*Article* **Insights into Mechanisms of Electrochemical Drug Degradation in Their Mixtures in the Split-Flow Reactor**

#### **Aleksandra Pieczy ´nska 1, Stalin Andres Ochoa-Chavez 2, Patrycja Wilczewska 1, Aleksandra Bielicka-Giełdo ´n 1 and Ewa M. Siedlecka 1,\***


 2019

**\*** Correspondence: ewa.siedlecka@ug.edu.pl; Tel.: +48-58-523-5228

Academic Editor: Jolanta Kumirska Received:21October2019;Accepted: 27November2019;Published:28November

**Abstract:** The recirculating split-flow batch reactor with a cell divided into anolyte and catholyte compartments for oxidation mixture of cytostatic drugs (CD) was tested. In this study, kinetics and mechanisms of electrochemical oxidization of two mixtures: 5-FU/CP and IF/CP were investigated. The order of the CD degradation rate in single drug solutions and in mixtures was found to be 5-FU < CP < IF. In the 5-FU/CP mixture, kapp of 5-FU increased, while kapp of CP decreased comparing to the single drug solutions. No effect on the degradation rate was found in the CP/IF mixture. The presence of a second drug in the 5-FU/CP mixture significantly altered mineralization and nitrogen removal efficiency, while these processes were inhibited in IF/CP. The experiments in the different electrolytes showed that •OH and sulphate active species can participate in the drug's degradation. The kapp of the drugs was accelerated by the presence of Cl− ions in the solution. Chlorine active species played the main role in the production of gaseous nitrogen products and increased the mineralisation. Good results were obtained for the degradation and mineralisation processes in mixtures of drugs in municipal wastewater-treated effluent, which is beneficial from the technological and practical point of view.

**Keywords:** ifosfamide; cyclophosphamide; 5-fluorouracil; cytostatic drug; BDD anode; electrochemical oxidation; intermediates
