Enhancing hydrogen peroxide activation of Cu[sbnd]Co layered double hydroxide by compositing with biochar: Performance and mechanism

Abstract

In this study, Cu[sbnd]Co layered double hydroxide/biochar composite (Cu[sbnd]Co LDH/BC) was prepared and employed for activating H2O2 to degrade ciprofloxacin (CIP), a common fluroquinolone antibiotic detected in water environment. The as-synthesized catalysts were also comprehensively characterized to study the physiochemical properties. For the catalytic activity, the degradation rate of Cu[sbnd]Co LDH/BC to CIP was approximately 1.5 times higher than that of Cu[sbnd]Co LDH. The improved catalytic activity can be ascribed to the synergistic effect between Cu[sbnd]Co LDH and BC, such as more functional groups, accelerated electron transfer, and varied charge distribution. Meanwhile, Cu[sbnd]Co LDH/BC/H2O2 could degrade CIP efficiently in a wider pH range comparing with Cu[sbnd]Co LDH/H2O2, and the efficiency was approximately 84.7% at neutral pH within 90 min. The generation of [rad]OH, O2[rad]− and 1O2 in Cu[sbnd]Co LDH/BC/H2O2 system were then verified by electron spin resonance (ESR) technology. The quenching experiments indicated that both non-radical pathway (1O2) and radical pathway ([rad]OH, O2[rad]−) led to CIP degradation, in which O2[rad]− and 1O2 made major contribution. Then, the intermediate products of CIP during catalytic reaction were monitored by high-performance liquid chromatography-mass spectrometry (HPLC-MS), and the environmental risk of these degradation intermediates was tested through seed germination experiments. This study tends to provide valuable information for LDH/BC application in heterogeneous Fenton-like reaction.