Waste refrigerator foam tested as oil-spill sorbent

The study examined how reducing the foam to different particle sizes and treating its surface with nonionic surfactants affected its ability to absorb crude oil, diesel and used motor oil.

Rebeka Bejczi and Roland Nagy, from the Department of MOL Hydrocarbon and Coal Processing at the University of Pannonia, processed the waste foam into three particle-size fractions. Selected samples were then treated with either Span 80, also known as sorbitan monooleate, or an alkyl polyglucoside surfactant.

Particle size had a strong effect on performance. The smallest foam particles recorded the highest sorption capacity for all three hydrocarbon liquids tested.
Surface treatment increased oil uptake further, particularly when Span 80 was used. The best result came from foam particles measuring 2–5mm that had been treated with Span 80. These absorbed 12.49g of crude oil for every gram of foam.

The researchers said the results were influenced by several interacting factors, including particle size, the viscosity of the oil, the affinity between the oil and the treated foam surface, and the amount of oil retained while the sorbent was allowed to drain.

Reducing the foam to smaller pieces may expose more of its cellular structure, increasing the surface area available to collect oil. The surfactant treatment is thought to alter the wettability of the foam and strengthen its affinity for hydrocarbons.

However, the authors said these proposed mechanisms still needed to be confirmed through more detailed structural analysis.

Rigid PU foam is widely used to insulate refrigerators and freezers because of its low thermal conductivity and dimensional stability. Recovering that foam at the end of an appliance’s life remains difficult, and it is commonly incinerated or disposed of after the appliance has been dismantled.

Using the recovered material as an oil sorbent would therefore give the foam a second application while potentially reducing the consumption of purpose-made clean-up materials.

The researchers described the work as a preliminary basis for developing waste rigid PU foam for oil-spill mitigation and soil protection. Further work will be required to establish its sorption kinetics, oil-and-water selectivity and performance under realistic environmental conditions.

The study also did not determine how effectively the material could be reused. The authors identified reusability, statistical validation and testing outside the laboratory as priorities for further development.

The paper, Valorization of waste rigid polyurethane foam as a sorbent for oil spill mitigation and soil protection: Effect of particle size and surface modification was published online in Chemical Engineering Journal Advances on 10 July.

Image: an AI-generated illustration of rigid foam holding back an oil slick