Zibo, China – Polyurethane foam can be used to mop up oil spills without having to resort to in situ burning or the use of dispersant chemicals. Now, scientists at Shandong University of Technology have developed a modified polyurethane foam based on lignin as the polyol that has better oil-adsorbing capabilities than standard foam.
First, they made the lignin-based foam via a one-pot method, and then improved the superhydrophobic and photothermal properties by modifying the foam with octadecyltrimethoxysilane. This had the effect of reducing its surface energy, resulting in a foam that exhibited superhydrophobicity. This foam proved very efficient at adsorbing several different organic solvents, with a maximum adsorption capacity of 20g per gram, and an oil-water separation efficiency in excess of 97%.
They found that sunlight increased the surface temperature very rapidly – an intensity of 1kWm-2 pushed the temperature up to almost 80°C within six minutes. This significantly reduced the viscosity of crude oil at the foam’s surface, increasing the rate of adsorption.
Another advantageous discovery was the fact that the lignin-based foam had self-cleaning properties, and could be completely degraded after five hours in an alkaline solution.
The foam also had good elastic recovery properties, with its adsorption capacity dropping by just 1.5% after 10 cycles of adsorption and desorption, It should, therefore, be possible to re-use the foam for recovery multiple times, they said.
Overall, they believe the new foam has potential as an efficient tool for the removal of oil removal. It could also provide a new avenue for the use of a cheap renewable resource – crude lignin waste – in place of petroleum-based raw materials. They are now looking at how it might be made more cheaply by reducing energy consumption during its manufacture.
The work has been published in the journal RSC Advances.
