WITHDRAWN: Do we need an alternative to polyvinylidene fluoride-based membranes and where will it come from?

Abstract

Recently, there has been widespread news coverage regarding the potential ban on polyvinylidene fluoride (PVDF) as one of thousands of per- and poly-fluoroalkyl compounds by the European Union, the United States and several U.S. states including California (the 5th largest economy in the world). This could greatly impact the membrane manufacturing industry as well as its downstream users in biopharma, automotive, water, dairy, food and beverage industries. Herein, we evaluate the performance and physical-chemical properties of membranes made from PVDF, polyethersulfone (PES) and chlorinated polyvinyl chloride (CPVC) polymers. Both PVDF and PES are widely used in commercial membrane products, but CPVC – while used extensively in water, harsh chemicals, and high temperature piping systems – has not been widely explored as a polymer for use in filtration membranes. We fabricate a series of tight, mesoporous ultrafiltration membranes by a simple nonsolvent induced phase separation (NIPS) process, and systematically characterize and quantitatively rate the performance and physical-chemical properties of all three polymers. All three polymers produce membranes with excellent separation performance and thermal, chemical and mechanical stability. Finally, we explore a range of casting conditions for CPVC to evaluate its potential to make membranes with performance spanning the range of tight UF (typically served by PES) to standard MF (typically served by PVDF). CPVC appears to a viable alternative to both PES and PVDF as it spans the entire range of UF and MF separation performance while offering excellent pure water permeability and solute rejection as well as thermal, chemical, and mechanical stability.