浮石催化水中臭氧分解研究

Catalytic ozone aqueous decomposition promoted by pumice

为考察浮石表面化学性质对水中臭氧分解的影响,测定了浮石催化水中臭氧分解的速率常数并探讨催化臭氧分解的途径.结果表明:浮石促进水中臭氧一级分解速率常数提高了37.4%;利用叔丁醇捕获生成的羟基自由基,催化臭氧分解速率常数降低了45.2%,浮石催化臭氧分解生成了羟基自由基;浮石表面羟基密度与催化臭氧分解率成正相关;随着溶液初始pH值增大,单独臭氧分解和浮石催化臭氧分解率均增加;由浮石pHpzc决定的表面电荷状态与催化臭氧分解效果有关,表面接近电中性时对催化臭氧分解有利.水中臭氧分解主要发生在浮石表面,浮石表面的金属氧化物可能是催化水中臭氧分解的活性物质。

To investigate the influences of pumice chemical surface properties on catalytic ozonation,the decomposition rate of ozone in water was measured over pumice and the mechanism of ozone catalytic decomposition was discussed.The results showed that the pseudo-first order rate of ozone decomposition increased by 37.4 % for pumice catalysts.When t-BuOH was added,the rate constant decreased by 45.2 % for pumice catalysts,suggesting that the decomposition of ozone followed the mechanism of hydroxyl radical（·OH）.The removal of ozone increased with the increasing of surface hydroxyl groups.High initial pH presented a positive effect in the ozone alone and ozone/pumice system.The pumice surface at nearly zero charged point was favorable for the decomposition of ozone in aqueous solution.Ozone aqueous decomposition in the presence of pumice takes place mainly on the natural material surface.The presence of metal oxides in pumice might catalyse ozone decomposition into more active radicals.