Liquid–Liquid Equilibrium Data of Various Micellar Aqueous Two-Phase Systems for the Extraction of Rhodamine B and Hexavalent Chromium

Micellar aqueous two-phase systems (ATPSs) find prominent applications in the extraction of hydrophobic solutes owing to their low interfacial tension. In this study, we investigated the liquid–liquid equilibrium (298.15 T/K and 101.325 P/kPa) and phase-forming abilities of organic (trisodium-citrate dihydrate and potassium sodium tartrate tetrahydrate) and inorganic (ammonium sulfate and ammonium phosphate dibasic) salts with an amphiphilic surfactant, Triton X-100. The experimental binodal curves for four micellar ATPSs were determined employing the cloud point method, and tie-line compositions were calculated using the gravimetric approach. The experimentally determined equilibrium data were thermodynamically correlated using effective excluded volume theory. For tie-line data accuracy, the Othmer–Tobias and Bancroft equations were used, and the corresponding correlation coefficients were reported. The phase separation ability of organic and inorganic salts was analyzed by using the Hofmeister series. Furthermore, we explored the effectiveness of micellar ATPSs in extracting hazardous pollutants from the textile industry, Rhodamine B (RB) and Chromium(VI) (Cr6+). Extraction experiments showed RB partitioning almost entirely (%E ∼ 99%) into a surfactant-rich phase, and ammonium sulfate-based ATPSs offered the highest extraction for the Cr6+ metal ion (% E = 81%). This study showcases the cost-effective way for the extraction of harmful hydrophobic industrial pollutants.