Magnetically separable silica-chitosan hybrids for efficient phosphate adsorption in aqueous solution

In the present study, magnetic silica-chitosan hybrid (NMP@SiO₂/CPTMS/Chi) was synthesized via a convenient and green sol-gel technique under room temperature, and the material was used as a highly efficient magnetic adsorbent for the removal of phosphate ions in water. While the magnetic properties of NMP from iron enable the material to be quickly separated via magnetic separation, the abundant active sites from the chitosan made the hybrid exhibit high adsorption capacity for phosphate ions. At pH 6, the removal of phosphate ions followed the pseudo-second-order (PSO) kinetic model with the adsorption rate constant (k₂) of 5.9 × 10^-3 mg g⁻¹ min⁻¹ and obeyed the Langmuir isotherm model with a maximum adsorption capacity (q_max) of 15.06 mg g⁻¹, outperforming most of the previously reported adsorbents. Stability tests and derivative thermogravimetry (DTG) analysis demonstrated that NMP@SiO₂/CPTMS/Chi remained stable even under strongly acidic conditions and possessed high thermal stability, respectively. The synergistic combination of high adsorption capacity, acid stability, thermal stability, and facile magnetic separation renders NMP@SiO₂/CPTMS/Chi a promising adsorbent for wastewater treatment and environmental remediation. Overall, this innovative material represents a significant advancement in phosphate removal, offering a sustainable and effective solution to address the global challenge of water pollution and protect aquatic ecosystems.