Abstract
A novel complex absorbent composed of polyethylene glycol 200 (PEG200) and ionic liquids (ILs) was prepared for the absorption of volatile organic compounds (VOCs) such as dichloromethane (DCM) and benzene. We prepared complex absorbents composed of [EMIM][Cl], [BMIM][Cl], [HMIM][Cl], [BMIM][BF4], [BMIM][PF6], [BMIM][NTF2], and PEG200, respectively, and studied the absorption properties of these six complex absorbents for DCM and benzene. The results show that under the optimized situation, the absorptivity of [HMIM][Cl]–PEG200 complex absorbent for DCM is 85.46% in the first 5 min, and 87.15% for benzene. No obvious decay in the absorptivity of [HMIM][Cl]–PEG200 for DCM and benzene was observed in five cycles, indicating an impressive regeneration performance. Furthermore, the mechanism of ionic liquid absorption for VOC is explored by thermodynamic analysis and quantum chemical calculations. The theoretical calculation results show that the [HMIM][Cl]–DCM interaction is stronger than the [HMIM][Cl]–benzene interaction, which is consistent with the results of the absorption experiment. Moreover, the strong hydrogen bonds can be formed between both [HMIM][Cl]–DCM and [HMIM][Cl]–benzene.
Highlights
Various volatile organic compounds (VOCs) are produced in the petrochemical industry, including benzene, dichloromethane, acetone, and phenol [1,2]
The results showed that 1-butyl-3-methylimidazolium thiocyanate ([BMIM][SCN]) had the highest DCM solubility (1.46 g·g−1, 303.15 K, 60 kPa) among these ionic liquids (ILs), and theoretical calculations prove that the reason for the excellent performance of [BMIM][SCN] is the existence of hydrogen bonds between the anion [SCN] and dichloromethane
The results show that when the concentration of DCM was 20,000 mg·m−3, the concentration of benzene was 5000 mg·m−3, the flow rate of the inlet gas (Q) was 0.036 m3 ·h−1, and the absorption temperature was 298.15 K, the absorptivities of 40 g [HMIM][Cl]–polyethylene glycol 200 (PEG200) with 60% mass concentration of [HMIM][Cl] for DCM and benzene at 5 min were 85.46% and 87.15%, respectively
Summary
Various volatile organic compounds (VOCs) are produced in the petrochemical industry, including benzene, dichloromethane, acetone, and phenol [1,2]. More and more attention has been paid to the treatment of dichloromethane and benzene because they are highly toxic, leading to the risk of human cancer [3,4,5]. The technologies for destroying VOCs mainly include thermal or catalytic oxidation [8], biodegradation [9], and plasma methods [10]. These technologies convert VOCs into carbon dioxide and water, mainly through physical methods or chemical reactions. The recovery techniques include absorption [7,11], adsorption [12,13], condensation [14], and membrane separation [15,16]
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