| Photocatalytic oxidation technology is an advanced wastewater treatment technology, whose virtues are high treatment efficiency, low energy expense, simple technological equipment, the easy control of operating condition, no secondary pollution, so it is a promising wastewater treatment technology. However, the use of conventional photocatalyst that is typically delegated by titanium dioxide has disadvantages of low quantum efficiency and difficult recycling, which confine its industrial application. Thus, different methods including surface modification of titanium dioxide, support, deposition of heavy metals, the compound semiconductors, the mixture of the rare elements are being studied systematically by researchers abroad and at home.In the light of disadvantages of titanium dioxide above-mentioned, the synthesis conditions of bulk nanocomposite photocatalysts TiO2-SiO2/rectorite and its general laws of the photocatalytic degradation of a organic dye methylene blue and the adsorption of copper ions have been researched in this dissertation, by which we look forward to adding data to the further research in support and modification technology of photocatalyst and its application in wastewater treatment.In the research, a kind of bulk nanocomposite photocatalyst has been synthesized first by sol-gel process, taking silica dioxide as modifier and rectorite as carrier. Different factors that influence the photocatalytic activity of samples, including the concentration of R-suspended solution, the ratio of Ti and rectorite(Ti/R), the ratio of the Si and Ti, pH, synthesis temperature, calcinations temperature, etc., have been discussed in detail and the mechanism has been explained primarily, too. Through the orthogonal tests, the influential order of four main factors has been ascertained that: calcinations temperature>Ti/R>synthesis temperature>calcinations time, and the optimum synthesis conditions have been concluded that: calcinations for 2 hours at 600 ℃, Ti/R at 10 mmol/g, synthesis at 60 ℃.Some testing methods such as X-ray diffraction(XRD), transmission electron microscope(TEM), infrared spectrum(IR), the measure of specific surface area(BET method) are used to characterize the samples in order to analyze its micro-features of appearance and interface in the research. And the test results have indicated that though the level of composite's crystallization is not high, anatase titanium dioxide appears obviously in it, the particles of which are distributed well-proportionedly with 25-30nm of diameter, and are fixed by Ti-O-Si bond on the surface of rectorite. It can be also seen from results that the structure of rectorite has been changed obviously in the samples, and the specific surface area of samples has become much larger than that of raw rectorite and pure titanium dioxide. All ofthose are the key reasons why the photocatalytic activity of samples is enhanced.To evaluate the photocatalytic activity of synthesized composite photocatalyst, photocatalytic degradation tests to artificial methylene blue (MB) pollutant have been carried out in self-made device of photocatalytic degradation system with the illuminant of UV light in the study. And laws of effect of different factors on the photocatalytic activity of samples, including the dosage of photocatalyst, degradation time, initial concentration of pollutant, pH, distance form illuminant, reuse, etc., have been further discussed and the mechanism has been explained primarily, too. The results of tests indicated that: the decoloration rate can achieve above 90% for 8mg/L of MB's initial concentration in the condition of 5g/L of dosage and 3 hour of degradation time under UV light; alkaline condition advantages process of degradation, and degradation effects are the best with 20cm of the distance form illuminant; the decoloration rate of MB can still achieve above 70% after the fourth reuse of samples.Moreover, the synthesized composite photocatalyst's adsorption tests to artificial copper-containing wastewater are carried out in the research. By analyzing results of the single factor tests, the best adsorption conditions of copper ion( II) has been concluded that: 18g/L of dosage, about 8 of pH, 5mg/L of initial concentration of copper ion( II), 15 minutes of mixing time, 25 of temperature. Thereby, removal rate has achieved 92.5%. |
