Magnetite nanoparticles for removal of heavy metals from aqueous solutions: synthesis and characterization

Fe₃O₄ magnetic nanoparticles were synthesized by co-precipitation method. The structural characterization showed an average nanoparticle size of 8 nm. The synthesized Fe₃O₄ nanoparticles were tested for the treatment of synthetic aqueous solutions contaminated by metal ions, i.e. Pb(II), Cu(II), Zn(II) and Mn(II). Experimental results show that the adsorption capacity of Fe₃O₄ nanoparticles is maximum for Pb(II) and minimum for Mn(II), likely due to a different electrostatic attraction between heavy metal cations and negatively charged adsorption sites, mainly related to the hydrated ionic radii of the investigated heavy metals. Various factors influencing the adsorption of metal ions, e.g., pH, temperature, and contacting time were investigated to optimize the operating condition for the use of Fe₃O₄ nanoparticles as adsorbent. The experimental results indicated that the adsorption is strongly influenced by pH and temperature, the effect depending on the different metal ion considered.