Physicochemical properties of ionic liquids with indole removal function

Indole exists in coal tar, gasoline, diesel oil and other oil products, in the process of using oil products, will cause serious pollution to the environment, so it is necessary to remove indole from oil products. In this paper, 1-hydroxy-3-methylimidazolserine was synthesized and characterized. Its density, surface tension, and refractive index were measured every 5 K in the range of 293.15–333.15 K using standard addition method. The relationships between temperature and water content were discussed. The mass change with time was measured by thermogravimetric analyzer, and its evaporation enthalpy was discussed. Furthermore, the polarity was predicted using these data. Finally, it was used to separate indole from simulated oil. A simulated oil solution containing 0.2 g/L indole was extracted under conditions of a mass ratio of 1:5 between ionic liquid and simulated oil, temperature of 30 °C, and time of 60 min. The extraction rate reached 88.9 %, indicating that the prepared ionic liquid can be used as an extractant for removing indole from simulated oil. In addition, the extraction mechanism was also investigated, and it was found that the indole was successfully extracted from the simulated oil because of the hydrogen bond between the indole and the ionic liquid.