UV/TiO_2光催化还原Cr(Ⅵ)过程中吸附作用的影响及其消除

研究了水体中Cr(Ⅵ)离子在UV/TiO₂体系中光催化还原过程.结果表明,Cr(Ⅵ)离子UV/TiO₂光催化还原过程符合Langmuir-Hinshelwood动力学规律.不存在有机物时,TiO₂吸附作用是该反应的前提.pH=1.5～2.5时吸附性能较好,而且pH=1.5～10的初始反应速率同pH值有线性关系.在TiO₂表面的竞争吸附能力按PO₄^3->SO₄^2->Cl^->NO₃^-依次减弱.甲酸、甲醛有机物的协同作用可提高Cr(Ⅵ)离子的光催化还原速率和效率,并消除由暗态吸附对反应所起的作用,磷酸根离子极强的竞争吸附能力,使有机物的协同作用减弱.

Effects of absorption on photo-reduction of Cr (VI) by UV/TiO2 process and its elimination

Reduction of Cr(VI) in aqueous solution were studied by the UV/TiO2 photo-reduction process. The results show that the photo-reduction of Cr(VI) ion by UV/TiQ2 agrees with Langmuir-Hinshelwood equation well. In absence of organic matters, absorption of TiO2 is the key step for this process, and optimal condition is pH = 1.5-2.5. The initial reduction rate correlate with pH value within pH = 1.5-10. The ability to competitively absorb to the surface of TiO2 can be ordered by PO4(3-) > SO4(2-) > Cl- > NO3-. Photoreduction rate and efficiency can be enhanced greatly with synergia of formaldehyde or formic acid, meanwhile synergia eliminate the effect of absorption. But synergic effects were reduced with phosphate.