Effective Absorption of Dichloromethane Using Carboxyl-Functionalized Ionic Liquids.

Area of Science:

• Environmental Chemistry
• Materials Science
• Chemical Engineering

Background:

• Dichloromethane (DCM) is a volatile and persistent air pollutant, posing significant environmental and health risks.
• Ionic liquids (ILs) show potential for DCM absorption, but developing ILs with high absorption efficiency remains a challenge.

Purpose of the Study:

• To synthesize and evaluate novel carboxyl-functionalized ionic liquids for efficient dichloromethane capture.
• To investigate the absorption mechanism and thermodynamic properties of DCM-IL systems.

Main Methods:

• Synthesis of four carboxyl-functionalized ionic liquids: [N1888][Ac], [N1888][FA], [N1888][Gly], and [P66614][Gly].
• Experimental measurement of vapor-liquid equilibrium (VLE) data for DCM + IL binary systems.
• Application of the NRTL model for VLE data prediction.
• Spectroscopic (FT-IR, 1H-NMR) and quantum chemistry calculations to elucidate the absorption mechanism.

Main Results:

• The absorption capacity order was determined as [P66614][Gly] > [N1888][Gly] > [N1888][FA] > [N1888][Ac].
• [P66614][Gly] exhibited the highest absorption capacity (130 mg DCM/g IL at 313.15 K and 6.1% DCM), which is double that of previously reported ILs.
• The NRTL model accurately predicted VLE data with a relative root mean square deviation (rRMSD) of 0.8467.
• The absorption mechanism involves nonpolar affinity between the cation and DCM, and hydrogen bonding between the anion and DCM.
• Hydrogen bonding between the anion and DCM was identified as the primary interaction influencing the absorption process.

Conclusions:

• Carboxyl-functionalized ionic liquids, particularly [P66614][Gly], are effective for capturing dichloromethane.
• The study provides valuable insights into the absorption mechanism and thermodynamic behavior of DCM-IL systems.
• These findings contribute to the development of advanced materials for mitigating air pollution.