Charged surface modifying macromolecules hollow fiber nanofiltration membrane for the removal of bisphenol - a in domestic wastewater

Abstract

The substances that cause endocrine disruption are massive; nevertheless estrogenic hormones as Bisphenol-A (BPA) can produce disrupting potency several thousand times higher than other chemicals. Furthermore, BPA was selected as the focus of this study due to its widespread applications and large possible abundance in wastewater. Hollow fiber polyethersulfone (PES) nanofiltration (NF) membrane has been fabricated, characterized and applied for the removal of BPA from wastewater. The fabricated PES hollow fiber NF membranes are spun by phase inversion method formulated with water and charged surface modifying macromolecule (cSMM) as additives and N-methyl pyrrolidinone as solvent. The synthesized cSMM comprised of Poly(ethylene glycol) (PEG), end-capped with Hydroxybenzene-sulfonate (HBS). The study reveals that the sulfonic charge modification produces higher flux and improves the removal of ionic solutes when compared to the unmodified PES. The elemental modification of PES hollow fiber NF membrane surface is demonstrated through Energy Dispersive X-Ray (EDX), Fourier Transforms Infrared (FTIR) and X-ray Photoelectron (XPS) analysis. A small increase in the thickness of the hollow fiber outer layer is observed from the Field Emission Scanning Electron Microscopy (FESEM). Additionally, Differential Scanning Calorimetry (DSC) and FTIR analysis verify the miscibility of cSMM with PES and the presence of cSMM’s functional group. The fabricated PES hollow fiber NF membrane performs 90% removal under BPA concentration as much as 10 ppm in the wastewater of pH 8 condition. This is due to charge properties of the membrane and the negatively-charged solute under the influence of higher pH feed water matrix. Furthermore, the fabricated PES NF membrane has a high electrical characteristic of negative charge of 3.10±0.03 and a nano size pores of 1.2±4.1 nm.