Magnet-assisted selective oil removal from water in non-open channel and continuous oil spills clean-up

Abstract

• A superhydrophobic-superoleophilic, magnetic foam is synthesized. • The foam can selectively remove oil from water in both open and non-open environment. • The foam can be reused for multicycle oil adsorption, and shows long-term durability. • A novel magnetic attraction strategy is proposed to assemble the foam. 3D porous superhydrophobic materials have been widely developed for selective oil adsorption from open water surface, but it is still challenging for the oil removal from water in non-open environment. Herein, a superhydrophobic-superoleophilic, magnetic and 3D porous carbon-based foam, containing carbon-nanosheet frameworks (CNFs), iron/iron carbide nanoparticles (Fe/Fe 3 C NPs) and polydimethylsiloxane (PDMS) coating, is synthesized via ferric nitrate assisted chemical blowing and carbonization of polyvinylpyrrolidone (PVP), and post-treatment by PDMS. The PDMS-CNF-Fe/Fe 3 C foam shows low density (<90 mg cm −3 ), extremely high compressive strength (≈47.7 kPa) and selective oil removal ability with high oil adsorption capacity (>2700% for chloroform). The remarkable paramagnetic property of the foam enables it to be capable of removing oil selectively from water in non-open channels under assistance of a magnet bar. Additionally, the foam can be easily reused for oil adsorption by heating or releasing in other solvents with negligible adsorption capacity decline. The chemically stable carbon-based matrix and PDMS coating impart the foam with excellent high/low temperature stability and certain corrosion resistance, which facilitate effective oil removal from caustic aqueous solutions (especially in alkaline and salty conditions) or under extreme temperature environment. The 3D porous and self-similar micro structures enable the foam to be mechanical abrasion resistant, and the foam retains its water repellence and oil adsorption capacity after repeated and intensive abrasion by sandpaper. Moreover, we propose to assemble the foam with a vacuum pumping system by ring-shaped magnet to realize continuous oil removal. The mechanochemically durable PDMS-CNF-Fe/Fe 3 C foam with magnetic response capacity and outstanding reusability is therefore a promising candidate for selective oil removal from water in both open and non-open environments under remote control of magnet. The novel magnet assisted assembly strategy also provides a simple, reliable and automatable method to integrate magnetic 3D oil adsorbent with pumping system for large-scale oily wastewater remediation.