Abstract
Despite extensive research efforts focusing on tackling membrane biofouling, one of the biggest problems associated with membrane technology, there has been little headway in this area. This study presents novel polyethersulfone (PES) membranes synthesized via a phase inversion method at incremental loadings of functionalized oxidized multiwalled carbon nanotubes (OMWCNT) along with 1 wt. % arabic gum (AG). The synthesized OMWCNT were examined using scanning electron microscopy and transmission electron microscopy for morphological changes compared to the commercially obtained carbon nanotubes. Additionally energy-dispersive X-ray spectroscopy was carried out on the raw and OMWCNT materials, indicating an almost 2-fold increase in oxygen content in the latter sample. The cast PES/OMWCNT membranes were extensively characterized, and underwent a series of performance testing using bovine serum albumin solution for fouling tests and model Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli) bacterial species for anti-biofouling experiments. Results indicated that the composite PES membranes, which incorporated the OMWCNT and AG, possessed significantly stronger hydrophilicity and negative surface charge as evidenced by water contact angle and zeta potential data, respectively, when compared to plain PES membranes. Furthermore atomic force microscopy analysis showed that the PES/OMWCNT membranes exhibited significantly lower surface roughness values. Together, these membrane surface features were held responsible for the anti-adhesive nature of the hybrid membranes seen during biofouling tests. Importantly, the prepared membranes were able to inhibit bacterial colonization upon incubation with both Gram-positive and Gram-negative bacterial suspensions. The PES/OMWCNT membranes also presented more resilient normalized flux values when compared to neat PES and commercial membrane samples during filtration of both bacterial suspensions and real treated sewage effluents. Taken together, the results of this study allude to OMWCNT and AG as promising additives, for incorporation into polymeric membranes to enhance biofouling resistance.
Highlights
As the human population continues on its exponential growth rate, the global demand for water and wastewater treatments has increased [1]
The results indicate that the stiffness increased up to a certain loading of oxidized multiwalled carbon nanotubes (OMWCNT) (0.5 wt. %) and decreased at higher loadings (M6 to M8)
Such tremendous inaflux was expected asthe it isneat well accepted that membranes showed a superior initialimprovement
Summary
As the human population continues on its exponential growth rate, the global demand for water and wastewater treatments has increased [1]. Membranes 2019, 9, 32 the last decade, whilst the average cost of membrane installations have seen a sharp decrease over the same time period [3] This has been the case with wastewater treatment where the use of membranes to compliment more conventional methods of wastewater treatment has become common place as evidenced by the increasing popularity of membrane bioreactors (MBRs) [4]. These bioreactors offer valuable advantages when compared to activated sludge systems. Membrane systems have proven themselves as the more attractive alternatives to traditional methods of filtration and sedimentation due to the higher-grade filtered water achieved by ultrafiltration (UF)
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