Highly efficient removal of heavy metals from waters by magnetic chitosan-based composite

Magnetic chitosan composite (MCC) made by chitosan matrix embedding magnetite/maghemite were developed for the removal of toxic Cu(II), Pb(II), and Ni(II) from water. Thermogravimetric (TGA) and Zeta potential analyses showed that MCC contains ca. 50 wt % of chitosan and presents a value of isoelectric point (pH_IEP) around 8-8.5. The magnetization curve revealed a saturation magnetization of 12 emu g⁻¹, which indicates that MCC can be easily recovered by magnetic separation. Adsorption of the heavy metals to MCC reached equilibrium within 120 min with maximum uptakes of 108.9 mg g⁻¹, 216.8 mg g⁻¹ and 220.9 mg g⁻¹ for Ni(II), Cu(II) and Pb(II), respectively. The results show that the amino and hydroxyl functional groups of chitosan are involved in the adsorption process. The reported adsorption capacity from organic pollutants, such as hydrocarbons, along with the high adsorption capacity shown for heavy metals, point out MCC being a promising versatile adsorbent for wastewater treatments.