Surface functionalization of ceramic membranes with 3-aminopropyl groups using the sol-gel method

Planar ceramic Al₂O₃ membranes were functionalized with polysiloxane and polysilsesquioxane layers containing 3-aminopropyl groups using the sol-gel method. SEM images show the formation of polysiloxane or polysilsesquioxane layers on the membrane surfaces with the thickness of 0.35 and 4.4 nm, respectively. Infrared spectroscopy data confirmed the presence of the polysiloxane network and functional groups introduced during the synthesis. Measurements of the contact angles on the membrane surfaces showed that the hydrophilicity of the active layer is practically independent of the type of the structuring agent (tetraethoxysilane or 1,2-bis(triethoxysilyl)ethane), and the introduction of the methyl groups increases the hydrophobicity of the surface layer. According to the filtration studies, all functionalized membranes are capable of retaining Cu(II) ions during filtration of diluted solutions due to the complexation of the amino groups in the selective layer with these ions.