Molecular traits of phenolic moieties in dissolved organic matter: Linkages with membrane fouling development

Phenolic moieties are important constituents in dissolved organic matter (DOM) in natural and engineered systems. However, their roles in membrane fouling mechanism during drinking water treatment by ultrafiltration (UF) have remained elusive. Herein, by using water insoluble polyvinylpolypyrrolidone (PVPP) resins, we sequestered the phenolic moieties from a model DOM (Suwannee River DOM, SRDOM) and characterized their molecular profiles using electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS). Subsequently, their roles in UF membrane fouling propensity were investigated using reconstituted DOM solutions with various concentrations of phenolic moieties. The results showed that the phenolic moieties were of higher molecular weight and rich in unsaturation cyclic structures and oxygen-rich groups. Van Krevelen diagrams revealed that the sequestered sample was rich in aromatics structures and tannins-like compounds while contained less alicyclic organic acids in comparison with the original SRDOM, which was consistent with the aromaticity index (AI) analysis. UF experiments showed that the more phenolic moieties in DOM solution, the severer decline of flux was observed. The phenolic moieties played a significant role in membrane irremovable fouling due to the hydrophobic interactions and their higher molecular weight as evidenced by membrane cleaning tests. By surface characterization, the SRDOM fouled membrane was identified to have a higher water contact angle value and abundant C-O groups, likely due to the adsorption of more hydrophobic phenolic moieties. Overall, these findings highlighted links between phenolic moieties and membrane fouling development, and implied that membrane performance could be improved by pre-removal of phenolic moieties in DOM.