| In this paper, micro/nanostructured manganese oxides materials MnO2and Mn2O3have been prepared by hydrothermal and template methods, respectively. X-raydiffraction (XRD) and field-emission scanning electron microscopy (FESEM)are used to characterize the compositions, structures and morphologies of theproducts. Their adsorption properties have also been investigated.-MnO2micronests composed of nanowires and γ-MnO2microspheres composed ofnanorods have been fabricated via a hydrothermal reaction of manganese salt(MnSO4·H2O) and oxidants (K2S2O8, Na2S2O8). The-MnO2has been proved to possesan enhanced adsorption capacity than γ-MnO2due to its large specific surface area. Theeffects of the concentrations of the Congo red solutions, pH and temperature on theadsorption process have been investigated. The results indicated that the amount ofCongo red adsorbed on the-MnO2increased with the concentration of Congo redsolution, but the amplification decreased, acidic environment did benefit to adsorptionprocess and temperature had no obvious effect. Furthermore, adsorption kinetics of-MnO2has been examined. Pseudo-second-order kinetics described the adsorptionprocess very well which fitted the Langmuir isotherm, with maximum monolayeradsorption capacity of625mg·g-1. Thermodynamic studies revealed that the adsorptionwas spontaneous and endothermic.Micro/nanostructured Mn2O3was obtained by annealing MnCO3precursor at750℃for4h in the air. We investigated the effect of reactant molar rate, reaction temperatureand time on the morphology of MnCO3precursor, which did further influence themorphology and inner structure of Mn2O3. The results showed that the remove rates ofCongo red on Mn2O3at120min were73.58%,78.64%,84.63%when the reactantmolar ratio of MnCO3precursor were1:20,1:4and1:2, which were78.98%,85.75%,78.64%when the reaction temperature of MnCO3precursor were90℃,140℃and180℃, which were92.65%,78.64%,84.94%when the reactiontime of MnCO3precursor were1h,5h and12h. |
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