Preparation Of Magnetic Bismuth Composites And Their Visible Light Catalytic Degradation Performance For Organic Pollutant

The photocatalytic degradation is one of the most efficient and promising methods for the treatment of organic wastewater containing complex structure,degradation-resistant,and high toxicity.The preparation of photocatalytic materials with excellent catalytic degradation performance and low cost is the key to obtain good catalytic degradation effect and make it have application value.In this study,several new type of magnetic bismuth composite visible light catalytic materials were designed and synthesized,and its photocatalytic degradation performances for antibiotics and organic dyes were systematically studied,and the photocatalytic degradation mechanisms were preliminarily discussed.Two novel magnetic composite photocatalytic materials of Fe3O4@SiO2@Bi2O2CO3/rGO consisting of uniform core-shell-structured Fe3O4@SiO2@Bi2O2CO3 microspheres mounted on reduced graphene oxide（rGO）nanosheets and Fe3O4@SiO2@BiFeO3/rGO consisting of flower-like core-shell structured Fe3O4@SiO2@BiFeO3 microspheres mounting on rGO nanosheets were successfully fabricated via a facile hydrothermal method,and the photocatalytic degradation performance were evaluated by degrading ciprofloxacin（CIP）,tetracycline hydrochloride（TC–H）,methyl orange（MO）,rhodamine B（RhB）,methylene blue（MB）,and mixed solutions of MO,RhB,and MB under visible light.The mechanism of visible light catalytic degradation was discussed.The results show that the suitable amount of rGO could decreased the energy band gap,inhibit the recombination of photogenerated e^-/h⁺pairs,and broaden and enhance the response of the catalyst to visible light,thereby enhancing the performance of visible light catalytic degradation of organic pollutant.The specific surface areas（SBET）,magnetization saturation（Ms）,and band gap energy（Eg）of Fe3O4@SiO2@Bi2O2CO3/rGO（x=0.15 g）were 102.12 m~2/g,25.4 emu/g,and 3.05 e V,respectively.The degradation rates of CIP,TC–H,and MO were 96.1%,94.2%and 99.3%,and the mineralization rates were 57.5%,59.7%and 88.2%under visible light irradiation for 90min.It also showed excellent decolorization performance for MO,RhB and MB mixed solution.The active species produced in photocatalysis included·O₂^-,·OH,and h⁺,with·O₂^-being the dominant active species.The SBET,Ms,and Eg of Fe3O4@SiO2@BiFeO3/rGO（x=0.15 g）were139.26 m~2/g,20.3 emu/g,and 1.91 e V,respectively.The degradation rates of CIP,TC–H,and MB were 98.2%,95.6%and 99.6%,and the mineralization rates were 59.6%,61.1%,and 91.7%under visible light irradiation for 90 min.It also showed excellent decolorization performance for MO,RhB and MB mixed solution,and·OH is the dominant active species.The novel magnetic materials of Fe3O4@SiO2@BiFeO3–sepiolite that Fe3O4@SiO2microspheres as a core and the surface was composed of BiFeO3 and Sepiolite as functional layer was successfully fabricated via a facile hydrothermal method.The SBET,Ms,and Eg of Fe3O4@SiO2@BiFeO3–sepiolite（x=0.4 g）were 126.68 m~2/g,18.2 emu/g,and 2.09 e V,respectively.The unique structure,large surface area,and mesoporous channels because of adding the suitable amount of Sepiolite to the as-prepared photocatalyst resulted in the synergistic effect between Sepiolite and BiFeO3,which significantly improved the separation ability of e^-/h⁺and thus enhanced the photocatalytic performance,and the optimal additive amount is 0.4 g.The degradation rates of CIP,TC–H,and MB were 90.3%,100%,and 99.3%,and the mineralization rates were 53.6%,61.9%,and 92.3%after adsorption in a dark for 30min and visible light irradiation for 60 min.It also showed excellent decolorization performance for MO,RhB and MB mixed solution.The active species produced during photocatalysis include·OH,·O2^-,and h⁺;of these,·OH is the dominant active species.In conclusion,the above three kinds of magnetic composite photocatalytic materials not only have excellent photocatalytic degradation performance for the organic dyes of MO,RhB,and MB,and the antibiotics of CIP and TC–H,but also have good magnetic separation recovery performance,stability and recycling performance.In particular,Fe3O4@SiO2@BiFeO3–sepiolite prepared by sepiolite instead of rGO also reduces the preparation cost.Therefore,the prepared Fe3O4@SiO2@Bi2O2CO3/rGO,Fe3O4@SiO2@BiFeO3/rGO,and Fe3O4@SiO2@BiFeO3–sepiolite have broad application prospects in organic wastewater treatment.