Characteristics and Mechanism of the Adsorption of Imidazole Ionic Liquids in Wastewater by Montmorillonite: Effect of Carbon Chain Length and Dosage of Ionic Liquids

Abstract This paper studied the adsorption characteristics and mechanism of four kinds of ionic liquids (ILs) with different carbon chain lengths in montmorillonite (Mt). The results of isothermal adsorption at 25 °C show that the adsorption of four kinds of IL in Mt conforms to the Modified‐Langmuir model, and the adsorbance of IL in Mt is positively correlated with the dosage and the carbon chain length of IL. The dynamics research results show that the adsorption of IL in Mt fits well with the quasi‐second‐order dynamics equation. The reaction constant k is negatively correlated with the dosage of IL but positively correlated with the carbon chain length. The thermodynamics results show that the adsorption of IL in Mt is exothermic. The carbon chain length and the dosage of IL have a cross effect on the adsorption capacity of Mt for IL and the structure of the adsorption products. The adsorption capacity of Mt increases first and then decreases with the increase of dosage, and it increases with the increase of carbon chain length. The dosage of IL has little effect on the d (001) of IL/Mt with the short carbon chain, but the d (001) of IL/Mt with the long carbon chain increases with the increase of the dosage of IL. The carbon chain length has little effect on the d (001) of IL/Mt with a low dosage of IL, however, when the dosage of IL is high, the d (001) of IL/Mt increases with the increase of carbon chain length. The specific surface area, pore volume and the most probable radius of IL/Mt decrease with the increase of the dosage and carbon chain length, but excessive amounts of IL will still increase the most probable radius. Molecular dynamics simulation results show that when the dosage of IL is 0.3CEC, four ILs with different carbon chain lengths are arranged in a monolayer between Mt layers, N (N in IL) coordinates with O t (O on the tetrahedral surface) at a distance of 3.0 Å, and the coordination strength increases with the increase of the carbon chain length of IL.