Synthesis of a novel composite nanofiltration membrane incorporated SiO2 nanoparticles for oily wastewater desalination

A novel composite nanofiltration membrane incorporated with silica nanoparticles was prepared by interfacial polymerization on polysulfone (PSF) ultrafiltration membrane. The silica nanoparticles (∼15 nm) were homogeneously dispersed in poly(amidoamine) (PAMAM) dendrimer aqueous monomers and incorporated in situ into the polyamide films. Series of tests including FTIR-ATR, AFM, XPS, etc. were performed to characterize the polyamide (PA)-SiO2 membrane's morphologies, structure, physical and chemical characteristics, separation properties and permeability, etc. The results showed that silica loading into the PA membrane resulted in roughness and hydrophilicity promotion. The permeation performance for PA-SiO2 membrane increased nearly 50% without loss of salt rejection rate by adding 1.0% (wt.) nano-SiO2 nanoparticles in aqueous solution. The order of rejection to inorganic salts is Na2SO4 > MgSO4 > MgCl2 > NaCl revealed both PA and PA-SiO2 membrane were nagatively charged. The zeta potentials testing results indicated addition of SiO2 will increase the negative charge quantities on the surface of PA-SiO2 membrane for negatively charged hydroxyl groups and silanol-covered nano-SiO2 surface. The value of molecular weight cutoff (MWCO) for PA-SiO2 membrane was about 1000 g/mol and the additive of SiO2 nanoparticles to PA membrane enlarges the pore size slightly. The PA-SiO2 membrane had a higher stable flux and could remove nearly 50% salts when treated with oily wastewater in one-cycle filtration. Desalination of oily wastewater using the nacomposite PA-SiO2 membrane is feasible.