# Effect of Washing Temperature on Adsorption of Cationic Dyes by Raw Lignocellulosic Biomass
## 3 Results and Discussion
### Results of Methylene Blue and Crystal Violet Adsorption on Raw Materials
#### 3.2.1 The Effect of Various Physico-Chemical Parameters
Additionally, a high initial concentration generates a large number of collisions between the dye ions and the adsorbent surface, improving the adsorption process [75]. Similar findings have also been reported by other researchers [76]. We also noted that the equilibrium time was more quickly reached for low concentrations, as concentrated dye solutions required more contact time to reach equilibrium due to the higher number of molecules to be adsorbed. Figure 11: Adsorption kinetics of MB and CV on raw materials (C\({}_{0}\) = 100 mg L\({}^{-1}\), natural pH, T = 23 \(\pm\) 2 \({}^{\circ}\)C, V = 250 rpm, r = 1 g L\({}^{-1}\)). Effect of Adsorbent Mass  
To study the influence of adsorbent mass, the solid/liquid ratio was varied, and the results are shown in Figure 14. The data indicated that the removal efficiency of MB by MPC and CC increased as the solid/liquid ratio increased. This is understandable, as increasing the biosorbent dose enhances the specific surface area and thus the number of adsorption sites [77,78], which consequently increases the amount of dye adsorbed. While the percentage of discoloration increases with a higher solid/liquid ratio, the amount adsorbed per unit mass (mg g\({}^{-1}\)) decreases. Many researchers have attempted to explain this phenomenon. [PERSON] and [PERSON] suggested that this decrease in Q\({}_{\rm e}\) is due to a split in the concentration gradient between the core of the solution and the surface of the adsorbent [79]. [PERSON] et al., on the other hand, attributed the decrease in the quantity adsorbed to the fact that an adsorbate particle at the same initial concentration (C\({}_{0}\)) is shared by more adsorbent particles when the solid/liquid ratio increases. Each solid particle has fewer chances of binding the pollutant, thus reducing the adsorption capacity [80]. Another possible explanation for this phenomenon was provided by [PERSON] and [PERSON], who suggested that with an increase in the solid/liquid ratio, there is a possibility of particle agglomeration. This agglomeration results in a reduction in the specific surface  
Figure 12: The effect of initial concentration on the elimination of MB and CV by MPC (natural pH, T = 23 \(\pm\) 2 \({}^{\circ}\)C, V = 250 rpm, r = 1 g L\({}^{-1}\)). Figure 13: The effect of initial concentration on the elimination of MB and CV by CC (natural pH, T = 23 \(\pm\) 2 \({}^{\circ}\)C, V = 250 rpm, r = 1 g L\({}^{-1}\)). area of the adsorbent and the lengthening of the diffusion paths, which negatively impact the adsorption process [81]. Textile industry waste contains numerous chemicals, including salts used in the stages preceding dyeing. The presence of these salts can significantly affect the adsorption of dyes during the treatment of such waste products. The curves in Figure 15 illustrate the impact of NaCl on the adsorption of MB by the raw materials. These curves show that for all raw materials, any increase in the quantity of dissolved salt led to a decrease in the quantity of dyes adsorbed. [PERSON] and [PERSON] interpreted this decrease as a shielding effect caused by the salt ions against the electrostatic attraction between the negative surface of the adsorbent and the dye cations [82]. [PERSON] et al. and [PERSON] et al. attributed this effect to competition between the dye cations and the salt cations [83; 84]. [PERSON] et al. added that the compression of the electrical double layer, caused by the increase in ionic strength, contributes to this phenomenon [85]. However, [PERSON] et al. suggested an expansion of the electrical double layer when the ionic strength increased to explain the decrease in MB adsorption [86]. Figure 14: Effect of MPC and CC mass on MB adsorption (C\({}_{0}\) = 100 mg L\({}^{-1}\), natural pH, T = 23 \(\pm\) 2 \({}^{\circ}\)C, V = 250 rpm). Figure 15: Effect of ionic strength on the adsorption of MB by raw materials (C\({}_{0}\) = 100 mg L\({}^{-1}\), natural pH, T = 23 \(\pm\) 2 \({}^{\circ}\)C, V = 250 rpm, r = 1 g L\({}^{-1}\)).