Ionic liquid-modified magnetic nanoparticle composite for the selective adsorption of chromium ions in water

Adsorption methods are widely used in the removal of heavy metals from aquatic environments, and adsorbents are crucial for adsorption efficiency. In this study, a magnetic nanoparticle composite material, Fe₃O₄@PEG@IL, modified with an imidazole-based ionic liquid [C _n MI _m ]HCO₃ (n = 2, 4, 6, 8) was used as an adsorbent to adsorb the heavy metal chromium (Cr(vi)) in aquatic environments, and the adsorption conditions were optimized. Moreover, the selective adsorption of Cr(vi) by the adsorbent was explored. The results show that when the pH value of the aqueous solution was 3.0, the solution temperature was 65℃, the amount of Fe₃O₄@PEG@IL added was 25 mg, and the time of adsorption reaction was 2.5 h, a good adsorption effect would be achieved, with an adsorption rate of 99.5%. Meanwhile, Fe₃O₄@PEG@IL had high adsorption selectivity for Cr(vi), and heavy metal cations, such as Pb²⁺, Hg²⁺, Cd²⁺, and Cu²⁺, did not interfere with the adsorption of Cr(vi). Moreover, the adsorbent was easy to recover and had good reusability.