A polymeric-ceramic hybrid membrane with a self-cleaning and super-wettable surface decorated with polypyrrole-G-C₃N₄ photocatalyst for oily wastewater treatment

Treating oily wastewater is an enormous challenge as it leads to excessive membrane fouling due to the deposition of components of oily feed onto the membrane surface. Hence, the current work has been focused on developing a polymeric-ceramic hybrid membrane with photocatalytic self-cleaning antifouling properties. To yield the desired membrane, a polypyrrole-graphitic carbon nitride (PPy-G-C₃N₄) photocatalyst was decorated in the polyamide (PA) active layer of the membrane by interfacial polymerization (IP) onto the surface of alumina support. The chemistry of the active layer of the PPy-G-C₃N₄/PA@Alumina ceramic membrane led to the special wettability feature of being underwater superoleophobic which is reflected by underwater oil contact angle of θ_{O, W} = 159.9°. Even though the membrane surface features do not allow the oil to wet the membrane surface during filtration, the membrane surface fouling was inevitable during filtration experiments. With distilled water as feed, the permeate flux of PPy-G-C₃N₄/PA@Alumina ceramic membrane reached 650 L m⁻² h⁻¹ (LMH) at a pressure of 8 bar. A separation efficiency of >99 % was observed by using a feed of 100 ppm oil-in-water (O/W) emulsion. However, the permeate flux declined while using O/W emulsion as feed, where a 92 LMH to 50 LMH was observed after 60 min of continuous filtration. The performance of the membrane was recovered after exposure to solar-simulated light owing to the presence of PPy-G-C₃N₄ photocatalyst in the active layer where a recovery of ∼90 % of permeate flux was recorded. Hence, the current approach of fabricating a hybrid membrane proved to be useful for efficiently treating a challenging feed consisting of a complex oily matrix.