稀水溶液中Cr(Ⅵ)的光催化还原研究

PHOTOCATALYTIC REDUCTION OF HEXAVALENT CHROMIUM IN ITS LOW CONCENTRATION SOLUTION

以甲醇、正丙醇、丙三醇和苯酚作为俘获剂,研究稀水溶液中Cr(VI)的光催化还原过程,考察Cr(VI)在催化剂表面上的界面吸附行为及溶液pH值、俘获剂类型等对其光催化还原过程的影响.结果表明,溶液pH值对Cr(VI)吸附的影响为:(1)溶液pH<2.4时,随pH值升高,吸附量减少;(2)pH值在2.4—5.0时,随pH值的升高,吸附量上升,在pH=5.0时吸附量达到最大;(3)pH>5.0时,吸附量迅速下降.但溶液pH值对Cr(VI)光催化还原的影响与其对Cr(VI)吸附的影响存在显著差异,随pH值的升高,Cr(VI)的还原率下降,在溶液pH=1.0时60min内可还原完全,而在pH=9.0时经相同时间后Cr(VI)仍残余65.18%.俘获剂类型对Cr(VI)的还原也有一定影响.

The photocatalytic reduction of chromium （Ⅵ） in low concentration solution was studied with the presence of organic additives and P25. The effects of some factors, such as surface adsorption, solution pH and the molecule structure of organic additives on the photocatalytic reduction of Cr（ VI ） were explored. When solution pH was less than 2.4, the adsorption decreased with pH increasing. When pH was greater than 5.0, the ad- sorption decreased drastically with pH increasing. When solution pH is between 2.4 and 5.0, the adsorption increased with pH decreasing. The optimum pH for the adsorption of Cr（Ⅵ） was measured to be 5.0. Howev- er, the reduction rate of Cr（ Ⅵ）decreased with pH increasing, different from the adsorption amount of Cr（Ⅵ） changed with pH varying, because of redox potential decreasing, production precipitation and photochemical reduction. The reduction of Cr（Ⅵ） was affected by the type and the structure of organic additives too.