Photo-Fenton-Like Degradation of Imidazolium Ionic Liquids: A Combined Experimental and Theoretical Study

Imidazolium ionic liquids (ILs) have gained significant attention in recent years due to their unique properties and potential applications. However their degradation and toxicity have become a growing concern. This study investigated the UV-light assisted photo-Fenton-like degradation of three imidazolium ILs, viz., 1-ethyl-3-methylimidazolium chloride (IE), 1-butyl-3-methylimidazolium chloride (IB), and 1-hexyl-3-methylimidazolium chloride (IH) and explored the degradation pathway by computational approach using density functional theory (DFT). This process efficiently degraded the ILs in the range 79.78%-84.78% in 120 min at 25 ± 1°C. The degradation rate follows the sequence IE > IH > IB with rate constants (k) 1.511 × 10^-2, 1.34 × 10^-2, and 1.30 × 10^-2 min^-1, respectively. The DFT calculations revealed that the degradation pathway involves hydroxyl radical attack on either the methyl or alkyl substituted chain followed by imidazolium ring opening. This study provides new insights into the degradation pathway of imidazolium ILs and highlights the potential of the photo-Fenton-like process for wastewater treatment.