SEM studies show that the diffusion of Fe(III) ions into a gel-type matrix is severely hindered. By contrast, macroporous acrylic resins are efficient and selective extractants of Fe(III). The extraction rate is relatively slow, but it can be increased significantly by raising the temperature and decreasing the particle size. A macroporous methacrylic resin can also extract Fe(III) selectively, but the reaction is strongly dependent on the pH. Both acrylic and methacrylic carboxylic resins can be readily eluted with relatively dilute H2SO4. These characteristics make carboxylic resins useful for removing Fe(III) selectively from metallurgical solutions and effluents with the purpose of producing compact and stable iron products for safe disposal or marketing.