## 3 Results and Discussion
### The Adsorption Properties of the Mesoporous Materials
It can be assumed that the relative proportion of the individual intermolecular interactions involved in the adsorption mechanism of the two dyes differs significantly. By comparing the adsorption isotherms of crystal violet on carbon and polymer materials (Figure 14D,E), one can conclude that polymers are worse adsorbents for crystal violet, similar as it was in the case of methylene blue, but the difference in adsorption efficiency is not as significant. Crystal violet is an analogue of malachite green, which contains an additional second-order amino group on the phenyl ring in its structure, which leads to an enlargement of the molecule (Figure S1 in Supplementary Materials). In the group of carbons, a deeper differentiation of their adsorption capacities is observed as a result of the sieving effect, which excludes large adsorbate molecules from the small pores of the adsorbent C3. The adsorption capacity values of the carbons C3 and C4 for crystal violet are 0.33 and 0.44 mmol/g, respectively. In the group of polymers, P1 reveals a higher adsorption efficiency for the dye. The values \(\mathrm{a_{m}}\) and log K are for P1: 0.050 mmol/g and 2.41 and for P2: 0.038 mmol/g and 2.26. It is worth noting that the trend is reversed compared to systems with methylene blue. The main reason for this is the change in the relations between the adsorbate size and the pore diameters of the polymer P1. Moreover, the higher polarity of the polymer P1 (both monomers, i.e., 1-vinyl-2-pyrrolidone and trimethylpropane trimethacrylate are polar) determines its higher affinity for crystal violet compared to the polymer P2 with lower polarity (polar or non-polar monomer: 1-vinyl-2-pyrrolidone and divinylbenzene, respectively). Figure 15A,B compare the adsorption isotherms of three dyes on selected activated carbon and polymer materials. In general, different trends can be observed in the affinity of the two material groups for dyes. The efficiency adsorption of the carbon decreases in the following order: MB > MG > CV, and of the polymer: CV > MB. The observed decrease in the amount of adsorbed dyes on the carbon material is determined by the increase in the size of the subsequent adsorbates and their different spatial shape. The porous structure of the mixed type (micro- and mesopores) carbon C3 gives the highest efficiency in the removal of pollutants characterized by a small molecular size, such as methylene blue. The effect is enhanced by the linear structure of the adsorbate, which results in larger packing in the pore spaces. For adsorbates with larger molecule sizes and non-linear structures, such as malachite green and crystal violet, some pores are excluded from participating in the adsorption process due to the sieving effect. The greater adsorption of a larger molecule with a more extended spatial structure, i.e., crystal violet on the surface of the polymer material, seems to be due to the greater compatibility of the adsorbate with the pore size (Table 3 and Figure S1 in Supplementary Materials). Moreover, it should be added that the course of the isotherm CV (P1) in Figure 15B may indicate an incorrect selection of the concentration range for CV dye in combination with the used sorbent dosage. The same isotherm is compared in Figure 14E with a CV adsorption isotherm on polymer P2 (the range of the X-axis adjusted to the values of experimental data) where we can observe the equilibrium establishing. Figure 15: Comparison of the adsorption isotherms for various dyes on selected activated carbons (**A**) and polymer material (**B**). To describe the experimental adsorption isotherms the Generalized Langmuir (GL) equation was applied. Generally, the adsorption of dyes on carbon and polymeric materials may be described by special cases of GL, i.e., the General Freundlich (GF) and Langmuir (L) equations, respectively (Table 6). Low values of parameter m for adsorption systems with carbons (m\(\sim\)0.22-0.32) means a high heterogeneity effect.