A sustainable methodology to extract bismuth from secondary sources

Abstract

Bismuth is a critical metal broadly used in cosmetic, medicine and metallurgy. However, its scarcity in Earth’s crust may impair further applications. An alternative is to recover bismuth from secondary sources. In this work, a methodology to extract bismuth from safety valves of discharged gas cylinders is proposed. Extraction and purification of bismuth were carried out using aqueous two-phase systems (ATPS) prepared with poly(ethylene oxide) polymer or poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) copolymer (L35) and electrolytes (NaNO3, NH4NO3, sodium citrate or Na2SO4). The influence of iodide extractant concentration, tie-line length, electrolyte nature and polymer hydrophobicity on the bismuth extraction behavior were evaluated. Bismuth was significantly recovered in the absence of extractant, and its extraction depends on the ATPS composition, macromolecule and electrolyte nature. After three consecutive extractions bismuth was obtained with high purity (94.7%), resulting on a recovery of 38.5 g of bismuth per 1.00 kg of fusible plug, using L35 + NH4NO3 + H2O ATPS, without any extractant.