Influence of polyethersulfone polymer–metal oxide nanoparticle affinity interactions in preventing nanoparticle leaching during membrane cleaning with harsh chemical agents

Abstract

Nanoparticles leach from the polymer matrix during fabrication and application, and this is envisaged to deteriorate membrane performance. Leaching is mainly ascribed to weaker polymer-nanoparticle interactions which determine polymer-nanoparticle compatibility. Nonetheless, nanoparticle leaching due to membrane exposure to harsh cleaning chemicals has not been related to polymer-nanoparticle affinity interactions. Therefore, this work sought to uncover this discrepancy. Polyethersulfone membranes incorporated with various nanoparticles were exposed to NaOCl and HCl over 4 weeks, and the amount of leached nanoparticles as well as changes in physicochemical properties were monitored. The nanoparticles leached more when the membranes were exposed to NaOCl (14.4–37.7 µg/L) compared to HCl (5.5–21.7 µg/L). More nanoparticles were released when the polymer-nanoparticle affinity interactions were less attractive (37.7 µg/L Zn leached at PES-ZnO interaction energy of −11.7 mJ/m 2 ). The interaction energies were estimated following the acid-based approach through advanced contact angle membrane characterization techniques. Raman and FTIR spectra revealed changes in the membrane functionality, with NaOCl having more effect. SEM micrographs revealed an increase in membrane microvoids after chemical cleaning, while the membrane surfaces became rougher (e.g., from 11.4 nm to 47.3 nm for the ZnOGO membrane after cleaning with NaOCl) as revealed by AFM analysis. Additionally, the mean pore radius increased by approximately 10–15 % depending on the cleaning agent. The chemically cleaned membranes had weaker mechanical properties (0.34–3.79 N/mm 2 ) due to degradation of the membrane polymer. This work offers a quick approach to predict polymer-nanoparticle compatibility based on quantifiable membrane-nanoparticle interaction energies. • Chemical cleaning weakens nanoparticle-polymer interactions leading to leaching. • NaOCl has more effect on leaching due to extra polymer degradation (OCl attack). • Nanoparticle (NP) stability relates to polymer-nanoparticle affinity interactions. • Leaching alters membrane physicochemical and mechanical properties. • The Lifshitz acid-base method is a good tool to estimate polymer-NP compatibility.