β-环糊精对亚甲基蓝光脱色表观动力学的影响

Effect of Apparent Kinetics of Photo-degradation of Methylene Blue by β-cyclodextrin

用紫外-分光光度法研究了β-环糊精（β-CD）对亚甲基蓝（MB）在紫外光照射下光脱色表观动力学和表观速率常数的影响．结果表明，纯MB的光脱色符合表观一级动力学反应过程，光脱色表观速率常数随pH值升高，先增大，然后趋于恒定．β-CD的存在，使MB光脱色表观动力学在pH≤10时为表观零级反应过程，在pH〉10时为表观一级脱色过程，光脱色表观速率常数在pH为2～12时，先增大，然后趋于恒定，最后再升高．β-CD／MB光脱色表观速率常数在pH≤4时大于纯MB光脱色表观速率常数，在pH〉4时小于纯MB光脱色表观速率常数．

Using ultraviolet spectrophotometric method, to reseach the influence of β-cyclodextrin （β-CD） to photo-degradation apparent kinetics and rate constants of methylene blue （MB） under irradiation of UV. The experiment results show that the apparent kinetics of MB photo-degradation were the pseudo-first-order reaction and the rate constants of MB photo-degradation were first increasing then invariable with increasing pH values. As the existence of β-CD, the apparent kinetics of MB photo-degradation were the pseudo-zero-order reaction at pH value less than 10.0 and the pseudo-first-order reaction at pH value more than 10.0 because of the formation of β-CD and MB complexes in the solution. The rate constants of photo-degradation of MB solution containing β-CD were first increasing then invariable at last increasing at pH value from 2 to 12. The rate constants of photo-degradation of β-CD/MB were larger than that of MB in pH≤4 and smaller than that of MB in pH 〉 4.