Simple and efficient strategy for α-MnO2/C by in-situ synthesis and its performance for degrading urea process wastewater

A simple and low-cost method for the synthesis of α-MnO2/C catalyst was proposed, in which KMnO4 was reduced in-situ by cellulose in urea solution. The heterogeneous catalytic degradation of urea wastewater were carried out over α-MnO2/C. The effect of KMnO4-urea solution concentration on the structure and performance of the catalysts was investigated. The results indicate that δ-MnO2 tends to curl and collapse into tunnel structure of α-MnO2 as the concentration of KMnO4-urea solution increases, leading to α-MnO2 is evenly distributed on carbon carrier. When the concentration of KMnO4-urea solution is appropriate, the catalyst has not only a large specific surface area but also high oxygen vacancy density, which is the key to be able to completely degrade the urea process wastewater. The reaction kinetics show that the catalytic hydrolysis of urea behaves as a pseudo-first-order reaction. A possible catalytic mechanism of urea hydrolysis over α-MnO2/C was proposed. In addition, the reusability experiments show that the α-MnO2/C catalyst has a good recycling ability. [Display omitted] •α-MnO2/C was synthesized through KMnO4 in-situ reduced by cellulose.•The uniform distribution of MnO2 on carbon carrier improves the utilization of MnO2.•Mn3+ and oxygen vacancy over α-MnO2/C are critical for urea hydrolysis.•Urea in wastewater can be almost completely degraded using this catalyst.