Development and application of Fe₃O₄-Pd nanospheres as catalyst for electrochemical-heterogeneous Fenton process

Fe₃O₄ nanospheres with uniformly distributed Pd nanoparticles (Fe₃O₄-Pd) were prepared and used to catalyze the electrochemical-heterogeneous Fenton (EC-HF) degradation of pentachlorophenol (PCP). Synthesis of the catalyst was confirmed by X-ray diffraction and high-resolution transmission electron microscopy/energy-dispersive X-ray spectroscopy. The catalytic performance of the developed catalyst was assessed and the roles of Pd in the mechanism of Fe ion leaching and PCP degradation enhancement were elucidated. The conditions of 5V, pH 2.3, and 288K gave a removal efficiency of 100% within 30min with the catalyst, compared with 17.2% for the EC process alone. Pd nanoparticles altered the Fe leaching mechanism and enhanced both homogeneous and heterogeneous Fenton reactions when they were loaded on the Fe₃O₄ surface. The effects of operating conditions such as applied potential, pH, catalyst dose, solution temperature and initial PCP concentration were investigated. The results showed that a higher applied potential and solution temperature favored larger kinetic constants, whereas kinetic constants decreased with increasing solution pH. As the initial PCP concentration increased, the initial degradation rate increased while the kinetic constant decreased. The optimal catalyst dose was 50ppm. In addition, the Fe₃O₄-Pd reusability was evaluated.