Mesoporous magnetic MnFe2O4@SiO2-chitosan nanocomposite for efficient adsorptive removal of Zn(II) and Cd(II) ions from aqueous media

This work is conducted on chitosan functionalized MnFe2O4@SiO2@chitosan mesoporous magnetic nanocomposites as efficient adsorbents for the treatment of Zn(II) and Cd(II) ions from aqueous solution. The nano-adsorbents were produced using a simple co-precipitation route, followed by silica coating and chitosan functionalization. These modifications were done to improve surface activity and the adsorption of metal ions. The adsorption of metal ions was systematically performed at different initial metal concentrations (20–300 mg·L⁻¹), pH levels (2–7), contact times (5–500 min), and temperatures (25–60°C). The experimental equilibrium adsorption capacities (qₑ) reached 204.08 mg/g for Zn(II) and 172.41 mg/g for Cd(II), while the Langmuir maximum adsorption capacities (qₘₐₓ) were 294.46 mg/g and 288.18 mg/g, respectively. Kinetic analysis showed that the adsorption data best fit the pseudo-second-order model, with rate constants (k2) of 5.1 × 10⁻4 g·mg⁻¹ ·min⁻¹ for Zn(II) and 1.8 × 10⁻4 g·mg⁻¹ ·min⁻¹ for Cd(II), suggesting chemisorption as the primary mechanism. After the first cycle, the adsorption efficiency was 92 % for Zn(II) and 86 % for Cd(II), and even after five cycles, the adsorbent maintained 87 % (Zn) and 78 % (Cd) efficiency, showing excellent stability and reusability. These findings underscore the potential of MnFe2O4@SiO2@chitosan as a sustainable and effective adsorbent for removing heavy metals from wastewater.