Preparation And Catalytic Degradation Of Berberine Hydrochloride Of CoFe₂O₄/BiFeO₃ Magnetic Nanocatalysts

There is a large amount of antibiotic residues in the water environment with an urgent need for economical,green and efficient treatment technologies.Photocatalytic oxidation technology is considered to be the most promising technology for degrading organic pollutants in water bodies because of its green and pollution-free characteristics and mild reaction conditions.However,its treatment efficiency is low because of low light-chemical energy conversion efficiency and easy carrier compounding,which limits its large-scale practical application,while the use of semiconductor compounding and magnetic field assisted method can significantly improve photocatalytic efficiency.Semiconductor compounding can improve the light absorption performance,inhibit carrier separation and promote free radical generation.The magnetic field-assisted method can use Lorentz force to disperse the catalyst,separate electrons and holes,and change the spin polarization to improve the catalytic performance.And CoFe₂O₄/BiFeO₃can form heterojunctions with good potential to produce magnetoelectric coupling effect in magnetic field.In this paper,CoFe₂O₄/BiFeO₃was used as the catalyst and Berberine hydrochloride（BH）was selected as the target pollutant,and the degradation of BH by photocatalytic and magneto-photocatalytic techniques were investigated respectively.The main research results are as follows:（1）CoFe₂O₄,BiFeO₃ and CoFe₂O₄/BiFeO₃composite catalysts were successfully prepared and characterized by hydrothermal method.XRD,XPS and EDS confirmed the successful preparation and compounding of CoFe₂O₄with BiFeO₃.SEM photographs observed that CoFe₂O₄was 20～40 nm diameter nanospheres and BiFeO₃was 20～30 nm diameter nanospheres,and the CoFe₂O₄and BiFeO₃in the composite catalysts were uniformly compounded together.UV-vis DRS and VSM tests showed that the composite catalysts have good light absorption performance and magnetic recovery performance.（2）The photocatalytic degradation performance of CoFe₂O₄,BiFeO₃and their composite catalysts was investigated with BH as the target pollutant,among which the composite catalyst（CFO-BFO-2）with the molar ratio of CoFe₂O₄/BiFeO₃of 1:2 had the best degradation effect.In the influence factor experiment with this composite catalyst,the photocatalytic degradation of BH was able to reach 86.76%with a degradation rate of0.01699 min^-1and TOC degradation rate of 25.39%at the catalyst dosage of 20 mg,pollutant concentration of 5 mg/L and p H of 3.It indicates that the CoFe₂O₄/BiFeO₃composite catalyst has good photocatalytic degradation performance.（3）Based on the study of photocatalysis,the degradation performance of CoFe₂O₄/BiFeO₃composite catalyst in magneto-photocatalysis was investigated to reveal the promotion effect of the addition of magnetic field on photocatalysis.The optimum working conditions of the magneto-photocatalytic reaction were determined by controlling the magnet speed,stirring speed and magnetic field strength.The highest efficiency of magneto-photocatalytic degradation of BH reached 96.49%,the degradation rate was 0.02665min^-1and the TOC removal rate reached 32.11%when the magnet speed was 700 rps,the stirring speed was 500 rps and the magnet was close to the edge of the beaker.It indicates that the addition of magnetic field can enhance the photocatalytic degradation effect.（4）The efficiencies of CoFe₂O₄/BiFeO₃,CoFe₂O₄and BiFeO₃under magneto-photocatalysis were 96.49%,55.45%and 62.20%,respectively.The degradation rates of the composite catalysts were 4.19 and 3.46 times higher than those of the single catalysts,respectively.The efficiencies of magneto-photocatalytic,photocatalytic,and magnetocatalytic degradation of berberine hydrochloride using CoFe₂O₄/BiFeO₃composite catalysts were 96.49%,84.44%,and 19.56%.The reaction rate of magneto-photocatalysis was1.74 times higher than that of photocatalysis.The enhancement of degradation performance was attributed to the synergistic magnetoelectric effect of CoFe₂O₄and BiFeO₃under magneto-photocatalysis.（5）Different quenching agents were used to capture the radicals in the photocatalytic and magneto-photocatalytic systems,respectively,and it was determined that·O₂^-and h⁺were the main active species controlling the reaction.Five cycles of degradation experiments were conducted for the two systems respectively,which showed that the CoFe₂O₄/BiFeO₃composite catalysts have good stability in the photo-and magneto-photocatalytic systems,and the degradation rates were above 90%for the five times,indicating that the CoFe₂O₄/BiFeO₃composite catalysts have good stability in the magneto-photocatalytic system and can be recycled.