| Summary: | 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 (<i>C</i>). One portion was doped with magnetite (<i>Fe</i><sub>3</sub><i>O</i><sub>4</sub><i>+C</i>) and the other with cobalt ferrite (<i>CoFe</i><sub>2</sub><i>O</i><sub>4</sub><i>+C</i>). Characterization studies showed that <i>C</i> has a high surface area (1635 m<sup>2</sup> g<sup>−1</sup>) due to the development of microporosity. For <i>Fe</i><sub>3</sub><i>O</i><sub>4</sub><i>+C</i> the magnetic particles were nano-sized and penetrated the material’s texture, saturating the micropores. In contrast, <i>CoFe</i><sub>2</sub><i>O</i><sub>4</sub><i>+C</i> 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<sup>−1</sup> (1.88 mmol g<sup>−1</sup>) and 249 mg g<sup>−1</sup> (1.20 mmol g<sup>−1</sup>); while for Cd(II) was 269 mg g<sup>−1</sup> (2.39 mmol g<sup>−1</sup>) and 264 mg g<sup>−1</sup> (2.35 mmol g<sup>−1</sup>) for the <i>Fe</i><sub>3</sub><i>O</i><sub>4</sub><i>+C</i> and <i>CoFe</i><sub>2</sub><i>O</i><sub>4</sub><i>+C</i>, 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 HNO<sub>3</sub>. 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.
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