Preparation and performance evaluation of high-density polyethylene/silica nanocomposite membranes in membrane bioreactor system

Abstract

In this study, in order to improve the antifouling properties of high-density polyethylene (HDPE) membrane in the membrane bioreactor (MBR) system, HDPE/SiO2 nanocomposite membrane was developed and evaluated for its physicochemical changes with different contents (0, 0.25, 0.5, and 1wt.%) of SiO2 nanoparticles (NPs). Flat sheet membranes were fabricated via thermally induced phase separation (TIPS) method and characterized by field emission scanning electron microscopy (FESEM), contact angle, energy dispersive X-ray analysis (EDX), tensile test and pure water flux. The filtration experiments and FESEM confirmed that certain dosages of SiO2 NPs (0.5wt.%) can increase the membrane porosity. Fouling analysis revealed that the presence of SiO2 NPs in the membrane matrix results in respectively 27% and more than 70% reduction in the total fouling ratio (TFR) and irreversible fouling ratio (IFR) and a little bit increase (16%) in the reversible fouling ratio (RFR). The obtained results showed high efficiencies of chemical oxygen demand (COD) removal rates like more than 95% for both membranes coupled biological filtration tests. In order to identify the most likely fouling mechanism, Hermia’s model was used and the obtained results revealed the existence of two fouling phases; in the first phase, cake filtration is the main fouling mechanism for both membranes, while complete blockage model is the prevailing fouling mechanism in the second phase.