Electrocatalytic generation of homogeneous and heterogeneous hydroxyl radicals for cold mineralization of anti-cancer drug Imatinib

Abstract

The effective removal of anti-cancer drug Imatinib (IMA) from water was explored by electrochemical advanced oxidation processes electro-Fenton (EF) and anodic oxidation (AO-H2O2) using different kinds of anode material: Pt, DSA (Ti/RuO2-IrO2), BDD and sub-stoichiometric titanium oxide (Ti4O7) and carbon felt cathode. IMA was then destroyed by hydroxyl radicals (OH) generated in the system. A series of comparison experiments including oxidative degradation kinetics of IMA, total organic carbon (TOC) removal and mineralization efficiency were conducted at ambient temperature. In both cases, DSA and Pt anodes were less effective for the anodic oxidation and mineralization of IMA compared to Ti4O7 and BDD anodes. Complete mineralization of 0.07 mM (34.5 mg L−1) IMA solution (corresponding to 24.11 mg L−1 initial TOC) was obtained both in EF and AO-H2O2 processes with BDD anode at 300 mA. The Ti4O7 anode was proved not advantageous to decay kinetics of IMA under high current densities (12.5 and 20.8 mA cm−2), while exhibited better mineralization performance than DSA and Pt anode, reaching 82% TOC removal efficiency in EF and 73% in AO-H2O2 processes at 8 h electrolysis with 12.5 mA cm−2. Besides, the formation and evolution of intermediate products including short-chain carboxylic acids and N-based inorganic ions (NH4+, NO3−) during mineralization of IMA solution were monitored by GC–MS, ion exclusion HPLC and ion chromatography, respectively. Finally, a plausible degradation pathway for degradation of IMA by OH was proposed according to the intermediates detected by HPLC and GC–MS.