Urea Hydrolysis Over α-MnO2 Catalyst: Preparation, Characterizations and Influencing Factors

Abstract MnO 2 was screened from various metal oxides and different crystal structures of MnO 2 were prepared, which were used to hydrolyze urea process wastewater for energy conservation and environmental protection. The characterizations of XRD, SEM, Raman, FT-IR, XPS and H 2 -TPR were employed and the hydrolysis experiments were carried out, demonstrating that oxygen vacancy on the surface of MnO 2 might be the catalytic activity source on urea hydrolysis. By optimizing reaction influencing factors, the residual urea concentration reduced to 1.61 mg/L over α -MnO 2 , far below the effluent standard. Meanwhile, the temperature of heterogeneous hydrolysis over α-MnO 2 dropped drastically compared with that of thermal hydrolysis. Further, the kinetic parameters of hydrolysis were obtained over α -MnO 2 . And α -MnO 2 also showed excellent recycling ability on the reused test. Graphical Abstract Effect of different crystal structures MnO2 on urea degradation rate. (Catalyst dosage is 50 g/L, reaction time is 60 min, temperature is 165oC.)