纳米T_iO₂光催化氧化聚乙二醇降解反应的研究

【作者】 吴缨；

【导师】 徐洪耀；

【作者基本信息】 安徽大学 ， 高分子化学与物理， 2004， 硕士

【摘要】 半导体光催化氧化技术是一种新型的现代水处理技术，由于它能广泛地利用天然能源——太阳能，且对多种有机物有明显的降解效果，具有广阔的应用前景。论文简述了半导体光催化氧化法的基本原理，概述了纳米二氧化钛降解废水中高聚物的应用进展。以聚乙二醇为研究对象，考察了纳米二氧化钛光催化氧化聚乙二醇的降解效果。 以钛酸四丁酯为主要原料，通过溶胶-凝胶法制得纳米TiO₂粉末，用透射电镜（TEM）和X射线衍射（XRD）对其结构进行表征，表明所制备的TiO₂粉末的晶型主要为锐钛矿型和金红石型。 聚乙二醇浓度采用硫氰酸铁铵-氯仿体系光度法间接测定，最大吸收波长为515nm，振摇时间30min后Fe（SCN）₃在两相中分配达到平衡并能够稳定至少20min。不同聚合度PEG的回归方程线性关系较好。本方法平均回收率97.3-99.4％，相对标准偏差（RSD）不超过1.5％。测定方法准确、可靠。 用纳米TiO₂为光催化剂，研究了不同实验条件对光催化降解反应的影响。发现使用锐钛矿型催化剂的降解率高于金红石型，光照和催化剂同时存在是反应的必要条件，汞灯作光源的氧化速率高于白炽灯，适宜的催化剂用量是2.5g／L。 实验条件下，纳米TiO₂光催化氧化聚乙二醇水溶液的反应速率与平均分子量大小有关，分子量越大，反应速率越低。生成物CO₂及剩余反应物浓度随时间变化的实验结果表明，该种反应为零级反应。 热重分析、傅立叶变换红外光谱、核磁共振波谱检测结果均表明：光催化氧化过程中间产物有低分子量聚乙二醇、热稳定性较低的甲酸酯以及其他低分子量酯等，最终矿化为CO₂和H₂O。降解产物的出现证实了该断链过程。更多还原

【Abstract】 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.更多还原