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

Abstract

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° and UOCA = 154°, respectively, showing significant super-hydrophilicity and underwater super-oleophobicity. 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.