Complete process for the selective recovery of textile dyes using aqueous two-phase system

Environmental problems arising from the release of dyes through industrial aqueous effluents are an emerging concern. To mitigate the problem, this work provides an experimental study on the use of aqueous two-phase systems (ATPS) for the selective separation and posterior recovery of dyes. Additionally, the complete recycling of the phase forming components is achieved. Azo dyes used in real textile industries, Direct Red 80 - DR80 and Direct Yellow 86 - DY86, were used. An initial screening of the ATPS forming elements was performed and the ATPS composed of 63 wt% acetonitrile (ACN) + 20 wt% cholinium bitartrate ([Ch] [Bit]) + water at 25 degrees C were selected. An extraction efficiency of around 91% of DY86 to the ACN-rich phase and of approximately 99% of DR80 to the [Ch] [Bit]-richphase was obtained. The Kamlet-Taft parameters of the ATPS coexisting phases were measured aiming to understand the partitioning mechanism, especially for the migration of DY86 to the ACN-rich phase. The recovery of the DR80 from [Ch] [Bill-rich phase was of about 93% using a chitosan adsorbent (1:75, m/v) under constant stirring and at 45 degrees C, while ACN was completely recovered by evaporation. It was herein demonstrated that an ATPS based on a common organic solvent and a cholinium-based ionic liquid has potential for the separation and recovery of textile dyes.