Fluorine-Free Sustainable Three-Dimensional Superhydrophobic and Superoleophilic Robust Foam for Efficient Oil/Water Separation

Abstract

The development of sustainable, environmentally friendly, and efficient materials for oil/water separation is the need of the hour. The utilization of renewable or waste resources to develop value-added materials poses as the key toward sustainability. This work reports the fabrication of an economical, salt-tolerant, superhydrophobic, and superoleophilic waste rice husk-derived silica (SiO2)/reduced graphene oxide (rGO)-coated polyurethane (PU) foam for effective oil/water separation. Herein, SiO2 and graphene oxide (GO) are synthesized from rice husk by using precipitation and thermal exfoliation methods. A simple dip-coating method was carried out to coat the materials on PU foam, followed by a reduction process to form SiO2/rGO@PU foam. The adhesion of SiO2 on rGO enhances the surface roughness and thus promotes superhydrophobic (water contact angle = 164�) and superoleophilic (oil contact angle = 0�) behaviors. The SiO2/rGO@PU foam exhibits excellent adsorption capacity of different oils as well as stability at extreme pH, ultraviolet irradiation, salt concentration, pressure, and humidity with a separation efficiency above 98%. The foam is used to separate a wide range of oil and water mixtures. Utilizing this foam, a device is fabricated, which demonstrated successfully the separation and recovery of crude oil from water. Therefore, the SiO2/rGO@PU foam has the potential to be a promising adsorbent for oil spill cleanup.