Phase Behavior, Dye Extraction, and Potential for Pretreating Textile Effluents in Aqueous Two-Phase Systems of Nonionic Surfactants (Tween 20 or Tween 80) and Organic Salts (Sodium Citrate or Sodium Tartrate)

Abstract

Aqueous two-phase systems (ATPSs) based on nonionic surfactant (Tween 20 or Tween 80) and organic salt (sodium citrate or sodium tartrate) are proposed as alternatives for dye extraction and pretreatment of textile effluents. The newly studied ATPSs exhibited an upper phase rich in surfactant and a lower phase rich in salt. An increase in temperature expanded the biphasic region, altered the phase compositions, and increased the tie-line length. Systems containing citrate exhibited larger biphasic regions due to its higher hydration capacity, while Tween 80 promoted greater phase separation than Tween 20, attributed to its higher hydrophobicity. Partitioning studies with rhodamine B and methyl orange showed preferential dye transference to the surfactant-rich phase, with extraction percentages above 98.7% and 99.2%, respectively. When applied to a textile effluent, the formation of ATPSs using the effluent as solvent led to an expanded immiscibility region in tartrate-based systems. Additionally, color removal efficiency remained above 91.52%, regardless of overall system composition or phase mass ratio, demonstrating the practical feasibility of using these ATPSs for the pretreatment of textile effluents. To the best of our knowledge, this is the first study to evaluate the effect of textile effluent composition on both the formation and dye extraction performance of Tween-based ATPSs.