2024 AIChE Annual Meeting
Functionalized Membranes for Organic Ion Capture to Nanoparticle Recovery
Separation of negatively charged nanoscale particles, viruses, and macromolecules have a variety of applications that affect human health. Negatively charged per- and polyfluoroalkyl substances, or PFAS, are of great concern in water systems. These “forever chemicals” are resistant to natural degradation, posing a threat to human health due to their ability to bioaccumulate. Recent EPA regulations regarding these potentially toxic substances have caused a push towards better understanding of these compounds and remediation techniques. While current water treatment methods such as coagulation, sedimentation, and disinfection are inefficient at removing PFAS, recent research in anion exchange has taken advantage of the electronegativity of these fluorinated compounds to show promising results in improved PFAS remediation. In other applications, one of the most common methods of gene delivery involves the use of viral vectors, or viruses that have been modified to carry the healthy copy of a gene into the body for therapeutic effect. Adeno-associated virus (AAV) vectors are a widely preferred platform for viral vector gene therapy. However, the challenge of separating and purifying full AAV nano sized (20 – 25 nm) capsids from empty capsids remains a major challenge that is often solved today with costly methods that prevent AAV viral vector therapy from being accessible to much of the population. Traditionally, full and empty AAV capsids are separated based on a slight difference in their isoelectric points—full capsids have an isoelectric point of ~5.9 and empty capsids have an isoelectric point of ~6.3. In these two and various other applications involving charged-based separations, resins and packed columns are the standard. However, this technology presents challenges due to limited diffusivity and extended absorption times. Membranes that have been functionalized to include active positively charged (similar to PFAS capture aspects) sites within their porous structure present an alternative platform for ion exchange. The addition of convective flow in membrane applications has the potential to increase the efficiency of the separation and decrease run times, saving on operations costs. We found that membranes functionalized with primary and quaternary amine-containing polymers were able to capture negatively charged dye and carboxylate-modified nanoparticles, which were used to model substances like PFAS and full viral vector capsids, better than pristine alternatives. Additionally, we explored different release mechanisms (i.e. high pH and high salinity solutions) for recovering the captured organics. These findings provide insight into a possible direction to continue research to improve the capture and recovery of negatively charged substances toward environmental and biotherapeutic applications. This research was supported by NSF EPSCOR Track 2 Program, NIEHS Superfund Research Program, and the National Science Foundation REU Program, University of Kentucky.