Superhydrophobic home-made polyurethane sponges for versatile and cost-effective oil and water separation

Abstract Utilizing 3D and 2D porous materials modified by a superhydrophobic/philic coating for quick removal of oil from water and a continuous process of oil/water separation, respectively, has attracted a lot of attention recently. Here we report the separation capacities of one commercial and three home-made sponges, sprayed by a superhydrophobic coating, for a broad range of oils and solvents. The contact angle of water on the coated sponges is 162.5˚, whereas the pristine sponge shows a contact angle of 91.8˚ (these values are for sponge D which had the highest absorption capacity). We investigate the effects of the density of sponges and the dynamic viscosity of oils and solvents on the absorption capacity. The results reveal that the least dense sponge possesses the highest absorption capacity. On the other hand, the absorption capacity varied erratically with the variation of the dynamic viscosity. In addition to the absorption capacity, the retention of the coated sponge is an essential factor to gain a better understanding of the performance of the sponges. This quantity is examined by using a centrifugal device. To examine the durability of the coated sponges against chemically harsh environments, the coated sponges are exposed to solar irradiation, alkaline, acidic, and saline solutions. Further, a mechanical force is imposed on the as-prepared samples to study their resistance against physical stimuli. The coated sponges maintain their superhydrophobicity after being subjected to these extreme conditions. The fabricated coating is non-fluorinated, cost-effective, and very facile.