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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-MnO 2 and δ-MnO 2 catalysts were synthesized by hydrothermal method under acidic and basic conditions. The synthesized samples were characterized by XRD, N2-BET, Raman and H2-TPR. The synthesized α-MnO 2 and δ-MnO 2 catalysts were used to catalyze the urea hydrolysis in waste water. The catalytic activities of the two catalysts were compared at different hydrolysis temperature, hydrolysis time and catalyst mass concentration. The results show that δ-MnO 2 catalyst has higher catalytic activity. The optimum conditions of urea hydrolysis were obtained with δ-MnO 2 as catalyst: the hydrolysis temperature was 165 ℃, the hydrolysis time was 60 min, and the catalyst concentration was 50 g / L. Under the optimum conditions of hydrolysis, the degradation rate of urea was more than 99.9%. At this time, the concentration of residual urea in the hydrolyzate was only 7.2 mg / L, which reached the emission standard below 10 mg / L.