## 4 Application of Cyclodextrin-Based Adsorbents
### Removal of Organic Compounds
#### 4.3.1 Endocrine Disruptors
It was also possible to remove metals simultaneously with this material as it has been suggested that the carboxyl groups should react by chelating metal ions. In the one-component system, the qmax parameter of Zr/CM-\(\beta\)-CD towards estradiol was 210.53 mg/g. The adsorption capacity of the Zr/CM-\(\beta\)-CD remained high after five cycles. Interestingly, the material was very economical at concurrent removal of EDCs and metals [98]. The mechanism of EDC adsorption by CD-based adsorbents is different than that for the removal of heavy metals and dyes described in this paper. The CD cavity does not have the role of enriching the uptake of contaminants but also plays a role as the location of in situ catalytic degradation [136]. On the other hand, selective matching between guest and host can be a limiting step in the adsorption process [137]. 3.2 Pharmaceutical contaminants have been found in water bodies and pollute the entire ecosystem. For example, carbamazepine, a dibenzoazepine derivative, is used as a psychotropic, anticonvulsant, and mood-stabilizing drug, mainly to treat epilepsy and bipolar disorder. The drug is widely detected in European and North American water [138]. Its presence has also been demonstrated in green algae, crustaceans, stinging beetles, and hydroids [139]. This toxic compound is tough to degrade [140]. For this reason, studies have been conducted that showed that the maximum adsorption capacity (qmax) of carbamazepine by cyclodextrin material is 136.4 mg/g [141]. The above-described case of finding pharmaceuticals in water is not an isolated one. Another example is non-steroidal anti-inflammatory drugs (NSAIDs), which include ibuprofen, ketoprofen, and diclofenac. In one of the articles, the authors used CDs combined with nano-filters to eliminate these pollutants from the aquatic environment. The tested nano-filters were of different thicknesses and chemical compositions. In the study, the maximum adsorption capacity was estimated using ibuprofen as a model by measuring the removal of pharmaceutical residues from municipal wastewater. After use, nano-filters can be regenerated using ethanol, and the qmax of chemicals can be improved [142]. A notable example of attempts to remove NSAIDs from water is the use of CD polymer as the third step in treating biomechanical municipal wastewater in a wastewater treatment plant. [PERSON] and colleagues found a very high level of contamination removal in a relatively short time [143]. In another study, the hydrothermal method was used to obtain a composite of reduced graphene oxide immobilized with \(\beta\)-cyclodextrintrin (\(\beta\)-CD/rGO) in one step to eliminate naproxen from water. The material with a high porosity structure with numerous hydroxyl groups showed the stable removal of NSAID and an excellent adsorption capacity of 361.85 mg/g at 313 K temperature [144]. In another research, innovative Fe3O4/CD/AC/SA polymer gel beads, consisting of functionalized iron oxide activated carbon particles, sodium alginate polymer, and \(\beta\)-cyclodextrintrin, were obtained by a straight, repeatable, and cheap method. The maximum adsorption capacity of this material was 3.125 mg/g for ciprofloxacin, the most potent drug among the fluoroquinolones, with a bactericidal effect, showing its activity by inhibiting bacterial DNA topoisomerase and DNA gyrase [124]. Moreover, Fe3O4/CD/AC/SA can be regenerated and smoothly separated from solutions without losing removal efficiency. After regeneration, they have the same adsorption capacity for up to four desorption and adsorption cycles [145]. The problem of the presence of drugs in sewage can be reduced by absorbing the substances with derivatives of cyclodextrin polymers. The CD polymer/pulsed light sequential method was tested for contaminant removal to overcome this problem, and the simulations showed that the cyclodextrin 3D network gives the CD polymer amphiphilic features, which help to reduce the concentration of impurities by 77%.