Extraction of soluble dyes from aqueous solutions with quaternary ammonium-based ionic liquids

In this work, four quaternary ammonium-based ionic liquids are used to extract methyl orange and methylene blue (major dye species in industry) from water. The influence of extraction time, temperature, salt effect, and pH on extraction efficiency is systematically investigated. Tricaprylmethylammonium thiocyanate ([N1888][SCN]) exhibits optimal ability for extracting both dyes; the extraction efficiency reaches 89.09% and 64.14% for methyl orange and methylene blue, respectively. It is also observed that the efficiency is remarkably increased by adding NaCl in the extraction system except in the extraction of methyl orange using [N1888][SCN]. This work shows that ionic liquids might provide new options in the disposal of dye-wastewater.

► New quaternary ammonium-based ILs are used to extract soluble dyes.
► Quaternary ammonium-based ILs are very stable for extraction.
► Significant effects of extraction are interestingly observed.
► This work shows a new option for dealing with dyes wastewater.