In this dissertation, we have combed the influence of synthetic dyes wastewater on the environment and the current treatment methods. Through comparison, the advantages of advanced oxidation processes (AOPs) in practical applications were clarified. We also focused on the application of photocatalytic degradation technology using semiconductor nanomaterials as photocatalysts in the degradation of organic dyes wastewater. Tin dioxide (SnO₂), cadmium selenide (CdSe), and cuprous oxide (Cu₂O) were selected as the representatives of semiconductor nanomaterials, and they were synthesized in the laboratory by appropriate methods. In order to further improve their photocatalytic performance, they were modified by metal doping and combination with carbon nanomaterials. Through the comparative studies of organic dyes degradation, the effectiveness of metal doping and combination with carbon nanomaterials to improve photocatalytic performance were confirmed, and the possible enhancement mechanisms of photocatalytic performance were proposed.
In SnO₂ section, SnO₂ nanoparticles were synthesized successfully by using a chemical precipitation method. The photocatalytic activity of as-prepared SnO₂ nanoparticles was studied by the degradation of MB, MO, and RhB under 254 nm UV lamp illumination. Fullerene (C60) was used as a suitable carbon nanomaterial for improving the photocatalytic performance of SnO₂. As-synthesized samples were confirmed through various characterization methods such as X-ray diffraction (XRD), Raman spectroscopy, and Scanning electron microscopy (SEM). The kinetics study showed that the photocatalytic activity of SnO₂ nanoparticles was obviously improved after the combination of SnO₂ nanoparticles with C60. And the photocatalytic degradation order of the organic dyes with SnO₂ nanoparticles and SnO₂-C60 nanocomposites was MB > RhB > MO.
In CdSe section, CdSe nanoparticles were effectively synthesized by a facile microwave irradiation method. Metallic Mn was doped on the surface of CdSe nanoparticles as a electron acceptor due to the narrow band gap of CdSe. Moreover, CdSe-Mn-C60 nanocomposites with heterogeneous structure were synthesized by co-heating with C60. XRD, SEM, and Raman spectroscopy were used to characterize the crystal structures, surface morphologies, and lattice vibrations of the samples. The photocatalytic activities of Mn-doped CdSe nanoparticles and CdSe-Mn-C60 nanocomposites were investigated by the photocatalytic degradations of organic dyes such as MB, MO, and RhB under ultraviolet irradiation at 254 nm. As a result, the CdSe-Mn-C60 nanocomposites showed better photocatalytic degradation efficiency of organic dyes than Mn-doped CdSe nanoparticles, confirming the improvement of photocatalytic performance was caused by C60.
In Cu₂O section, Cu-doped Cu₂O nanoparticles were prepared by the reduction reaction of copper (II) sulfate pentahydrate and sodium hydroxide. D (+)-glucose and sodium dodecyl sulfate were used as reducing agent and capping surfactant, respectively. Graphene with strong electrical conductivity and adsorption capacity was used for their further modification. As-synthesized Cu-doped Cu₂O nanoparticles and Cu₂O-Cu-Graphene nanocomposites were characterize by XRD, SEM, and Raman spectroscopy. The effectiveness of graphene in enhancing the photocatalytic activity of Cu-doped Cu₂O nanoparticles was further revealed by comparative investigation of the photocatalytic degradation of organic dyes (MB, MO, and RhB) under 254 nm UV light irradiation. In addition, the photocatalytic degradation of organic dyes was well fitted by the pseudo-first-order kinetics model.