Li Jun Toxic phenol clean-up has high eco-costs. New biocatalyst offers a solution

ADVANCED MATERIALS

18 Mar 2026

Toxic phenol clean-up has high eco-costs. New biocatalyst offers a solution

“We’ve developed something very promising – a sustainable platform for the remediation of contaminated water.”

Professor Li Jun

NUS Biomedical Engineering

ADVANCED MATERIALS

18 Mar 2026

Toxic phenol clean-up has high eco-costs. New biocatalyst offers a solution

“We’ve developed something very promising – a sustainable platform for the remediation of contaminated water.”

Professor Li Jun

NUS Biomedical Engineering

A new, sustainable material developed by NUS researchers promises to supercharge phenol removal from wastewater via enzyme catalysis. The study, published in Advanced Materials, showed that the new biocatalyst achieved a phenol removal rate of over ninety percent in twenty minutes.

But what are phenols?

Phenols are organic compounds with at least one hydroxyl group attached to an aromatic ring. Many may recognise the most notorious phenol, Bisphenol A, better known as BPA, due to its links to cancer and reproductive harm. However, BPA is just one of many phenolic pollutants that seep into natural water bodies from human activities.

Many synthetic phenols are found in industrial discharge. Even in tiny amounts, these compounds can be dangerously toxic. They are chemically resistant to degradation, and stay in the environment for a long time, often disrupting entire ecological structures. Easily absorbed through the skin, they pose a serious threat to human health. Prolonged exposure can lead to liver or kidney failure – even death.

Examples of toxic phenolic compounds and their associated hazards to health and the environment.

Current phenol removal strategies

Proper disposal of phenol-containing industrial wastewater is critical in managing environmental phenols. Yet, it is difficult to remove phenols from water using conventional physical treatments like sedimentation, and chemical treatments like advanced oxidation processes (AOPs) are energy intensive and require expensive acids to work.

Enzyme-catalysed treatments, on the other hand, are highly efficient, environmentally friendly and work well under mild conditions. However, these enzymes have limitations, explained the study’s lead author, Professor Li Jun from NUS Biomedical Engineering and NUS Environmental Research Institute (NERI).

Take horseradish peroxidase (HRP) for example, which the researchers used as their study’s focus. Extracting and purifying the enzyme is quite expensive, which restricts its scalability, said Li.

He elaborated: Once HRP hits water, it is difficult to recover, and this limits its reusability. To counteract this limitation, scientists have tried stabilising the enzyme within a nanoscale structure – a method called enzyme encapsulation. But past studies using polyacrylamide hydrogels for HRP encapsulation showed slower diffusion and reduced reaction efficiency.

The missing ingredient

Taking inspiration from their work in biodegradable waste, Li’s research team met this challenge by integrating a new ingredient into hydrogel-encapsulated HRP: Biochar.

Biochar is a porous, carbon-rich material produced by burning organic materials in a high temperature, oxygen-deficient environment – a cleaner process than regular burning. Biochar can be sourced from food waste, agricultural residues and more, making it relatively cheap, according to Li. For their study, they used biochar carbonised from pig manure.

Reaction performance soared, found the study, when biochar was synthesised with hydrogel-HRP composites. The close binding of HRP with biochar stabilised the enzyme, while hydrogel and biochar concentrated reactants near the HRP, accelerating the oxidation process.

“The –NH₂ groups within the gel generate an electro-rich domain, facilitating the absorption of H₂O₂,” explained the study’s first author, Dr Wang Shengzhe, a research fellow at NERI. Meanwhile, within the gel pores, “the –COOH groups on the biochar surface create an electro-deficient domain, thereby facilitating the adsorption of phenol,” he said.

Polyacrylamide gel and biochar create an optimal microenvironment that keeps HRP stable and draws in reactants, boosting catalytic efficiency.

Comparing treatments

The new biocatalyst removed phenols 91.4 times faster than composites without biochar, and maintained high removal efficiency for longer, giving it superior recyclability. It also exhibited an exceptionally high turnover frequency, which measures the efficiency of its active sites in driving a reaction; the biochar-based biocatalyst was at least 11.2 times more efficient than state-of-the-art AOPs, single-atom Fenton-like catalytic systems.

The biocatalyst also consumed significantly less hydrogen peroxide than Fenton-like systems. Plus, in contrast to the acidic conditions required by Fenton-like systems, the biocatalyst was most efficient at a neutral pH, negating the need for additional energy-intensive inputs.

Proposed mechanism of phenol degradation (left) and the key performance metrics (right) of the Gel/BC₂₅-HRP catalyst, showing its speed, durability and adaptability for practical applications.

Wang, however, did note a caveat. Their biocatalyst is less effective in wastewater with high concentrations of phenols. Therefore, this hydrogel-biochar-HRP composite will work best in combination with AOPs, rather than replacing them entirely.

Green, greener, greenest

The researchers noted that the system offers potential for further optimisation, to reap even more green benefits; the removed phenol, for example, may potentially be reused in plastic manufacturing. But for now, this study already serves as a compelling proof of concept for integrating biochar into encapsulated enzymes, opening up new possibilities for raising the catalytic efficiency of other enzymes for phenol removal.

“We’ve developed something very promising – a sustainable platform for the remediation of contaminated water,” said Li.

References

Wang, S., Zhu, J., Xue, W., Wen, Y., Zhang, Z., Song, X., ... & Li, J. (2025). A Biochar‐Based Composite Hydrogel Microenvironment for Enhanced Biocatalysis. Advanced Materials, e17616.

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Li Jun Toxic phenol clean-up has high eco-costs. New biocatalyst offers a solution

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