One-Step Preparation Of ZnFe₂O₄@C And Its Catalytic Properties For Binary Dyes

Dye wastewater in real life is mostly discharged in the form of mixture,which has the characteristics of difficult separation,overlapping spectrum,difficult detection and difficult degradation.Derivative spectroscopy is widely used in drug detection because of its simple operation,high sensitivity and low cost,while derivative spectroscopy is rarely used in dyes.Due to its unique magnetism and narrow band gap width（1.9 e V）,ZnFe₂O₄ plays an increasingly important role in the field of adsorption catalysis.Carbon,due to its low cost and reproducible properties,is often used as a carrier to combine with other materials.The recombination of ZnFe₂O₄ with carbon can slow down the photoelectron and hole recombination rate and improve the photocatalytic degradation efficiency of ZnFe₂O₄.In this paper,a simple one-step method was used to prepare ZnFe₂O₄@C magnetic composite material from eucalypt powder as raw material and carbon source,and it was used for photofenton degradation of rhodamine B（RB）and reactive brilliant red X-3B（RBR）binary component dyes,and its catalytic performance and catalytic mechanism were investigated.The detection of binary components was conducted by first-order derivative spectroscopy.The feasibility of derivative spectrum detection of RB and RBR binary component dyes was analyzed,and the prepared materials were characterized and analyzed.The specific research contents and results are as follows:（1）In order to solve the problem of zero order visible spectrum overlap between RB and RBR,the first order derivative spectrometry was used to simultaneously detect RB and RBR contents in water samples and the method conditions were analyzed.RB and RBR showed a linear relationship with the first derivative spectrum in the concentration range of 0.3～14 mg/L and 0.3～14mg/L respectively.The detection limits were 0.19 mg/L and 0.06 mg/L,respectively.There was no interference in RB and RBR detection under the condition of p H 2.99～9.00 and concentration of common ions(K⁺,Ca²⁺,Na⁺,Mg²⁺,Cl^-,NO₃^-,NO₂^-)≤2 mg/L.In the simultaneous determination of RB and RBR in the actual water samples,the recovery rates of RB and RBR are96.6～102.6%and 97.3～100.5%,respectively,and the relative standard deviation（RSD）is 0.76～4.4%and 0.97～3.0%,which all meet the requirements for the analysis of each component in the binary system of RB and RBR.The precision and accuracy of the first derivative spectrometry in detecting RB and RBR binary components at the same time meet the requirements of analysis.The operation is simple and convenient,the cost is low,and it can be popularized and applied.（2）Using eucalyptus powder as raw material,FeCl₃·9H₂O and ZnCl as activators and reaction reagents,C,ZnFe₂O₄,Zn O@C,Fe₃O₄@C and ZnFe₂O₄@C were prepared by one-step method,and the preparation conditions of ZnFe₂O₄@C were optimized.The results show that the best preparation conditions of ZnFe₂O₄@C are:Fe-Zn ratio 2,Fe-Chip ratio 1.8,calcination temperature 600℃,calcination time 120 min.XRD,FT-IR,SEM-EDS,VSM,XPS and specific surface area and porosity analyzer were used for characterization.The study showed that ZnFe₂O₄ was successfully loaded on the surface of carbon,with spherical shape and uniform element distribution.The contents of C,O,Fe and Zn were 77.27%,18.78%,3.78%and 0.56%,respectively.The specific surface area of ZnFe₂O₄@c is 324.704 m2/g,and the average aperture is 12.61 nm.The high saturation magnetization of ZnFe₂O₄@C is 36.6 emu/g,and the coerce force is 25.153 Oe,which is superparamagnetic.（3）The prepared materials were used as catalysts and RB and RBR were used as target degradants.The results showed that the rate and efficiency of photo-Fenton degradation of RB and RBR mixed dyes were much higher than that of ZnFe₂O₄,Zn O@C,Fe₃O₄@C and C,which proved that the combination of ZnFe₂O₄ and C had synergic effect.In addition,in the p H range of 3～9,the removal rate of ZnFe₂O₄@C to these two mixed dyes within 60 min of reaction time was higher than 90.00%,indicating that the catalytic system has a strong p H stability,greatly expanding the application range of the photofenton catalyst.At the same time,the influence of the amount of H₂O₂ and the amount of catalyst on the degradation effect of Photofenton was investigated.The experimental results showed that under the irradiation of visible light,p H=4.62（original p H）and the initial concentration of the mixed dye was 100 mg/L,the optimal amount of hydrogen peroxide was 3 mmol/L and the optimal amount of catalyst was 0.7 g/L,under these conditions,the degradation rate of RBR and RB was over 99.00%.In the experiment of free radical capture,it was found that photogenic holes and hydroxyl radicals were the main active substances of ZnFe₂O₄@C photo-Fenton.The results of recycling experiments show that ZnFe₂O₄@C has better stability.