## 3 Results and Discussion
### The pH Effect on Adsorption Kinetics of CPs on MPs
At pH 10, the highest adsorbed amount was obtained for 4-CP on powdered MPs (about 137 \(\upmu\)g/g for PEp, 89.4 \(\upmu\)g/g for PE_PCPs_1 and 87.5 \(\upmu\)g/g for PE_PCPs_2). The adsorption affinity toward powdered MPs decreased with increases in hydrophobicity and molecular sizes in the selected CPs at pH 10. The results shown in Figure 2 imply that the selected CPs had significantly lower affinities toward granulated types of MPs (6.04-202.4 \(\upmu\)g/g). Furthermore, pH effects were evident in the adsorption behavior of all CPs on MPs. In terms of pH effects, the highest impact on the adsorption behavior of CPs was detected for PP, which adsorbed the lowest amounts of all the CPs at pH 4 (6.04-23.3 \(\upmu\)g/g). The same trend was seen in the obtained results, but with much lower differences between the adsorbed amounts of CPs being detected for all selected MPs at both pH 4 and pH 10. The lowest matrix effect was observed for PLA at both pH 4 and pH 10 (17.3-45.5 \(\upmu\)g/g). In order to obtain more comprehensive information about the influence of pH on the adsorption kinetics of CPs on MPs, three kinetic models were used: the pseudo-first-order, the pseudo-second-order and Elovich models. The obtained modeling data are summarized in Table S5. Based on the obtained results and the highest correlation coefficient (R\({}^{2}\) = 0.862-0.998), the PSO kinetic model fit the data better than the PFO and E models. The R\({}^{2}\) values calculated for the PSO for the adsorption kinetics of 4-CP, 2,4-DCP and 2,4,6-TCP on the seven materials were greater than 0.900. Slightly lower R\({}^{2}\) values were obtained for PCP, but the values were still high, ranging from 0.862 to 0.983. Since all the correlation coefficient values for the PFO and E models within the CP experiment were higher than 0.800, the PSO kinetic model fit the data better. Figure 2 illustrates that the results for fitting the experimental data in the exponential form using the PSO model was the most appropriate. The calculated q\({}_{\text{e}}\), k\({}_{2}\) and R\({}^{2}\) values for the pseudo-second order model are listed in Table S5. Based on the q\({}_{\text{e}}\) values obtained with the PSO model and the experimentally obtained q\({}_{\text{e}}\) values, it can be concluded that this kinetic model gave the best fit for the obtained data. Therefore, the PSO model can successfully be used to describe the adsorption process of the selected CPs onto MPs regardless of the pH value of the water from the beginning of the sorption process to the equilibrium stage. This means that CPs can be adsorbed to different binding sites on the investigated MPs [24]. The sorption kinetics of organic pollutants on PE can be described using the PSO model, which is in agreement with the findings of other authors [38, 46, 47, 54]. The high values of the R\({}^{2}\) obtained for the PSO kinetic model by other studies for the adsorption of organic compounds on MPs, indicate a possible chemisorption mechanism during the adsorption process [12, 36, 48, 57]. The results presented in Figure 3 imply that the adsorption speed of CPs on the MPs was significantly faster at the beginning of the adsorption process and that this may be a consequence of the free active sites on the surface of MPs [46, 49, 58]. The obtained results of the kinetic experiments indicate that the PSO kinetic model is suitable for describing the adsorption kinetics of CPs on MPs, which is In line with the observations of other authors [59, 60, 61, 62, 63, 64].