The novel activated biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More derived from rice husk ashAsh is the non-combustible inorganic residue that remains after organic matter, like wood or biomass, is completely burned. It consists mainly of minerals and is different from biochar, which is produced through incomplete combustion.   Ash Ash is the residue that remains after the complete More and modified with polyethyleneimine can capture twice as much formaldehyde as untreated versions. This sustainable material reaches a maximum adsorption capacity of 256 milligrams per gram by using nitrogen-rich groups to chemically trap harmful gases. The production process uses low-temperature activation and ultrasonic treatment to create a high-surface-area filter without the energy costs of traditional high-heat manufacturing. Scientists successfully demonstrated that this bio-based composite provides a cost-effective and environmentally friendly way to purify indoor air.

According to a study published in the journal Carbon Research by Thanh Luu Huynh, Bang Tam Thi Dao, and their research team, a new type of eco-friendly air filter material has been developed to combat indoor air pollution. Formaldehyde is a common indoor pollutant found in furniture, paints, and adhesives that is recognized as a human carcinogen even at very low concentrations. While traditional filters often rely on expensive or energy-intensive synthetic materials, this research explores the potential of using rice husk ash, an abundant agricultural byproduct, to create a sustainable solution. By converting this waste into activated biochar and enhancing it with a polymer called polyethyleneimine, the researchers created a composite that is exceptionally efficient at trapping toxic gas molecules.

The findings indicate that the modification process fundamentally changes how the material interacts with indoor air. While standard activated biochar primarily relies on its porous structure to physically trap pollutants, the addition of polyethyleneimine introduces a high density of amine functional groups. these groups act as chemical anchors that form stable bonds with formaldehyde molecules through a process known as chemisorption. This dual action allowed the modified material to reach a breakthrough time of nearly seventeen minutes, more than doubling the performance of unmodified versions. The maximum adsorption capacity recorded was 256 milligrams per gram, representing a significant leap in efficiency for biomass-derived adsorbents.

One of the most notable results of this study is the development of a production method that aligns with green chemistry principles. Traditional activated carbonActivated carbon is a form of carbon that has been processed to create a vast network of tiny pores, increasing its surface area significantly. This extensive surface area makes activated carbon exceptionally effective at trapping and holding impurities, like a molecular sponge. It is commonly More manufacturing often requires extremely high temperatures and complex chemical steps that leave a large carbon footprint. In contrast, this study utilized a low-temperature activation process combined with ultrasonic treatment, which effectively eliminated the need for high-heat calcination. This approach not only preserved the complex network of pores within the biochar but also ensured that the material remained cost-effective for large-scale use. The researchers confirmed that the resulting structure possessed a high surface area of over 887 square meters per gram before the polymer was added, providing ample space for the chemical modification to take hold.

The experimental results further demonstrated that the adsorption process follows a predictable and efficient pattern. Kinetic analysis showed that the rate at which the modified biochar captures formaldehyde is nearly three times faster than that of the untreated material. This rapid response is critical for indoor environments where air circulation and pollutant levels can fluctuate. The study also determined that the adsorption behavior fits the Langmuir model, suggesting that the formaldehyde forms a consistent layer over the active sites of the adsorbent. This predictability is essential for designing future air purification systems that can reliably protect residents from chronic exposure to volatile organic compounds.

By successfully transforming agricultural waste into a high-performance air purification tool, the researchers have provided a blueprint for more sustainable environmental management. The use of rice husk ash reduces the reliance on coal-based activated carbons and offers a way to repurpose waste from the rice industry. Because the material is both highly efficient and relatively simple to produce, it represents a viable alternative for improving indoor air quality in both residential and industrial settings. This study highlights the growing importance of bio-based materials in solving modern public health challenges, offering a promising path toward cleaner and safer living spaces through innovative chemical engineering.

Source: Huynh, T. L., Dao, B. T. T., Le, M. T., Doan, K. A. T., Nguyen, T. D., Le, H. N., & Ha-Thuc, C. N. (2026). Polyethyleneimine-modified activated biochar derived from rice husk ash: material development and preliminary formaldehyde adsorption study. Carbon Research, 5(5).