Nano Fe <sub> 2 </ Sub> The O <sub> 3 </ Sub> And Of Mn <sub> 2 </ Sub> O <sub> 3 </ Sub>, And Mixtures Thereof Surface Acid-base Properties And Adsorption Behavior

Iron and manganese are common variable valence elements in nature. In the sedimentary environment, the natural Iron and manganese oxides and hydroxides with surface charges is typical of the potential oxidant. Iron and manganese oxides as well as hydroxide minerals are very active constituents in soils because they are sensitive to environmental changes and they could control the availability of many nutrients and the toxicity of heavy metals.Fe₂O₃ and Mn₂O₃ nanoparticles were synthesized by precipitation method. Powder X-ray diffraction (XRD), and nitrogen adsorption-desorption, transmission electron microscopy (TEM) analysis methods were used to characterize the crystal graphic, structure, morphology and the specific surface area. And we made preliminary analysis about its solubility in aqueous solution, then we found that Iron oxides makes manganese oxides more stable in their mixtures. According to the experimental data of acid base titration of mesoporousα-Fe₂O₃ suspention, using FITEQL computer software and Constant Capacitance Model (CCM), the protonation and deprotonation constants of Fe₂O₃ and Mn₂O₃ were determined. Base on the acid-base constants the adsorption of heavy metal ions (Cd2+) at the surfaces of Fe₂O₃ and Mn₂O₃ was studied as a function of different pH. The solution components were distributed using computer soft ware MEDUSA and the surface complexation constants of Cd2+ at the surfaces were determined using computer software WinSGW. We calculated the free energies of adsorption reaction through the constants of Fe₂O₃ and Mn₂O₃ which belongs to the scope of chemical adsorption.The adsorption of As(V) at the surfaces of Fe₂O₃ and Mn₂O₃ was studied as a function of different pH and initial concentrations of As(V). The results showed that Fe₂O₃ and Mn₂O₃ and its mixture have a very strong adsorption capacity for As(V), which can be used to remove the As(V) ions in waste water. The experimental data from different As(V) initial concentration of the adsorption fitted the Langmuir equation and obtain the maximum adsorption capacity. The type of its adsorption complexes was analysed by testing Zeta potential.