The Application of Ionic Liquids and Deep Eutectic Solvents in Separation and Extraction Processes

A special issue of Separations (ISSN 2297-8739). This special issue belongs to the section "Separation Engineering".

Deadline for manuscript submissions: 10 November 2026 | Viewed by 730

Editor


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Guest Editor
Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China
Interests: ionic liquids; deep eutectic solvents; green separation; green catalysis

Special Issue Information

Dear Colleagues,

Ionic liquids (ILs) and closely related deep eutectic solvents (DESs) are attracting growing interest as green, tunable media for separation and extraction due to their negligible vapor pressure, wide liquid temperature ranges, high stability, and adjustable hydrogen-bonding networks. This Special Issue highlights recent advances in both fundamental understanding and practical applications, including liquid–liquid, solid–liquid, gas, and membrane separations, extractive distillation, and biomass dissolution. Contributions focused on solvation behavior, hydrogen-bond networks, phase behavior, mass transfer, and molecular interactions, in addition to studies demonstrating enhanced selectivity, efficiency, or sustainability, are particularly encouraged for submission.

I am therefore pleased to invite you to submit your research articles, communications, or review papers to this Special Issue, with the aim of promoting the rational design and effective utilization of ionic liquids and deep eutectic solvents in modern separation and extraction technologies.

Dr. Mi Feng
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-anonymized peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Separations is an international peer-reviewed open access monthly journal published by MDPI.

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Keywords

  • ionic liquids
  • deep eutectic solvents
  • separation processes
  • extraction processes
  • solvation behavior
  • hydrogen bonding network
  • biomass separation and extraction
  • liquid–liquid extraction
  • gas separation
  • membrane separation

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Published Papers (1 paper)

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Research

13 pages, 1321 KB  
Article
Extractive Purification of Sulfur and Nitrogen Fuel Contaminants Using p-Toluenesulfonic Acid-Based Deep Eutectic Solvents
by Salim Mokraoui, Lahssen El Blidi, Irfan Wazeer, Attiyah A. Al-Zahrani and Mohamed K. Hadj-Kali
Separations 2026, 13(4), 122; https://doi.org/10.3390/separations13040122 - 18 Apr 2026
Viewed by 481
Abstract
This study demonstrates the high efficiency and selectivity of p-toluenesulfonic acid-based deep eutectic solvents (DESs) for simultaneous extractive denitrogenation (EDN) and desulfurization (EDS) of model fuel. Three DESs—TBPB:PTSA, TBAB:PTSA, and ChCl:PTSA (1:1 molar ratio)—were synthesized and evaluated for their effectiveness against representative heteroaromatic [...] Read more.
This study demonstrates the high efficiency and selectivity of p-toluenesulfonic acid-based deep eutectic solvents (DESs) for simultaneous extractive denitrogenation (EDN) and desulfurization (EDS) of model fuel. Three DESs—TBPB:PTSA, TBAB:PTSA, and ChCl:PTSA (1:1 molar ratio)—were synthesized and evaluated for their effectiveness against representative heteroaromatic pollutants: thiophene, dibenzothiophene, pyridine, and carbazole. The phosphonium-based TBPB:PTSA exhibited the highest extraction performance, achieving over 96% removal of nitrogen species and up to 85% removal of sulfur species at 40 °C. Increasing the temperature enhanced desulfurization by reducing viscosity, thereby improving mass transfer kinetics. Additionally, a 3:1 ratio of DES to fuel provided an optimal balance between solvent economy and operational efficiency. Denitrogenation was driven by strong acid–base protonation facilitated by PTSA, while desulfurization was governed by π–π and dispersion interactions, modulated by the hydrophobicity of the cations. The DES achieved nearly quantitative nitrogen removal and satisfactory sulfur extraction after three reuse cycles, while multistage operation enabled complete purification within four extraction steps. 1H NMR analysis confirmed that no DES components were found in the raffinate phase, verifying the immiscibility and stability of the solvent. These results indicate that TBPB:PTSA is a robust, regenerable, and environmentally benign solvent, effectively enabling simultaneous EDN–EDS of hydrocarbon fuels and positioning it as a promising green alternative to traditional hydrogen-based refining methods. Full article
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