New filtration technology developed by Rice University may absorb some Pfas “forever chemicals” at 100 times the rate than previously possible, which could dramatically improve pollution control and speed remediations.
Researchers also say they have also found a way to destroy Pfas, though both technologies face a steep challenge in being deployed on an industrial scale.
A new peer-reviewed paper details a layered double hydroxide (LDH) material made from copper and aluminum that absorbs long-chain Pfas up to 100 times faster than commonly used filtration systems.
“This material is going to be important for the direction of research on Pfas destruction in general,” said Michael Wong, director of Rice’s Water Institute, a Pfas research center.
Pfas are a class of at least 16,000 compounds often used to help products resist water, stains and heat. They are called “forever chemicals” because they do not naturally break down and accumulate in the environment, and they are linked to serious health problems such as cancer, kidney disease, liver problems, immune disorders and birth defects.
Current filtration technology like granular activated carbon, reverse osmosis or ion exchange absorbs Pfas in water, and the chemicals caught in the filter must be stored in hazardous waste facilities, or destroyed. Destruction of the chemicals typically involves a thermal process that subjects them to high heat, but that leaves toxic byproducts, or essentially breaks larger Pfas into smaller Pfas. There is no technology that fully destroys Pfas on an industrial scale.
Wong said Rice’s non-thermal process works by soaking up and concentrating Pfas at high levels, which makes it possible to destroy them without high temperatures.
The LDH material Rice developed is a variation of similar materials previously used, but researchers replaced some aluminum atoms with copper atoms. The LDH material is positively charged and the long-chain Pfas are negatively charged, which causes the material to attract and absorb the chemicals, Wong said.
“There you go – it just soaks it in to the order of 100 times faster than other materials that are out there,” Wong added.
Pfas are virtually indestructible because their carbon atoms are bonded with fluoride, but Rice found that the bonds could be broken if the chemicals in the material were heated to 400-500C – a relatively low temperature. The fluoride gets trapped in the LDH material and is bonded to calcium. The leftover calcium-fluoride material is safe and can be disposed of in a landfill, Wong said.
The process works with some long-chain Pfas that are among the most common water pollutants, and it also absorbed some smaller Pfas that are commonplace. Wong said he is confident the material can be used to absorb a broad array of Pfas, especially if they are negatively charged.
Most new Pfas elimination systems fail to work at an industrial scale. Wong said the new material has an advantage because its absorption rate is so strong, it can be used repeatedly and it is in a “drop in material”, meaning it can be used with existing filtration infrastructure. That eliminates one of the major cost barriers.
Laura Orlando, a Pfas researcher with the Just Zero non-profit and a civil engineer who works on waste-management design, said she is always skeptical of claims around total destruction of Pfas, and new filtration technologies, because the processes are so complex in real-world conditions. Other challenges like occupational safety, or regulations and permitting, would have to be considered.
“We’re going to need as many technologies as we can possibly find to deal with Pfas in drinking water, and if this works to scale on wastewater, then it would be really something to pay attention to,” Orlando said.
