Magnetically Driven Floating Foams for the Removal of Oil Contaminants from Water

TLDR

Untreated foam surfaces are hydrophobic and oleophobic, but can be made water‑repellent and oil‑absorbing via a solvent‑free electrostatic PTFE particle deposition technique. The study introduces a composite polyurethane foam functionalized with superparamagnetic iron oxide nanoparticles and PTFE particles to efficiently separate oil from water. Microscopic and wettability studies show that surface morphology and chemistry of the functionalized foams govern oil‑absorption dynamics, and the magnetic responsiveness allows the foams to be moved by a magnet to capture floating oil and purify the water. The functionalized foams absorb oil rapidly, with nanoparticle capping molecules enhancing the effect, and their magnetic responsiveness, water‑repellency, and buoyancy enable a low‑cost, scalable method for cleaning large oil spills.

Abstract

In this study, we present a novel composite material based on commercially available polyurethane foams functionalized with colloidal superparamagnetic iron oxide nanoparticles and submicrometer polytetrafluoroethylene particles, which can efficiently separate oil from water. Untreated foam surfaces are inherently hydrophobic and oleophobic, but they can be rendered water-repellent and oil-absorbing by a solvent-free, electrostatic polytetrafluoroethylene particle deposition technique. It was found that combined functionalization of the polytetrafluoroethylene-treated foam surfaces with colloidal iron oxide nanoparticles significantly increases the speed of oil absorption. Detailed microscopic and wettability studies reveal that the combined effects of the surface morphology and of the chemistry of the functionalized foams greatly affect the oil-absorption dynamics. In particular, nanoparticle capping molecules are found to play a major role in this mechanism. In addition to the water-repellent and oil-absorbing capabilities, the functionalized foams exhibit also magnetic responsivity. Finally, due to their light weight, they float easily on water. Hence, by simply moving them around oil-polluted waters using a magnet, they can absorb the floating oil from the polluted regions, thereby purifying the water underneath. This low-cost process can easily be scaled up to clean large-area oil spills in water.