Peroxydisulfate Activation By Fe₃O₄-GO Nanocomposites For Organic Pollutants Destruction

In recent years,surface water and groundwater pollution caused by industrialization has become a more and more serious problem and drawn great attention.Organic pollution is one of the dominant water pollution,which has a large amount of emissions,and a wide range of pollutants.In particular,some of the organic pollutants are refractory,persistent and toxic and can be enriched through the food chain,which pose serious threat to human health and development.How to effectively treat the organic polluted waste water and reduce the environmental load is an urgent issue that needs to be solved.Advanced oxidation processes?AOP?is a common treatment technology for organic wastewater due to its simplicity and high efficiency.The activation of peroxydisulfate?PDS?to generate reactive species such as sulfate radical?SO4·-,E0=2.5³.1V?is one of the emerging AOPs and has attracted much attention in recent years.Sulfate radical is highly reactive and can degrade nearly all organic pollutants through addition,substitution,electron transfer and bond breaking reactions,which leads to the degradation of macrolecular toxic pollutants to low toxic or non-toxic small molecules,or even directly to CO2 and H2 O.The performance of catalyst is the key to the efficiency of peroxydisulfate activation.The heterogeneous catalyst can overcome the drawbacks of the homogeneous catalyst such as inability to be recycled and so on.This paper reports the preparation of a magnetite-graphene oxide nanocomposites?Fe₃O₄-GO?,and its use as an efficient heterogeneous catalysts of PDS for the degradation of phenol and other aromatic compounds.Particular attention was paid to the mechanism of peroxydisulfate activation by Fe₃O₄-GO.The main contents are as follows:Fe₃O₄-GO nanocomposite was synthesized through a co-precipitating method.Scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,X-ray diffraction?XRD?,and Fourier transform infrared?FTIR?were used to characterize the Fe₃O₄-GO nanocomposites,and the results showed that the nano Fe₃O₄ particles were uniformly distributed on the surface of GO.In addition,the formation of Fe-O-C bond between Fe₃O₄ and GO can facilitate the electron transfer form GO to the reactive sites during the catalytic reaction.The reaction system of Fe₃O₄-GO/PDS can efficiently degrade phenol and other aromatic compounds in the pH range of 3.0⁹.0.The kinetic study showed that the phenol degradation process followed the pseudo first order kinetics.The quenching experiments and electron paramagnetic resonance?EPR?tests suggested that the Fe₃O₄-GO/PDS system degraded organic pollutants through a non-radical pathway.The results from both the influence of ionic strength and the in-situ Fourier transfer infrared?ATR-FTIR?tests showed that the interaction between Fe₃O₄-GO nanoparticles and PDS was inner-sphere.As ?Fe?II?was easily oxidized to higher valence,the strong interaction leads to the transfer of electron and the decomposition of PDS.Based on the above information,it can be inferred that ?Fe???was the main oxide in the Fe₃O₄-GO/PDS system.The influence of the anion?such as Cl-,HCO3-,H2PO4-and so on?and natural organic matter?HA?on the degradation of phenol in Fe₃O₄-GO/PDS system was also evaluated,which showed that Cl-and HA had little influence on phenol degradation.The Fe₃O₄-GO/PDS system was also compared with a traditional radical reaction system for the degradation selectivity of the aromatic compounds.The results from this study provide an alternative mechanism for PDS activation and should contribute to the development of PDS-based advanced oxidation technologies.