Using octadecylsilane coated iron oxide magnetic nanoparticles as adsorbent for removal of dicyclohexyl phthalate

Todays, magnetite nanoparticles (Fe3O4 MNPs) are widely used in various fields such as, biomedical, drug delivery, catalysis and magnetic separations. They showed broad applications for isolation and pre-concentration of some target analytes. However, naked Fe3O4 MNPs are very likely to be oxidized and aggregate and are not suitable for extraction or removal of chemicals. Therefore, it is necessary to protect these MNPs with proper organic or inorganic groups to improve their surface as a selective and applicable adsorbent. Normally, coating with silica is viewed to improve the stability and prevent oxidation of the Fe3O4 MNPs [1]. In the present study, magnetic Fe3O4@SiO2 NPs functionalized with octadecyl groups (Fe3O4@SiO2-C18) were synthesized, characterized and employed as powerful nano sorbent for removal of dicyclohexyl phthalate (DCP) from aqueous solutions. For this purpose, after chemical synthesis of Fe3O4 NPs via co-precipitation method, a silica layer was coated on the surface of NPs to form Fe3O4@SiO2 NPs and subsequently, ocatdecyl silane groups were chemically synthesized on the Fe3O4@SiO2 surface using octadecyl trichlorosilane. The structure, magnetic property and morphology of the prepared NPs were investigated by FT-IR, DRS, VSM, XRD and SEM instruments. The results showed the good functionalization with a nanometric size of synthesized particles. The experimental factors affecting the DCP adsorption including solution pH, ionic strength, adsorbent dosage and contact time were studied via orthogonal array design (OA16) using 50 mL solution containing 50 mg L-1 DCP and optimum values were determined with UV-Vis spectrophotometer. In order to study the kinetic and isotherm of adsorption, four kinetic models (pseudo-first-order, pseudo-second-order, intra-particle diffusion and Elovich) and three well-known isotherm models (Langmuir, Freundlich and Tempkin) were studied in the optimized conditions. The results showed the high adsorption efficiency ( 95 %) in a short time. Finally, the applicability of proposed adsorbent for removal of DCP from real water samples was examined and satisfactory results were obtained.