## 3 Results and Discussion
### Batch Desorption Studies
#### 3.6.2 Detailed Adsorption Studies
Figure 11: Weber–[PERSON] intra-particle diffusion plot to remove (**A**) 10 mg L\({}^{-1}\) ZDV and (**B**) 50 mg L\({}^{-1}\) phenol onto biochar/rGO/DES-glycerol. Figure 13 shows that the adsorbent after regeneration during the adsorption of phenol had no detectable functional groups attached to the material's surface. After the adsorption of phenol, only the -OH functional group was eliminated. The elimination of functional groups showed an interaction between the adsorbent's surface functional groups and the pollutants molecules. Functional group elimination methods included \(\pi\)-\(\pi\) interactions, hydroxyl and C-O group precipitations, and complexation with functional groups. These processes affect whether chemisorption or physisorption predominates. As a result, the strong chemical connections in chemisorption cause regenerated biochar/rGO/DES- glycerol to lose part of its active sites every cycle, which adversely affects the regeneration process [40]. Moreover, solution pH, biochar/rGO/DES- glycerol pHpzc, and contaminant pKa affect how functional groups function. Pollutants chemically interact with the active adsorbent sites to form complexes or precipitate on the adsorbent surface, which might not be reversible during desorption. As the adsorbent pores become clogged, the adsorbent progressively loses its active sites with each cycle. This might cause the biochar/rGO/DES- glycerol to decompose with the adsorption/desorption cycles, losing its properties and characteristics [45]. Figure 12: Regeneration/desorption chart for Biochar/rGO/DES-glycerol by (**A**) 10 mg L\({}^{-1}\) ZDV and (**B**) 100 mg L\({}^{-1}\) phenol. Figure 13: FTIR spectra of (**A**) biochar/rGO/DES-glycerol after adsorption of ZDV and (**B**) biochar/rGO/DES-glycerol after adsorption of phenol. Comparison Studies between the Developed Modified Biochar Nanocomposite and Other Biochar-Based Composite Adsorbent Materials  
Table 5 shows previous studies that used biochar nanocomposites and other biochar-derived composites to absorb phenols from wastewater. The data show that unmodified tea waste biochar had lower absorption capacities than modified tea waste-based biochar. This is because biochar has a lower surface area, limiting its adsorption capabilities and efficiency [10]. This biochar disadvantage led to biochar modification, which can be achieved by chemical, physical, magnetic, and mineral impregnation. Biochar modification aims to increase surface area and increase its adsorption capability. As seen in Table 5, modified biochar showed higher adsorption efficiencies than unmodified biochar. The current study uses timeless adsorbent synthesis, easy modification methods, and inexpensive chemicals. In this study, the adsorption capacity of synthesized novel modified tea waste biochar was comparable to the other reported studies listed below, with the highest adsorption capacity of 61.65 mg/g. The current study also reports on the rapid pollutant uptake and ease of separating the adsorbate and adsorbent. Table 5 reveals that most studies are based only on the quantification of ARVs in wastewater rather than remediation. South Africa has the largest ARV drug consumption in the world. ARV drugs easily find their way into the environment and main water streams. Several of these drugs and their derivatives have been quantified in tap and wastewater [53; 54; 55; 56; 57]. These findings are disturbing and strongly indicate that more reliable wastewater treatment methods are needed to remove these pharmaceutical wastes. Techniques such as photolysis [37], electro-Fenton [52], UV photolysis and advanced oxidation processes [58], and photo-catalytic degradation [36] have been used for the removal of ARV drugs from wastewater. However, adsorption is the easiest and simplest technique for the remediation of ARVs from water sources. Although some studies have reported the removal of ARVs from contaminated water, most are vague and very broad.