## 3 Results and Discussion
### Co-Action of ILs and Alternative Sorbents for RB8 Separation  
Subsequently, our next research was focused on the application of BAC or A336 to enhance BC or BT sorption capacity. Several authors tested the impregnation of BC [33] or BT [27; 29; 36] using quaternary ammonium compounds such as cetyltrimethylammonium bromide/chloride. These conventional impregnation methods are usually based on the intensive stirring of the adsorbent with impregnation agents such as quaternary ammonium compounds. After the mentioned impregnation, the modified sorbents are applied for the separation of dyes [27; 29; 33; 36]. The authors [27; 33; 36] reported an improvement in the sorption capacity of these sorbents via impregnation prior to adsorption. Figure 5: Separation of RB8 (1 g L\({}^{-1}\) model aq. solution) using (**A**) 50% BAC and (**B**) A336 within 30 min of action. However, we have earlier [32; 44] discovered the simple and technologically undemanding method of the co-action of carbonaceous sorbents with ILs for the effective separation of halogenated organic acids from aqueous solutions. The RB8 separation cycle layout using the co-action of alternative sorbents with benzalkonium chloride is illustrated and presented in Scheme S1 and Figure S3 in the Supplementary Materials. The comparison and description of impregnation methods and the co-action of sorbents with ILs are also detailed in our previous works; see refs. [32; 44]. Based on these previous observations, we optimized the co-action of BC as well as BT using A336 or BAC. Figure 6 compares the sorption of RB8 on BT or BC, the separation of this dye using A336 alone and the co-action of A336 with BT or BC. The addition of A336 (3 g L\({}^{-1}\)) to 15 g L\({}^{-1}\) of BC or BT does not lead to an increase in the decolorization efficiency compared to the action of A336 alone (3 g L\({}^{-1}\)). Moreover, not even two times higher doses of A336 (6 g L\({}^{-1}\)) and the respective sorbent (30 g L\({}^{-1}\)) per the same amount of RB8 in an aqueous solution did not result in a significant increase in the dye removal efficiency; see Figure 6.  
However, the co-action of BAC with the examined alternative sorbents proved very satisfactory results; see Figure 7. For example, the co-action of 1.5 g L\({}^{-1}\) of BAC with 2 g L\({}^{-1}\) of BC provides 99% decolorization of the RB8 dye solution, an almost 95% COD decrease and 98% removal of AOXs (for AOX results, see Figure S7 in the Supplementary Materials). The action of 1.5 g L\({}^{-1}\) of BAC or 2 g L\({}^{-1}\) of BC alone does not reach these high removal efficiencies of RB8; see Figure 7. Even 50 g L\({}^{-1}\) of sole BC does not allow the described separation capacity compared with the co-action of BC (2 g L\({}^{-1}\)) and BAC (1.5 g L\({}^{-1}\)). For similar efficiencies of decolorization and COD decrease, BAC can also be co-acted with BT. The application of BT (1 g L\({}^{-1}\)) in co-action with BAC (2 g L\({}^{-1}\)) required only the slightly higher doses of this IL than the application of BC with BAC (1.5 g L\({}^{-1}\)); for a comparison of the co-action of BAC with BC or BT, see Figure 7.  
On the basis of the obtained results, the most promising method of RB8 dye removal is the direct co-action of BAC with the tested alternative sorbent (BC or BT) in verified optimized dosages. However, BT is an easily available material on many markets, and this alternative sorbent is also cheaper than BC [21; 56]. Figure 6: Optimization of the co-action of A336 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. Furthermore, Figure 8 presents the comparison of the sorption rates of the RB8 dye sorption on PAC, MTM, BC and BT alone or BC/BT in co-action with BAC. As can be seen, only the co-action of BC or BT with BAC and PAC alone provided an almost 100% removal efficiency of RB8 from the aqueous solution (1 g L\({}^{-1}\)).