无机界矿物天然自净化功能之矿物光催化作用

Mineralogical photocatalysis in natural self-purification of inorganic minerals

在简述半导体光催化理论及TiO2 多相光催化作用近 30年研究现状的基础上 ,重点对国内外一直处于空白状态的天然含钒金红石光催化性能进行研究。天然含钒金红石中部分Ti4+ 被V5+ 包括Fe3 + 、Cu2 + 和Zn2 + 等杂质离子替代可引起其晶格畸变与缺陷。机械粉碎到 70～ 80 μm后可使其晶胞膨胀 0 .33% ,原位加热 70 0～ 110 0℃其晶胞可膨胀 0 .93%～ 2 .13% ,淬火改性其晶胞收缩 0 .0 1%～ 0 .0 7%。受热改性其体相中V5+ 向表面偏析。对晶格畸变的修复可表现为晶面重构和再结晶作用及微应力释放作用。粉碎的金红石对卤代烃三氯乙烯和四氯乙烯具有一定的降解效果而表现出良好的光催化活性。加热 10 0 0℃ ,金红石对卤代烃的降解率明显提高。淬火 10 0 0℃和110 0℃ ,金红石对卤代烃的降解速度大大加快。而电子辐射金红石对三氯乙烯的降解率则明显降低。通过 5 2种金属氧化物和金属硫化物半导体矿物的初步研究 ,发现大多数金属氧化物矿物产生光电子的波长范围是 2 4 9～ 777nm ,吸收光主要是可见光。而大多数金属硫化物矿物产生光电子的最大波长大于 92 1nm ,吸收光主要是红外光 ,充分表明无机界具有光催化功能的半导体在可见光条件下就可以产生光电子与空穴。系统开展无机界矿物光催化作用研究 。

Based on a brief review of semiconductor photocatalytic mechanism and researches in the past 30 years on TiO 2 heterogeneous photocatalysis, this paper emphasizes that the natural vanadiferous rutile and its modified products, which have not been investigated by either Chinese or foreign research groups, degrade halogenated organic contaminants. By means of grinding, heating in situ, heating, quenching and electron irradiation, the natural rutile could be modified. The results show that the lattice distortion and defects in the natural rutile are attributed to the fact that part of Ti 4+ ions are replaced by V 5+ and other impurity ions such as Fe 3+ , Cu 2+ and Zn 2+ . Grinding rutile samples into powder with the particle size of 70～80 μm results in 0.33% increase of their lattice volumes. The lattice volumes distinctly increase by 0.93%～2.13% via heating in situ at 700～1?100℃. On the contrary, quenching causes the lattice volumes decrease by 0.01%～0.07%. V 5+ ions in rutile are modified by heating segregation outwards to the surface, and the corresponding lattice distortion is rehabilitated by the role of reconstruction in certain crystal faces, recrystallization and release of the microstrain. Rutile modified by grinding shows some degree of photocatalystic efficiency in degrading trichloroethylene and tetrachloroethylene and has fair photoactivity. Heating at 1?000℃ evidently improves the degradation ratio of rutile for the halohydrocarbons and the rutile quenched at 1?000℃ and 1?100℃ distinctly shows a higher degradation rate. The rutile modified by electron irradiation, however, has obviously lower degradation ratio for trichloroethylene. Furthermore, through the tentative study of 52 kinds of semiconducting metal oxides and metal sulfide minerals, it is found that, for most metal oxide minerals, the maximal wavelength of the light, which can excite photoelectron, ranges from 249 to 777 nm, corresponding to the visible light, whereas that of metal sulfide minerals is 921 nm, corresponding to the infrared light. Therefore, the photogenerated electron_held pairs could be excited by the visible light. Systemic researches on photocatalysis in minerals can play an unique role in revealing the life process of the earth and the environmental evolution. The researches are very important to the realization of oxidization of organic contaminants, especially the permanent organic contaminants that cannot be degraded by themselves, in the system of the earth's surface.