Nano T <sub> I </ Sub> O <sub> 2 </ Sub> Photocatalytic Oxidation Of Polyethylene Glycol Degradation Reactions

The technique of photocatalytic oxidation, which utilizes a semiconductor as catalyst, is a new kind of treatment process with great potential application in water treatment for its good ability to utilize natural resource, solar energy, and its outstanding effect on degradation of organic substances. The basic principle of photocatalytic oxidation, the development of photocatalytic degradation of polymer in waster by using nano TiO2 are summarized in the dissertation. The degradation efficiency of photocatalytic oxidation of polyethylene glycol (PEG) with nano TiO22 is investigated.The nanosized TiO22 photocatalysts in the anatase, rutile are prepared by sol-gel method with Ti(OBu)4 as a precursor. The resulting materials have beencharacterized by transmission electron microscope(TEM) and X-ray diffraction(XRD).PEG can be determined indirectly by spectrophotometry using ammonium ferrothiocyanate aqueous-chloroform system. The maximum absorbance wavelength is 515 nm. The partition equation of Fe(SCN)3in two-phase system is persisted 20 min after vigorous mixing for 30 min. Regression equation of PEG with different degree of polymerization are satisfied. The recovery of PEG is 97.3-99.4% and relative standard deviation is less than 1.5%.The photocatalytic degradation of polyethylene glycol with different experimental conditions by titanium dioxide is investigated. The nano TiO2 in the anatase phase shows higher photocatalytic activity than that in the rutile phase. Both of light resource and catalysts are necessary to degradate PEG. The rate of photocatalytic oxidation under mercury lamp is faster than that under wolfram lamp. The optimum dosage of TiO22 in photocatalytic degradation of PEG is 2.5 g/L.Under above conditions, degradation rates of PEG depends on different molecular weight of PEG. The more the molecular weight is, the slower the rate is.From the change of the concentration of the reactant and product CO2 detected by gas chromatographs, the reaction's order is confirmed as zero order.From the experimental results of TG, FT-IR and NMR, it is obvious that the intermediates generated by photocatalytic degradation of PEG are lower molecular weight PEG, low molecular weight esters, including formic ester. PEG is mineralized to CO2 and H2O finally. Carbon-carbon bonds scissored is supported by degradated products.