## 1 Introduction  
Ionic liquids (ILs) are a kind of organic salt with low melting points (mainly \(<\)100 \({}^{\circ}\)C). Generally, the ILs are composed of organic cations and organic/inorganic anions. In the past few years, ILs have attracted increasing attention of researchers due to their unique characteristics, such as low vapor pressure, non-flammability under ambient conditions, high solvent capacity, a wide electrochemical window, and so forth [1,2]. The physical and chemical properties (e.g., solubility, polarity, viscosity, and acidity) of ILs could be designed simply by careful selection of the ions, thereby allowing \"IL tailoring\" for a particular application [3]. These unique and versatile properties suggest ILs as potential substituents for traditional volatile organic solvents in a wide range of fields such as synthesis and separation [4,5].  
Recently, some imidazolium-based ILs have been used to enhance solvent extraction of bitumen from oil sands. Compared to conventional solvent extraction, bitumen recovery could be highly improved (at least 10%) with the assistance of ILs. In addition, due to the strong surface modification by the ionic liquids, the mineral surfaces become more hydrophilic, allowing much less clay and fines to be entrained into the recovered bitumen [6, 7, 8, 9]. However, during the ILs-assisted solvent extraction, there are still some ionic liquids being attached in the residual solids due to the direct contact with the minerals. Our previous results showed that these residual ionic liquids in the waste solids could be washed away by water because of their hydrophilicity. Unfortunately, much more detailed investigation on how to remove these ionic liquids from the residual solids is still needed.  
To recover the ionic liquids from solutions, different kinds of methods have been proposed, such as distillation [10,11], extraction [12,13], aqueous two-phase systems [14,15], membrane technology [16,17], adsorption [18,19], and so on. The adsorption is regarded as an eco-friendly and cost-effective way. Among the reported adsorbents (e.g., activated carbons [20,21], clays [22], and bacterial biosorbents [23], etc.), ion-exchange resins are considered to be candidates for treatment of low-concentration ionic liquids solutions [24, 25, 26, 27] due to the high adsorption efficiency and reusability. [PERSON] et al. [24] investigated removal of the cationic part of 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) from aqueous solution by twelve ion-exchange resins. The sulfonic acid ion-exchange resins showed the most efficient adsorption, while the particle size and crosslinking degree of resin exerted slight influence on the uptake of [Emim] cations. [PERSON] and coworkers [25] demonstrated that the anions of imidazolium-based ILs insignificantly affected the adsorption performance of ion-exchange resins, and enhanced adsorption capacity was observed for ILs with longer alkyl chains. However, the regeneration and reusing of the ion-exchange resins were not studied in their work. [PERSON] et al. [27] used ion-exchange resin to recover three benzothiazol ILs from coexisting glucose, but the adsorption mechanisms of ILs onto ion-exchange resins were still unclear.  
Accordingly, the aims of this study are to: (i) investigate the effect of operation parameters and water chemistry on ILs adsorption onto ion-exchange resin after oil-solid separation; (ii) understand the adsorption mechanisms of ILs onto ion-exchange resin; (iii) test the regeneration and recyclability of ion-exchange resin.