Improving the anti-fouling and fouling-release of PVDF UF membrane by chemically modified SiO2 nanoparticles

摘要

The highly hydrophobic nature of the PVDF membrane makes it prone to fouling. One approach to mitigate fouling is to alter membrane via surface modification. Under optimum conditions of membrane fabrication, in-situ membrane surface modification may achieve as a result of the spontaneous migration of hydrophilic/low surface energy component to the membrane upper surface; so-called surface segregation. Non-polar low surface energy polymers, such as polysiloxane, could render the surface with permanent fouling release ability. However, they cannot spontaneously segregate onto the polymer-water interface during phase separation due to the unfavorable solution thermodynamics. While some hydrophilic polymers such as polyethylene glycol (PEG) may improve the surface hydrophilicity and inhibit the adsorption and deposition of foulant onto surface, their low compatibility with the membrane matrix and consequent depletion during filtration process is considered as drawback. In this study, commercial SiO2 nanoparticles were chemically functionalized by silane coupling agent, which were then specifically designed either to form non-polar hydrophobic PDMS chains or PEG molecules on their surface. Modified nanoparticles were directly dispersed in casting solution and modified SiO2/PVDF blend membranes were prepared. These membranes were characterized with a wide range of techniques. Membrane performance was assessed by static protein adsorption and filtration experiments using BSA as a model foulant. Some of the highlights are as follows:•Surface functionalized SiO2 nanoparticles SiO2-COOH significantly improved the dispersion of particle in membrane matrix and the membrane with 2 wt.% nanoparticle loading showed more than 30% increase in flux recovery compared with control membrane and 20% improvement than membrane prepared with 2 wt.% unmodified SiO2;•With addition of only 0.5 wt.% surface modified SiO2 nanoparticles SiO2-COOH-PEG into the membrane solution, the resulting PVDF blend membrane showed 27% improvement in flux recovery after physical cleaning compared with the PVDF/unmodified SiO2 membrane.The conclusion is that the modified SiO2 nanoparticles acted as a carrier facilitated the migration of PDMS or PEG molecules that were encapsulated on SiO2 to the surface of the membrane, thus contribution to the change of surface composition of the membrane and therefore enhance the membrane fouling resistance property.