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.

Abstract Fe(II) and Fe(III) have distinct chemical and biological functions. Consequently, it is more important to determine the fraction of both oxidation state that knowing the total iron concentration in a sample. However, green methods for iron speciation are still limited. This work uses aqueous two-phase system, a safe alternative to liquid–liquid extraction, to perform the chemical speciation of iron. This method is based on the reaction of Fe(II) with 1,10-phenanthroline extractant, forming a complex of Fe(II)-phenanthroline that concentrates in the top phase of the system. The Fe(III) specie concentrated in the bottom phase of the system. Iron speciation was affected by the electrolyte nature, macromolecule type, quantity of phenanthroline added, and pH. The system formed by PEO1500 + Na3C6H5O7 + H2O at pH 6.00, containing 5.00 mmol kg-1 of phenanthroline, was successfully used to separate the iron species before determination by flame atomic absorption spectrometry. Under these optimal conditions, a separation factor of 233 was obtained between Fe(II) and Fe(III) with extraction percentages of (95.1 ± 1.0)% and (7.68 ± 0.50)%, respectively The proposed method was successfully applied for iron speciation in water samples, and provided recovery percentages ranging between 90 and 106%.