*3.4. Adsorption of Atenolol and Propranolol*

The adsorption of AT and PR was carried out in the presence of AC and AC-OH. A commercial activated carbon (AC) was also evaluated for removing AT and PR from contaminated water. To investigate the parameter effects on the adsorption of pharmaceutical products, temperature, initial concentration, and pH were studied in terms of adsorption capacity. The results are shown in detail in the Supplementary File. As seen in Figures S2–S4, the high temperature was not suitable for the adsorption of AT nor PR molecules due to their limited temperature stability. The adsorption capacity increased as the concentration of pollutants increased to achieve the equilibrium phase, indicating its saturation [14,26,35]. Measurements on the effect of pH displayed that the adsorption of pharmaceutical molecules could have been performant in basic media, while the acidic solution avoided competition with a proton. The removal capacities of the samples, which had the same experimental conditions, i.e., the synthetic and the commercial AC, are reported in Figure 5. The results show that both samples adsorbed the pharmaceutical products in two distinct phases. A rapid adsorption process describes the first phase, while equilibrium steps characterize the second phase. The large number of active sites available at the AC surface for the adsorption of AT and PR explains this result. Meanwhile, over 60 min, the main part of these active sites became saturated by adsorbate, resulting in limited access to more molecules in the solution. Therefore, the second step was reached to achieve the adsorption equilibrium [14].

**Figure 5.** Removal capacity of (**a**) AT and (**b**) PR over AC, AC-OH and commercial AC.

A comparison of the adsorption capacity of commercial and prepared AC shows that AC synthesized from date stems produced a higher adsorption uptake (60%) than commercial AC (32%). This trend can be explained by the key role of treatment and carbonization in this work. It was found that our prepared AC's equilibrium time is longer than the commercial AC's. Interestingly, the best performance is observed for the AC-OH sample, where the adsorption capacity is over 93% for the removal of PR in 120 min. The adsorption kinetic is also faster with AC-OH because the equilibrium was reached after 60 min, and only 10 min is required to adsorb 56% of the PR. This result can be explained by the negative charge surface of AC-OH, as supported by the Zeta potential measurement. For the atenolol molecule, the performance of AC and AC-OH is still higher than that of AC, but the adsorption was more difficult than for propranolol. Indeed, 67% of the AT was adsorbed on AC-OH compared to 36% and 23% for AC (from date stem) and commercial AC, respectively.

#### *3.5. Photocatalytic Degradation of Atenolol and Propranolol*

The effect of TiO2 concentration is considered the first parameter that can affect the removal efficiency of the catalyst. The photocatalytic activity of AC-TiO2 was measured for various concentrations of TiO2 (30%, 50%, and 70%); the results are shown in Figure S6. The results show that AT and PR's photocatalytic degradation depends on the TiO2 quantity. While the TiO2 concentration increased, photocatalytic degradation increased. The rise of photocatalyst radicals can explain this. The degradation continued until reaching an optimum close to 50%. Measurements on the AC-OH-supported TiO2 were investigated regarding adsorption capacity for both molecules AT and PR. Figure 6 depicts the results obtained for the photocatalytic efficiency of AC-OH/TiO2 and AC-TiO2.

**Figure 6.** Removal of PR (**a**) with and (**b**) without light using AC, TiO2, AC-OH, AC-OH-/TiO2, and AC-TiO2 catalysts.

According to the obtained results, it is clear that AC-OH/TiO2 can eliminate more than 45% of PR, while AC-TiO2 achieves 94% degradation. Photolysis and pure TiO2 are tested separately to understand the high degradation capacity. Only 10% PR removal is obtained for the materials, suggesting the potential role of the coating process for AC-OH and TiO2.

Experiments were carried out in the presence of and without light to demonstrate the beneficial effect of irradiation light combined with AC-OH-TiO2 and AC-TiO2. Figure 7 demonstrates that light is combined with AC-TiO2 to obtain high adsorption uptake. The removal of PR and AT by AC-OH-TiO2 and AC-TiO2 without light is mainly due to their adsorption on the active surface. Results showed that the photocatalytic degradation efficiency increased significantly for all AC-TiO2 composites compared to pure TiO2. When (PR and AT) are adsorbed on the AC surface, they react with reactive radicals by an oxidation reaction; this improves the catalyst activity. Hayati et al. [36] confirmed that AC is very important because it could act as an electron sink, which allows for the interfacial transfer of photo-induced electrons from TiO2 to AC and the inhibition of the electron recombination rate.

**Figure 7.** Removal of AT (**a**) with and (**b**) without light using AC, TiO2, AC-OH, AC-OH/TiO2, and AC-TiO2 catalysts.
