| Spinel ferrite nanomaterials have receive extensive attention due to their stability and magnetism separation.Especially,nickel ferrite as a superparamagnetic nanomaterial are widely used in gas sensing components,magnetic fluids,magnetic storage,magnetic resonance imaging,drug delivery,microwave devices and catalysts because of their controllable morphology,high crystallinity and large specific surface area.Ni0.3Fe2.7O4 with high saturation magnetization was synthesized and the effect of surfactant on the growth mechanism of Nio.3Fe2.7O4 nanoparticles was studied by in-situ microthermal technique.Composites based on nickel ferrite were conducted by a series of structural and compositional characterizations.Besides,the composites was applied in Fenton catalytic reaction and catalytic mechanism was reseached.The main contents are listed as follows:1.In situ calorimetric technology was firstly applied to research the influence of surfactants on the materials formation mechanism.In the present study,different kinds of surfactants were selected as additives during cluster-shaped Ni0.3Fe2.7O4 synthesis.The research results demonstrate that the surfactants decreased the particle size and modified the cationic distribution,compositions and magnetic properties of Ni0.3Fe2.7O4 samples.The microcalorimetric results demonstrate that the sample formation was endothermal and divided into five processes based on the heat-flow versus time curves.No significant effects of the surfactants on these processes were found.However,the surfactants addition affected the heat flow and the temperatures for peaks in these curves.The surfactant adsorption on the crystal facet and nuclei of the sample,and the interactions among surfactants and ions contained in the system may be mainly the reason for these effects.These results demonstrate different actions of surfactants and ligands on materials formation.2.The reductioL reaction from Fe3+ to Fe2+ in solid catalysts during heterogeneous Fenton processes restricted the catalytic activity.In order to accelerate this reduction process,heterojunctions composed of Nio.3Fe2.7O4 nanoparticles(OD)and two-dimension(2D)SnS2 nanosheets were successfully synthesized.The interactions between the S atoms in SnS2 and the cations(Fe3+,Fe2+ and Ni2+)in the solid Ni0.3Fe2.7O4 were demonstrated by experimental results.The heterojunctions formation accelerated the reduction from Fe3+ to Fe2+.The composite exhibited higher photo-Fenton activity than Ni0.3Fe2.7O4,SnS2 and the mixture of Ni0.3Fe2.7O4 and SnS2.The RhB degradation degrees are about 97%and 47%for the composite and the mixture within 60 min,28%and 89%for the Ni0.3Fe2.7O4 and the SnS2 within 180 min,respectively.The composite displayed good stability for the Fenton reaction.The degree of RhB degradation was higher than 90% in the pH range from 3.42 to 9.06 for 60 min.Simultaneously,the composite showed excellent photo-Fenton catalytic activity for different dyes as cationic dye MB and anionic dye MO.A possible photocatalytic mechanism was proposed.3.NiFe2O4/NiS composites were obtained by a hydrothermal method.It was found that with the contents of NiS increasing,the Fenton catalytic activity enhanced.In particular,the nanoflower-like NiS exhibited high Fenton catalytic activity,which was not previously discovered.However,when the pH?11.23,NiS is extremely unstable in the Fenton system.A mass of dissolved Ni2+caused secondary pollution of the environment.To improve the stability of NiS in Fenton system,the effect of pH value on the Fenton catalytic activity was studied.When the pH value was 12.21,the Fenton catalytic rate constant of the NiS was 0.088 L·mg-1·min-1 and the dissolved content of nickel ions was only 0.37 mg/L.It was also found that NiS exhibited good stability and reusability when the pH was 12.21.We have studied the Fenton catalytic mechanism of NiS at different pH conditions,which provides a new idea and experimental evidence for the application of sulfide in Fenton reaction. |
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