Nanosilica-decorated sponges for efficient oil/water separation: role of nanoparticle's type and concentration

Oil absorption by porous materials is currently regarded as a very efficient method for water purification and oil spill cleanup. Simultaneous induction of superhydrophobic and superoleophilic properties into porous materials was conducted in this study via surface decoration of sponges by nanosilica. The main aim was to investigate the effects of nanosilica concentration on the final wetting behavior of the sponges. To this end, the sponges were treated with both modified and unmodified nanosilica particles through a simple dipping process. It was found that only a moderate concentration of nanoparticles (2 vol%) causes the sponges surface to be uniformly decorated with silica. Based on X-ray photoelectron spectroscopy results, it was postulated that surface energy of the sponges was a more influential factor in the final wetting behavior as compared with the surface roughness. The values of oil absorption capacity were varied in the range of 51-72 g/g (gram of oil per gram of sponge) for the superhydrophobic sample using four different oils and organic liquids. It was concluded that the prepared sponges definitely possess promising potential in the separation of oil/water mixtures provided that an optimum concentration of nanosilica with proper surface modification is used.