纳米T_iO_2光催化氧化聚乙二醇降解反应的研究
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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TiO_2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TiO_2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TiO_2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TiO_2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CO_2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CO_2和H_2O。降解产物的出现证实了该断链过程。
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 been
characterized 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.
以钛酸四丁酯为主要原料，通过溶胶-凝胶法制得纳米TiO_2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TiO_2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TiO_2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TiO_2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CO_2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CO_2和H_2O。降解产物的出现证实了该断链过程。
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 been
characterized 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.
引文
1．龚云峰，丁桓如，吴春华．给水处理工程中去除有机物的方法．工业水处理，2000，20(8)：1-4。
2．刘转年，金奇庭，周安宁．膜过滤技术在废水处理中的应用研究新进展．工业水处理，
2000，22(5)：1-4．
3．刘芳，顾国维．废水生物处理技术新进展．能源环境保护，2002，16(3)：17-20．
4．孙晓君，冯玉杰，蔡伟民，等．废水中难降解有机物的高级氧化技术．化工环保，2001，2(5)：264-269．
5. Minabe T, Tryk D A, Sawunyyama P, et al. TiO_2-mediated photodegradation of liquid and solid organic compounds. J Photochem Photobio A: Chem, 2000, 137:53-62.
6. Hoffmann M R, Martin S T, Choi W, et al. Environmental applications of semiconductor photocatalysis. Chem Rev, 1995, 95, 69-96.
7．严煦世．水和废水技术研究．北京：中国建筑工业出版社，1992年2月．
8．张天永，谢银德，赵进才．连续光催化净化染料废水放大实验的研究．感光科学与光化学，1999，17(4)：303-308．
9. Chen J, Ollis D F, Rulkens W H, Bruning H. Photocatalyzed oxidation of alcohols and organochlorides in the presence of native TiO_2 and metallized TiO_2 suspensions. Part (Ⅱ):photocatalytic mechanisms. Water Research, 1999, 33(3):669-676.
10．魏宏斌，徐迪民，严煦世．光催化氧化水中有机物污染机理探讨．同济大学学报，1997，2(5)：553-558．
11. Schonberger H, Baumann A, Keller W. Study of microbial degradation of polyvinyl alcohol in waste water treatment plants. American dyestuff reporter, 1997, 86(8):9-18.
12. Chen Y X, Sun Z S, Yang Y, et al. Heterogeaeous photocatalytic oxidation of polyvinyl alcohol in water. J Photochem Photobio, 2001, 142:85-89.
13．孙振世，陈英旭，杨晔．Pt／TiO_2膜光催化氧化降解高聚物的研究．太阳能学报，2001，22(1)：87-90．
14．孙振世，陈英旭，方士，等．TiO_2表面特性的改变对其光催化降解高聚物活性的影响．浙江大学学报(农业与生命科学版)，2001，27(2)：195-199．
15．陈颖，王宝辉，盖翠萍，等．不同半导体非均相光催化聚丙烯酰胺水溶液．黑龙江石油化工，2001，12(2)：23-27．
16．陈颖，崔军明，王宝辉，等．光催化氧化降解水中聚丙烯酰胺的可行性研究．大庆石油学院学报，2001，25(2)：82-83．
17．陈颖，王宝辉，张海燕，等．纳米级TiO_2光催化氧化聚丙烯酰胺．催化学报，1999，
20(3):309-312.
18．严瑞萱．水溶性高分子．北京：化学工业出版社，1998年6月．
19．陈庆春，邓慧宇，马燕明．聚乙二醇在新材料制备中的作用及其机理．日用化学工业，2002，32(5)：35-38．
20. Costa L, Gad A M, Camino G, et al. Thermal and thermooxidative degradation of poly(ethylene oxide)-metal salt complexes. Maeromolecules, 1992, 25:5512-5518.
21. Scheirs J, Bigger S W, Delatycki O. Characterizing the solid-state thermal oxidation of poly(ethylene oxide) powder. Polymer, 1991, 32(11):2014-2019.
22. Han Seongok, Kim Chongyoup, Kwon Dongsook. Thermal degradation of poly(ethylene glycol). Polymer Degradation and Stability, 1995, 47:203-208.
23．罗善国，陈福泰，谭惠民，等．NMR研究聚乙二醇的热氧降解．高分子材料与工程，2001，17(4)：128-130．
24．王君，王亚兵，刘树清．H_2O_2-Fe~(2+)法处理聚乙二醇(PEG)生产废水研究．化学推进剂与高分子材料，2003，19(1)：35-38．
2．刘转年，金奇庭，周安宁．膜过滤技术在废水处理中的应用研究新进展．工业水处理，
2000，22(5)：1-4．
3．刘芳，顾国维．废水生物处理技术新进展．能源环境保护，2002，16(3)：17-20．
4．孙晓君，冯玉杰，蔡伟民，等．废水中难降解有机物的高级氧化技术．化工环保，2001，2(5)：264-269．
5. Minabe T, Tryk D A, Sawunyyama P, et al. TiO_2-mediated photodegradation of liquid and solid organic compounds. J Photochem Photobio A: Chem, 2000, 137:53-62.
6. Hoffmann M R, Martin S T, Choi W, et al. Environmental applications of semiconductor photocatalysis. Chem Rev, 1995, 95, 69-96.
7．严煦世．水和废水技术研究．北京：中国建筑工业出版社，1992年2月．
8．张天永，谢银德，赵进才．连续光催化净化染料废水放大实验的研究．感光科学与光化学，1999，17(4)：303-308．
9. Chen J, Ollis D F, Rulkens W H, Bruning H. Photocatalyzed oxidation of alcohols and organochlorides in the presence of native TiO_2 and metallized TiO_2 suspensions. Part (Ⅱ):photocatalytic mechanisms. Water Research, 1999, 33(3):669-676.
10．魏宏斌，徐迪民，严煦世．光催化氧化水中有机物污染机理探讨．同济大学学报，1997，2(5)：553-558．
11. Schonberger H, Baumann A, Keller W. Study of microbial degradation of polyvinyl alcohol in waste water treatment plants. American dyestuff reporter, 1997, 86(8):9-18.
12. Chen Y X, Sun Z S, Yang Y, et al. Heterogeaeous photocatalytic oxidation of polyvinyl alcohol in water. J Photochem Photobio, 2001, 142:85-89.
13．孙振世，陈英旭，杨晔．Pt／TiO_2膜光催化氧化降解高聚物的研究．太阳能学报，2001，22(1)：87-90．
14．孙振世，陈英旭，方士，等．TiO_2表面特性的改变对其光催化降解高聚物活性的影响．浙江大学学报(农业与生命科学版)，2001，27(2)：195-199．
15．陈颖，王宝辉，盖翠萍，等．不同半导体非均相光催化聚丙烯酰胺水溶液．黑龙江石油化工，2001，12(2)：23-27．
16．陈颖，崔军明，王宝辉，等．光催化氧化降解水中聚丙烯酰胺的可行性研究．大庆石油学院学报，2001，25(2)：82-83．
17．陈颖，王宝辉，张海燕，等．纳米级TiO_2光催化氧化聚丙烯酰胺．催化学报，1999，
20(3):309-312.
18．严瑞萱．水溶性高分子．北京：化学工业出版社，1998年6月．
19．陈庆春，邓慧宇，马燕明．聚乙二醇在新材料制备中的作用及其机理．日用化学工业，2002，32(5)：35-38．
20. Costa L, Gad A M, Camino G, et al. Thermal and thermooxidative degradation of poly(ethylene oxide)-metal salt complexes. Maeromolecules, 1992, 25:5512-5518.
21. Scheirs J, Bigger S W, Delatycki O. Characterizing the solid-state thermal oxidation of poly(ethylene oxide) powder. Polymer, 1991, 32(11):2014-2019.
22. Han Seongok, Kim Chongyoup, Kwon Dongsook. Thermal degradation of poly(ethylene glycol). Polymer Degradation and Stability, 1995, 47:203-208.
23．罗善国，陈福泰，谭惠民，等．NMR研究聚乙二醇的热氧降解．高分子材料与工程，2001，17(4)：128-130．
24．王君，王亚兵，刘树清．H_2O_2-Fe~(2+)法处理聚乙二醇(PEG)生产废水研究．化学推进剂与高分子材料，2003，19(1)：35-38．