Synthesis And Doping Of NiFe₂O₄ And Their Properties Of Photocatalytic Decomposition For Methylene Blue

Textile industrialization expands quickly,which exacerbates environmental pollution because of a large number of printing and dyeing wastewater discharge. Dyeing wastewater is difficult to dispose due to their complex composition, high water solubility and poor biodegradability. Photocatalytic oxidation treatment is a novel and efficient method to deal with dyeing wastewater. Spinel ferrites have been paid many attentions for their good photocatalytic activity and can be recycled by magnetic. It is necessary to prepare the ferrite with high photocatalytic activity under visible light in practical application. In this work,NiFe2O4 and NiFe2O4/NiO were prepared with sol-gel method and in-situ solid-state method,respectively. The NiFe2O4 was modified by doping N and Nd3+. The structure, morphologies,magnetic and photocatalytic activity of ferrites were studied, and the repeatability and recovery rate were tested. In addition, the influence of visible light and ultra violet(UV) on the photocatalytic activity of NiFe2O4 was compared.NiFe2O4 was synthesized with sol-gel method. The effects of additive amount of different dispersants, ceresin, CTAB and ceresin with CTAB (ceresin + CTAB), and the effect of calcinating temperature on ferrites' structure, morphologies, magnetic property and photocatalytic activity of degradation of MB under visible light were studied. Results show that the ceresin and CTAB can improve the saturation magnetization and photocatalytic activity of NiFe2O4 under visible light. The NiFe2O4 obtained with ceresin + CTAB at 600?for 5 h show the best photocatalytic activity and magnetic recycling performance. The Ms of the NiFe2O4 is 44.7 emu/g and the pure degradation rate of the low concentration of MB solution (remove adsorption and self decomposition) can reach more than 89% under visible light.The NiFe2O4 doping with Nd3+ and N from Nd(NO3)3·6H2O and C2H,1N3O5 was prepared in optimal conditions, respectively. Results show that the crystallinity and photocatalytic activity of Ni1-xNdxFe2O4 (x=0.05,0.10,0.15,0.20,0,25,0.30) are lower than undoped Nd3+ NiFe2O4 under visible light. Among the ferrites doped N synthesized at different temperature, the photocatalytic activity of NiFe2O4 which was doped N at 700 ?show a higher photocatalytic activity under visible light and the pure degradation rate of MB solution that concentration range from 5 to 70 mg/L are more than 80%. In addition,the NiFe2O4 can be used twice and the recovery rate are more than 90%.NiFe2O4 was synthesized by an in-situ solid-state method using the flake NiO prepared by coprecipitation as raw material and the preparation mechanism of NiFe2O4 was studied.The effects of synthesis temperature and additive amount of NiO on ferrites' structure and properties were studied. Results show that the sample with the best photocatalytic activity under visible light is prepared at 700? and additive amount of NiO excess 5% more than theoretical value(reactant mole ratio is Ni2+ : Fe3 =1: 2). The NiFe2O4/NiO prepared under this condition has a higher photocatalytic activity under visible light, and the pure degradation rate of MB solution that concentration range from 5 to 50 mg/L are more than 90% and the NiFe2O4/NiO can be used 4 times by magnetic recycling. Comparing with the properties of NiFe2O4/NiO with NiFe2O4 prepared by Ni2O3 (purchased by the commercially) in optimal conditions, results show that the crystallinity and Ms of the sample prepared by homemade NiO are better. The former's pure degradation rate of MB solution is 85.9%; more than 26.4%of the latter's 59.5% in the experiments of degrade of MB solution that concentration is 30 mg/L.