【作者】 周波；

【导师】 鲍长利；

【作者基本信息】 吉林大学 ， 分析化学， 2004， 硕士

【摘要】 利用半导体光催化剂降解有机污染物已在农药废水的治理方面得到了较为深入的研究。N型半导体TiO2既具有较高的光催化活性，又能抗光腐蚀，而且还具有价廉、无毒和在酸碱条件下难溶、对光稳定等优点。因此，TiO2已成为一种重要的，有较好应用前景的光催化剂。由于光催化法可在常温常压下短时间内将污染物完全降解至无毒的物质，因而该法将成为处理各类污染物废水最为有效的方法之一。但是，由于通常所用的TiO2粉末存在催化剂易聚集、易失活、较难回收和再利用等特点，严重限制了TiO2的应用发展，克服这一缺点的有效方法是制备复合型光催化剂，进而提高其光催化性能。本实验以钛酸丁酯为钛源，应用天然沸石作载体制备的TiO2/沸石复合光催化剂使TiO2和矿物之间实现了一定的化学结合，经200℃热处理所得样品的锐钛矿型TiO2结晶状况最好，其表面复合氧化钛样品具有较大的比表面积和光催化活性，且易于回收和重复利用，不会产生二次污染，发挥了矿物和锐钛矿的双重效应，克服了TiO2存在的缺点，具有更好的应用前景。 采用酸催化溶胶－凝胶法制得TiO2溶胶后，将其负载于天然沸石上制成负载型TiO2/沸石光催化剂，其表面的复合氧化钛样品具有较大的比表面积(211.68m2/g) 。实验表明，经200℃热处理得到的光催化剂对农药敌敌畏的光降解速度最快，结构测试表明负载于天然沸石上的TiO2颗粒为锐钛矿型TiO2。合成TiO2随着焙烧温度的升高逐渐地由锐态矿形态转变为金红石形态，由于锐态矿形态的TiO2比金红石形态的TiO2更易产生“电子—空穴对”，所以其光催化活性比金红石形态的高。用合成TiO2光催化剂降解有机磷农药，敌敌畏在一般条件下光照150min可达到完全降解，最易降解，甲拌磷次之，对硫磷达完全降解所需时间最长，这与它们的分子结构有关。三种农药完全降解时COD去除率均达90%左右。实验采用的载体天然沸石具有较好的吸附性能，在用沸石原样做空白实验时，发现农药敌敌畏有10%左右的降解；同时用可见光做了平行试验，发现敌敌畏几乎没有降解，这说明可见光对农药的光催化降解没有贡献。试验中甲拌磷的臭味消失，说明了光催化法有很好的除臭作用。 <WP=54>另外，以农药敌敌畏为研究对象，研究了溶液的初始pH值、H2O2加入量、TiO2用量及一些外加无机离子等诸多影响因素对光催化降解的影响。研究结果表明，农药敌敌畏在强碱条件下最易降解，在pH2.0时较易降解，而在pH3.0、6.0、8.0时，降解率没有明显区别，实验中采用溶液pH为6.0左右。二氧化钛作为光催化剂进行光催化降解的问题在于电子—空穴对的重新复合，抑制其重新复合的一种办法是加入其他的电子接受体，减少电子—空穴对的复合，从而使光催化剂TiO2表面产生更多的·OH自由基，加强农药的光催化降解。加入H2O2能促进农药的降解，敌敌畏的光降解率随过氧化氢浓度的增大而增大，但加入过量则会降低农药的光降解率，因此过氧化氢的加入量有一个最佳值；为了促进敌敌畏的降解程度，提高光催化性能，我们还加入了一些金属离子，其中Fe3+、Cu2+、Zn2+等的加入会促进敌敌畏的降解，它们的加入量都有一个最佳值；而实验中发现，有些金属离子（如Al3＋、Au3+等）会减慢光催化降解的进程，一些阴离子（如Cl－、SO42-等）的加入也对敌敌畏的降解起抑制作用。农药敌敌畏的光催化降解率与其浓度有较大关系，浓度越小，光照相同时间内光催化降解率越大。另外，还讨论了光源高度及光照面积、合成光催化剂的不同TiO2负载量、天然沸石的粒度及农药的纯度等因素对光催化降解的影响。合成光催化剂在催化活性变稳定后可以重复利用；另外，用太阳光作了室外实验也得到了较好的降解效果，只要光照时间足够长（7~8h），有机磷农药均可完全降解为无害物质，这为有机磷农药废水的实际处理提供了依据。更多还原

【Abstract】 It has been deeply studied on the treatment of organic pollutants in pesticide wastewater by semiconductor photocatalytic degradation. Titanium dioxide has become an important and developing photocatalyst for its higher stability and activity, cheapness, intoxicity, difficult to dissolve in the acid and alkali conditions. The pollutants can be entirely broken down to innoxious matters by photocatalytic degradation which can be finished at normal temperature and pressure in short times, so photocatalysis method has become one of the most effective method to degrade vary kinds of polluters. However, usual suspension photocatalysis oxidation had some disadvantages, such as photocatalyst was apt to inactivate and agglomerate, difficult to reuse and easy to cause the second pollution. These shortcomings limited the development of titanium dioxide. So researchers focused the emphasis on the synthesis of the immobilized photocatalyst that could enhance its photocatalytic activity. This paper prepared titanium dioxide photocatalyst supported on a natural zeolite with tetrabutyl titanate as titanium source. The chemical combination was achieved between titanium dioxide and the mineral. The anatase had the best crystal at calcinating temperature of 200℃ which had a bigger specific surface area and photocatalytic activity. At the same time, it was easy to reuse and could not cause the second pollution. The mineral and the anatase achieved good combination, which overcome the disadvantages of titanium dioxide. As a result, the composite titanium dioxide had better using foreground than the suspension one. The titanium dioxide sol was synthesized by acid-catalyzed sol-gel method and then the TiO2/zeolite photocatalyst with which supported on natural zeolite was obtained. The chemical combination was achieved between titanium dioxide and the mineral that has a bigger specific <WP=56>surface area. The experimental results showed that titanium dioxide supported on a natural zeolite treated at 200℃ had the best photocatalytic activity. Structure test showed it was anatase that had the best crystallization and the biggest content at 200℃. The synthesized titanium dioxide transformed from anatase to rutile gradually with the calcinating temperature increased. The electron and hole produce easier for anatase than that of rutile, so it has a high photocatalytic activity.The organophosphorous pesticides were photocatalytic degraded by the synthesized titanium dioxide. Dichlorvos can be entirely decomposed with general conditions in irradiation for 150min and it was the easiest one, Phorate was the easier one, and Parathion was the most difficult one to break down, which had relation with their molecular structure. The COD removal rate were all about 90 percent when they had been entirely degraded. Since the natural zeolite had better absorption, dichlorvos had 10 percent degradation when the blank experiment was carried out by the zeolite only. At the same time, the parallel experiment was done and there was no degradation. That is to say, the vision light had no contribution to the photodegradation. During the course, the odor of the Phorate disappeared which showed the photocatalytic method could remove the odor. The influence factors such as the initial pH, the additional hydrogen peroxide, the content of titanium dioxide and some additional inorganic anion on photocatalysis degradation with dichlorvos as aim contaminants were further studied. The results showed that dichlorvos could be easily decomposed at strong alkaline conditions and could be broken down at pH2.0. There was no obvious difference in the degradation rate at the initial pH of 4.0, 6.0 and 9.0, and the final pH of reaction solutions were around 6.0 in the study. The problem in using <WP=57>titanium dioxide as a photocatalyst is recombination of electron and hole. One strategy for inhibiting theirs recombination is to add other electron accepters to the reaction. It can reduce the electron/hole recombination and then produce more ·OH on the surface of t更多还原