Maghemite (?- Fe 2 O 3 ) nanoparticles which synthesized by a novel method were purchased and the properties of this magnetic nanoadsorbent were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis system of X-ray (EDAX) . The synthesized nanoparticles were used for treating the wastewater contaminated with the metal ions, such as Pb(II) , Zn(II) and Cd(II). A Response Surface Method (RSM) based on the Box–Behnken Design (BBD) was used to evaluate the effects of pH, temperature, initial metal concentrations and adsorbent dosage. The effects of pH and initial metal concentration showed signi?cant effects on ef?ciency, in terms of percent cadmium removal. The effects of pH and adsorbent dosage were significant effects on lead removal and the significant factors on zinc removal were pH, temperature and initial metal concentration. Signi?cant interactions between factors occurred on removal of lead and zinc with positive or negative effects either. The competitive adsorption of Pb(II), Zn(II) and Cd(II) onto Maghemite nanoparticles was systematically investigated in single and ternary systems. In single system, equilibrium studies showed that the adsorption of Zn(II) and Cd(II) followed the Freundlich model while the adsorption data of Pb(II) well fitted with Langmuir model. The maximum adsorption capacities were found to be 19.66, 12.43 and 22.27 mg/g respectively. In ternary system , the combined action of the metals was found to be antagonistic and the metal sorption followed the order of Pb(II) Cd(II) Zn(II) : the Langmuir isotherm fitted the data of Zn(II) and Pb(II) well but the isotherm data of Cd(II) correlated well with the Freundlich model. Kinetic data in ternary system are well fitted by pseudo second order model for all three kinds of heavy metal cations with correlation coefficients higher than 0.99 . The results obtained indicate that the adsorption capacity of Maghemite nanoparticles was strongly influenced by the adsorption conditions and would be optimized by controlling the significant factors for each heavy metal cations.
