## 3 Results and Discussion
### Co-Action of ILs and Alternative Sorbents for RB8 Separation
The removal efficiencies of RB8 dye increase in the following order: BT \(<\) BC \(<\) MTM \(<\) PAC \(\leq\) BT \(+\) BAC \(\leq\) BC \(+\) BAC. As we mentioned above (Section 3.1), BT and BC reached the lowest removal efficiencies due to the low specific surface area (see Table 1 above). The satisfactory removal of RB8 from aqueous solutions was achieved using commercial PAC with a high specific surface area. The highest separation capacity was provided by the co-action of alternative sorbents and BAC. It can be caused by the parallel effect of several separation mechanisms detailed in the section below. In addition, the equilibrium of RB8 sorption on BC or BT sorbents in co-action with BAC is established after 30 min. In comparison, the state of equilibrium of RB8 adsorption on other sorbents alone (PAC, MTM, BC and BT) is attained from 3 to 5 h. The co-action of BC or BT with BAC is not only efficient and consumes significantly lower amounts of reagents, but it is also very rapid. Moreover, it provides an improved technological implementation (agitation of reaction mixture, filtration after the separation process, etc.) compared to the action of sole ILs. Figure 8: A rate of sorption of RB8 (1 g L\({}^{-1}\) model aq. solution) on different types of sorbents (40 g L\({}^{-1}\)) and co-action of BC (2 g L\({}^{-1}\)) with BAC (1.5 g L\({}^{-1}\)) or BT (2 g L\({}^{-1}\)) with BAC (2 g L\({}^{-1}\)). Figure 7: Optimization of the co-action of BAC (50%) and BC or BT within the separation of RB8 (1 g L\({}^{-1}\) model aq. solution). Action of sorbents alone within 5 h or within 30 min in co-action with ILs, respectively. The time dependencies of the sorption capacity of RB8 are shown in Figure S8 in the Supplementary Materials. Clearly, the equilibrium sorption capacities (\(q_{e}\) in mg g\({}^{-1}\); derived from the experimental data) decrease in the following order: BC + BAC \(\geq\) BT + BAC \(\geq\) PAC \(>\) BC \(>\) MTM \(>\) BT. It corresponds well with the above-mentioned removal efficiency sequence. For example, virgin PAC provides the equilibrium sorption capacity of around 24.5 mg g\({}^{-1}\) for the RB8 dye. On the other hand, BC enables this parameter to be only approximately 17.8 mg g\({}^{-1}\). However, the \(q_{e}\) for the BC in co-action with BAC reaches a value over 495.8 mg g\({}^{-1}\). Analogically, the \(q_{e}\) for the BT in co-action with BAC achieved a comparable value (489.8 mg g\({}^{-1}\)), such as the BC + BAC system. It can be noted that MTM alone provided the equilibrium adsorption capacities of only ca. 12 mg g\({}^{-1}\). The great sorption capacities of alternative sorbents co-acted with BAC are caused by the high separation efficiency of RB8 dye using only 2 g L\({}^{-1}\) of BC or 1 g L\({}^{-1}\) of BT in co-action with BAC (1.5-2 g L\({}^{-1}\)). The high sorption capacities of the tested alternative sorbents in the co-action of BAC can be explained by the parallel effect of the proposed mechanisms (a-c):  
1. A sorption-based mechanism: The sorption of dyes on different types of biochar or bentonite is a well-known separation process [22; 57]. However, (ad)sorption is also a multistage process, and sorption models are not able to describe these complex mechanisms and distinguish between physical and chemical sorption [58]. 2. The rapid formation of less polar ion pairs: The formation of water-insoluble ion pairs was discussed in Section 3.2. Separation of RB8 using ILs above and was also proved in our previous studies [44; 45] using analytical techniques such as NMR. 3. (i) In the case of BC application, the better affinity of formed ion pairs to the BC surface: As [PERSON] et al. [59] suggested, the biochar-based sorbents show rather the non-polar nature of its surface. Therefore, the less soluble ion pairs can be well adsorbed on the described BC surface. We also suggested this mechanism in our earlier publications [32; 44]. Furthermore, BAC alone can be well adsorbed on BC.