Facile preparation of superhydrophobic melamine sponge for efficient underwater oil-water separation

When oil spills occur at sea, surface oil can be collected or dispersed using methods that are now routine in the industry. However, a significant proportion of the oil may reside sub-surface, as discrete droplets, undispersed bulk oil or water-in-oil emulsion 'mousses', which may not be responsive to the conventional procedures. Therefore, the topic of the present paper is the preparation of an oil-selective absorbent sponge, surface modified using biowaxes, of potential use for the selective absorption of oil in the presence of water. In this work, stable, surfactant-free biowax-in-water emulsions have been prepared as a low-cost and non-toxic method for the production of superhydrophobic absorbent surfaces of commercial melamine sponge. Different pre- and post-treatment methods have been investigated to improve the selective oil absorption performance of the sponge in the presence of water. The results of this study suggest that an economic and efficient melamine-based sponge exhibiting efficient underwater oil absorbency can be produced by treating the sponge with a beeswax-in-ethanol/water Ouzo emulsion, followed by annealing.