## 3 Results and Discussion
### Effect of Operation Parameters on ILs Adsorption  
The resin dose is an important parameter to obtain the quantitative uptake of IL. Figure 4a shows the adsorption of [Bmim][BF\({}_{4}\)] and [Emim][BF\({}_{4}\)] as a function of the resin dose. It was indicated that the adsorption ratio of two ILs increased up to an optimum dosage (10 g), beyond which the removal efficiency (>90% for both ILs) did not significantly change. This is anticipated for a fixed initial IL concentration, because a higher amount of adsorbents provides more available exchangeable sites (or higher surface area) for the ions [31]. The maximum adsorption ratios were determined to be 95% and 90% for [Bmim][BF\({}_{4}\)] and [Emim][BF\({}_{4}\)], respectively, when the resin dosage was above 10 g. This resin dose was obtained as the optimal dosage for both ILs.  
Figure 3: Infrared spectrum of the residual sands with different water washing times after ionic liquid ([Bmim][BF\({}_{4}\)]-enhanced oil sands extraction.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**ILs**} & \multirow{2}{*}{**Washing Times**} & \multicolumn{6}{c}{**Residual Sands (w/w \%)**} \\ \cline{3-8}  & & **C** & **O** & **Si** & **Al** & **F** \\ \hline \multirow{3}{*}{[Bmim][BF\({}_{4}\)]} & 2 & 5.6 & 51.6 & 38.5 & 3.0 & 1.3 \\  & 3 & 7.4 & 46.2 & 43.1 & 3.3 & - \\  & 4 & 10.5 & 43.1 & 39.4 & 7.0 & - \\ \hline \multirow{3}{*}{[Emim][BF\({}_{4}\)]} & 2 & 6.5 & 47.3 & 38.9 & 6.0 & 1.3 \\  & 3 & 11.2 & 46.3 & 36.0 & 6.5 & - \\ \cline{1-1}  & 4 & 12.1 & 42.5 & 43.5 & 1.9 & - \\ \hline \hline \end{tabular}
\end{table}
Table 3: Elemental composition in the residual sands with different washing times after ionic liquids ([Bmim][BF\({}_{4}\)] and [Emim][BF\({}_{4}\)])-enhanced oil sands extraction.  
The effect of temperature on the adsorption of ILs onto resins is shown in Figure 4b. For both [Bmim][BF\({}_{4}\)] and [Emim][BF\({}_{4}\)], the adsorption ratio decreased slightly (<4%) as adsorption temperature increased from 20 \({}^{\circ}\)C to 60 \({}^{\circ}\)C. It suggested that the [Bmim][BF\({}_{4}\)] and [Emim][BF\({}_{4}\)] ions were well accessible onto Amberlite IR 120 Na adsorption sites at low temperature. A similar result has been obtained during the adsorption of benzothiazzolium ionic liquid ([HBth][CF\({}_{3}\)SO\({}_{3}\)]) onto strongly acidic ion-exchange resin (732/H resin) [27]. This is different from those of some metal ions (e.g., Cu\({}^{2+}\), Zn\({}^{2+}\), Ni\({}^{2+}\), Pb\({}^{2+}\), and Cd\({}^{2+}\)) onto the resins (Dowex 50W [32], Amberlite IR 120 Na [33]). The adsorption of these divalent metal ions was found to be an endothermic ion exchange process, which could be facilitated by increasing the temperature. However, herein, increasing the temperature played little role in the adsorption of ionic liquids by the resins, indicating the adsorption process of ionic liquids onto the resins would be an exothermic process [27].  
The influence of contact time on the adsorption of two ILs is depicted in Figure 4c. At initial stages, the uptake of ILs was rapid. This is because all the resin sites are vacant at the beginning, hence the extent of adsorption is high [34]. Subsequently, due to the decrease in the number of adsorption sites as well as ILs concentration, the adsorption rate of ions on the resins became slow. After 30 min, no remarkable adsorption was observed for the two ILs, indicating the adsorption equilibrium was reached in 30 min. More than 95% of [Bmim][BF\({}_{4}\)] and 90% of [Emim][BF\({}_{4}\)] were adsorbed onto the resins when the equilibrium was attained.