Removal of Cadmium and Lead Ions from Aqueous Solution by Nanocrystalline Magnetite Through Mechanochemical Activation

In this study, the removal of cadmium and lead ions from aqueous solution by nanocrystalline magnetite was investigated. The nanocrystalline magnetite was synthesized by mechanochemical activation of hematite in a high energy planetary mill in argon atmosphere for 45 hours. The ability of the synthesized nanocrystalline magnetite for removal of Cd(II) and Pb(II) from aqueous solutions was studied in a batch reactor under different experimental conditions with different pHs, contact times, initial metal ion concentrations and temperatures. The solution’s pH was found to be a key factor in the adsorption of heavy metal ions on Fe3O4. The optimum pH of the solution for adsorption of Cd(II) and Pb(II) from aqueous solutions was found to be 6.5 and 5.5, respectively. The best models to describe the kinetics and isotherms of single adsorption were both the pseudo first and second-order kinetic models and Langmuir models, respectively, indicating the monolayer chemisorption of Cd(II) and Pb(II) on Fe3O4 nanoparticles. Moreover, the thermodynamic parameters (i.e., ∆H°, ∆S°, ∆G°) were evaluated which indicated that the adsorption was spontaneous and exothermic. The results suggested that the synthesized material (magnetite nanocrystalline particles) may be used as effective and economic absorbent for removal of Cd(II) and Pb(II) from aqueous solutions.