The Photocatalytic Hydrogen Evolution Performance Research On Magnetic Nano-Material

Based on the previous study of our group, three kinds of spinel ferrite were successfully synthesized through a sol-gel method: Cu Fe2O4、Ni Fe2O4 and Zn Fe2O4; Cu Fe2O4 showed the best photocatalytic performance and was loaded on the layered double hydroxide to prepare the Cu Fe2O4/Zn2Cr-LDH via a microwave-hydrothemal method; electroplating wastewater and pickle waste liquor were used as the raw materials to synthesize ferrite and magnetic composite(CFL) through a two-step microwave hydrothermal method and realized the purification of metal ions in these wastewater. The photocatalytic hydrogen evolution properties ofthese materials were tested under the irradiation of simulated visible-light. The different effects on the hydrogen evolution performance and the optimal synthetic conditions of CFL were also investigated.(1) The Cu Fe2O4 synthesized by sol-gel method showed several advantages, such as small size, good dispersion, visible and smooth edge, strong magnetism, with the grain size of 20 nm and the saturation magnetization of 18.16 emu/g. The hydrogen evolution experiments showed that: Cu Fe2O4 had the best visible-light response and the stability, with the total hydrogen amount of 791.9 μmol·g-1 in 6 hours. The best catalyst concentration was 0.8 g/L and the best sacrificial agent was ethanol with the addition of 10% solution volume.(2) Cu Fe2O4/Zn2Cr-LDH was synthesized via the combination of sol-gel and microwave hydrothermal method with the saturation magnetization of 8.47 emu/g. The total hydrogen amount was 1567.7 μmol·g-1 in 6 hours which was almost twice amount of pure Cu Fe2O4 or Zn2Cr-LDH. The electron migration from ferrite to LDH part occurred inside of the composite which contributed to the separation of hole-electron pairs increasing the photocatalytic performance.The single-factor experiments showed the optimal hydrogen evolution conditions of magnetic composite material: preparation p H of 7, Cu Fe2O4 loading amount of 0.20 g, Cu Fe2O4/Zn2Cr-LDHconcentration of 1.0 g/L, using ethanol as the sacrificial agentat 10% in volume. The magnetic composite can be readily recycled and reused for three times, after that it still kept stable structure and photocatalytic performance.(3) Through the preparation of ferrite via microwave hydrothermal method, the heavy-metal wastewater could be effectively purified. The alkaline environment contributed to the formation of ferrite crystal structure. Experiments showed that that 90% of heavy metal ions could be effectively removed by synthesizing CFL with the p H of 7~10, time of 15~40 min, temperature of 100~180 oC.CFL showed better photocatalytic performance than Cu Fe2O4 withthe total hydrogen amount of 343.9 μmol·g-1 in 4 hours. Influenced by the complex constituents in heavymetal wastewater, photocatalytic performance of CFL was inferior comparing with thematerial synthesized by reagents. After the continuous illumination, CFL kept the intact structure with the low metal ions release indicating the stability as photocatalyst. The single-factor experiments were conducted to study the influence of different synthesis conditions on the photocatalytic performance. The response surface methodology(RSM) based on Box-Behnken design was successfully applied to optimize the preparation conditions.