Native plant shows promise for tackling `forever chemicals’

One of Aotearoa New Zealand’s taonga plants, harakeke, shows promise as a treatment for removing “forever chemicals” from drinking water.

Known as per- and polyfluoroalkyl substances (PFAS), the chemicals are one of the greatest environmental challenges.

Linked to cancer and reduced fertility, PFAS are in the blood of humans and animals around the world.

In lab experiments at Waipapa Taumata Rau, University of Auckland, chemically treated harakeke outperformed other water treatment methods that were tested.

“Our research findings suggest there is a potential for developing a cost- effective PFAS treatment approach based on this native plant,” says Dr Lokesh Padhye.

He’s an honorary academic in the Faculty of Engineering and Design and the Associate Director of Emerging Contaminants Research at the New York State Center for Clean Water Technology.

“There is more work to be done, but the sustainability and availability of the material make it particularly promising,” says Padhye.

The “forever” name comes from the chemicals’ resistance to breaking down.

“Capturing forever chemicals would only add to the story of harakeke’s remarkable versatility,” says Professor Melanie Kah, of the School of the Environment.

Before colonisation, Māori used harakeke fibres for baskets, ropes, clothes, mats, bird snares and fishing nets, the nectar as a sweetener, dried flower stalks for rafts, the sap as a medicine, and root juice as a disinfectant. (By the way, the plant is a lily, not a flax.)

In the lab, treated harakeke fibre removed five PFAS from water, including three “short chain” PFAS, the most difficult ones to remove, says PhD student Shailja Data.

In the harakeke experiments, small containers held contaminated water and strands of processed harakeke chemically treated to attract the PFAS.

Mechanical shaking of the containers for 24 hours removed between 70 percent and 99 percent of individual short-chain PFAS, outperforming other materials tested in the study, says Data.

“The strength of the plant’s fibres is a big plus – they don’t easily fall apart,” she says.

The project spun off research by Professor David Barker, of the School of Chemical Sciences.

Back in 2019, Māori parents at his kids’ school objected to a harakeke cull, saying the plant cleaned stream water at the school.

Intrigued, Barker researched the plant under the University of Canterbury-led government-funded Science for Technological Innovation project. In tests, treated harakeke fibres removed nitrate from water, although his team moved on to other materials for that task.

The PFAS project is a collaboration between the University’s environmental, engineering, material and chemical scientists, stretching around the world now Padhye is at the New York State Center for Clean Water Technology at Stony Brook University.

Materials scientist Associate Professor Erin Leitao, who is in the School of Chemical Sciences and a co-author of a paper on the experiments, is leading research seeking alternatives to forever chemicals.

“Dealing with forever chemicals is a daunting task, but it must be done,” she says. Data, Barker and Leitao are all part of the MacDiarmid Institute for Advanced Materials and Nanotechnology.