Removal of Textile Industry Pollutants from Water Using Ethyl Lactate-Based Aqueous Biphasic Systems: Reactive Red 180 and Acid Blue 9

Abstract

Abstract In this work, two different aqueous biphasic systems (ABSs) were applied for the recovery of Reactive Red 180 (RED), an azo dye, and Acid Blue 9 (BLUE), an anthraquinone dye. Experimental studies were carried out using the systems {ethyl lactate (1) + trisodium citrate (Na3[Cit]) or potassium carbonate (K2CO3) (2) + water (3)}, at 298.15 K and 0.1 MPa. Both ABSs achieved high extraction efficiencies (E), close to 99 %, which were positively influenced by increasing tie-line lengths (TLLs). Larger TLLs also promoted higher partition coefficient (K) values, indicating enhanced dye partitioning in both systems. In the Na3[Cit]-based ABS, the RED dye exhibited higher values for the partition coefficients (14.0 ± 0.6 < K < (39 ± 4) × 101) than BLUE (15.5 ± 0.2 < K < 70 ± 0.5), revealing greater selectivity, whereas in the K2CO3-based system, both dyes displayed similar partition behavior (RED: 70 ± 3 < K < (21 ± 3) × 101; BLUE: 46 ± 3 < K < (15 ± 3) × 101), resulting in a more balanced but less selective extraction process. Overall, the studied ABSs may represent viable alternatives to conventional industrial effluent treatment processes. Future work should focus on evaluating new ABS compositions to enhance selectivity and enable the simultaneous separation of dyes.