## 3 Endocrine-Disrupting Compounds EDCs
### Psychotropic Drug Degradation  
#### 3.6.1 Carbamazepine  
Carbamazepine (CBZ) is a first-generation anticonvulsant drug widely used in the clinical treatment of epilepsy, trigeminal neuralgia, and some psychiatric diseases. The  
Figure 5: Chemical structure and potential degradation pathways of the main atrazine by-products by ionizing radiation [74].  
negative effects of carbamazepine on aquatic microorganisms and human health have been observed [77,78]. Due to its stable chemical structure, CBZ is resistant to both conventional and advanced wastewater treatment processes, and thus is one of the most persistent pharmaceutical micropollutants in the aquatic environment [79].  
The use of an electron beam has brought satisfactory results in the decomposition of an aqueous solution of carbamazepine with an initial concentration of 50 mg dm\({}^{-3}\)[80]. The obtained results suggest that low pH promotes the degradation process as does the presence of HSO\({}_{3}\)\({}^{-}\) and SO\({}_{3}\)\({}^{2-}\) in solution. Naturally occurring CO\({}_{3}\)\({}^{2-}\), NO\({}_{2}\)\({}^{-}\), NO\({}_{3}\)\({}^{-}\), NH\({}_{4}\)\({}^{+}\), and Cl\({}^{-}\) in water negatively affected the degradation efficiency of carbamazepine.  
The use of an electron beam for acidic aerated carbamazepine solutions containing 2.5 mM of H\({}_{2}\)O\({}_{2}\) allowed for both 100% degradation and mineralization [81]. Compared to the UV/H\({}_{2}\)O\({}_{2}\) process, the use of an electron beam made it possible to obtain a greater degree of decomposition with less energy [82]. Anions naturally occurring in surface waters had a much greater impact on reducing the effectiveness of the UV/H\({}_{2}\)O\({}_{2}\) process than in the case of the electron beam. A high degree of mineralization, about 40%, was obtained by adding 50 mM hydrogen peroxide at an absorbed dose of 2.63 kGy [20]. Moreover, it was found that supporting electron beam irradiation with the addition of H\({}_{2}\)O\({}_{2}\) also allows it to permanently remove some mutagenic and carcinogenic decomposition products from the solution, such as acridine.  
As with diclofenac (DCF), studies have also been carried out on the degradation efficiency of carbamazepine at relatively low concentration levels of 10 mg dm\({}^{-3}\) in real samples such as surface water and hospital wastewater [83]. Compared to the results presented earlier for DCF and ibuprofen (IBU), carbamazepine did not achieve such high yields, with only 37% for hospital effluent after a 250 Gy dose. To improve the degradation efficiency and to increase the degree of mineralization, the addition of persulfate was used [84,85]. It was shown that for an initial carbamazepine concentration of 0.04 mM, irradiation in the presence of PMS (peroxymonosulfate) increased the degradation and mineralization, which increased to 45% after applying a dose of 300 Gy. Importantly, the molar ratio of PMS to carbamazepine was not significant [84]. Furthermore, Zhang et al. [85] found that the biodegradability of carbamazepine was enhanced by the combination of gamma irradiation and PS (persulfate) addition. As presented in Figure 6, hydroxyl radical OH provided a powerful impact on CBZ degradation.  
Figure 6: Proposed mechanism of gamma radiolysis of CBZ [85].