α-MnO_2和δ-MnO_2催化剂的合成及其在尿素废水处理中的应用研究

Synthesis of α-MnO_2 and δ-MnO_2 catalysts and their applications in treatment of urea containing wastewater

采用水热法分别在酸性和碱性条件下合成了α-MnO_2和δ-MnO_2催化剂,利用XRD、N2-BET、Raman、H2-TPR对合成样品进行表征。将合成的α-MnO_2和δ-MnO_2催化剂用于催化废水中尿素水解,在不同水解温度、水解时间和催化剂质量浓度下比较了2种催化剂的催化活性。结果表明,δ-MnO_2催化剂具有较高的催化活性。以δ-MnO_2为催化剂,得到了尿素水解的最佳工艺条件:水解温度为165℃,水解时间为60 min,催化剂质量浓度为50 g/L。在最佳水解工艺条件下,尿素的降解率可达99.9%以上,此时水解液中剩余尿素的质量浓度仅为7.2 mg/L,达到了10 mg/L以下的排放标准。

The α-MnO2 and δ-MnO2 catalysts are synthesized under acidic and alkaline conditions respectively by hydrothermal method. The synthesized samples are characterized by XRD,N2-BET,Raman and H2-TPR. These two catalysts are respectively used for catalytic hydrolysis of urea in wastewater. The catalytic activities of α-MnO2 and δ-MnO2 catalysts are compared under different hydrolysis temperatures,hydrolysis time and catalyst dosage,respectively.The results illustrate that the catalytic activity of δ-MnO2 catalyst is higher than that of α-MnO2 catalyst.With δ-MnO2 as catalyst,the optimum process conditions for hydrolysis of urea are obtained that the temperature is 165℃,hydrolysis time is 60 min and catalyst dosage is 50 g·L-1.At the optimum conditions,the degradation rate of urea can exceed 99. 9%,and the remaining urea concentration in the hydrolysis solution is 7. 2 mg·L-1,which meets the 10 mg·L-1emission standard.