Ag_(3)PO_(4)-Fe_(3)O_(4)/g-C_(3)N4非均相臭氧催化剂的制备及表征

Optimization of preparation conditions and characterization of Ag_(3)PO_(4)-Fe_(3)O_(4)/g-C_(3)N4 heterogeneous ozone catalyst

以MCM-41分子筛为模板剂采用热缩聚合成法制备g-C_(3)N_(4)载体,通过浸渍法对其进行负载制备Ag_(3)PO_(4)-Fe_(3)O_(4)/g-C_(3)N_(4)非均相臭氧催化剂,以油田废水预处理后水中COD的去除率为评价指标考察其制备条件,并利用响应曲面法Box-Behnken试验设计优化。结果表明:当MCM-41分子筛添加量为15%,g-C_(3)N_(4)载体焙烧温度为520℃、Fe_(3)O_(4)负载质量分数为50%,Ag_(3)PO_(4)负载质量分数为20%的,Ag_(3)PO_(4)-Fe_(3)O_(4)/g-C_(3)N_(4)非均相臭氧催化剂对油田废水预处理后,水中COD去除率达83.06%。通过微观表征可知,由模板剂引入制得的有序管状g-C_(3)N_(4)载体与Ag_(3)PO_(4)、Fe_(3)O_(4)负载后改变了其晶面的有序性并增大了催化剂的比表面积。通过负载改性提高了Ag_(3)PO_(4)的稳定性,以及与Fe_(3)O_(4)协同作用对臭氧催化的活性。磁性材料Fe_(3)O_(4)负载利于催化剂的回收,经磁性分离干燥后重复使用,仍具有良好的催化活性,同时经高温焙烧活化后的再生性能亦较好。

Using the MCM-41 molecular sieve as a template,g-C_(3)N_(4) catalyst carrier was prepared by thermal condensation.g-C_(3)N_(4) was used as a carrier,and the Ag_(3)PO_(4)-Fe_(3)O_(4)/g-C_(3)N_(4) supported catalyst by impregnation method.The COD removal rate in the water after the pretreatment of oilfield wastewater was used as an evaluation index to investigate its preparation conditions.The Box-Behnken experiment design of the response surface method was applied to optimize the preparation conditions.The results show that the Ag_(3)PO_(4)-Fe_(3)O_(4)/g-C_(3)N_(4) catalyst possesses good activity under the condition of template dosage of 15%(mass fraction),calcination temperature of 520℃,loading of 50%Fe_(3)O_(4)(mass fraction)and loading of 20%Ag_(3)PO_(4)(mass fraction).When the pH was 11,catalyst dosage was 500 mg/L,ozone intake flow rate was 200 L/h,the removal rate of COD can reach 83.06%after 30 min reaction.Based on the results of characterization of microstructure,the tubular g-C_(3)N_(4) prepared by the templates was successfully loaded with Ag_(3)PO_(4) and Fe_(3)O_(4),which changed the orderliness of crystal surface and increased surface area of the catalyst.The stability of Ag_(3)PO_(4) and the synergistic effect with Fe_(3)O_(4) on the catalytic activity of ozone were improved.Thus,it increases the contact probability and contact area between organic pollutants and catalysts and hydroxyl radicals in wastewater,which is helpful to improve the degradation of COD in wastewater.The Fe_(3)O_(4) loading in the catalyst has good magnetic properties.After magnetic separation drying and three times repeated use,the COD removal rate is still above 95%,showing good activity and catalytic stability.Besides,after roasting and activation at high temperatures,the COD removal rate is still above 83%.The results indicate that the catalyst has good regeneration performance and repetitive-use performance.Therefore,the catalyst is of important significance for effectively improving efficiency and reducing the cost of wastewater treatment.