Partitioning behavior of dyes in ionic liquids induced aqueous biphasic systems of PPG 725 & ammonium salts

ABSTRACT

Polypropylene glycol (PPG) is one of the most utilized polymers in aqueous biphasic systems. The low polarity of the polymer-rich phase restricts the application of the ABSs. The applicability of polymer rich ABSs can be induced by adding little amount of ionic liquids as adjuvants. Therefore, an analysis involving the introduction of a small amount of imidazolium-based ILs to PPG 725 + ammonium salts ABSs was performed. The phase diagrams as well as the partitioning behavior of dyes: Orange II (OII), Eriochrome Black T (EBT) and Brilliant Green (BG) were investigated. The addition of 5% 1-butyl-3-methylimidazolium acetate, [BMIM][AC] modulates the partition behaviors of all the investigated dyes. The employed ILs and dyes partitioned preferentially into the polymer-rich phase. The partition coefficients (K_dye) for all the dyes follow the sequence: BG > EBT > OII in all investigated ABSs. The results obtained are in accordance with the logarithm of octanol-water partition coefficients (log Kow) of the respective dyes. The recovery of BG dye from polymer phase has been studied successfully by adsorption onto chitosan.

KEYWORDS:

• Aqueous biphasic systems
• phase behavior
• ammonium salts
• ionic liquids
• dyes

Acknowledgments

Emmanuel A. Oke acknowledges the financial assistance of Africa Scholarship-MEA under the scheme of the Indian Council for Cultural Relations (2019-2020).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Statement of novelty

The main objective of this paper is to study the effect of addition of small amount of imidazolium based ILs on aqueous biphasic systems of PPG 725 + inorganic ammonium salts: (NH₄)₂CO₃, NH₄H₂PO₄, (NH₄)₂SO₄ and (NH₄)₂HPO₄. Many researchers conducted similar kind of work on ABS of polymer but the present work is first report on ABS of PPG 725 and ammonium salts. The obtained results shows that require comparatively less amount of ammonium salts. The partitioning of dyes: Orange II (OII), Eriochrome Black T (EBT) and Brilliant Green (BG) were investigated in theses ABSs. The addition of 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF₄]; 1-butyl-3-methylimidazolium acetate, [BMIM][AC]; and 1-butyl-3-methylimidazolium trifluoromethanesulfonate, [BMIM][OTF] were investigated. The present of 5% 1-butyl-3-methylimidazolium acetate, [BMIM][AC] modulates the partitioning behavior of all the investigated dyes. The employed ILs and dyes partitioned preferentially into the polymer-rich phase. [BMIM][AC] is referred as greener ILs hence the studied ABSs can serve as eco-friendly separation systems for removal of dyes.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/01496395.2023.2259600