Investigating the impact of iron oxide nanoparticles on the stability of class A foam for wildfire suppression

This study investigates the effect of Iron Oxide Nanoparticles (IONPs) on the stability of a class A foam. IONPs are synthesised via two different pathways, namely the reflux and the hydrothermal methods. The synthesised nanoparticles are then added to the foam solution at different concentrations, applying various techniques to test how they affect properties and processes such as particle size distribution, surface tension, and coalescence. Results show that (𝑖) the addition of IONPs improves the foam stability by reducing the bubble coarsening and disproportionation; (𝑖𝑖) the IONPs assemble at the plateau borders and nodes of the bubbles creating a protective layer on the gas–liquid interface, which delays foam drainage hence improving foam stability; and (𝑖𝑖𝑖) stability is also improved by the increase in the foam half-life due to the accumulation of nanoparticles on the surface of the bubble. IONPs obtained using the reflux method are shown to affect the firefighting foam more positively.