In-situ Synthesis Of Cu-Fe₃O₄@Peanut Shell-derived Carbon And Its Application In Heterogeneous Fenton Catalytic Degradation Of Rhodamine B

Dyes are of diversity,complexity,stability and nondegradability.They not only affect the growth of aquatic organisms,but also have carcinogenicity.It is extremely urgent for the treatment of dye waste water.Fenton oxidation is a widely used effective technology for treatment of dye wastewater.The problems of the traditional Fenton reaction was also put forward about the difficulties in recycle of catalyst,secondary pollution from iron sludge and strong acid（pH=3）conditions.One of the main research areas at present is the heterogeneous Fenton reaction.Among them,the Fe₃O₄-based heterogeneous Fenton reagent can widen the pH range of the reaction with the reduced secondary pollution and easy recycle for the catalyst.However,the Fe₃O₄-based Fenton catalytic reaction efficiency was low due to the surface reaction by which the organic pollutants were degraded.The agglomeration of the Fe₃O₄nanoparticles also decreased the catalytic effect..In this study,peanut shell-derived carbons derived from cheap raw materials and prepared by simple method were used as carriers,on which Cu-doped Fe₃O₄was loaded.It is expected to significantly improve the catalytic efficiency of active components by copper doping while to further improve the stability and catalytic activity of the catalyst by reducing the agglomeration of Cu-Fe₃O₄nanoparticles on the surface of peanut shell-derivedcarbon.Firstly in this study,three kinds of peanut shell-derived carbons（labeled PAC,PAC01,PAC02）were prepared by the carbonization and the water vapor activation.Using PACs as carriers,three kinds of Cu-Fe₃O₄@peanut shell-derived carbon catalysts（Cu-Fe₃O₄@PAC,Cu-Fe₃O₄@PAC01,Cu-Fe₃O₄@PAC02）were synthesized in situ by one-step solvothermal method.N₂adsorption and desorption,SEM,XRD,XPS,FT-IR and VSM were employed to characterize the PAC carriers and Cu-Fe₃O₄@peanut shell-derived carbon for the specific surface area,pore size,surface morphology,pore structure,crystal structure and surface properties.It was found that PAC01 prepared by water vapor activation at 800℃was dominated by micropores blocked with nano Cu-Fe₃O₄,resulting in a significant decrease in the specific surface area and a relatively high degree of dispersion of nanoparticles.PAC prepared by carbonation at 500℃and PAC02 prepared by water vapor activation at600℃were mainly mesoporous.Nano Cu-Fe₃O₄was dispersed on their surface.The loading of Cu-Fe₃O₄increases the specific surface area and mesoporous pore volume of the catalyst.Load of Cu-Fe₃O₄with saturation magnetic intensity higher above14.06 emu·g^-1favored the solid-liquid separation.The crystal structure of the three Cu-Fe₃O₄@peanut shell-derived carbon catalysts was elemental copper and Fe₃O₄.The surface was rich in Fe（Ⅱ）,Fe（Ⅲ）and Cu（0）sites.Absorption peaks of Fe-O bond and Cu-O bond appeared in the infrared spectra of the three kinds of Cu-Fe₃O₄@peanut shell-derived carbons.Combined with the degradation process kinetics,the effects of different Cu-Fe₃O₄@peanut shell-derived carbon catalysts,Cu-Fe₃O₄,Fe₃O₄on the degradation of rhodamine B dye were investigated by varying dosages of H₂O₂,temperatures,and pH values.The results showed that the three kinds of Cu-Fe₃O₄@peanut shell-derived carbon catalysts displayed strong catalytic oxidation ability in a wide range of pH=4.5-9.5 with a higher degradation rate of 90%.Under the condition of that the dosage of nano Cu-Fe₃O₄@PAC02 was 0.3g/L,the dosage of H₂O₂was 20mmol/L,the pH of the solution was 4.5,the reaction temperature was 40℃,and the reaction time was 2 hours,the degradation rate of rhodamine B reached 98.2%.,which was27.8%higher than that of Cu-Fe₃O₄without peanut shell-derived carbon as carrier and9 times of that of Fe₃O₄,showing good catalytic degradation performance.The first-order reaction rate constant was 0.0376min^-1.After five times of repeated recycling and use of catalysts,the degradation rate of rhodamine B can still reach more than 90.5%,showing good catalytic cycle performance.The degradation kinetics,XPS and FT-IR characterization analysis before and after the reaction,free radical scavenging experiment,and the catalytic cycle performance test were used to explore the reaction mechanism of the heterogeneous Fenton catalytic degradation of rhodamine by Cu-Fe₃O₄@peanut shell-derived carbons.The results revealed that the degradation of rhodamine B by Cu-Fe₃O₄@peanut shell-derived carbon catalyst conformed to the first-order kinetic equation.The radical species existed in the catalytic degradation reaction was hydroxyl radical.Cu（0）participated in the reaction and was oxidized to Cu（Ⅱ）.The presence of Cu（0）can inhibit the oxidation of Fe²⁺on the surface of the Cu-Fe₃O₄@Peanut shell-derived carbon catalyst so as to accelerate the cycle of Fe²⁺/Fe³⁺and generate more hydroxyl groups.