Tunability and Pollutant Degradation by PNIPAm Functionalized MF Membranes: Modeling, Simulation, and Experimental Results
Anthony Saad (speaker), Li Xiao, Minghui Gui, Dibakar Bhattacharyya
Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506
This study is aimed at creating predictive models to estimate the temperature responsive behavior of poly-N-isopropylacrylamide (PNIPAm) as it relates to water flux behavior and partitioning of toxic pollutants, specifically PCBs. Flow through PNIPAm functionalized PVDF MF membranes is modeled mathematically to predict effective pore size based on the swelling extent of the temperature-responsive PNIPAm polymer around its LCST. PNIPAm is known to show a sharp transition to a hydrophobic state at its lower critical solution temperature (LCST) at around 32oC, making PNIPAM attractive for biomedical applications. A model is developed to predict the effect of changing temperature about the LCST of NIPAm on water flux through the membrane, caused by a change in effective pore size. Swelling ratios of PNIPAm polymeric networks have been reported in water, and are utilized to estimate changes in both flux and pore diameter. Water permeation is tested at various temperatures to verify model predictions.
Furthermore, the entrapment of reactive Fe/Pd nanoparticles in the temperature responsive PNIPAm polymer network for dechlorination and contaminant degradation of PCBs has been reported. This study also aims to model PCB degradation by reactive immobilized nanoparticles in a PNIPAm functionalized PVDF MF membrane. The model accounts for diffusion through the membrane, as well as reactivity of the nanoparticles. Solute concentration is predicted as a function of length through the membrane, and also as a function of time. Changing the temperature of the reaction affects inter-particle spacing and solute adsorption because of the changing PNIPAm conformation, as well as the intrinsic rate constant for the reaction. These effects are predicted, and verified by experimental degradation results. This research is supported by the NIEHS-SRP grant P42ES007380, and by the NSF KY EPSCOR program. Full-scale PAA functionalized PVDF membranes were developed through collaborative work with Nanostone-Sepro (Oceanside, CA, USA).