Developing a facile graphitic carbon nitride (g-C3N4)-coated stainless steel mesh with different superhydrophilic/underwater superoleophobic and superoleophilic behavior for oil–water separation

Mir, Sonia; Naderifar, Abbas; Rahidi, Alimorad; Alaei, Mahshad

Developing a facile graphitic carbon nitride (g-C3N4)-coated stainless steel mesh with different superhydrophilic/underwater superoleophobic and superoleophilic behavior for oil–water separation

2022

Mir, Sonia | Naderifar, Abbas | Rahidi, Alimorad | Alaei, Mahshad

There is an increasing demand for the development of inexpensive and effective approaches for the oil–water separation due to the global concern in oil industries. The present study was conducted to fabricate graphitic carbon nitride/thermoplastic polyurethane (g-C₃N₄/TPU)-coated stainless steel meshes via the dip-coating method to investigate the capability of g-C₃N₄ nanosheets (CN-NS) in oil–water separation. CN-NS was synthesized using the polycondensation process followed by exfoliation with Hummer’s method. We studied the effect of TPU and CN-NS concentration on wettability behavior to obtain an optimized coating solution. CN-NS-coated mesh showed superoleophilic/hydrophobic behavior at CN-NS:TPU ratio of 50:50, and it efficiently passed oil from the emulsified water-in-oil mixture (with 50 wt.% oil) with the efficiency of 99%. The wettability behavior of superhydrophilic/underwater superoleophobic was also obtained at CN-NS:TPU ratio of 80:20, and it was able to separate water from the emulsified water-in-oil mixture with the efficiency of 79% under gravity. Both filters were able to separate free water and oil mixtures with flux and efficiency of 6114 L.m⁻².h⁻¹ and ~ 99.99%, respectively. The mechanism of wettability behavior of the coating is mainly related to the functional groups on the edge of g-C₃N₄-NS, thus increasing the hydrophilic properties of the surface. In addition, the micro-nano hierarchical structure of the surface coating improves its roughness due to the presence of CN-NS, which is effectively embedded into the hydrophilic TPU. More importantly, commercially available TPU chemical and simple fabrication of g-C₃N₄ from an inexpensive precursor make the method reported herein as a significant alternative for large-scale application.

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