CoFe2O4 and NiFe2O4@graphene adsorbents for heavy metal ions – kinetic and thermodynamic analysis

Abstract

Magnetic cobalt and nickel ferrites (CoFe₂O₄ & NiFe₂O₄) with graphene nanocomposites (CoFe₂O₄–G & NiFe₂O₄–G) were synthesized via a solvothermal process and used as an adsorbent for the removal of lead (Pb(II)) and cadmium (Cd(II)) ions from aqueous solution. The as-prepared materials were characterized by field emission-scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), a Brunauer–Emmett–Teller (BET) surface area analyzer, transmission electron microscopy (TEM) and VSM analysis. To probe the nature of the adsorbent, various experiments were investigated like contact time, adsorbent dose, solution pH and temperature were optimized. The isotherm model fitting studies demonstrated that the data fitted the Langmuir isotherm model well. The highest adsorption equilibrium for Pb(II) is 142.8 and 111.1 mg g⁻¹ at pH of 5 and 310 K for CoFe₂O₄–G & NiFe₂O₄–G; while for Cd(II) it was 105.26 and 74.62 mg g⁻¹ at pH of 7 and 310 K. The results show that such type of materials could be used for the removal of heavy metal ions from water for environmental applications.