Heterogeneous catalysts for electro-Fenton degradation of cytostatic drug cytarabine.

In the present work, a reduced graphene oxide (rGO) modified-Fe₃O₄ doped bifunctional carbon felt cathode (rGO-Fe₃O₄/CF) that is capable of generating and converting H₂O₂ into hydroxyl radicals (^•OH) on-site was fabricated, thus removing the need for an external catalyst. In addition, an rGO-modified cathode (rGO/CF) with high H₂O₂ production efficiency and a heterogeneous Fenton catalyst (CNT-Fe₃O₄) with magnetic properties were fabricated. The study examined the degradation and mineralization of the cytostatic drug cytarabine (CYT) using two HEF configurations: (i) a bifunctional cathode rGO-Fe₃O₄/CF and (ii) a combination of the rGO/CF cathode with CNT-Fe₃O₄ catalyst. The effects of parameters such as catalyst concentration, initial pH, and applied current were studied. HPLC and ion chromatography analyses were used to identify carboxylic acids and inorganic end-products, respectively. The results show that 0.1 mM CYT was completely degraded within 18 min at an applied current of 300 mA in the HEF system with the rGO-Fe₃O₄/CF bifunctional cathode. Total organic carbon (TOC) analysis revealed that the bifunctional cathode system achieved 98.2% mineralization of CYT after 4 h of treatment at 300 mA. Using the rGO/CF cathode and CNT-Fe₃O₄ catalyst cell, total degradation of 0.1 mM CYT occurred within 7 min, and nearly total mineralization (97.3% TOC removal) was achieved at 300 mA after 4 h.