Effect of Sodium Chloride and pH on the Composition of the Equilibrium Phases and the Partition of Palladium(II) in the Aqueous Two-Phase System PEG1500–Na₂SO₄–Water

Abstract

Binodal curves for aqueous two-phase systems (ATPS) polyethylene glycol 1500 (PEG1500)−sodium sulfate− water with additions of sodium chloride and hydrochloric or sulfuric acids were determined by turbidimetric titration and analysis of coexisting phases. The results are compared with published data for the ATPS PEG1500−sodium sulfate−water without additions, and the influence of additions on the width of the two-phase field, tielines length, and slopes was traced. The influence of initial concentration of palladium, time of phase contact, pH, concentration of sodium chloride and sodium sulfate on the extraction of palladium(II) was studied. The coefficients of distribution of palladium(II) between the phases of ATPS were measured as a function of the concentrations of sodium chloride (0.1, 1.0, and 2.0 mol•L −1 ) and pH values. At lower concentrations of Cl − ions Pd(II) is extracted as a mixture of ions [Pd(H 2 O)Cl 3 ] − and [PdCl 4 ] 2− , whereas the growth of C(Cl − ) leads to prevalence of the latter, which has poorer extraction properties. Maximal values of the distribution coefficient D Pd of about 9.5 ± 0.75 were achieved in the ATPS PEG1500−Na 2 SO 4 −0.1 M HCl and PEG1500− Na 2 SO 4 −(0.05 M H 2 SO 4 + 0.1 M NaCl).

Alternative Extraction Systems for Precious Metals Recovery: Aqueous Biphasic Systems, Ionic Liquids, Deep Eutectic Solvents

“…The effect of acid and chloride ion concentrations on phase equilibria of an ABS PEG-1500 − Na 2 SO 4 − H 2 O and the partition of palladium were investigated by Milevskiy et al [26]. The maximum distribution coefficients of palladium were achieved under extraction in ABSs PEG-1500 − Na 2 SO 4 − 0.1 M HCl and PEG-1500 − Na 2 SO 4 − (0.05 M H 2 SO 4 + 0.1 M NaCl).…”

Application of Alcohol-Salt Aqueous Biphasic System for the Recovery of Ectoine

“…The enhanced capability of the alcohol-rich top phase for biomolecule recovery mainly attributes to the presence of benzyl groups or double bonds in the IL cation, forming a strong interaction between ectoine and the ionic liquids [34]. Additionally, ionic liquids with longer alkyl chain length exhibit greater hydrophobicity, thereby causing the transportation of more ectoine, along with the ionic liquid molecules, towards the hydrophobic alcohol-rich top phase [35].…”

“…In the presence of 1% (w/w) NaCl, a slight increase in both the K E (9.61 ± 0.05) and Y B (97.50% ± 0.21) was observed compared to the ABS without adjuvant (K E = 9.46 ± 0.08 and Y B = 97.29% ± 0.02). The hydrophobic difference between the two aqueous phases improves with the NaCl addition, thereby promoting the repulsion of ectoine towards the salt-rich bottom phase [35,36]. However, a further increase in NaCl concentration, from 1.5% (w/w) to 3% (w/w), gradually reduced the recovery efficiency.…”

Liquid–Liquid Equilibria Determination and Modeling of ATPS Based on PEG4000 and PVP29000 at 298.15 K and 0.1 MPa

“…The least soluble component in the consolute is named as salting-out agent and causes phase splitting by competing for the consolute molecules . The phase separation of ATPS has been increasingly studied given its promising potential for industrial application, particularly to what pertains their biocompatibility and nontoxicity (suitable for protein purification and cell culture − ), selectivity and extraction efficiency (advantageous for bioprocessing and biotechnology , ), and low environmental impact (crucial in waste treatment and recovery − ).…”