Degradation of cytostatics methotrexate and cytarabine through physico-chemical and advanced oxidative processes: influence of pH and combined processes on the treatment efficiency.

Environmental release of wastewater that contains cytostatic drugs can cause genotoxic impact, since these drugs act directly on the genetic material of aquatic organisms. Thus, the aim of this study was to evaluate the removal of the cytostatic drugs cytarabine (CTR) and methotrexate (MTX) using different physicochemical methods individually (i.e., US, O 3 , H 2 O 2 and UV) and combined (i.e., O 3 /US, US/H 2 O 2 , O 3 /H 2 O 2 and O 3 /US/H 2 O 2 ) under different pH conditions (4, 7 and 10). In the degradation tests, the efficiency of the methods applied was found to be dependent on the pH of the solution, with the degradation of CTR being better at pH 4 and MTX at pH 7 and pH 10. The US, H 2 O 2 and US + H 2 O 2 methods were the least efficient in degrading CTR and MTX under the pH conditions tested. The highest MTX degradation rate after 16 min of treatment at pH 7 was achieved by the O 3  + H 2 O 2 method (97.05% - C/C 0  = 0.0295). For CTR, the highest degradation rate after 16 min of treatment was achieved by the O 3 process (99.70% - C/C 0 = 0.0030) at pH 4. In conclusion, most of the treatment methods tested for the degradation of CTR and MTX are effective. Notably, ozonolysis is an efficient process applied alone. Also, in combination with other methods (US + O 3 , O 3  + H 2 O 2 and O 3  + H 2 O 2  + US) it increases the degradation performance, showing a rapid removal rate of 70 to 94% in less than 4 min of treatment.