| Three kinds of crystal structure of manganese dioxide ?-MnO 2,?-MnO2 and 8-MnO2 were prepared by hydrothermal method through different conditions. These materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). Using electrolytic manganese dioxide (EMD)??-MnO2,?-MnO2 and 8-MnO 2 as adsorbents,the effects of parameters such as the contents of adsorbent?pH value and adsorption time, the removal of methylene blue(MB) and methyl orange(MO) from aqueous solutions were investigated. In addition, the adsorption thermodynamics and kinetics were also studied. The results showed that 8-MnO 2 is the best adsorbent for MB and MO; Langmuir model and pseudo-second-order kinetic model fits the experimental data more adequately; the adsorption process of MB and MO are spontaneous endothermic process, after the completion of the adsorbed molecules of disorder degree increased; When using 3mg 8-MnO2 adsorption 30ml MB and MO solution, the maximum adsorption quantities are 195 mg/g and 119 mg/g,respectively.Preparing of three kinds of powder electrodes by tabletting method, the ratio of 8-MnO2 and graphite were 1:1,2:1 and 3:1,respectively. Analyzed the electrode by oxygen evolution potential and the experiment of strengthen of the electrode life, and compared the electrical catalytic performance of the three electrodes by electrical catalytic degradation of methylene blue simulated wastewater. The results showed that when the ratio of ?-MnO 2 and graphite is 2:1, the performance of the electrode is most stable. The influence of different conditions on the effect of degradation of methylene blue were investigated,such as the initial organic matter concentration, current density, temperature, plate spacing, etc. The results showed that when the initial concentration of methylene blue is 50 mg/L, current density is 20 mA/cm2,temperature is 25?, for optimal plate spacing is 2 cm, the removal of methylene blue by electrode is best. |
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