Design of a super-hydrophilic/super-oleophobic g-C3N4/Ti(OH)4/PFOA nanocomposite coated mesh as a smart nanofilter with robust anti-fouling properties for separation of oil and water emulsions

The design and development of efficient approaches for water-oil separation have had widespread interest. This study aimed to synthesize nanocomposites based on Ti(OH)4 and g-C3N4 nanosheets (CN-NS) to show experimentally that the inclusion of Ti(OH)4 nanoparticles of 9.2 nm size into CN-NS leads to an improved oil-water separation efficiency and anti-fouling performance. So, a novel, reusable, and recyclable super-hydrophilic/ underwater super-oleophobic CN-NS/Ti(OH)4 nanocomposite-coated stainless steel mesh was developed to separate oil-in-water emulsions. Super-wettability was obtained in the CN-NS/Ti(OH)4 nanocomposite with WCA = 0 degrees and UOCA = 154 degrees, respectively, showing significant super-hydrophilicity and underwater superoleophobicity. Surface hydrophilicity increased after anchoring Ti(OH)4 on the CN-NS surface, resulting from oxygen-containing functional groups and consequently making defects on the mesh surface. Enhanced underwater oleophobicity of nanocomposite coated mesh is attributed to its higher surface roughness, which is a result of its micro-nano meter and mesoporous hierarchical structure. Moreover, the self-cleaning property of the as prepared mesh was demonstrated by visible light irradiation on the contaminated mesh. In addition, perfluorooctanoic acid (PFOA) reduced energy in CN-NS/Ti(OH)4/PFOA mesh, resulting in a super-hydrophilic/ super-oleophobic mesh. The CN-NS/Ti(OH)4/PFOA nanocomposite-coated filter was observed to separate water from a 1 wt% water-in-oil emulsion at 0.2 bar pressure with a filtration flux of 317.2 L m-2 h-1 and 95% separation efficiency.