Improving the flux of PDMS membranes via localized heating through incorporation of gold nanoparticles

Noble metal nanoparticles (NPs) can efficiently release heat under optical excitation. Applying this principle of photothermal heating, it is possible to locally heat membranes containing noble metal NPs to increase the membrane flux during the separation process by mere light irradiation, while not altering selectivities. Earlier work involved rather polar membrane polymers in which NP dispersion is quite straightforward. The concept of localized membrane heating was now proven to be applicable for hydrophobic membranes as well, for which dispersion of the NPs cannot be realized by the approach used in earlier work. The PDMS membranes containing gold nanoparticles (GNPs) were prepared by an in-situ method. TEM images showed that the GNPs were well-dispersed in the membrane matrix. Moreover, the photothermal heating improved PDMS membrane fluxes without significantly lowering their selectivity, as proven in a dead-end filtration coupled to laser irradiation with appropriate wavelength. Application feasibilities of the technique for membrane separation are discussed, including requirements for feed, potential application fields, alternatives for GNPs and scaling-up issues.