The Study On Removal Of Organic Pollutants In Water By Modified Semiconductor Materials MoSe₂ And TiO₂

Scholars at home and abroad pay more attention to transition metal dichalcogenides（TMDs） in the treatment of domestic and industrial wastewater,MoSe₂ and TiO₂ is highly representative of metal dichalcogenides. There are some difficulties in the preparation of MoSe₂ due to the molecular binding force of MoSe₂ is weak. This study cleverly prepared MoSe₂ by solid phase method without impurity phase. In addition, TiO₂ and MoSe₂ was modified with hydrothermal method, which improves the performance of the two kinds of materials to remove the organic pollutants in water.These two substances were analyzed and characterized by means of X ray diffraction（XRD）, Scanning electron microscopy（SEM）, Transmission electron microscopy（TEM）, Specific surface area（BET）, X ray fluorescence（XRF）. Test results show that the MoSe₂ prepared by solid phase method contains no other impurity phase. Morphology is hexagonal lamellar structure, and the lamellar size is not uniform, stacked on top of each other. The surface of MoSe₂ is smooth without pores, the structure is orderly, and the lattice fringes is clear. The specific surface area of MoSe₂ is about 2.0816 m²/g. The modified MoSe₂ by hydrothermal method is petal shaped spherical structure and Se element stores on the surface of MoSe₂ in free state form. In addition, the modified MoSe₂ surface area increased to 34.9465 m²/g,and the adsorption performance has been improved. The size of TiO₂/tourmaline composite materials prepared by hydrothermal method is uniform. The crystallinity of TiO₂ increased gradually with the increase of reaction temperature and reaction time. In addition, the dense TiO₂ is loaded on tourmaline. TiO₂ loaded on tourmaline can be clearly observed by high resolution transmission electron microscopy（HRTEM）, which is like a grain of rice. The surface area of TiO₂ increased with the increase of the content of tourmaline and the maximum value of the surface area of TiO₂ reaches 113.2637 m²/g.The performance of the modified TiO₂ and MoSe₂ to remove organic pollutantsin water is studied taking Rhodamine B（RHB） as the target pollutant. The results shows that the preparation conditions for the modified MoSe₂ with the best activity: the dosage of hydrazine hydrate is 2 m L, the synthesis temperature is 270 ℃,reaction time is 12 h. 1 g/L adsorbent prepared in the above conditions can make the100 m L Rhodamine B that the concentration is 20 mg/L decolorization rate reach97.8%. The preparation conditions for TiO₂/tourmaline with the best activity:tourmaline tourmaline content is 3 %, the synthesis temperature is 160 ℃, the reaction time is 2 h. 2 g/L TiO₂/tourmaline prepared in the above conditions can make 100 m L Rhodamine B that the concentration is 10 mg/L decolorization rate reach 99.4 %. Through the comparison of the experiment found that the catalytic activity of the modified TiO₂ was higher than pure TiO₂, and the realization of the visible light response.The TiO₂ first principle simulation with the software of Materials studio 7.0reveals the influence of electric field on the band structure of TiO₂. First principles calculation results show that: The band structure of TiO₂ under the action of tourmaline spontaneous polarization electric field do not change obviously. But the band gap of TiO₂ decreases from 2.252 e V to 2.188 e V. The decrease of band gap of TiO₂ is advantageous to produce more electrons and holes, which shows that the catalytic activity of TiO₂ under the electric field is significantly increasing.