Preparation Of Bismuth-based Materials-titanium Dioxide Nanocomposites And Insights Into Their Promoted Adsorption And Photocatalysis Capability

Adsorption and photocatalysis technologies are widely applied in environmental remediation due to their advantages of high efficiency,easy operation,and low energy consumption.It is of significant importance to design highly-efficient adsorbents and photocatalytic materials with good stability and reutilization ability to remove environmental pollutants.Ti O₂ and Bi-based semiconductor micro/nano structures show potential applications in the adsorption and photocatalytic removal of organic dyes duo to their unique structure and chemical properties.Meanwhile,single Bi-based material or Ti O₂ nanostructure display poor adsorption,regeneration,and recycling performances in the removal of dyes.Besides,they also show some disadvantages of poor light-response capability and high recombination rate of photoinduced electron-hole pairs,resulting in low photocatalytic activity.In this thesis,combining with their unique properties,favorable advantages,and suitable band position,Ti O₂ nanoparticles decorated Bi-based semiconductors were successfully fabricated to improve the adsorption and photocatalytic capability towards environmental pollutants removal through synergistic effect.And the insights into promoted adsorption and photocatalysis capability were further discussed.The main work can be divided into three parts as follows:1.Inspired by the superhydrophobic property of lotus leaf derived from its unique surface micro/nano structures,the composites of Bi OCl nanoplates decorated with Ti O₂ nanoparticles were biomimetic fabricated.The adsorption performance of Bi OCl-Ti O₂ composites and mechanism of its enhanced adsorption capability for Congo red?CR?removal were studied.The results indicated that the Bi OCl-Ti O₂ composites exhibited promoted adsorption capability towards CR removal compared with bare Bi OCl microspheres and Ti O₂ nanoparticles,and the maximum adsorption amount is 254.7 mg/g.It was found that the larger surface area of Bi OCl-Ti O₂ composite and the electrostatic attraction between CR and the composite facilitated its adsorption capability towards CR.In addition,the Bi OCl-Ti O₂ composites displayed a suitable hydrophilic property compared to superhydrophilic Bi OCl microspheres and Ti O₂ nanoparticles,relatively restraining the adsorption of water molecules on adsorbent andweakening the competitive adsorption of solvent water toward target pollutant on adsorbents and further promoting adsorption capability of composites towards CR removal.And the CR-adsorbed Bi OCl-Ti O₂ adsorbents can be regenerated through the photocatalysis method and the regenerated adsorbents also showed good repeated adsorption capability for CR removal.Meanwhile,the other Bi-based/Ti O₂ composites such as Bi2O₂CO3-Ti O₂,Bi2S3-Ti O₂,Bi2 Mo O6-Ti O₂,Bi₂O₃-Ti O₂ composites prepared by the same synthetic method also exhibit improved adsorption capability towards CR than that of their single components,indicating that Ti O₂ nanoparticle decoration could be an effective strategy to improve the adsorption capability of Bi-based nanomaterials toward CR removal.2.The hollow Bi OCl/Bi2S3 binary hybrids were synthesized through an ion exchange method using porous Bi OCl microspheres as template and thiacetamide?TAA?as sulfur source,respectively.Then,the Bi OCl-Bi2S3-Ti O₂ ternary composites were prepared by introducing Bi OCl/Bi2S3 binary hybrids into the hydrothermal formation process of Ti O₂ nanoparticles.The photocatalytic activities of above photocatalysts for Cr?VI?reduction were studied.It was found that the Cr?VI?removal was the photogenerated electron reduction process in the Bi OCl-Bi2S3-Ti O₂ photocatalytic system and the ternary composites exhibited enhanced photocatalytic activity than that of Bi OCl,Ti O₂,Bi2S3 and Bi OCl-Bi2S3 composites.The photocurrent response and electrochemical impedance spectroscopy?EIS?measurements demonstrated that the Bi OCl-Bi2S3-Ti O₂ ternary composites could effectively promote the separation and transfer of the photogenerated carrier,leading to the improved photocatalytic performance for Cr?VI?reduction.3.The composites of TiO₂ nanoparticles decorated Bi₂O₃ quadrangular prisms were successfully fabricated by introducing Bi₂O₃ nanospheres into the hydrothermal formation process of Ti O₂ nanoparticles.The photocatalytic activity of Bi₂O₃-Ti O₂ composites was tested by degradation of methyl orange?MO?.The results showed that the Bi₂O₃-Ti O₂ composites exhibited more excellent photocatalytic performance compared to pure Bi₂O₃ and Ti O₂ materials,and the photogenerated hole was mainactive species in MO degradation.Besides,it was found that the highly efficient photocatalytic activity of Bi₂O₃-Ti O₂ composites was not only attributed to the favorable light-response property,but also the high separation and transfer efficiency of photogenerated electron-hole pairs through characterizations of optical absorption properties,electrochemical tests,and photoluminescence spectra.