Molecular insights into dicationic versus monocationic ionic liquids as a high hydrophobic alternative for the separation of phenol from waters

Congfei Yao; Haisong Wu; Xiaoyu Li; Qiuyu Chen; Wanxiang Zhang; Gangqiang Yu; Hongqi Liu; Yuqing Miao; Weize Wu

doi:10.1016/j.envres.2024.118420

Molecular insights into dicationic versus monocationic ionic liquids as a high hydrophobic alternative for the separation of phenol from waters

Environ Res. 2024 May 1:248:118420. doi: 10.1016/j.envres.2024.118420. Epub 2024 Feb 3.

Authors

Congfei Yao¹, Haisong Wu², Xiaoyu Li², Qiuyu Chen², Wanxiang Zhang³, Gangqiang Yu⁴, Hongqi Liu², Yuqing Miao⁵, Weize Wu⁶

Affiliations

¹ Institute of Bismuth and Rhenium Science, School of Materials and Chemistry, University of Shanghai for Science and Technology, Shanghai, 200093, China; State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, 100029, China. Electronic address: congfeiyao@usst.edu.cn.
² Institute of Bismuth and Rhenium Science, School of Materials and Chemistry, University of Shanghai for Science and Technology, Shanghai, 200093, China.
³ State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, 100029, China.
⁴ Faculty of Environment and Life, Beijing University of Technology, Beijing, 100124, China.
⁵ Institute of Bismuth and Rhenium Science, School of Materials and Chemistry, University of Shanghai for Science and Technology, Shanghai, 200093, China. Electronic address: yqmiao@usst.edu.cn.
⁶ State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, 100029, China. Electronic address: wzwu@mail.buct.edu.cn.

PMID: 38316384
DOI: 10.1016/j.envres.2024.118420

Abstract

The hydrophobic nature of an extractant is particularly critical in the treatment of wastewater. Considering that dicationic ionic liquids (DILs) are likely to be more hydrophobic, a comparative study of the separation of phenol from waters using [NTf₂]^- based monocationic ionic liquids (MILs) and DILs is carried out both from experimental and theoretical analysis perspectives. Experimental results revealed that DILs exhibited superior extraction ability compared to MILs, with extraction efficiencies of 93.7% and 97.4% using [BMIM][NTf₂] and [C₆(MIM)₂][NTf₂]₂ as extractants, respectively. The microscopic examination through theoretical calculations elucidated the higher hydrophobicity and extraction efficiency of DILs over MILs. The results indicated that the DIL showed stronger hydrophobicity than the MIL because the hydrogen bond strength between the DIL and water was lower than that of the MIL. Although the hydrogen bond strength between the DIL and phenol was lower than that of the MIL, the stronger van der Waals forces existed between DIL and phenol, so DIL was more efficient in extracting phenol. In addition, the experimental parameters were optimized to provide basic data for application, such as mass ratio of ILs to water, extraction time and temperature, pH, and initial phenol content. Finally, the DILs were recovered using rotary evaporation apparatus, and the results demonstrated that DILs had good recovery and reuse performance. In brief, this work could provide an effective method for the treatment of phenol-containing wastewater. And the revelation of molecular mechanism is expected to positively impact the design of high-performance task-specific ILs.

Keywords: Dicationic ionic liquid; Hydrophobicity; Phenol; Quantum chemistry calculation; Weak interactions.

MeSH terms

Hydrophobic and Hydrophilic Interactions
Ionic Liquids* / chemistry
Phenol
Phenols
Wastewater
Water / chemistry

Substances

Ionic Liquids
Phenol
Wastewater
Phenols
Water