Harakeke Flax PFAS Remediation: UoA's Native Plant Breakthrough Against Forever Chemicals

The Growing Threat of Forever Chemicals in New Zealand and Beyond

Per- and polyfluoroalkyl substances, commonly known as PFAS or 'forever chemicals,' pose a significant environmental and health challenge worldwide, including in New Zealand. These synthetic compounds, used for decades in products like non-stick cookware, waterproof clothing, firefighting foams, and cosmetics, do not break down naturally in the environment. Instead, they persist, accumulating in soil, water, and living organisms, leading to bioaccumulation in humans. In New Zealand, PFAS contamination has been detected around military bases such as Ohakea and Woodbourne, where firefighting foams were historically used, as well as in urban wastewaters and surface waters. Health risks associated with PFAS exposure include links to cancer, reproductive issues, and immune system disruption, prompting regulatory actions like New Zealand's ban on PFAS in cosmetics effective from the end of 2026.

Despite relatively low levels in most drinking water sources—often below one part per trillion according to a 2024 University of Auckland study—the presence of these mobile, short-chain PFAS variants remains a concern, as they evade conventional treatment methods like granular activated carbon filters. This underscores the urgent need for innovative, sustainable remediation strategies tailored to New Zealand's context.

Harakeke: New Zealand's Native Flax with Cultural and Remediation Potential

Harakeke, or Phormium tenax (New Zealand flax), is more than a resilient native plant; it holds deep cultural significance for Māori, who have traditionally used it for weaving, medicine, and even water purification. Historical accounts note that Māori communities selected settlement sites near harakeke stands because the plant's roots naturally absorb pollutants, cleaning streams—a practice echoed in modern science. Thriving in diverse conditions, harakeke's fibrous structure makes it an ideal candidate for phytoremediation, where plants extract contaminants from soil or water.

Researchers at the University of Auckland (UoA) have leveraged this native resource, modifying harakeke fibers to target PFAS. This approach aligns with sustainable practices, utilizing a renewable, low-cost material abundant in New Zealand while honoring mātauranga Māori (Māori knowledge).

UoA's Breakthrough Research on Modified Harakeke Fibers

Led by Associate Professor Lokesh Padhye, Associate Professor Erin Leitao, Professor David Barker, and collaborators including Shailja Data and Melanie Kah, UoA's team published a pivotal study in September 2025 in ACS ES&T Engineering. Titled "Quaternary-Ammonium-Grafted Flax Fibers for Removal and Release of Short-Chain PFAS from Water," the paper details a novel functionalization process. The work builds on UoA's prior PFAS research, including ball milling for destruction and nationwide drinking water surveys.

The study tested fibers from Phormium tenax, grafting 20% by weight of poly-[2-(methacryloyloxy)ethyl]trimethylammonium chloride (poly-METAC) via atom transfer radical polymerization (ATRP)—a two-step process creating permanent cationic sites on the fiber surface. This modification enhances electrostatic attraction to negatively charged PFAS anions while retaining hydrophobic interactions from cellulose and lignin.Read the full study

How the Grafting Process Transforms Harakeke for PFAS Capture

The ATRP method involves first esterifying flax fibers with 2-bromopropionyl bromide to create initiation sites, followed by grafting METAC monomers in water at 40°C using copper catalysts. Fourier-transform infrared spectroscopy (FTIR) confirmed new peaks for quaternary ammonium groups, while scanning electron microscopy (SEM) revealed rougher surfaces ideal for adsorption. The modified fibers became hydrophilic (instant wetting) yet rigid, suitable for packed-bed filters.

In batch tests, 50 mg/L of grafted fibers removed 86% perfluorobutanesulfonic acid (PFBS) and 57% perfluorobutanoic acid (PFBA)—stubborn short-chain PFAS—from 100 μg/L solutions in 24 hours. Kinetics followed pseudo-first-order models, reaching equilibrium in 4-24 hours. Isotherms fit Langmuir (monolayer) and Freundlich models, with PFBS showing the highest capacity at 43 mg/g.

Superior Performance Compared to Conventional Sorbents

UoA's grafted harakeke outperformed granular activated carbon (GAC) like Norit and matched strong-base ion-exchange resins (Amberlite IRA-900). At low doses (25 mg/L), it achieved over 95% removal for longer-chain PFAS like PFOA and PFOS. Natural organic matter (1 mg/L tannic acid) had minimal impact (<8% reduction), unlike GAC. In tap water, performance held at higher PFAS concentrations despite competing ions.

• 86% PFBS removal vs. lower for GAC
• Regenerable: >78% PFBS, 97% PFBA recovered with methanol/1% NaCl
• No competitive effects in multi-PFAS mixes
• pH-stable from 5-7

This positions harakeke as a greener alternative, avoiding polystyrene-based resins.

Regeneration and Scalability: A Path to Practical Application

Regeneration is key for sustainability. Desorption with methanol and 1% NaCl recovered most PFAS, allowing reuse without performance loss in initial cycles. The nonporous, rigid fibers suit flow-through systems like filters in wastewater plants or stormwater raingardens. As a low-cost, renewable native plant, harakeke scales easily—New Zealand produces ample supply.Learn more about Lokesh Padhye's work

Challenges include optimizing graft density for short-chain selectivity and field trials. UoA plans lifecycle assessments and pilot tests at contaminated sites like airbases.

Implications for New Zealand's Contaminated Sites

PFAS hotspots in NZ include RNZAF bases (Ohakea, Woodbourne) from AFFF foams, with rising groundwater levels reported in 2024. UoA's ball milling destroyed 99.9% PFAS in such soils (2023 study), complementing fiber sorption for water. Harakeke filters could treat leachate, protecting aquifers and Māori waterways (awa).

Government efforts include EPA site management guides and the 2026 cosmetics ban. For careers in this field, explore research jobs or NZ opportunities in environmental engineering.

Global Potential and Sustainability Advantages

Short-chain PFAS mobility makes them a global issue; UoA's bioderived sorbent offers a model for other nations. Unlike plastic-based filters, harakeke is carbon-neutral, biodegradable post-use, and culturally resonant. Antimicrobial properties from quaternary groups add disinfection benefits.

Integration with constructed wetlands or urban green infrastructure could enhance stormwater treatment, aligning with NZ's Te Mana o te Wai policy prioritizing waterway health.

Challenges, Future Outlook, and UoA's Role

While promising, challenges remain: long-term regeneration cycles, cost comparisons at scale, and regulatory approval for water treatment. UoA's ongoing work includes field pilots and co-design with iwi.Recent coverage

This research exemplifies UoA's leadership in sustainable engineering. Aspiring researchers can pursue higher ed career advice or research assistant jobs.

Photo by Ethan Johnson on Unsplash

Career Opportunities in PFAS Remediation and Environmental Science

UoA's innovation highlights demand for experts in environmental engineering. New Zealand needs specialists for site remediation, policy, and green tech. Explore higher ed research jobs, university jobs, or NZ positions. Rate professors like Padhye on Rate My Professor for insights.

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