Facile fabrication of g-C3N4/Bi2S3 coated melamine foam for oil/water separation applications

Abstract

Regular occurrences of oil leaks are recognized as a significant contributor to water pollution, resulting in substantial environmental and ecological challenges, as well as posing potential for fires and explosions. Therefore, it is imperative to create a cost-effective and exceptionally effective absorbent material for separating oil and water. Hydrophobic, foam-like materials have garnered considerable attention as potential absorbers for addressing oil spills and recovering oil from water sources. In this experimental study, simple, low-cost, environmentally friendly, highly hydrophobic, and super oleophilic g-C₃N₄/Bi₂S₃ nanocomposite-coated melamine foam was introduced for oily wastewater treatment. The g-C₃N₄ and Bi₂S₃ were synthesized by thermal decomposition and hydrothermal methods, and the g-C₃N₄/Bi₂S₃ composite-coated foam was prepared by a simple dip-coated method. The g-C₃N₄/Bi₂S₃ composite-coated melamine foam shows excellent absorption capacity, and it can absorb various oils and solvents and separate different oils and solvents from water. Hence, the developed g-C₃N₄/Bi₂S₃ foam absorbent has excellent potential in oil/water separation applications.

Fig. 1. Schematic diagram for the preparation of g-C₃N₄/Bi₂S₃ coated melamine foam.

Fig. 2. XRD patterns of synthesized g-C₃N₄, Bi₂S₃, and g-C₃N₄/Bi₂S₃ nanocomposite.

Fig. 3. FESEM images of (a and b) pure melamine foam and (c and d) g-C₃N₄/Bi₂S₃ coated melamine foam at different magnifications.

Fig. 4. XPS (a) survey scan of g-C₃N₄/Bi₂S₃ foam. (b)–(d) Narrow scan XPS of g-C₃N₄/Bi₂S₃ foam: (b) C 1s and (c) N 1s and (d) Bi 4f.

Fig. 5. (a) TGA for the g-C₃N₄/Bi₂S₃ foam and pure melamine foam. (b) FTIR spectra of g-C₃N₄/Bi₂S₃ foam before and after absorption.

Fig. 6. (a) The water and oil droplets on the g-C₃N₄/Bi₂S₃ foam surface. Inset (b): WCA of g-C₃N₄/Bi₂S₃ foam; inset (c): water and oil droplets on a pure melamine foam. (d and e) photographs of the g-C₃N₄/Bi₂S₃ foam and a pure melamine foam immersed in water. (f–h) Present sequential photographs demonstrating the oil removal process from water using the g-C₃N₄/Bi₂S₃ foam.

Fig. 7. (a) Stability test of the g-C₃N₄/Bi₂S₃ foam after 24 h in the solutions with different pH values. (b) Variation in the WCA of g-C₃N₄/Bi₂S₃ foam with exposure to air over a period of 0 to 90 days.

Fig. 8. (a) The absorption capacity of g-C₃N₄/Bi₂S₃ foam with different organic solvents and oils. (b) Recyclability of g-C₃N₄/Bi₂S₃ foam absorption using manual squeezing for oil recovery.

Fig. 9. The separation of oil from water using the g-C₃N₄/Bi₂S₃ foam by: (a) continuous separation facilitated by a peristaltic pump, and (b and c) continuous stirring of oil in water.

Fig. 10. Photograph of the prepared oil-in-water emulsion (a) before and (b) after separation.