Construction of Fe3O4/xSiO2/ySiO2 Nanoparticles for Pesticide Removal from Water: Improved Dispersion Stability and Adsorption Capacity

Highly efficient and reusable adsorbents for pesticide removal from wastewater have received increasing attention. In this study, Fe₃O₄ was synthesized using the solvothermal method. Fe₃O₄/xSiO₂ and Fe₃O₄/xSiO₂/ySiO₂ were obtained through layer-by-layer silica (SiO₂) coating on the surface of Fe₃O₄. SiO₂ coating improved the dispersibility of the adsorbent, which can be separated from water rapidly under the action of the external magnetic field. The adsorption capacity of the adsorbent was investigated through removing pyraclostrobin from synthetic wastewater. The adsorbent showed the highest adsorption effect at the adsorbent concentration of 1 mg mL^-1, at a pH of 7, and the adsorbent time of 110 min. The fitting model of the adsorption process conformed to the second-order kinetic model and the Langmuir model. The maximum adsorption capacity of Fe₃O₄/xSiO₂/ySiO₂ nanoparticles was 94.89 mg g^-1, and the removal efficiency was about 96% at adsorption equilibrium. Acetone as the eluent can effectively desorb the adsorbent, and the desorbed adsorbent had high reusability. Particularly, the removal efficiency was still greater than 86% after 9 times of reuse. These results provide a reference for designing reusable nanoparticles to effectively absorb pesticides in wastewater.