Synthesis of FeO@SiO₂-DNA core-shell engineered nanostructures for rapid adsorption of heavy metals in aqueous...

Creating novel and innovative nanostructures is a challenge, aiming to discover nanomaterials with promising properties for environmental remediation. In this study, the physicochemical and adsorption properties of a heterogeneous nanostructure are evaluated for the rapid removal of heavy metal ions from aqueous solutions. Core-shell nanostructures are prepared using iron oxide cores and silica dioxide shells. The core is synthesized via the co-precipitation method and modified in situ with citric acid to grow a carboxyl layer. The shell was hydrolyzed/condensed and then functionalized with amine groups for ds-DNA condensation via electrostatic interaction. The characterization techniques revealed functional FeO@SiO₂-DNA nanostructures with good crystallinity and superparamagnetic response (31.5 emu g^-1). The predominant superparamagnetic nature is attributed to the citric acid coating. This improves the dispersion and stability of the magnetic cores through the reduction of the dipolar-dipolar interaction and the enhancement of the spin coordination. The rapid adsorption mechanism of FeO@SiO₂-DNA was evaluated through the removal of Pb(ii), As(iii), and Hg(ii). A rapid adsorption rate is observed in the first 15 min, attributed to a heterogeneous chemisorption mechanism based on electrostatic interactions. FeO@SiO₂-DNA shows higher adsorption efficiency of 69% for Pb(ii) removal compared to As(iii) (51%) and Hg(ii) (41%). The selectivity towards Pb(ii) is attributed to the similar acid nature to ds-DNA, where the ionic strength interaction provides good affinity and stability. The facile synthesis and rapid adsorption suggest a promising nanostructure for the remediation of water sources contaminated with heavy metal ions and can be extended to other complex molecules.