Synthesis, characterization, and application of the novel nanomagnet adsorbent for the removal of Cr(vi) ions

The synthesis of an efficient adsorbent to remove chromium ions from water is challenging. Therefore, in this study, a new nanomagnet composite (Fe3O4/biochar/ZIF-8) was synthesized by a one-pot hydrothermal method using a metal–organic framework (MOF, ZIF-8) as a sacrificial template, citrus peels as a source of biochar, and iron oxide nanoparticles for magnetization. The synthesized nanocomposite showed a high efficiency toward the adsorption of Cr(vi) ions. The adsorption study showed that the experimental data were well-described using the Langmuir isotherm model and pseudo-second-order model. According to the Langmuir model, the adsorption capacities toward Cr(vi) adsorption were 77 and 125 mg·g−1 for Fe3O4/biochar and Fe3O4/biochar/ZIF-8, respectively, indicating the role of MOF in improving the adsorption performance. The Fe3O4/biochar/ZIF-8 showed an excellent adsorption performance in the presence of coexisting ions at a wide pH range using different eluents to study reusability up to five successive cycles. We can conclude from this study that this nanoadsorbent is a promising material for removing pollutants from environmental water samples.