Absorption and Biodegradation of Hydrophobic Volatile Organic Compounds in Ionic Liquids

Abstract

Four room temperature ionic liquids, [BMIM][PF6], [BMIM][NTf2], [PEGMIM][PF6], and Aliquat, were investigated regarding their use in a two-phase partition bioreactor dedicated to remove two hydrophobic VOC, dimethyldisulfide and toluene. Aliquat and [PEGMIM][PF6] cannot be further considered, owing to the toxicity of the former shown during glucose uptake inhibition tests and the water solubility of the latter. The partition coefficients of [BMIM][PF6] and [BMIM][NTf2] were found comparable to those recorded for typical liquid solvents used in multiphase bioreactors. They were also non-biodegradable, showed during long-term biodegradability tests. After 1 day of lag time, similar glucose biodegradation rates were recorded in the presence of 5 % [BMIM][PF6] or [BMIM][NTf2], if compared to controls deprived of ionic liquid. However, a clear inhibitory effect of the ionic liquids was observed during VOC biodegradation experiments. This phenomenon was significantly minimized after acclimation of activated sludge to VOC, since nearly similar consumption rates of toluene were recorded in the control deprived of IL and in the presence of 5 % bmimPF6, 0.49 and 0.48 g m−3 h−1, respectively. These promising results showed that more complex acclimation strategies, including microbial acclimation to both ionic liquids and VOC, will have to be considered.