*2.2. Materials Synthesis*

According to our previously published work, activated carbon was obtained from agro-waste, specifically from date stems [32,33]. The date stems were washed with distilled water, dried at 105 ◦C for 24 h, and cut at around 0.2 cm. For activation, 48 g of date stems were stirred with 96 g of ZnCl2 (m(ZnCl2)=2 × m(AC)) for 4 h and carbonized at 600 ◦C for 2 h under dried air. Afterward, the obtained product was washed with HCl 37% and dried at 80 ◦C overnight. The product obtained wais dentified as AC. To increase the number of the hydroxyl group (-OH) at the surface of activated carbon (AC), AC was impregnated into a solution of hydrogen peroxide, nitric acid, and deionized water (1:1:5 *v*/*v*/*v*, respectively) at 70 ◦C for 4 h. The obtained powder was filtrated, washed with deionized water, and dried at 80 ◦C overnight. The resulting material is denoted as AC-OH a refers to OH-enriched activated carbon. In parallel, activated carbon was coated with a TiO2 solution via an in situ impregnation method, according to a method described elsewhere [34]. Briefly, 0.1 g of AC is added to different quantities of TTIP (30, 50, and 70%) and dissolved in 20 mL of isopropanol. The mixture was stirred for 1 h, washed with isopropanol, and dried at 70 ◦C for 6 h. The final obtained powder is identified as activated carbon over titanium dioxide (AC-TiO2).
