From rice fields to fresh air: Transforming agricultural waste into a shield against indoor pollution

Researchers in Vietnam develop a sustainable biochar "sponge" that doubles the efficiency of removing toxic formaldehyde from the air

Biochar Editorial Office, Shenyang Agricultural University

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Polyethyleneimine-modified activated biochar derived from rice husk ash: material development and preliminary formaldehyde adsorption study

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Credit: Thanh Luu Huynh, Bang Tam Thi Dao, My Thoa Le, Khanh An Thi Doan, Trung Do Nguyen, Hon Nhien Le & Chi-Nhan Ha-Thuc

Formaldehyde is a common but unwelcome guest in many modern homes, leaking silently from furniture, flooring, and household products. While this colorless gas is a known respiratory irritant, cleaning it out of the air usually requires expensive or energy-heavy technology. Now, a research team from Vietnam National University has found a clever way to turn agricultural waste into a high-tech filter that breathes new life into indoor spaces.

In a study published in Carbon Research, the team describes how they successfully transformed rice husk ash—a byproduct of rice production—into a specialized "activated biochar." By modifying this charred material with a polymer called polyethyleneimine (PEI), they created a powerful adsorbent specifically designed to hunt down and trap formaldehyde molecules. The research was led by corresponding authors Bang Tam Thi Dao and Chi-Nhan Ha-Thuc from the Faculty of Materials Science and Technology at the University of Science, Vietnam National University. Their approach not only tackles air pollution but also offers a brilliant second life for the massive amounts of rice husk waste generated in Southeast Asia.

"We wanted to create a solution that was as sustainable as it was effective," say the lead researchers. "By using rice husk ash and a low-energy ultrasonic treatment, we avoided the high-temperature calcination usually required in manufacturing. The result is a material that is cheaper to make and much kinder to the environment."

Science Behind the Sponge:

1. The PEI Advantage: By adding PEI to the biochar, the researchers increased the density of amine functional groups on its surface. These chemical "hooks" are perfect for grabbing formaldehyde, effectively doubling the material's adsorption capacity compared to standard biochar.
2. Smart Manufacturing: The team used a combination of chemical activation and ultrasonic treatment. This skip the traditional high-heat steps, significantly reducing the carbon footprint of producing the filter material itself.
3. Precision Characterization: Using advanced tools like scanning electron microscopy (SEM) and infrared spectroscopy (FT-IR), the team proved that the PEI-modified biochar has a unique porous structure that acts like a microscopic labyrinth, trapping pollutants deep within.
4. Proven Performance: Kinetic and isotherm studies confirmed that the adsorption process is highly stable and follows predictable scientific models, making it a reliable candidate for commercial air purifiers.

This breakthrough from Vietnam National University highlights the growing importance of "circular chemistry"—where the waste from one industry (agriculture) becomes the raw material for another (environmental protection). As urban populations spend more time indoors, the work of Bang Tam Thi Dao and Chi-Nhan Ha-Thuc provides a scalable, cost-effective way to ensure the air we breathe at home is safe. By turning local agricultural remnants into high-value environmental tools, these Vietnamese scientists are proving that the keys to a cleaner future might already be sitting in our fields.

Corresponding Authors:

Bang Tam Thi Dao

Faculty of Materials Science and Technology, University of Science, Ho Chi Minh City, Vietnam. Vietnam National University, Ho Chi Minh City, Vietnam.

Chi-Nhan Ha-Thuc

Faculty of Materials Science and Technology, University of Science, Ho Chi Minh City, Vietnam. Vietnam National University, Ho Chi Minh City, Vietnam.

 

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Journal reference: Huynh, T.L., Dao, B.T.T., Le, M.T. et al. Polyethyleneimine-modified activated biochar derived from rice husk ash: material development and preliminary formaldehyde adsorption study. Carbon Res. 5, 5 (2026).   

https://doi.org/10.1007/s44246-025-00244-2  

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About Carbon Research

The journal Carbon Research is an international multidisciplinary platform for communicating advances in fundamental and applied research on natural and engineered carbonaceous materials that are associated with ecological and environmental functions, energy generation, and global change. It is a fully Open Access (OA) journal and the Article Publishing Charges (APC) are waived until Dec 31, 2025. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of carbon functions around the world to deliver findings from this rapidly expanding field of science. The journal is currently indexed by Scopus and Ei Compendex, and as of June 2025, the dynamic CiteScore value is 15.4.

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Journal

Carbon Research

DOI

10.1007/s44246-025-00244-2 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Polyethyleneimine-modified activated biochar derived from rice husk ash: material development and preliminary formaldehyde adsorption study

 

Turning orange waste into powerful water-cleaning material

Biochar Editorial Office, Shenyang Agricultural University

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Hierarchical porous biochar with Fe/Zn co-activation derived from orange waste: enhanced methylene blue adsorption and mechanistic insights

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Credit: Lei Zhang, , Xin Liu, Wenbo Liu, Hongying Du & Junkang Guo

Researchers have developed an environmentally friendly way to transform discarded orange peels into a highly efficient material that can remove toxic dyes from wastewater, offering a sustainable solution to two growing global challenges: agricultural waste management and water pollution.

Industrial dye pollution is a major environmental problem worldwide. Each year, more than 700,000 tons of synthetic dyes are produced, and a significant portion enters waterways due to incomplete treatment. Even at low concentrations, dyes can discolor water, block sunlight essential for aquatic life, and produce harmful compounds that pose risks to human and ecosystem health. Adsorption using carbon-based materials has emerged as a promising cleanup strategy, but many existing materials face limitations in performance, cost, and sustainability.

In a new study, scientists created an advanced biochar adsorbent using orange peel waste, a byproduct generated in large quantities during citrus processing. The research introduces a dual-activation method using zinc chloride and iron chloride to engineer a hierarchically porous biochar with enhanced surface reactivity.

“This work shows how agricultural waste can be transformed into high-value materials for environmental protection,” said corresponding author Lei Zhang. “By combining two activation strategies, we created a biochar that not only has a large surface area but also contains multiple active sites that work together to capture pollutants efficiently.”

The new material, known as Fe/Zn-OPBC500, demonstrated exceptional performance in removing methylene blue, a commonly used industrial dye that often contaminates textile wastewater. Laboratory tests showed the material achieved an adsorption capacity of 237.53 milligrams of dye per gram of biochar and removed nearly 97 percent of the dye within one hour. The material also maintained strong performance across a wide range of water conditions and retained significant removal capacity even after seven reuse cycles.

The material’s performance is driven by its unique structure. The dual chemical activation process creates a network of pores ranging from microscopic to nanometer scale, dramatically increasing the available surface area for pollutant capture. At the same time, iron-based active sites and oxygen-containing functional groups provide multiple mechanisms for binding dye molecules, including electrostatic attraction, chemical bonding, hydrogen bonding, and interactions between aromatic carbon structures and dye molecules.

“Traditional biochar often suffers from limited adsorption capacity or poor recyclability,” Zhang explained. “Our synergistic modification strategy solves these challenges by integrating structural engineering with surface chemistry design, resulting in both high efficiency and durability.”

The research also highlights the environmental benefits of valorizing citrus processing waste. Orange peels account for approximately 40 to 50 percent of total fruit mass during processing, and they are often discarded through landfilling or burning, which can contribute to secondary pollution. Converting this waste into advanced adsorbents provides a sustainable alternative that supports circular economy principles while reducing environmental impact.

Beyond dye removal, the researchers believe the material could be adapted for treating other types of industrial contaminants. The study provides new insights into how engineered biochar structures can be tailored to target specific pollutants, potentially expanding applications in wastewater treatment, environmental remediation, and resource recovery.

“Our findings provide a roadmap for designing next-generation carbon materials from renewable biomass,” Zhang said. “With further scaling and optimization, this approach could contribute to cleaner water systems while reducing agricultural waste.”

The research demonstrates how innovative material science can transform common food waste into powerful environmental technologies, helping address pollution challenges while promoting sustainable resource utilization.

 

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Journal reference: Zhang L, Liu X, Liu W, Du H, Guo J. 2026. Hierarchical porous biochar with Fe/Zn co-activation derived from orange waste: enhanced methylene blue adsorption and mechanistic insights. Biochar X 2: e004 doi: 10.48130/bchax-0026-0001 

https://www.maxapress.com/article/doi/10.48130/bchax-0026-0001  

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About the Journal: 

Biochar X (e-ISSN: 3070-1686) is an open access, online-only journal aims to transcend traditional disciplinary boundaries by providing a multidisciplinary platform for the exchange of cutting-edge research in both fundamental and applied aspects of biochar. The journal is dedicated to supporting the global biochar research community by offering an innovative, efficient, and professional outlet for sharing new findings and perspectives. Its core focus lies in the discovery of novel insights and the development of emerging applications in the rapidly growing field of biochar science. 

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DOI

10.48130/bchax-0026-0001 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Hierarchical porous biochar with Fe/Zn co-activation derived from orange waste: enhanced methylene blue adsorption and mechanistic insights

Article Publication Date

 

KTU researcher’s study: Why Nobel Prize-level materials have yet to reach industry

For more than two decades scientific attention has been focused on metal–organic frameworks (MOFs) – highly advanced porous materials widely regarded as one of the most promising tools for tackling climate change and environmental pollution.

Kaunas University of Technology

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Kaunas University of Technology (KTU) scientist Dr Samy Yousef

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Credit: KTU

Excess carbon dioxide in the atmosphere, polluted water, and increasingly strict environmental regulations are driving the search for materials that can efficiently trap pollutants at the molecular level. For more than two decades, this challenge has drawn scientific attention to metal–organic frameworks (MOFs) – highly advanced porous materials widely regarded as one of the most promising tools for tackling climate change and environmental pollution.

The importance of this research field was recognised in 2025, when the Nobel Prize in Chemistry was awarded to the scientists who developed MOFs. Despite this recognition and their exceptional properties, MOFs remain largely confined to laboratories. Their use in industry is still limited, mainly due to complex manufacturing processes and unpredictable production costs.

From Air Purification to Water Filtration – A Wide Range of Applications

This gap between strong scientific potential and limited real-world application is the focus of the research carried out by Kaunas University of Technology (KTU) scientist Dr Samy Yousef. In his study, he examines how materials developed within a Nobel Prize–winning field could be produced reliably and consistently at an industrial scale.

MOFs are porous crystalline materials formed by linking metal ions with organic molecules into highly orderly three-dimensional structures. This unique architecture allows researchers to precisely control pore size and chemical functionality, making it possible to tailor the materials for very specific technological tasks.

“These unique properties give the materials exceptional potential in environmental applications, including carbon dioxide capture, gas storage, wastewater treatment, separation processes, and catalysis, where they act as highly selective molecular filters,” explains Dr Samy Yousef, a researcher at KTU.

Because MOFs operate at the molecular level, they are seen as particularly promising in addressing pollution and climate change challenges. Their potential, however, extends well beyond environmental technologies.

“In addition to environmental applications, metal–organic frameworks are also regarded as promising platforms for optical sensing, controlled drug delivery, biomedical technologies, and antioxidants,” notes KTU researcher.

This broad range of potential uses, combined with the ability to adapt the materials to specific tasks, is one of the main reasons why MOFs have remained at the centre of intensive scientific research for more than two decades.

Advanced Materials Still Confined to Laboratories

“Laboratory-scale production does not take into account many aspects that are crucial at the industrial level, particularly secondary waste management, solvent regeneration, and long-term material stability,” says Dr Yousef.

As a result, MOFs are still typically produced only in small quantities and are mainly used in scientific research or highly specialised applications.

Building on the process sequences used in laboratory synthesis, the KTU researcher designed integrated production lines for the industrial-scale manufacture of MOFs. To do this, he selected commercially available industrial equipment and assessed individual production stages, their integration, and overall production capacity.

The analysis included a detailed assessment of raw material, chemical, and electricity consumption, as well as labour costs. Calculations were carried out under the economic and legal conditions applicable in Lithuania, allowing a realistic evaluation of whether such production lines could operate in practice.

The study showed that, depending on the production method chosen, industrial-scale manufacturing of MOFs can be financially viable, with investments in such production lines potentially paying off within a relatively short period of time.

“I believe that within a few years we will see fully operational production lines with capacities of several tonnes,” predicts Dr Yousef. In that case, MOFs could begin to appear in everyday technologies, although mostly indirectly.

“People would most likely encounter these materials in everyday devices such as air purifiers, building ventilation systems, or water filters, where their large surface area enables them to trap pollutants and toxins very efficiently. In most cases, MOFs would operate behind the scenes, improving performance, efficiency, and sustainability,” says the KTU researcher.

The scientific article Techno-economic assessment of scale-up of metal-organic framework production can be found here.

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Journal

Journal of the Indian Chemical Society

DOI

10.1016/j.jics.2025.102316 

Article Title

Techno-economic assessment of scale-up of metal-organic framework production