Pharmaceuticals and personal care products (PPCPs) have recently been recognized as emerging contaminants that pose potential hazards to environment and human health. Conventional nanofiltration membranes relies heavily on the size exclusion and charge repulsion for the separation of contaminant from water and herein are less effective in rejecting neutral micropollutants. In this research, graphene oxide (GO) nanosheets were stacked into 50 nm thin film as a tight nanofiltration membrane to remove pharmaceuticals and PPCPs in water. The layer-stacked GO membranes has sub-nanometer-sized channels that enhance the interactions between GO and the targeting contaminants which lead to hindered diffusion of neutral micropollutants. The diffusion and partitioning coefficient of three representative PPCPs were for the first time characterized based on their adsorption kinetics into the GO thin films using quartz crystal microbalance with dissipation (QCM-D). The results suggest that the diffusion coefficient of caffeine, acetaminophen and carbamazepine in the confined GO nanochannels are 1.1310-9 cm2/s, 2.0510-9 cm2/s and 0.4810-9 cm2/s, respectively, which are more than four magnitudes slower than that in the bulk water. By comparing the solute flux measured experimentally using a nanofiltration system and the theoretical values calculated from the diffusion and partitioning coefficient, we can confirm that the transport of neutral micropollutants in the GO membranes is dominated by the diffusion process. Impacts of water composition such as the presence of divalent cations (e.g. Ca2+ and Mg2+), urea and natural organic matters (NOMs) were also investigated to demonstrate the potential application of this type of membranes in complicated water systems.

Removal of neutral pharmaceuticals and PPCPs using graphene oxide membranes: Characterization of diffusion and partitioning coefficient of micropollutant in confined nanochannels

2019 Fall National Meeting

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