Preparation And Catalytic Properties Of MnO₂ Composites

Because of their abundant resources, low cost, environmental friendly, good adsorption performance and catalytic properties, MnO₂ have been widely used as catalyst for treatment of organic pollutants in the wastewater. In this paper, MnO₂/graphene?MnO₂/rGO? and Ce doped MnO₂?Ce/MnO₂? have been synthesized successfully. The property and structure of catalysts were characterized by XR, FT-IR, SEM, Raman spectra, BET, XPS and EIS. The catalytic activity of catalyst was studied with RhB as model contaminants.The MnO₂/rGO was prepared by co-precipitation method. The effects of reduction times and loading amounts of grapheme on the composition, electrical conductivity, adsorption and catalytic activity of catalysts were explored. Meanwhile, the effects of catalyst dosage, hydrogen peroxide concentration and initial concentration of Rh B on the catalytic oxidation process of RhB. The experiment results show that with the increase of reduction time, catalytic activity and electrical conductivity of the composite material increased first and then decreased, the crystal form of MnO₂ changed from ? to ?, then changed to cryptomelane; With the increase of graphene loading amounts, the electrical conductivity and adsorption of MnO₂/rGO increases, but the catalytic activity of MnO₂/rGO increased first and then decreased. The MnO₂/rGO with 10% graphene loaded, reducted for 2h with the pH of solution adjusted to 11 by ammonia, has best catalytic activity. The crystal form of MnO₂/rGO with best catalytic activity was ?; the catalyst was mesoporous material with aperture mainly distributing in 2.5 nm 4.5 nm and its specific surface area was 143m2/g; the electron transfer resistance of MnO₂/rGO is 0.18 times of manganese dioxide. After 1h, the degradation rate of RhB was 83%, when 5mg prepared catalyst and 2m L 30%H2O₂ was add into 100 mL 10mg/L Rhodamine B solution.Ce/MnO₂ was prepared by co-precipitation method as well. The effects of doping amount of Ce and calcination temperature on catalytic activity of Ce/MnO₂ were studied. The experimental results show that the catalytic activity of Ce/MnO₂, calcined at 200? for 2h and 10% Ce doped, was best. The crystal form of MnO₂ was ?. XPS test results show that the Ce exist in composite catalyst as Ce4+. After 1h, the degradation rate of RhB was 86%, when 5mg prepared catalyst and 2m L 30%H2O₂ was add into 100 m L 10mg/L Rhodamine B solution.