| The treatment of the nocuous organic pollution in water is vital for environmental protection. Comparing to the conventional physical and biological treatment methods, photocatalysis with widely applicability and sensitivity to organic compounds, attracts researchers’ attention. In this paper, the core of photocatalysis process is to prepare catalysts for degradation of recalcitrant organic pollutants. The material rational design, preparation, and performance test of spinel ZnFe2O4 composites were studied. The growth mechanism and structure control approach of the catalysts have been revealed with various microscopic techniques. In additon, the mineralization mechanism of organic pollutant and the relationship of composition -structure-catalytic properties have been explained. The major contents of this paper are described as follows:(1) Graphite oxides (GO) were generated by oxidation of graphite powder under acidic conditions according to the modified Hummers method. ZnFe2O4-reduced graphene oxide(rGO) hybrid was successfully synthesized through an in situ chemical deposition and reduction. The surface morphology and the structure of the ZnFe2O4-rGO hybrid was characterized by a series of microscopic techniques, the result showed that the ZnFe2O4 nanoparticles were anchored on rGO sheets to form a ZnFe2O4-rGO hybrid. The catalyst for photo-Fenton-like decolorization of various dyes uses peroxymonosulfate(PMS) as the oxidant under visible light irradiation, and the catalytic activities in oxidative decomposition of organic dyes were evaluated. The reaction kinetics, effect of ion species and concentration, the atability of catalytic, degradation mechanism, and the role of ZnFe2O4 and graphene were also studied. The fine magnetism of ZnFe2O4-rGO make it easy to seprarte from the water. Besides, the combination of ZnFe2O4 with graphene sheets provides much higher catalytic activity than pure ZnFe2O4, that is to say, graphene acts as not only a huge supporter, largely promoting the electron transfer in the hybrid material, but also a catalyst for activating PMS to produce sulfate radicals at the same time, improving the catalytic performance. In addition, the catalysis ability for degradation of dyes was improve by some sodium salte, the effect of varying dosages of Cl- ranged from 0 to 5 M, was examined, the ion could improve the removal performance and increase the reaction rate of the decolorizarion process from 150 min reduce to 35 min.(2) N-doped TiO2/ZnFe2O4 catalysts were successfully synthesized via a one-pot vapor-thermal method. The UV-Vis-light-driven photocatalytic activities of the hybrids were evaluated and the effects of the amount of catalyst, different types of dyes on photodegradation of organic dye were studied. The reaction kinetics and mechanism as well as the roles of N doping, ZnFe2O4 and TiO2 have been investigated. It was revealed that N-doped TiO2/ZnFe2O4 exhibited an improved performance compared with TiO2/ZnFe2O4 and ZnFe2O4. The reason for which is the formation of a heterostructure at the interface and the introduction of N species promote separation of the photoelectrons and holes, leading to the improved lifetime and transfer of photo-generated charge carriers. Active species involved in the photodegradation process were detected by different types of scavengers. Apart from the statements mentioned above, the presence of ZnFe2O4 in the hybrid helps the catalyst particle acquire ferr,magnetic properties, and thus it is easily separated from the catalytic solution. The newly synthesized catalyst retains its efficiency through five cycles of operation, and can be used as a recyclable photocatalyst for eliminating organic pollutants from waste water. |
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