From Nature, For Nature: Using Modified Driftwood Biochar to Treat PFAS Wastewater

Hello! My name is Lucia Chen and I am a grade 11 student in St. John's, Newfoundland.

Here's a bit about my project!

Background

My project, From Nature, For Nature, focuses on developing a driftwood derived filtration medium to remove per- and polyfluoroalkyl substances (PFAS) from Arctic Indigenous Canadian waters. PFAS or "forever toxins" are a class of synthetic chemicals used in a large percent of consumer products.

Inspiration

Last summer, I traveled to northern Canadian communities such as Inuvik, Tsiigehtchic, Tuktoyaktuk, Aklavik, and Cambridge Bay to volunteer for a community outreach and PFAS sampling project. Working alongside Métis and Inuit leaders, I learned the philosophy of “from nature back to nature,” which sums up the idea that because we are born from the land, in our lives we should remain in balance with and give back to the land. This perspective shaped both my purpose and approach.

Why?

During my trip, I spoke with locals and elders who brought up concerns for a lack of advanced wastewater treatment systems in many of the smaller communities. Simple filters, such as household filter cartridges, are often ineffective against PFAS, which persist in the environment and pose serious health risks. My project aims to address this gap by developing a low-cost, accessible solution using driftwood-derived biochar. I selected driftwood due to its abundance in the communities I visited and modified the biochar to target both long- (usually 8-20 carbons) and short-chain PFAS (usually 4-6 carbons).

Objective

This work aims to support safer drinking water in underserved communities through local solutions. I hypothesize that these modified biochars will remove PFAS more effectively than conventional household filters.

Literature Review

Before starting my experimentation, I read scientific journals, government reports, and trusted databases to learn about PFAS contamination and current filtration methods. This helped me identify modified biochar as a promising and low-cost medium. I also decided I would compare my modified biochars against a comercially available Cuisinart activated charcoal water filter.

Preparing the Biochar (Fig. 1)

I collected driftwood from Middle Cove Beach in St. John's, ground it into sawdust, and heated it in a low-oxygen environment at high temperatures. This process (also known as pyrolysis) created biochar, a porous material very similar to charcoal.

Modifying the Biochar (Fig. 1）

With my biochar, I did two types of modification:

One batch of biochar was treated with iron oxide to improve attraction to short-chain PFAS species.

One batch was treated with octadecyltrimethoxysilane (OTMS) to better adsorb long-chain PFAS

Preparing Synthetic Wastewater (Fig. 1.1)

I mixed two synthetic wastewater solutions of equal concentration: one with short-chain (3-carbon) perfluoropropanoic acid (PFPrA), and the other with long-chain (8-carbon) perfluorooctanoic acid (PFOA).

Batch Testing (Fig. 1.2)

Each medium (iron-oxide biochar, hydrophobic biochar, Cuisinart activated charcoal) was individually added to a flask containing synthetic wastewater (one group of flasks contained PFPrA solution and the other contained PFOA solution) and shaken on a shaker table. Duplicates were done to reduce random error.

Fluorescence Analysis (Fig. 1.3)

After testing, the PFAS left in the water of each flask was extracted into dichloromethane for fluorescence rapid testing using the compound C₆₀H₃₆N₆S. This compound will turn light blue in the presence of PFAS.

Characterization

FT-IR Analysis (Fig. 2)

FT-IR spectra confirmed that both biochars were successfully modified. The appearance of a peak corresponding to iron-oxygen bonds verified successful iron oxide modification, while peaks associated with silicon-oxygen bonds confirmed the addition of the hydrophobic coating. Importantly, the presence of aromatic carbon peaks showed that the main carbon structure of the biochar remained intact. This indicates that the modifications occurred primarily on the surface, which is ideal for filtration applications.

SEM Analysis (Fig. 3)

Scanning electron microscopy images showed that all biochars had porous structures, which are important for trapping contaminants. The raw biochar had a rough surface, while the iron oxide biochar appeared smoother and was coated with fine particles. The hydrophobic biochar displayed a more uneven surface with a gel-like layer. These structural differences visually confirmed that the surface modifications were successful.

Fluorescence Rapid Testing (Fig. 4)

Fluorescence analysis demonstrated that:

Both modified biochars were effective at removing PFAS from water, while the commercial Cuisinart filter was largely ineffective under the same conditions.

Both modified biochars showed strong performance in removing long-chain PFAS. However, neither modified biochar showed a clear advantage over the other for short-chain PFAS.

Overall, these results support the efficacy of modified driftwood biochar as a filtration medium for PFAS-contaminated water. As well, these modified biochars prove to be more effective than a commercial water filter.

Discussion and Conclusion

This study showed that:

Modified driftwood biochars are able to adsorb both short- and long-chain PFAS species more effectively than a commercial Cuisinart water filter.

FT-IR and SEM analyses confirmed successful modification of both biochars, indicating the presence of functional groups and surface characteristics necessary for PFAS adsorption.

Batch testing followed by fluorescence analysis demonstrated that:

While both modified biochars effectively removed PFAS, stronger adsorption was observed for long-chain PFOA compared to short-chain PFPrA. Neither modified biochar significantly outperformed the other in the presence of PFPrA, indicating limitations in targeting short-chain species. This was to be expected, given that shorter-chain PFAS are known to be more difficult to capture due to their higher solubility and mobility in water.

Overall, these findings suggest that modified driftwood biochar is a promising, low-cost, and locally sourced material for PFAS remediation, particularly for long-chain compounds. This is especially relevant for northern and remote communities where conventional treatment options are limited. However, the reduced efficiency for short-chain PFAS highlights the need for further optimization.

Future Work

The dichloromethane (DCM) extraction process should be optimized. A study can be conducted to determine the ideal number of DCM washes needed to achieve the highest concentration of extracted PFAS, ensuring that overwashing or underwashing does not occur. In this project, three washes per extraction were used, but it is unclear whether increasing or decreasing this number would have significantly impacted results.

The exact percent removal for each filtration medium should be determined using LC-MS analysis.

Column testing will be conducted to investigate breakthrough rates and better simulate real-world filtration conditions.

Acknowledgements

Extending sincere thanks to Memorial University of Newfoundland (MUN) Process and Civil Engineering for providing access to essential laboratory facilities, which made experimental work possible. Appreciation is also extended to CREAIT for access to SEM, FT-IR, and BET infrastructure. Special thanks to Hongjie Wang for providing technical advice in the lab, and Dennis Allen for the amazing Mackenzie River boat trip that inspired this project.

References

Nakayama, S. F. (2019). Worldwide trends in tracing poly- and perfluoroalkyl substances (PFAS) in the environment. TrAC Trends in Analytical Chemistry, 121.

Bline, A. P. (2024). Public health risks of PFAS-related immunotoxicity are real. Current Environmental Health Reports, 11.

Nasrollahpour, S. (2025). Functionalized biochar for the removal of poly- and perfluoroalkyl substances in aqueous media. iScience, 28.

Salami, F., Farshi, H., Zhao, Y., & Chen, B. (2025). Benzothiadiazole-centered donor–acceptor–donor systems: Synthesis, characterization, and PFAS-induced fluorochromism. The Journal of Organic Chemistry, 90.

North Carolina State University, METRIC. (2022). [PFAS panel illustration] [Photograph]. North Carolina State University. https://research.ncsu.edu/metric/2022/04/11/metric-launches-comprehensive-pfas-panel/