Generation of superoxide ion in pyridinium, morpholinium, ammonium, and sulfonium-based ionic liquids and the application in the destruction of toxic chlorinated phenols

Maan Hayyan, Farouq S. Mjalli*, Mohd Ali Hashim, Inas M. Alnashef

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)


Generation of superoxide ion (O 2 ̇-) was carried out in four ionic liquids (ILs) having the same anion, bis(trifluoromethylsulfonyl)imide [N(Tf) 2] -, and different cations, N-hexylpyridinium [HPy] +, N-methoxyethyl-N- methylmorpholinium [MO1,1O2] +, N-ethyl-N,N-dimethyl-2- methoxyethylammonium [N112,1O2] +, and triethylsulfonium [S222] +. Cyclic voltammetry (CV) and chronoamperometry (CA) electrochemical techniques were used in this investigation. It was found that O 2 ̇- is not stable in the [HPy] +-based IL. On the other hand, CV showed that the electrochemically generated O 2 ̇- is stable in [MO1,1O2] +-, [N112,1O2] +-, and [S222] +-based ILs for the time duration of the experiment. The long-term stability of the generated O 2 ̇- was then investigated by dissolving potassium superoxide (KO 2) in dimethyl sulfoxide (DMSO) in the presence of the corresponding IL. It was found that ILs containing [MO1,1O2] + and [N112,1O2] + offer a promising long-term stability of O 2 ̇- for various reactions to be used for several applications. However, it was found that after 2 h, about 92.5% of the generated O 2 ̇- in [S222] + based IL was consumed. The diffusion coefficient and solubility of O 2 in the studied ILs were then determined using CV and CA techniques simultaneously. It was found that diffusion coefficients and CA steady-state currents increase with temperature increases, while the solubility of O 2 decreased. To our best knowledge, this is the first time that morpholinium and sulfoniumbased ILs were utilized as media for chemical and electrochemical generation of O 2 ̇-. Additionally, the chemically generated O 2 ̇-, by dissolving KO 2, was then used for the destruction of 2,4-dichlorophenol (DCP) in [MO1,1O2][N(Tf) 2] under ambient conditions. The destruction percentage was higher than 98%. This work represents a novel application of the chemically generated O 2 ̇- for the destruction of toxic chlorinated phenols in ILs media.

Original languageEnglish
Pages (from-to)10546-10556
Number of pages11
JournalIndustrial and Engineering Chemistry Research
Issue number32
Publication statusPublished - Aug 15 2012

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Industrial and Manufacturing Engineering

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