Development of novel charged surface modifying macromolecule blended PES membranes to remove EDCs and PPCPs from drinking water sources

Abstract

The aim of this study was to develop novel surface-modified poly(ether sulfone) (PES) ultra-filtration (UF) membranes for removal of endocrine disrupting chemicals (EDCs) and pharmaceutical and personal care products (PPCPs). Seven tailor-made charged surface modifying macromolecules (CSMMs) were developed for use as additives in the preparation of PES UF membranes with a greater surface charge and improved PPCP and EDC removal through charge repulsion. Twenty three types of PES membranes were prepared using two amounts of different CSMMs and two drying (or evaporation) times. The experiments were designed to obtain the membranes' performances in terms of normalized standard flux (NSF), molecular weight cut-off (MWCO), surface charge (SC), static contact angle and their removal efficiency towards one EDC (bisphenol A) and three PPCPs (carbamazepine, ibuprofen, and sulfamethazine). The correlation between NSF versus SC, MWCO, pore density, and porosity was discussed. The filtration experiments showed an initial partial removal of the target compounds, but no removal in the later stages of operation, which indicated that charge repulsion was not the controlling removal mechanism. This is consistent with small changes in membrane surface charge achieved by addition of these additives. Given the decrease in the percent removal with time, removal by size exclusion was also not significant as expected because the membranes had a MWCO greater than 10 kilo-Dalton while the target compounds had molecular weights in the 200 to 300 Dalton range. Based on the decreasing level of removal with time, it appeared that adsorption was the main removal mechanism.