Abstract
Nano-enabled water treatment membranes are finding new applications and commercial opportunities, but the commonly used methods for embedding or coating the membranes with nanoparticles have limitations. There is an increasing need for controllable and high-throughput methods for applying nanoparticles uniformly across membrane surfaces in ways that preserve their unique nano-properties while assuring stable attachment. We demonstrate proof-of-concept for the use of aerosol impaction-driven assembly (AIDA) to coat polymeric water treatment membranes. AIDA is a dry-coating technique that has been demonstrated on other substrates. It involves using a pressure differential to accelerate aerosolized (premade or in situ-formed) nanoparticles onto a moving sample. The nanoparticles stick by chemical bonding or van der Waals interactions. To provide a proof-of-concept and comparison with other techniques, PVDF membranes with 0.1 mu m pore size were coated with functionalized 50-nm-diameter silver and gold nanoparticles using AIDA, spray-coating, and in situ synthesis, and then were characterized. The AIDA coating method produces controllable (i.e., proportional to deposition time) loadings of evenly dispersed, non-agglomerated nanoparticles on the membrane. The method is relatively agnostic to nanoparticle type. The loading efficiency varies with the surface functionality of the nanoparticles, but not their elemental composition. The method has no substantial effect on water flux and produces stable coatings with low nanoparticle release. The AIDA nanoparticle coating method is shown to have inherent flexibility, controllability, and other major advantages (i.e., dispersion, stability) in the quality of the coatings produced.