[Preparation of the Silane Monolayer on Magnetite Nanoparticles and Its Performance with Respect to Phosphate Removal...

We studied the loading of N-(2-Aminoethyl)-3-aminopropyl trimethoxy silane from aqueous solution as a monolayer on magnetite nanoparticles and examined the phosphate removal performance of the generated adsorbent (silane monolayer on magnetite nanoparticles, abbreviated as MSMNPs). The results indicate that silane monolayer adsorption on magnetite nanoparticles occurred at low concentrations (equilibrium silane concentration <300 mg·L^-1) and a~100% surface monolayer coverage by silane could be established at a temperature ≥ 90℃ or a NaCl concentration ≥ 0.1 mol·L^-1. The FTIR and XPS spectra indicate that hydrolyzed silane and magnetite nanoparticles are chemically linked. The loading of silane as a monolayer did not significantly change the saturation magnetization. The adsorption isotherm of phosphate based on MSMNPs fit the Langmuir model better, with a calculated maximum adsorption capacity reaching 7.59 mg·g^-1. The adsorption and desorption of phosphate by MSMNPs are very fast, exceeding 90% within 30 min and reaching an equilibrium within 1 h. In conclusion, MSMNPs are novel adsorbents with easy separability, which enables the repeated use, and rapid adsorption and desorption of pollutants.