Reversible Absorption of Volatile Organic Compounds by Switchable-Hydrophilicity Solvents: A Case Study of Toluene with N,N-Dimethylcyclohexylamine.

Abstract

Absorption is one of the most important treatment technologies for the removal of volatile organic compounds (VOCs) from tail gases, yet the separation of the absorbents and VOCs remains challenging because of concerns related to environmental impact and large energy requirements. Herein, we explored an absorption and desorption process using N,N-dimethylcyclohexylamine (CyNMe2) as a representative switchable-hydrophilicity solvent (SHS) and toluene as a representative VOC. The results showed that in comparison to common absorbents, CyNMe2 exhibits excellent toluene absorption performance. Desorption efficiencies of toluene from CyNMe2 of up to 94% were achieved by bubbling CO2 at 25 °C, and separation efficiencies of CyNMe2 from water up to 90% were achieved by bubbling N2 at 60 °C. Even after five absorption–desorption cycles, the toluene absorption capacity of CyNMe2 was comparable with that of the fresh absorbent, suggesting that CyNMe2 retains its absorption capacity. We demonstrate an innovative and reversible remediation strategy of VOCs based on SHSs, and the results indicate that SHSs can be used as an alternative to common absorbents for the removal of VOCs to reduce environmental pollution and energy consumption.