The ultimate dirt filter: 'Oxychar' offers a cheaper, smarter way to scrub toxic cadmium from farmland

Heavy metal pollution is quietly threatening global food security by poisoning agricultural lands. While environmental scientists have long used charred organic materials to trap toxins like cadmium in the soil, the traditional high-heat baking process is expensive and energy-intensive. Now, an international research team has developed a highly efficient, budget-friendly alternative called "oxychar" that pulls double duty, soaking up both agricultural ammonia and toxic cadmium at the same time.

Published in the journal Carbon Research, these findings deliver a practical win for sustainable farming. The cross-border initiative was spearheaded by corresponding authors Dr. Wei Liu from the College of Chemistry and Materials Science at Hebei University (China) and Dr. Bing Han from the School of Engineering at Deakin University (Australia). Their laboratories teamed up to completely rethink how we process agricultural waste into environmental remedies.

Rather than blasting rice straw with extreme heat, the researchers utilized a low-temperature partial-oxidation process. This method is exceptionally energy-efficient, waste-free, and yields over 55% usable oxychar. When the team tested this new material in contaminated environments, they found that introducing ammonia (NH3) into the mix actually turbocharged the charcoal's ability to lock away heavy metals.

"The chemistry here is fascinating," the research team noted. While standard oxychar uses phenolic groups to snag the cadmium, the addition of ammonia creates nitrogen-rich functional groups. These act like chemical super-glue, forming tough, covalent-like bonds that keep the toxic metal from leaching back into the water or soil.

Key Performance Metrics:

• Superior Trapping Power: Raw rice straw can only hold about 31.7 mg/g of cadmium. The newly engineered oxychar-NH3 complex pushed that capacity up to an impressive 53.8 mg/g.
• Rapid Soil Healing: During a 20-day soil incubation test, the amended dirt achieved a 69.3% cadmium immobilization rate, effectively locking the metal away so crop roots cannot absorb it.
• Microbial Revival: The treated soil isn't just cleaner; it is biologically active again. The team recorded a nearly 50% spike in microbial CO2 emissions on the very first day of treatment, a clear biological signal that the cadmium toxicity had plummeted and the soil microbiome was recovering.
• Major Cost Savings: Healing the earth shouldn't bankrupt farmers. The economic evaluation within the study calculates that switching to this new material slashes remediation costs by $120 to $310 USD per ton compared to standard biochar, without sacrificing an ounce of performance.

By bridging the analytical chemistry expertise at Hebei University with the engineering prowess at Deakin University, this project delivers a highly scalable, financially viable blueprint for cleaning up the world's compromised agricultural lands. As policymakers look for ways to secure clean food supply chains, the work of Dr. Liu and Dr. Han proves that sometimes the best way to treat agricultural pollution is by reinventing agricultural waste.

Corresponding Authors:

Wei Liu (Note: Kexin Zhao and Wei Liu contributed equally to this work.) College of Chemistry and Materials Science, Key Laboratory of Analytical Science and Technology of Hebei Province, Key Laboratory of Medicinal Chemistry and Molecular Diagnosis, Ministry of Education, Hebei University, Baoding, People’s Republic of China.

Bing Han School of Engineering, Deakin University, Geelong, VIC, Australia.

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Journal reference: Zhao, K., Liu, W., Hu, J. et al. Synergistic adsorption of ammonia and cadmium on oxychar for sustainable remediation of water and soil. Carbon Res. 5, 12 (2026).   

https://doi.org/10.1007/s44246-025-00254-0  

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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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