Water decolorization using tuned ternary Deep Eutectic solvents

Abstract

A method to totally decolorize textile wastewaters using new extraction solvents is proposed, with the aim of vastly reducing water consumption. This technique allows for water reuse while solving one of the biggest problems of the textile industry: the generation of huge amounts of liquid residues. In these effluents, dyes are the most common present pollutants, and are toxic to both human and aquatic life, and to the environment. Full decolorization is an indispensable prerequisite to obtain a clean water that can be repurposed following circular economy principles. To decolorize aqueous streams, liquid–liquid extraction is a widely used technique, achieving both the recovery of the pollutants and the used solvent. In this context, Deep Eutectic Solvents are a promising candidate for novel optimized processes. In this work, we propose several of these agents, formed from tetrabutylammonium chloride, thymol, menthol and decanoic acid, optimized for interaction with a wide array of dye classes and processable physicochemical properties. Across all the studied solvents, it was possible to achieve high extraction efficiency, with full decolorization for most dyes, at very low solvent to aqueous phase ratios. Furthermore, assays using synthetic effluents, containing dyes and other chemicals used to ensure a correct dyeing process, show that our solvents are good candidates to treat streams as those found in industry.