## 5 Mitigation of Pharmaceutical Pollutants by Nanomaterials
### Classification of Nano-Sorbents  
#### 5.1.1 Carbon-Based Nanomaterial  
One of the most cost-effective techniques to remove pharmaceuticals from aqueous solutions is the use of carbonaceous materials as adsorbents [94]. Each carbon adsorbent has a unique structure and activity, and they all feature active surface functional groups, which is critical for the physicochemical characteristics of carbon materials and pharmaceutical adsorption [95]. CNTs and graphene have received the most attention of all carbonaceous adsorbents due to their unusual surface properties [94]. Pharmaceutical adsorption on carbonaceous materials is primarily determined by interactions, such as hydrogen bonding, stacking, hydrophobic effects, electrostatic interactions, and covalent interactions. As a result, adsorbent surface parameters, such as porosity, surface area, and functional groups, have a significant impact on adsorption effectiveness. For example, graphene oxide was used for tetracycline, sulfamethoxazole (SMX), and ciprofloxacin (CIP) adsorption [96; 97], and the results show that graphene oxide effectively absorbed CIP and SMX at lower pH, with maximum sorption capacities of 379 and 240 mg g\({}^{-1}\), respectively. CIP sorption was primarily controlled by electrostatic attractions, whereas SMX sorption was primarily controlled by \(\pi\)-\(\pi\) FDA attraction on the basal planes of graphene oxide. Graphene nanoparticles were for acetaminophen, reduced graphene oxide for ketoprofen, carbamazepine [94], single-walled carbon nanotubes were for carbamazepine and ketoprofen [94; 98], and multi-walled carbon nanotubes were for sulfamethoxazole, ketoprofen, thiamphenicol carbamazepine, diclofenac and ibuprofen [98]. The surface area of activated SWCNTs increased from 410.7 to 652.8 m\({}^{2}\) g\({}^{-1}\), while the surface area of MWCNTs increased from 157.3 to 422.6 m\({}^{2}\) g\({}^{-1}\). As a result, the activated SWCNTs and MWCNTs increased the adsorption capacity for the tested antibiotics (sulfamethoxazole, tetracycline) by 2-3 and 3-8 times, respectively. Adsorption occurred in the following order: SWCNTs \(>\) reduced graphene oxides \(>\) MWCNTs \(>\) graphene \(>\) graphite. This arrangement corresponds to the arrangement of their surface areas and micro-pore volumes [94]. Carbon nanotubes (CNT) absorb various organic chemicals more efficiently than activated carbon. Organic compounds with carboxylic, hydroxyl, and amide functional groups form hydrogen bonds with the graphitic CNT surface, which donates electrons. CNTs have high adsorption competence for metal ions and are thus a good alternative to activated carbon [85]. For instance, using hydrothermal reduction and the chemical crosslinking method, a novel cyclodextrin immobilized the three-dimensional macrostructure of reduced graphene oxide, and multi-walled carbon nanotubes (CD/rGO-MWCNTs) were synthesized and used as an effective adsorbent for naproxen removal in aquatic environments [99]. The maximum naproxen adsorption capacity (qm) value of \(\beta\)-CD/rGO-MWCNTs stood at 132.09 mg g [99]. Figure 4 shows the SEM images of the above-mentioned adsorption respectively. After hydrothermal reduction, the stacking and agglomeration of GO and MWCNTs in 1.0-rGO-MWCNTs were alleviated; however, among GO and MWCNTs with respective concentrations of 0.5 and 1.5 mg mL\({}^{-1}\), MWCNT clusters were severely overlapped on GO lamellae, and curls on the GO lamellae were slightly open (Figure 4c,d,h).