Preparation And Catalytic Properties Of Cu?Fe?Co?₂O₄-based Nanomaterials

Due to an unique crystal structure,spinel Cu?Co,Fe?₂O₄ has excellent ferrimagnetic,thermal stability,catalytic properties,and low cost.However,as catalytic materials,metal nanoparticles are easy agglomeration due to their high surface energy,resulting in poor activity and stability and constricting its further application.By compounding with other materials,the interaction between metal nanoparticles and carriers is enhanced,and the dispersion on the carrier is promoted,which effectively prevents the agglomeration of the nanoparticles,leading to the improved catalytic performance.Activated carbons is a kind of carbon materials with high specific surface area,excellent thermal stability and easy to be prepared on a large scale.It is widely used as a catalyst carrier in the fields of catalytic hydrogenation,synthetic ammonia,and biomass conversion.This work uses Xinjiang's abundant coal resources as raw materials to prepare coal-based activated carbon?AC?which has high-performance and high-quality.Cu?Co,Fe?₂O₄-based catalytic materials are obtained by low-heat solid-phase method,co-precipitation method and co-precipitation combined with pyrolysis method using the activated carbon as a carbon source and template for the reduction of 4-nitrophenol?4-NP?,Methylene blue?MB?,Congo red?CR?.According to the material analysis and testing techniques,the composition,structure and morphologies of the composites are analyzed.The effects of material preparation conditions on the catalytic performance are explored,and the catalytic mechanism is studied.The experimental results indicate that Cu?Co,Fe?₂O₄-based catalytic materials exhibit excellent catalytic activity in the catalytic reduction reaction,and the as-synthesized catalyst with the best performance can catalytically degrade contaminants in 4 min.Its apparent reaction rate constant(k_app)reached 1.087 min^-1.These results are of great significance for the treatment of organic dye waste water and the enhancement of high value-added utilization of coal resources in Xinjiang.Specific research contents are follows:?1?Preparation and catalytic properties of Cu?Co,Fe?₂O₄-based materials by using low-heat solid state reaction:coal-based activated carbons as the carrier.Cu?Co,Fe?₂O₄ precursors were prepared by low-heat solid-state method and calcined to obtain Cu?Co,Fe?₂O₄-AC nanomaterials.CuFe₂O₄-AC,CuCo₂O₄-AC,and CuCo_xFe_2-xO₄-AC were used to the reduction of 4-nitrophenol?4-NP?,methylene blue?MB?,congo red?CR?,respectively.The effect of cobalt content in CuCo_xFe_2-xO₄-AC on catalytic performances of 4-NP was investigated.The results show the catalytic effect is the best?when x=1.It takes only 9 min for the catalytic reaction?.CuCo₂O₄-AC,CuCoFeO₄-AC,and CuFe₂O₄-AC achieved the expected catalytic effect in shorter time,respectively.The apparent rate constants(k_app)for the catalytic 4-NP reactions reached 0.769 min^-1?CuCo₂O₄-AC?,0.342 min^-1?CuCoFeO₄-AC?and 0.211 min^-1?CuFe₂O₄-AC?,respectively.At the same time,the three catalysts also exhibit the better catalytic performance on MB and CR.?2?Preparation andcatalytic performanceof Cu?Co,Fe?₂O₄/AC by co-precipitation method:coal-based activated carbons as a carrier,the Cu?Co,Fe?₂O₄/AC nanocomposites were prepared directly by co-precipitation without calcining.CuFe₂O₄/AC,CuCo₂O₄/AC,and CuCo_xFe_2-x-x O₄/AC were apllied for the reduction of 4-nitrophenol?4-NP?and congo red?CR?,respectively.The effects of AC addition on catalytic performance of 4-NP were discussed.When m?CuFe₂O₄?:m?AC?=1:1,m?CuCo₂O₄?:m?AC?=1:1,m?CuCoFeO₄?:m?AC?=1:1.5,the catalytic 4-NP effect is better than other ratios of AC addition.The catalysts exhibited excellent catalytic activity and moderate chemical stability owing to the high surface area and the porous structure of coal-based AC and the good dispersion of metal particles.After five cycles,the catalytic performance still remains well.?3?Preparation and catalytic performance of CuFe₂O₄/AC nanocomposites by co-precipitation and subsequent thermal treatment:coal-based activated carbons as a carrier,the composite precursors were prepared with the trisodium citrate?TSC?,after the calcination CuFe₂O₄/AC nanocomposites were obtained.The effects of the calcination temperature,calcination time,and AC addition content on the properties of catalysts were studied.Under the conditions of 500^oC,3.5h and Cu?Co,Fe?₂O₄:AC w/w ratios of 1:1.5,the obtained catalyst can completely convert 4-NP into 4-AP within 4 min.The apparent reaction rate constant(k_app)of the reaction reaches 0.950min^-1.In addition,CuFe₂O₄/AC nanocomposites were found to be very effective in reducing CR.The catalyst can be fast separated from the reaction system due to it magnetism.