A Novel ceramic tubular membrane coated with a continuous graphene-TiO2 nanocomposite thin-film for CECs mitigation

This work presents a ceramic tubular membrane coated with a continuous graphene-TiO2 nanocomposite thin-film for contaminants of emerging concern (CECs) removal from synthetic and real matrices in single-pass flow-through operation. Microfiltration ceramic membranes were coated in situ with graphene (G)-TiO2-P25 nano-composite using two different methods: Membrane type A - TiO2-P25 incorporated in the G preparation stage (1% [MA-1], 2% [MA-2] and 3% [MA-3] [w/v]), and Membrane type B - TiO2-P25 thin-film uniformly coated over the G film surface (coating layers: 3 [MB-1], 6 [MB-2], and 9 [MB-3]). After the catalyst deposition and before the pyrolysis step, air was forced to pass through the membranes pores (inside-outside mode), providing a porous film. The CECs solution (diclofenac-DCF, 17 beta-estradiol-E2, 17 alpha-ethinylestradiol-EE2 and amoxicillin-AMX) was prepared using Ultrapure water (UPW) or an urban wastewater after secondary treatment (UWW) fortified with 500 mu g L-1 of each CEC. Membranes were characterized by the following techniques: Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Fourier-Transform Infrared spectroscopy (FTIR), Diffuse Reflectance UV-Visible spectroscopy (DR UV-Vis) and Raman spectroscopy. The membranes coated with MA-3 and MB-2 catalyst films, irradiated by UVA light, showed the highest ability for CECs removal. Furthermore, the Relative flux reduction ratio (RFR) decreased around 45% in the absence of UVA light, owing to membrane fouling. The combination of filtration and oxidation (G-TiO2-UVA) provided a permeate with higher quality and minimized membrane fouling. Although membrane type B allowed for a permeate with higher quality, membrane type A provided a higher permeate flux.

Automated summary

This study demonstrated the successful removal of contaminants of emerging concern using a ceramic tubular membrane coated with graphene-TiO2 nanocomposite thin-film in a single-pass flow-through operation. Membranes coated with different methods showed higher removal efficiency under UVA light irradiation. The membranes were characterized and evaluated for their properties and contaminant removal performance using various techniques.