Alternatives to fluorinated firefighting foams

  • Saachi Sennik

Student thesis: Master's ThesisMaster of Science by Research (MScR)

Abstract

The purpose of this project is to analyse and find potential alternatives to fluorinated firefighting foams. The unique oleophobic and hydrophobic properties of fluorinated firefighting foams prevent them from mixing with oils, making them the current medium of choice for efficiently controlling oil fires. Unfortunately, these foams negatively impact the environment, are not biodegradable, and instead bioaccumulate. This can lead to the presence of fluorocarbons in animals and humans, which presents a currently unknown health risk. This project focusses on silica nanoparticles coated in various surfactants as a potential alternative to stabilise foams for these applications. Silica can be treated with alumina to form a positively charged surface, therefore anionic surfactants could also be considered and comparisons between cationic surfactants and anionic surfactants could be drawn. Small-angle neutron scattering (SANS) experiments showed that similarly charged surfactants and nanoparticles did not interact, whereas oppositely charged surfactants did interact with the silica nanoparticles. The foamability of these systems was analysed using a standard Ross-Miles set-up, and foam degradation was measured by looking at the change in foam height over time: this was validated by surface tension measurements. It was found that high concentrations of surfactant were necessary for adequate surfactant-coated silica nanoparticle foamability, however, these foams then proved to have better stability than pure surfactant foams. The oleophobicity of the systems was also evaluated by looking at spreadability on heptane, absorption of an oleophilic dye, and contact angles. The oleophobicity decreased with increasing surfactant concentration, until it reached a plateau at around 0.05 M. Combining this with the foamability experiments suggests there may be an optimum concentration to maximise oleophobicity and foamability, which would be interesting for further research.
Date of Award6 Dec 2022
Original languageEnglish
Awarding Institution
  • University of Bristol
SupervisorPaul Bartlett (Supervisor) & Julian Eastoe (Supervisor)

Keywords

  • Fluorocarbon
  • Firefighting
  • Foams
  • Colloids
  • Environmental pollution
  • Surfactants
  • Nanoparticles
  • Silica

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