New filtration technologies that could absorb “forever chemicals” at an “ultrafast” rate have been developed.
Researchers say their findings could greatly improve pollution control, although they face multiple challenges before the technology can be deployed at scale.
The scientists outline in a new paper how a layered double hydroxide (LDH) material made from copper and aluminium could absorb long-chain PFAS at an “ultrafast” speed.
This could be up to 100 times the rate of current filtration systems, according to reports.
“Forever chemicals” – so-called because they do not degrade – have been used in a variety of consumer and commercial applications since the 1950s. They can repel water and oil, resist high temperatures and act as “surfactants” by helping different types of liquids mix.
There are around 15,000 different PFAS chemicals. Each one has a slightly different chemical composition, but they all have at least two carbon-fluorine bonds. These extremely strong bonds mean that PFAS do not readily break down. So the bond that affords PFAS some of its unique characteristics also causes them to build up and persist in our bodies and the environment for decades.
Many PFAS are known to be toxic, including associations with altered liver and thyroid function, and various cancers.
Granular activated carbon, reverse osmosis and ion exchange are among the current filtration technologies being used, and they work by absorbing PFAS in water. However, the chemicals caught in the filter have to be stored in hazardous waste facilities or destroyed in a thermal process using high heat, which produces toxic byproducts or just breaks the PFAS down into smaller PFAS.
The new process works by soaking up and concentrating PFAS at high levels, meaning it is non-thermal as the chemicals can be destroyed without using high temperatures, according to Michael Wong, director of Rice University’s Water Institute, a PFAS research centre that developed the new technologies.
The LDH material is similar to those previously used, but copper atoms have replaced some aluminium ones, he said, so the positively charged material attracts and absorbs a broad array of negatively charged PFAS.
“It just soaks it in to the order of 100 times faster than other materials that are out there,” Mr Wong told The Guardian.
PFAS have been seen as almost indestructible due to the bonds between their carbon and fluoride atoms, but the team found heating the material to 400 to 500C, a relatively low temperature, broke the bonds and left a safe, disposable by-product.
Furthermore, new PFAS elimination systems generally do not work at scale, but the researchers say the LDH material has a strong absorption rate and can be used repeatedly and with existing infrastructure, which also removes a big cost barrier.
“This material is going to be important for the direction of research on PFAS destruction in general,” Mr Wong added.
