不同擔體表面處理程序對氧化鐵覆膜催化效能之影響

Abstract

粒狀活性碳（GAC）因為具有相當大的比表面積、多孔結構和多樣的表面物性及化性，因此為一種常被使用於處理污染物質的良好吸附劑，或被應用於充當異相催化反應的催化劑。近年來亦有部分研究將負載型鐵氧化物或顆粒狀的固體催化劑（如石墨或是活性碳）實際應用於氧化程序中，還考慮將此種方法實際應用於對環境處理程序。故本研究乃利用三種不同的表面處理程序及三種不同的氧化鐵覆膜方式製造新式的活性碳擔體觸媒，以了解這些方式製成的觸媒，催化過氧化氫分解氯酚類化合物之影響效能。從不同表面處理程序的實驗結果中顯示，用過氧化氫此種強氧化劑清洗GAC對其表面物性不會造成影響，但以硝酸清洗，則會造成BET比表面積急減，平均孔徑增加、微孔隙體積減少。雖然硝酸洗過之活性碳其比表面積下降，吸附有機物的能力降低。但是卻會提升了此觸媒在異相催化中有效去除、有效降解有機物的比例。 在不同的氧化鐵覆膜方式之結果中顯示，石英砂覆膜了氧化鐵後，其催化過氧化氫之反應速率明顯提升，且其反應類似氧化鐵。但石英砂僅為一良好的覆膜擔體，對反應速率的增進無任何幫助。 而活性碳覆膜了氧化鐵後，反應的性質已不同於一般氧化鐵，其反應速率明顯大於一般氧化鐵，且覆膜後之催化分解過氧化氫及去除有機物、和脫氯作用的反應速率均較未覆膜的活性碳來的高，而三種不同覆膜方式所製成的觸媒，尤其以階段式加藥含浸的覆膜方式的觸媒最佳，其在氧化分解4-氯酚的效果最好，此外三種觸媒的效果皆在低pH值之去除效果較佳。此外發現覆膜型觸媒效果的好壞與表面所覆膜上去的含鐵量無絕對的關係。

GAC, a good adsorption, is often used of disposing polluted materials, or used of acting as the catalyst of heterogeneous reaction, owing to its enormous surface area, porous structure and characteristic flexibility. Recently, some researches put iron oxides or granular size solid catalysts (for example, graphite and activated carbon) to use in oxidation process, and they even consider to put this way practically using in the process of environmental disposal. This research is order to understand the influence of the surface treatment processes on the catalytic activity of supported iron oxide. From the experiment of the disposal process, it shows that it doesn’t cause any effects on its surface by using H2O2 to wash GAC, but it does by using nitric acid; this may sharply reduce its specific surface area, make the average pore size increase, and the micropore volume decrease. Although GAC is washed by nitric acid which decreases the capability of absorbing organics, it highly increases the percentage of the rate of ER and ED in heterogeneous reaction. The stoichiometric efficiency, ER and ED, is defined individually as the ratio of the reduction and degradation amount of 4-CP to the decomposition amount of H2O2. From the outcome of different iron oxide coated ways, it shows that the raising reactive rate of catalyzing H2O2 decomposition after silica sand is coated by iron oxide, and the reactive is similar to iron oxide, implying the role of the silica sand is only as a support. So silica sand is a good carrier for coated, but it is helpless to affect on the decomposition rate of H2O2. However, after GAC is coated by iron oxide, the reaction is different from normal iron oxide; the rate of catalyst on certain modified base is faster than normal iron oxide apparently. Unlike the silica sand, GAC is not merely a carrier, and it does contribute to the catalytic activity on H2O2 decomposition. C-GAC has a better effect on decomposing H2O2, reducing and dechloring organics than uncoated GAC. The best coated way of GAC is to add drugs gradually and dip it in on multiple impregnation method. C-GAC gets its best removing effect at low pH condition; moreover, it doesn’t have any absolute relation between the iron quantity contained and the effects.