ZnOOH/浮石催化臭氧氧化对氯硝基苯的研究

Catalytic ozonation of p-chloronitrobenzene over ZnOOH-pumice

摘要:

为提高浮石催化臭氧氧化活性,以浮石为催化剂载体,硝酸锌为金属活性组分前驱物,采用等体积浸渍法制备了ZnOOH/浮石催化剂.以对氯硝基苯（p-CNB）为目标反应物,对ZnOOH/浮石、浮石催化臭氧化和单独臭氧氧化去除水中微量p-CNB的效果进行了比较.结果表明,与单独臭氧氧化相比,ZnOOH/浮石和浮石催化臭氧化工艺可以明显提高水中p-CNB的去除率,分别为93.4％和72.1％.反应体系添加叔丁醇对p-CNB催化降解效率产生明显抑制作用,说明催化臭氧化过程中羟基自由基（·OH）是主导氧化物种.催化臭氧分解和·OH捕捉实验表明,利用ZnOOH改性浮石,提高了浮石催化分解水中臭氧能力,增加了·OH生成量,从而提高水中p-CNB的降解效率.水质背景对催化臭氧化p-CNB的去除率影响较明显.ZnOOH/浮石催化剂重复使用10次,催化活性稳定.催化臭氧化过程中ZnOOH/浮石离子溶出量低.

Abstract:

Pumice-supported ZnOOH catalyst, taking zinc nitrate salt as precursor substance, was prepared by incipient wetness impregnation to enhance the catalytic ozonation capacity of pumice. Catalytic ozonation of p-chloronitrobenzene (p-CNB) in aqueous solution was conducted, wherein pumice and ZnOOH-pumice were used as the catalysts. The catalyst showed significant catalytic activity in the decomposition of p-CNB in aqueous solution. It was found that the processes of ozonation/ZnOOH-pumice and ozonation/pumice could increase the removal efficiency of p-CNB by 93.4 % and 72.1 %, respectively, compared with that achieved by sole ozonation. tert-Butyl alcohol remarkably increases the removal efficiency of catalytic p-CNB ozonation, which suggests that p-CNB degradation follows the mechanism of hydroxyl radical (·OH) oxidation. Catalytic ozone decomposition and ·OH captured show that ZnOOH-pumice catalyzed ozone generates the highest ·OH concentrations under the present experimental conditions compared with that obtained from the ozone/pumice and ozone-alone systems. Different water qualities show a very strong influence on the catalytic ozonation of p-CNB. From a practical point of view, ZnOOH-pumice shows promise for use in water treatment because it retains its catalytic activity for up to ten successive cycles and the residual ion content was minimal after catalytic ozonation.