Effective absorption of dichloromethane using deep eutectic solvents.

Chlorinated volatile organic compounds (VOCs), of which dichloromethane (DCM) has become one of the main components because of its extensive use and strong volatility, are recognized as extremely hazardous and refractory pollutants in the atmosphere. The efficient treatment of DCM is of great significance to the protection of environment and human health. In this work, the strategy of DCM capture with deep eutectic solvents (DESs) with different hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs) was proposed and systematically investigated. The experimental results show that tetrabutylphosphonium chloride: levulinic acid ([P4444][Cl]-LEV) presents the most excellent DCM absorption capacity among all DESs studied and considerable capacity in [P4444][Cl]-LEV (1:2) with 899 mg DCM/g DES (5.58 mol DCM/mol DES) at 30 °C and DCM partial pressure of 0.3 bar can be achieved. The microscopic absorption mechanism is explored by 1HNMR and FT-IR spectra as well as quantum chemistry calculations, indicating that the absorption is a physical process. The interaction energy analysis suggests that the greater the interaction energy between DES and DCM, the greater the saturated absorption capacity of DCM. The hydrogen bond (HB) contributes most to the weak interaction between DCM and HBA/HBD, and both HBA and HBD play an important role in the absorption of DCM.

Highly efficient capture of odorous sulfur-based VOCs by ionic liquids.

This study proposes the capture of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) from waste gas using an ionic liquid (IL), namely, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][Tf2N]), and examines the process from a molecular level to the laboratory scale, which is then scaled up to the industrial level. The binding energy and weak interactions between DMS/DMDS and the anion/cation in [EMIM][Tf2N] were investigated using quantum chemistry calculations to identify the capture mechanism at the molecular scale. A thermodynamic model (UNIFAC-Lei) was established by the vapor-liquid equilibrium data of the [EMIM][Tf2N] + DMS/DMDS systems measured at the laboratory scale. The equilibrium and continuous absorption experiments were performed, and the results demonstrated that [EMIM][Tf2N] exhibits a highly efficient capture performance at atmospheric conditions, particularly, absorption capacities (AC) for DMS and DMDS are 189.72 and 212.94 mg g-1, respectively, and partial coefficients (PC) as more reasonable evaluation metrics for those are 0.509 × 10-4 and 6.977 × 10-4 mol kg-1 Pa-1, respectively, at the 100 % breakthrough. Finally, a mathematical model of the strict equilibrium stage was established for process simulations, and the absorption process was conceptually designed at the industrial scale, which could provide a decision-making basis for chemical engineers and designers.