Removal of 4-nonylphenol using magnetite modified with silica based molecularly imprinted polymers

Abstract

This study developed and evaluated magnetic molecularly imprinted polymers (MMIPs) for detecting and identifying 4-nonylphenol (NP). The MMIPs were engineered by synthesizing magnetic Fe₃O₄ particles via co-precipitation, resulting in particles with an average size of approximately 204.7 nm. These particles were subsequently modified with silica using a sol-gel process to form Fe₃O₄.SiO₂. The molecular imprinting process involved polymerizing Fe₃O₄.SiO₂ with a mixture that included NP (template molecule), methacrylic acid (functional monomer), azo(bis)isobutyronitrile (initiator), and ethylene glycol dimethacrylate (cross-linker). Characterization techniques, such as FTIR spectroscopy, confirmed the presence of functional groups, indicating successful modification and imprinting. TGA demonstrated thermal stability up to 250°C, validating the robustness of the synthesized MMIPs. The optimal adsorption capacity was identified at pH 9.989, with a maximum adsorption capacity of 5 mg/g, which shows an enhancement over non-imprinted polymers. Isotherm adsorption studies indicated a better fit for the Freundlich model, with an R squared value of 0.98 for MMIPs, suggesting the occurrence of a multilayer adsorption process. Kinetic studies revealed that the MMIPs adhered to the pseudo-second-order kinetic model, confirming their efficiency in NP adsorption. The reusability test demonstrated that the MMIPs maintained a consistent adsorption capacity over three cycles, with a minimal decrease of 5 %.