Comparative analysis of performance of fabricated nitrogen-doped carbon-nanotubes, silicon/germanium dioxide embedded polyethersulfone membranes for removal of emerging micropollutants from water

Abstract

The occurrence of emerging micropollutants (EMPs) in water is a new challenge to scientific community and ecosystems health worldwide. There remains widespread data gaps regarding effective removal of EMPs from water. In this study, nitrogen-doped carbon nanotubes/polyethersulfone (N-CNT/PES), silicon dioxide (silica) (SiO2) and germanium dioxide (GeO2) embedded polyethersulfone (PES) membranes were fabricated using phase inversion method. A comparative multivariate statistical analysis was done to comprehend major underlying factors behind the performance of the membranes in the removal of EMPs from water using the cross flow filtration system. The EMPs were detected and quantified using GC xGc-HRTOFMS Strong statistically significant positive correlations were observed between removal efficiency of all analytes, namely carbamazepine (CBZ), tonalide (AHTN), galaxolide (HHCB), caffeine (CAF), technical 4-nonylphenol (NP) and bisphenol A (BPA) and various membrane characteristics such as pore density number, ultimate tensile strength, Young's modulus, flux recovery ratio (p-value < 0.05, 95% confidence level). Statistically significant negative corrections were observed between the removal efficiency of the EMPs with pore size, contact angle and surface roughness. The EMPs were observed to be removed from real water samples in the following order: HHCB > NP > AHTN > BPA > CBZ > CAF. The removal of the EMPs followed the order of the decrease in hydrophobicity. It was also observed that modification of PES membranes with N-CNTs, SiO2 and GeO2 nanoparticles enhanced the fouling resistance of the membranes. Generally, the performance of the fabricated membranes in the removal of all analytes followed the following order: SiO2/PES > GeO2/PES > N-CNT/PES > pristine PES. The order of increase in water flux (L/m2/h) was observed to be PES (200.60 ± 0), N-CNT/PES (265.01 ± 0), GeO2/PES (300.01 ± 0) and SiO2/PES (305.88 ± 0). However, lower nanoparticle loadings were required to bring statistically significant improvements in performance and characteristics of the N-CNT/PES membranes than that in the SiO2/PES and GeO2/PES membranes. The results showed that the capability fabricated membranes in removing EMPs from water was superior to the majority of methods reported in the literature.