Template-free microspheres decorated with Cu-Fe-NLDH for catalytic removal of gentamicin in heterogeneous electro-Fenton process

Abstract

Nano-layered double hydroxide (NLDH) decorated with Fe and Cu was applied as a novel heterogeneous catalyst for catalytic degradation of gentamicin by the electro-Fenton (EF) process. The EF process was equipped with graphite plate under aeration to electrochemically generate hydrogen peroxide in the solution. The characterization analyses confirmed the suitable structure of as-synthesized Cu-Fe-NLDH to be acted as catalyst for treating the target pollutant. The comparative study showed the highest removal efficiency of 91.3% when the Cu-Fe-NLDH-equipped EF process was applied in comparison with the Fenton (50%) and the electro-oxidation alone (25.6%). The acidic pHs favored the degradation of gentamicin. Increasing the current resulted in the enhanced degradation of gentamicin, while the excessive electrolyte concentration (0.1 mol/L) and catalyst dosage (1.5 g/L) led to the tangible drop in the reactor performance. At a specified reaction time, the injection of O3 gas enhanced the efficiency of the Cu-Fe-NLDH-equipped EF process. The presence of ethanol led to more suppressing effect than benzoquinone, indicating the dominant role of OH radical in the degradation of gentamicin compared with other free radical species such as O2- radical. Only 10% drop in the degradation efficiency of gentamicin was observed within 10 operational runs. The mineralization efficiency of about 77% was achieved after 300 min in terms of chemical oxygen demand (COD) removal. The intermediate byproducts generated during the destructive removal of gentamicin were also identified.