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

•ATPS were successfully applied for the separation of DY86 and DR80 dyes.•A screening of 27 different combinations of ATPS phase forming components was performed.•ATPS based on acetonitrile and cholinium bitartrate showed the greater selectivity for the dyes.•DY86 was recovery from the acetonitrile-rich phase by evaporating the solvent.•DR80 was recovery from the ionic liquid-rich phase using a chitosan-based adsorbent. 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 °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]-rich phase 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][Bit]-rich phase was of about 93% using a chitosan adsorbent (1:75, m/v) under constant stirring and at 45 °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.