Extraction of Lead Ions and Partitioning Behavior in Aqueous Biphasic Systems Based on Polyethylene Glycol and Different Salts

Lead ions are environmental pollutants often present in very low concentrations, which makes them difficult to detect and, thus, present problems for environmental monitoring. In this study, we examined the performance of aqueous biphasic systems based on polyethylene glycol (PEG, molecular mass of 4000 g mol–1) with ammonium sulfate (NH4)2SO4, magnesium sulfate (MgSO4), sodium sulfate (Na2SO4), and trisodium citrate (Na3C6H5O7) for the separation of lead(II) ions from aqueous solutions. We investigated the effects of salt types and the ratio of PEG4000 to salt on the extraction efficiency of lead(II) removal at constant temperatures of 303 K and 0.1 MPa. Additionally, we determined the cloud points (solubility equilibrium curve) and tie-lines for four ternary systems comprising PEG4000, water, and salt (either (NH4)2SO4, MgSO4, Na2SO4, or Na3C6H5O7) under the same conditions. A maximum lead(II) extraction efficiency of 74.4% was achieved using the PEG4000/(NH4)2SO4 system with a mass fraction ratio of PEG4000 to (NH4)2SO4 of 0.2:0.12. This outcome highlights the significant potential of utilizing aqueous biphasic systems based on PEG4000 to separate lead(II) from aqueous solutions efficiently.