Polyethersulfone-silicon dioxide hollow fiber ultrafiltration membrane for removal of bisphenol A

Abstract

Extensive utilization of bisphenol A (BPA) in industrial production of polycarbonate plastics has led to frequent detection of BPA in water sources. It is a main concern among society as BPA is one of the endocrine disruption compounds that can cause hazard to human health even at extremely low concentration exposure. In view of this, polyethersulfone-silicon dioxide (PES-SiO2) hollow fiber ultrafiltration (UF) membrane was developed in this study and used as advanced water treatment process to tackle the problem of BPA. The membrane is composed of PES as main membrane forming material, dimethylacetamide as solvent and two additives i.e. SiO2 nanoparticles and polyvinylpyrrolidone. The SiO2 nanoparticles were initially modified using sodium dodecyl sulfate (SDS) prior to blending into PES dope solution at different loadings (0, 1, 2 and 4 wt.%). The control PES and PES-SiO2 membranes were fabricated via dry-jet wet spinning process. The modified SiO2 nanoparticles and the membranes were characterized before the membrane performances were tested in filtration and batch adsorption study using water sample collected from a water treatment plant in Skudai, Johor. The transmission electron microscope results reveal that the surface modification of SiO2 nanoparticle using SDS was able to reduce agglomeration effect between the nanoparticles. The PES-SiO2 membranes improved mechanical, thermal, and hydrophilicity property compared to control PES membrane. The membranes also displayed higher water flux and BPA removal, owing to the presence of silanol and siloxane bonding groups which contribute to the BPA removal via adsorption mechanism. The blending of 2 wt.% SiO2 shows the highest membrane performances, recording 73.3 L/m2.h.bar water flux and 86% BPA removal. This membrane also shows 53 µg/g BPA adsorption capacity that is in accordance to the pseudo-secondorder kinetic model. Therefore, the membrane was selected for further studies under the effect of natural organic matter (NOM) and operating parameters towards removal of BPA. The presence of NOM exhibited negative impacts on the water flux and BPA removal due to membrane fouling and competition for adsorption site with BPA. The results for the effects of operating parameters demonstrated that promising BPA removal at 90-96% could be achieved. Furthermore, backwash cleaning of the membrane was able to recover more than 80% of BPA removal after three consecutive cycles of filtration. The optimization process of developed model via historical data design of research surface methodology (RSM) on the other hand, had predicted the optimum conditions for BPA removal were at the pressure of 1 bar, pH 7, 10 µg/L BPA concentration, and filtration time of 10 min that correspond to 99.61% BPA removal. In conclusion, the developed PES-SiO2 hollow fiber UF membrane system was found to have high potential for BPA removal and application in water treatment process.