Effects of soil components and solution inorganic cations on interactions of imidazolium-based ionic liquid with...

Effects of alkyl chain length of ionic liquid (IL), soil components and solution inorganic cations on a selected IL (1-methyl-3-octylimidazolium chloride, [OMIM]Cl) interaction with Chinese soils were investigated using batch sorption experiments. The results indicated that sorption energy was mainly controlled by chain length of [OMIM]Cl and contents of soil organic matter (SOM). [OMIM]Cl sorption on soils was mainly controlled by cation exchange process. Contributions of SOM and clay minerals (CMs) to [OMIM]Cl sorption were 7.3%-53.8% and 46.2%-92.7%, respectively. SOM possessed higher energy cation-exchange binding sites than CMs. To predict the sorption of [OMIM]Cl on soils, a model for the relationship between sorption coefficient (K_d) and cation exchange capacity (CEC) from soil components (SOM and CMs, i.e., CEC_SOM and CEC_CMs) as well as solution concentration (C_e) was established: LogK_d = Log(1.67*CEC_SOM + 3.22*CEC_CMs) - 0.58LogC_e. This model could provide a good prediction for sorption coefficients and the prediction errors were within 0.48 log unit. Competitive effects caused by inorganic cations followed the order of Ca²⁺ = Mg²⁺ > K⁺ > Na⁺. Concentrations and valence of coexisting ions both affect their competitive capability on [OMIM]Cl sorption. The finding of this study provided valuable information for evaluating the fate of [OMIM]Cl in soils.