小球藻引发水中Cr(Ⅵ)的光化学还原研究

Photoreduction of chromium(Ⅵ) in aqueous solutions with chlorella vulgaris under metal halide lamps

重点研究了在金属卤化物灯（λ≥365nm,250W）光照下由小球藻类引发水体中Cr（Ⅵ）的光化学还原反应,考察了小球藻浓度、光照时间Cr（Ⅵ）初始浓度及pH值在通N2的条件下对Cr（Ⅵ）还原的影响.结果表明：随着小球藻浓度的增大,Cr（Ⅵ）的还原速率及还原率均增大;随着小球藻浓度的增大,光照时间的增加,Cr（Ⅵ）的初始浓度降低以及溶液pH值的降低,Cr（Ⅵ）的光化学还原率逐步增大.当pH≥6时,Cr（Ⅵ）的光化学还原反应基本消失;当pH=4时,六价铬的浓度在0.4-1.0mg/L范围内,小球藻浓度对应的吸光度Aalga在0.025-0.180范围内,Cr（Ⅵ）的初始还原速率拟合方程为V0=kC0^0.1718Aalga^0.5235.

The photochemical reduction of hexavalent chromium Cr（Ⅵ） in the presence of algae,chlorella vulgaris,was investigated under the irradiation of metal halide lamps（λ≥365 nm,250 W）.The affecting factors of photochemical reduction were studied in detail under ventilating N2,including exposure time, initial Cr（Ⅵ） concentration,initial chlorella vulgaris concentration and pH.The rate of Cr（Ⅵ） photochemical reduction increases with the increase of algae concentration and exposure time.It also increases with the decrease of initial Cr（Ⅵ） concentration and the pH value.When pH ≥6,the process nearly vanishes.When initial Cr（Ⅵ） concentration ranges from 0.4 to 1.0 mg/L and initial algae concentration ranges from Aalga=0.025 to Aalga=0.180,according to the results of kinetic analyses,the kinetic equation of Cr（Ⅵ） photochemical reduction in aqueous solution with alga under the irradiation of metal halide lamps can be expressed as V0=kC0^0.1718Aalga^0.5235 under the condition of pH=4.