Synthesis of magnetic adsorbents based carbon highly efficient and stable for use in the removal of Pb(II) and Cd(II) in aqueous solution

In this study, two alternative synthesis routes for magnetic adsorbents were evaluated to remove Pb(II) and Cd(II) in an aqueous solution. First, activated carbon was prepared from argan shells (C). One portion was doped with magnetite (Fe3 O4 +C) and the other with cobalt ferrite (CoFe2 O4 +C). Characterization studies showed that C has a high surface area (1635 m2 g−1) due to the development of microporosity. For Fe3 O4 +C the magnetic particles were nano-sized and penetrated the material’s texture, saturating the micropores. In contrast, CoFe2 O4 +C conserves the mesoporosity developed because most of the cobalt ferrite particles adhered to the exposed surface of the material. The adsorption capacity for Pb(II) was 389 mg g−1 (1.88 mmol g−1) and 249 mg g−1 (1.20 mmol g−1); while for Cd(II) was 269 mg g−1 (2.39 mmol g−1) and 264 mg g−1 (2.35 mmol g−1) for the Fe3 O4 +C and CoFe2 O4 +C, respectively. The predominant adsorption mechanism is the interaction between-FeOH groups with the cations in the solution, which are the main reason these adsorption capacities remain high in repeated adsorption cycles after regeneration with HNO3. The results obtained are superior to studies previously reported in the literature, making these new materials a promising alternative for large-scale wastewater treatment processes using batch-type reactors.