Investigating Aqueous Two-Phase Systems Constituted by Benzyltributylammonium Chloride-Based Deep Eutectic Solvents for Efficient Extraction of Textile Dyes

Aqueous two-phase systems (ATPS) have been considered as an eco-friendly separation system for the extraction of value-added compounds from an aqueous matrix. Deep eutectic solvents (DESs) have been used as the latest phase - forming component in ATPS. The novel DES-based ATPS composed of DESs and with K3PO4, K2HPO4, and K2CO3 were investigated at 298.15 K and atmospheric pressure. DESs were synthesized using benzyltributylammonium chloride (BTBAC) with methanol, ethanol, propanol, and polyethylene glycol (PEG) of average molar mass: 200, 400, and 600 in a 1:3 molar ratio. The ability of the studied salt to induce phase separation follows the order: K3PO4 > K2HPO4 ≈ K2CO3. The investigated ATPS were evaluated as an extraction platform for malachite green (MG), indigo blue (IB), and Sudan III (SIII) from aqueous solutions. The highest partition coefficients (Kdyes) 211.01, 716.91, and 1350.35 were observed for MG, IB, and SIII, respectively, using BTBAC:PEG 600 and K3PO4 ATPS. The highest extraction efficiencies (EEdye %) around 100% were reported for all studied dyes by the same ATPS. The extraction capacity of studied ATPS depends upon log Kow values and functional groups present in the dye structure. The obtained results highlight the potential use of DES-ATPS in the purification of dye containing wastewater.