Researchers have developed a new eco friendly method to transform biochar into a highly hydrophobic material that can repel water and absorb large amounts of oil. The innovation could help advance sustainable materials for environmental cleanup and green coatings.
The study, published in the journal Biochar , introduces a solvent free mechanochemical process that functionalizes biochar using octadecylamine. The resulting material can be applied as a coating on natural hemp fibers, giving them strong water repellent properties while allowing them to absorb oil efficiently.
Biochar is a carbon rich material produced from biomass through pyrolysis. It is widely studied for applications in soil improvement, pollution control, and carbon management because of its porous structure and large surface area. However, modifying biochar to tailor its surface properties often requires solvent intensive chemical reactions that can be costly and environmentally harmful.
The new research offers an alternative approach. Instead of traditional wet chemical reactions, the scientists used a planetary ball milling technique to activate biochar and induce chemical bonding with long chain amine molecules under solvent free conditions. This mechanochemical method allows functional groups to form directly on the carbon surface while reducing chemical consumption and environmental impact.
“We aimed to develop a greener and more efficient strategy to modify biochar while maintaining its sustainability advantages,” the researchers explained. “Mechanochemical functionalization allows us to create hydrophobic biochar materials without the need for harsh reaction conditions or large volumes of solvents.”
The modification process introduces long alkyl chains onto the biochar surface. These chains reduce the material’s polarity and increase surface roughness, two factors that contribute to strong water repellency. When dispersed in a bio based solvent and applied through dip coating, the modified biochar forms a thin hydrophobic layer on hemp fibers.
Contact angle measurements showed that the coated hemp fibers reached a water contact angle of approximately 126 degrees after a single coating layer. In contrast, uncoated hemp fibers quickly absorbed water and lost their hydrophobic character. Microscopic analysis confirmed that the biochar coating altered the fiber surface morphology and increased surface roughness, helping maintain water resistance.
The coated fibers also demonstrated remarkable performance in oil absorption tests. When placed in oil water mixtures containing different oils such as sunflower oil, frying oil, motor oil, and pump oil, the coated fibers absorbed up to fourteen times their own weight in oil. This corresponds to an adsorption capacity approaching 1400 percent of the fiber’s initial mass.
Such performance highlights the potential of the material for environmental remediation. Oil spill cleanup and wastewater treatment often require materials that selectively absorb oil while repelling water. The hydrophobic biochar coated hemp fibers provide a renewable and biodegradable alternative to many synthetic sorbents currently used for these applications.
The study also emphasizes sustainability. Biochar originates from biomass waste, hemp fibers are renewable agricultural materials, and the coating process uses a green solvent derived from citrus waste. Together these elements contribute to a lower environmental footprint compared with conventional oil sorbent technologies.
According to the researchers, the approach demonstrates how mechanochemistry can open new pathways for designing advanced carbon based materials. By combining renewable resources with solvent free synthesis, the strategy may lead to scalable technologies for environmental protection and sustainable materials engineering.
The researchers note that further studies may explore large scale production and additional applications for hydrophobic biochar coatings in filtration systems, composite materials, and environmental remediation technologies.
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Journal Reference: Sozio, N., Kiani, A., Viscusi, G. et al. Mechanochemical functionalization of biochar for providing new eco-sustainable hydrophobic coating. Biochar 8 , 32 (2026).
https://doi.org/10.1007/s42773-025-00532-5
About Biochar
Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.
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Biochar
Experimental study
Mechanochemical functionalization of biochar for providing new eco-sustainable hydrophobic coating
24-Feb-2026