Efficient removal of cadmium ions from water by adsorption on a magnetic carbon aerogel

Carbon aerogels are attracting much attention as adsorbents due to their high specific surface and large accessible pores. Herein, we describe a successful synthesis of a magnetic carbon aerogel (MCA) using sodium alginate (SA) as the main carbon source, gelatin (G) as a cross-linking agent and secondary carbon source, and Fe₃O₄ nanoparticles as the magnetic component. A simple pyrolysis treatment at 550 °C under N₂ transformed a Fe₃O₄/SA/G hydrogel precursor into the MCA. The obtained magnetic carbon aerogel possessed a high specific surface area (145.7 m²/g), a hierarchically porous structure, and an abundance of surface hydroxyl (-OH) and carboxyl (-COOH) groups, resulting in outstanding sorption properties for aqueous Cd(II) (an adsorption capacity of 143.88 mg/Lmg/g). The mechanism of Cd(II) adsorption by the MCA was investigated, with the results obtained suggesting that the MCA removed cadmium ions from water by both electrostatic adsorption and complexation. Since the MCAs contained Fe₃O₄ nanoparticles, they could easily be separated and recovered from water using a magnet. This study thus identifies a promising and efficient technology for removing Cd(II) ions from aqueous solutions.