Removal Of MB And RB5 From Dye Wastewater By Lanthanum Ferrite Based Composites

Strategies for efficient and rapid degradation of organic pollutants in dye wastewater are hot topics in in many disciplines related to environmental science.LaFeO₃,a typical perovskite oxide（ABO₃）,is of bright application prospect in the field of photo catalytic degradation of organic pollutants owing to its excellent photo,electrical,magnetic and thermal stability properties.Based on LaFeO₃,a series of LaFeO₃-based composite materials were synthesized by sol-gel,hydrothermal and pyrolytic methods.Medehyl blue（MB）and Rctive black 5（RB5）,the dye wastewater typical pollutant,were used to investigated the degradation efficient of composite materials on the basis of degradation factors,Chemical stability and catalytic degradation mechanism,the details are summarized as follows:（1）Porous spherical LaFeO₃oxide powder fabricated by sol-gel method were further loaded on straw biochar（BC）to make BC/LaFeO₃magnetic composite material（BC-FL）.SEM and BET analysis showed that surface area,total hole volume and average aperture of BC-FL could reach 34.670 m²·g^-1,0.041 cm³·g^-1and 7.820 nm,respectively.The magnetic hysteresis loop test showed that the magnetic saturation intensity reached 32.752 emu·g^-1,and FT-IR analysis confirmed that the surface mainly contained functional groups such as C=O,C=C=N.The batch adsorption experiments showed that the adsorption removal rate of MB by BC-FL was up to 92.3%,which conformed to the quasi-second-order kinetic model.The Langmuir model could be used to describe the isothermal adsorption process.Chemisorption predominated and electrostatic adsorption,hydrogen bonding andπ-πconjugation played a leading role.（2）UV/BC-FL/PDS system was constructed by combining BC-FL composites with perdisulfide（PDS）under UV irradiation to further enhance the degradation efficiency of MB.Results indicated that the removal rate of MB could reach 93.9%in 30 minute at BC-FL dosage 0.25 g·L^-1and persulfate concentration 0.50 mmol·L^-1.The quenching experiment showed that SO₄·^-、h⁺and ¹O₂were mainly generated in the process of UV/BC-FL/PDS degradation of MB,and¹O₂played a dominant role.The system could dramatically improve the degradation efficiency on the condition of the fewer amount of BC-FL composites.（3）CNTs/TiO₂-LaFeO₃（CTF）ternary heterojunction composite photocatalytic material was successfully synthesized and applied in the degradation for reactive black 5（RB5）under UV irradiation.UV-Vis and PL analysis showed that CTF heterojunction composites could effectively narrow the TiO₂band gap width and reduce the composite probability of photogenerated carriers,showing excellent photocatalytic degradation performance for RB5 degradation.The quenching experiments showed that the contribution rates of three radicals on the removal of RB5 were h⁺>·O₂^->·OH.The catalytic degradation mechanism analysis revealed that carbon nanotubes could provide a channel for the transport of photogenerated carriers,which induced LaFeO₃photogenerated electronic accumulate on the conduction band while the h⁺produced by TiO₂accumulate on the valence band.Therefore,the redox ability of photocatalytic material was further enhanced,thus enhancing the degradation ability of organic pollutants.