Study On The Synthesis Of A Series Of Nano Iron Series Oxides And Their Thermal And Kinetic Studies On Surface Adsorption

Oxide nanoparticles of iron series elements exhibit a wide range of potential applications in environmental pollution treatment,because of their good adsorption ability.Aimed at the application of the series metal oxide nanoparticles in the field of water pollution treatment,a series of porous metal oxides were designed and synthesized.The adsorption properties of the synthesized nanoparticles as adsorbents for organic dye were studied.Several important factors,such as adsorption time,pH,temperature,and so on,were investigated.Based on the analysis of the thermal and kinetic data,the adsorption mechanism was proposed.The main contents of this paper are summarized as follows.（1）Mn doped-Fe₂O₃ nanoparticles were synthesized by a simple hydrothermal method.The adsorption performance of Congo red on this kind of new nano-material was studied.The results showed that the material had good removal ability to Congo red.The effects of temperature and adsorption time on the adsorption of Congo red were studied.The results showed that the adsorption kinetics of Congo red on Mn doped-Fe₂O₃ was consistent with the pesudo-second-order rate equation.The adsorption capacity of Mn doped-Fe₂O₃ nanoparticles for Congo red decreases with the enhancement of temperature,and the adsorption equilibrium states can be described by the Langmuir adsorption isotherm.Moreover,the adsorption capacity of the sample is different with different amounts of manganese.（2）NiO nanoparticles were synthesized by a one-step hydrothermal method,and then NiO nanoparticles were obtained by calcination at high temperature.The adsorption mechanism of NiO nanoparticles for Congo red was researched.The results show that the adsorption kinetics of Congo red on NiO nanoparticles follows the pseudo-second-order kinetic model,too.The adsorption capacity of NiO nanoparticles for Congo red also decreases with the temperature increasing,and the adsorption equilibrium can also be described by the Langmuir adsorption isotherm.The data of thermodynamic parameters（ΔH°,ΔS°,ΔG°）have been calculated and show that the adsorption of Congo red on NiO nanoparticles is a spontaneous process.The mainly driven force of Congo red being adsorbed on NiO nanoparticles is electrostatic attraction.（3）The synthesis of NiFe₂O₄ nanocrystal was performed by one-step high temperature calcination,the adsorption mechanism of the newly synthesized nanocrystal for methylene blue was explored.The results show that the adsorption process is also in accordance with the pseudo-second-order kinetic model and Langmuir isotherm model.The thermodynamic data of the results show that the interaction between NiFe₂O₄ nanocrystals and methylene blue is electrostatic attraction,and the process is endothermic and spontaneous.