The challenge of cleaning up pollution by toxic polyfluorinated alkyl substances (PFAS), commonly used in non-stick and protective coatings, lubricants and fire-fighting foams, could be solved by the discovery of a new low-cost, safe and environmentally friendly method that removes PFAS from water.
Researchers from Flinders University’s Institute for NanoScale Science and Technology and the University of South Australia have developed a new kind of absorbent polymer from waste cooking oil and sulphur combined with powdered activated carbon (PAC). The core technology they developed is protected by a provisional patent.
In Australia, fire-fighting foams containing PFAS have been extensively used at airports and defence sites, resulting in contaminated ground and surface water being reported in these areas, as PFAS does not break down readily in the environment.
The new polymer adheres to carbon in a way that prevents caking during water filtration. It provides faster uptake of PFAS than the commonly used and more expensive granular activated carbon method, and dramatically lowers the amount of dust generated during handling PAC that lowers the respiratory risks faced by clean-up workers.
“We need safe, low-cost and versatile methods for removing PFAS from water, and our polymer-carbon blend is a promising step in this direction,” says Justin Chalker, Senior Lecturer in Synthetic Chemistry at Flinders University and co-director of the study.
The team demonstrated the effectiveness of the polymer-carbon blend by purifying a sample of surface water obtained near an RAAF airbase. The new filter material reduced the PFAS content from 150 parts per trillion (ppt) to less than 23 ppt, well below the 70 ppt guidance value for PFAS in drinking water issued by the Federal Department of Health.
“Our canola oil polysulfide was found to be highly effective as a support material for powdered activated carbon, enhancing its efficiency and prospects for implementation,” says Nicholas Lundquist, a PhD candidate at Flinders University and lead author of a research paper published in ACS Sustainable Chemistry & Engineering.
Dr Chalker adds, “The next stage for us is to test this sorbent on a commercial scale and demonstrate its ability to purify thousands of litres of water. We are also investigating methods to recycle the sorbent and destroy the PFAS.”
During the testing phase, the research team was able to directly observe the self-assembly of PFOA hemi-micelles on the surface of the polymer.
“This is an important fundamental discovery about how PFOA interacts with surfaces,” he says.
The project was funded by the South Australian Defence Innovation Partnership, with further support from industry partners Membrane Systems Australia and Puratap and the City of Salisbury, in Adelaide’s northern suburbs.