Catalytic Removal Of Pollutants In Water By Bismuth-based Nanomaterials

With the rapid development of urbanization and industrialization,environmental pollution has become an important problem restricting the development of human society.The treatment of inorganic pollutants represented by heavy metal ions such as hexavalent chromium(Cr(Ⅵ))and organic pollutants represented by tetracycline is very important to solve environmental problems.The catalytic technologies represented by photocatalysis and the emerging piezoelectric catalysis are expected to become effective means to treat polluted wastewater,and the development of high-performance catalysts plays a key role in improving the catalytic efficiency.Among many semiconductor catalytic materials,bismuth-based catalyst has become a research hotspot due to its excellent light absorption and stable physical and chemical properties.In this paper,photocatalytic removal of tetracycline by bismuth molybdate and piezoelectric catalytic reduction of hexvalent chromium by bismuth sulfide were developed and their catalytic mechanisms were discussed in detail.The main research contents are as follows:1.Bismuth sulfide nanorods with a large number of interstitial sulfur atoms were obtained by hydrothermal preparation of bismuth sulfide with different sulfur content by adjusting the amount of sulfur source.Due to the excessive interstitial sulfur atoms,the symmetry-breaking effect of the bismuth sulfide lattice was induced.The piezoelectric properties were tested by piezopower microscopy and Kelvin probe force microscopy.The Bi2S3 nanorods with lattice defects showed piezoelectric catalytic performance,and successfully reduced Cr(Ⅵ)to Cr(Ⅲ)efficiently.2.Through qualitative and quantitative tests on the active species produced by the catalytic process,it is concluded that the main reducing active species are H2O2 and·O2-.3.The application of alternating magnetic field to the reaction system improves the efficiency and number of free electrons and holes generated by piezoelectric action based on Lorentz force.Compared with no external magnetic field,the catalytic performance of piezoelectric is significantly improved.The mechanism of piezoelectric catalytic enhancement of bismuth sulfide induced by symmetric breaking under a magnetic field was investigated.The active species produced during the catalytic process with or without magnetic field were measured.It was found that the magnetic field enhanced the generation rate of H2O2,thus improving the reduction efficiency of Cr(Ⅵ)in the reaction system.4.Bi/Bi2MoO6 nanocomposites were prepared by solvothermal method.Bi/Bi2MoO6 nanocomposites showed obvious photodegradation ability to tetracycline.5.Through qualitative and quantitative tests on the active species generated by the catalytic process,it is concluded that ·O2-is the main reducing active species,and both photoelectrons and holes can promote photodegradation by forming ·O2-.The effect of nano Bi0 on tetracycline photodegradation was attributed to plasmon resonance effect.