Mn3O4催化臭氧化钻井废水的作用机理

通过静态实验,探讨了Mn3O4对钻井废水臭氧化过程的催化作用机理,考察了Mn3O4及Cl-对臭氧分解、水体湍动程度、羟基自由基抑制剂碳酸氢根和叔丁醇的加入对COD去除率的影响,分析了反应过程中TOC和pH的变化。结果表明,催化剂加量为100 mg/L时,臭氧分解率由单独臭氧时的38.2%增加到81.4%,Mn3O4对钻井废水中有机物的吸附去除率仅为2%,O3/活性炭体系对COD去除率与单独臭氧效果接近,说明臭氧在催化剂表面存在吸附作用,促进臭氧分解;水体不搅拌与搅拌速度增加为900 r/min时,COD去除率由52%增加到58%,搅拌程度对钻井废水COD去除效果影响不大;HCO3-浓度为100 mg/L时,COD去除率降低到41.2%,说明了体系中有羟基自由基产生;氯离子浓度为1 000 mg/L,臭氧的分解率降低了9.2%,证明了臭氧在催化剂表面的吸附作用;羟基自由基抑制剂叔丁醇的加入,使得COD去除率由54.3%降低为40.8%,证实了反应体系中存在羟基自由基。同时在反应过程中,体系的TOC 由191.9 mg/L降低至37.6 mg/L;pH由原来的11.2降低到6.3。实验现象说明,臭氧吸附在Mn3O4催化剂表面,分解产生羟基自由基,进而氧化去除钻井废水中有机物,这在某种程度上证明了Mn3O4催化臭氧化对有机物的降解遵循羟基自由基机理。

Mechanism of Mn3O4-catalyzed ozonation of drilling wastewater

Through static test,the catalysis mechanism of Mn3O4 ozonation process on drilling wastewater was discussed.The influence of ozone decomposition by Mn3O4 catalyst and Cl-,and the influence of the degree of water turbulence,the adding of hydroxyl free radical inhibitor bicarbonate and tert-butanol on COD removal rate and the change in TOC,pH during the reaction were studied.The results showed that when catalyst dosage was 100 mg/L,ozone decomposition rate increased from 38.2% which was under the condition of ozonation alone to 81.4%.The COD removal rate in the drilling water was just 2% by Mn3O4.The effect of system of O3/activated carbon on COD removal rate was close to the effect of only ozone.It noted that ozone was adsorbed on the catalyst surface,which promoted the decomposition of ozone.COD removal rate increased from 52% to 58% when water was without stirring and with the stirring speed increasing to 900 r/min,indicating that the degree of water turbulence had little effect on the COD removal in drilling wastewater.When HCO3- concentration was 100 mg/L,the COD removal rate reduced to 41.2%,indicating the generation of hydroxyl radical.And when Cl- concentration was 1 000 mg/L,the ozone decomposition rate was reduced by 9.2%,proving the adsorption effect of ozone on the surface of the catalyst.Hydroxyl free radical inhibitor tert-butyl alcohol reduced the COD removal rate from 54.3% to 40.8%,confirming the presence of hydroxyl radicals in reaction system.At the same tims in the reaction process,TOC in the system reduced from 191.9 mg/L to 37.6 mg/L,and pH reduced from 11.2 to 6.3.The experimental phenomena described that ozone was adsorbed on the surface of Mn3O4 catalyst surface,then decomposed to produce hydroxyl free radicals,and finally the organic matter of drilling wastewater was oxidized.In a certain extent,this proved that the catalytic ozonation of Mn3O4 on the degradation of organic matter followed the hydroxyl free radical mechanism.