Study Of Microwave-assisted Fenton-like Catalytic Oxidation Of PNP In Waterbased On Cuo/Al₂O₃Catalyst

Refractory organic compounds have complex molecular structure, strongbiological toxicity and stable chemical and physical prosperities. They can causegreat harm to the water environment because they are not biodegradable. Thisarticle developed a novel Fenton-like catalyst CuO/Al₂O₃and microwave-assistedFenton-like system ands studied its performance on removing PNP in wastewater.Reaction mechanism of the system was also discussed.CuO/Al₂O₃catalyst was prepared by impregnation-deposition method.Factors of preparing the catalyst were optimized by PNP removal rate, whichwere as follows: immersing solution of0.6mol/L Cu（NO3）2, with20gAl₂O₃/100mL Cu（NO3）2ratio, precipitation solution of0.4mol/L NaOH,calcination temperature of350℃for4h. By analyzing the SEM and BET resultsof CuO/Al₂O₃catalyst,234.85m2/g specific surface area was found, with totalpore volume of0.38cm3/g, average pore volume of4.55nm. The catalystpresented copious mesoporous structure.Both static and dynamic processes of microwave-assisted Fenton-likesystem were developed to remove PNP in wastewater. The static process wasconducted in microwave chemistry experiment furnace. For100ml50mg/L PNPsolution, the optimal condition was as follows:4g CuO/Al₂O₃catalyst,microwave power of100W, radiation time of6min,25mmol/L H2O2.99.41%PNP and77.9%TOC was removed within6min. The dynamic process wasconducted in EXCEL platform. For3L50mg/L PNP solution, when the optimalcondition was as follows:3g CuO/Al₂O₃catalyst equally placed in three layers,flow rate of15ml/min,20mmol/L H2O2, effluent temperature of60℃, PNPremoval rate of effluent maintained more than80%in200min and71.2%TOCwas removed. The stability and working life of the CuO/Al₂O₃catalyst were alsostudied. High catalytic activity was maintained after8times of repetitive usesshowing a great perspective in future wastewater treatment.Reaction mechanism of the system was studied by comparing PNP removalrates and·OH generation in different conditions. Little·OH was generated andlittle PNP was removed when microwave and catalyst existed solely in thesystem. With the combination of microwave and catalyst,·OH was generatedfrom H2O2, leading to the increase of PNP removal rate. The enhancing effect ofmicrowave was stronger than that of catalyst, and the combination effect ofthese two factors was stronger than adding up of their enhancing effect solely. Itshows that synergistic effect can be performed in microwave and Fenton-like system.