The Load And Its Photocatalytic Properties Of ?-? Quantum Dots

The uniqueness of photocatalytic degradation of wastewater was briefly illustrated as referred to the traditional methods. The advantages and disadvantages of the semiconductor phtocatalysts, TiO2, CdS, and CdTe, based on their applications in this field, were comparatively discussed, including the current applications and developments of photocatalytic reagents in wastewater treatments, their photocatalytic mechanisms, their structures and the factors influencing the degradation process.The methods of preparing quantum dots CdS and CdTe, wildly used in a variety of fields, were summarized. A compound of CdS or CdTe with permutite (or bentonite) was synthesized in an aqueous phase. Thus, the preliminary photocatalytic conditions of the compound were surveyed, and the scheme of the thesis was basically determined. Details covered:1. Mercaptosuccinic acid capped CdSe quantum dots were prepared in aqueous solution by using SeO2 as selenium source and NaBH4 as reductant. Then, the CdSe quantum dots bentonite luminescent material was prepared by mixing the CdSe quantum dots solution and organic bentonite under stirring. The obtained sample was characterized using photoluminescence spectra, scanning electron microscopy and X-ray diffraction. The spectra analysis results disclosed that the illuminant color of quantum dots bentonite composites was similar to the corresponding quantum dots solution. The energy-dispersive X-ray spectra demonstrated that Cd and Se elements presented in the composites. X-ray diffraction measurements indicated that the (111), (220) and (331) diffraction peak of CdSe appeared in quantum dots bentonite composites, and the (001) diffraction peak at 20=4.3°for composites was the same as the raw bentonite. These results suggested that the preparation of CdSe quantum dots bentonite composites did not change the structures of quantum dots and bentonite.2. CdS/bentonite composites were successfully prepared by using CdCl2 and thioacetamide as reactants. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR) and ultraviolet-visible spectra (UV-Vis). The effect of CdS/bentonite composites on photocatalysis degradation of organic dyes (such as rhodamine B and methylene blue) were investigated in detail. Under irradiation for 3 h, it was found that 80.6%(for rhodamine B) and 88.3%(for methylene blue) of degradation rates were achieved when the dye initial concentration was 20mg/L. The performance of CdS/bentonite composites catalyst is superior to pure CdS or bentonite. 3. CdS QDs which using TGA as stabilizer and sodium borohydride as reducing agent were synthesized in permutite type permutite by reaction in alkaline aqueous solution at temperatures 100?. The optical properties of the samples were studied by diffuse reflectance and photoluminescence spectroscopy. Their crystalline structure and morphology were studied by X-ray diffraction (XRD), ultraviolet-visible spectra (UV-Vis) and. fluorescence spectroscopy. Be used as the photocatalytic, CdS/Permutite degrade the methylorange with the xenon as the light source. The results showed that after the photocatalytic reaction, the catalyst have a good effect to the degradation of methylorange, crystalviolet and alizarinred.4. CdTe/bentonite composites were successfully prepared by using CdCl2 and Na2TeO3 as reactants and ascorbic acid as reducing agent. The obtained samples were characterized by X-ray diffraction (XRD), Fluorescence spectrophotometer and ultraviolet-visible spectra (UV-Vis). The effect of CdTe/bentonite composites on photocatalysis degradation of methyl orange was investigated in detail. Under irradiation by mercury lamp for 60min, it was found that 66.23% of degradation rate was achieved when the dye initial concentration was 10mg/L. The performance of CdTe/bentonite composites catalyst was superior to pure CdTe quantum dots.