Managing agricultural waste presents a dual challenge: controlling harmful ammonia (NH₃) emissions and preventing the spread of toxic metals from manure. Scientists have now devised a sustainable approach that converts coal tailings, a common industrial byproduct, into a highly effective adsorbent. This innovative material, created through a catalytic oxidation process using silver and titanium dioxide (Ag/TiO₂), simultaneously captures ammonia and neutralizes hazardous metals, offering a cost-effective solution for sustainable farming.
A team from The University of Melbourne , Australia, pioneered the method, modifying coal tailings at a modest 250 °C. Unlike conventional high-temperature treatments, this catalytic process is exothermic, generating its own heat, which significantly reduces energy consumption and leads to lower CO₂ emissions. The core material harnesses Ag/TiO₂ to produce reactive oxygen species that functionalize the coal tailings, creating a network of ultramicropores and oxygen-containing chemical groups on its surface.
Engineered for Double Duty
The newly designed material demonstrates remarkable adsorption capabilities. It achieved an ammonia adsorption capacity of 56.80 mg·g⁻¹ , representing a substantial 16-fold improvement compared to untreated tailings. Intriguingly, once the material has adsorbed ammonia, its capacity to bind copper (Cu) increased threefold, reaching 33.29 mg·g⁻¹ . This coupled adsorption is a central aspect of the material's effectiveness, showcasing its ability to address multiple pollutants within complex agricultural waste streams.
Detailed analyses revealed the intricate mechanisms at play. Ammonia interacts with the newly formed oxygen-containing functional groups on the surface through acid-base reactions and the formation of amides. These amide groups then act as strong coordination sites, effectively immobilizing toxic metals such as copper. The optimized pore structure created during the catalytic oxidation also physically traps ammonia molecules, enhancing their retention and interaction with active sites.
Real-World Impact in Agriculture
The practical application of this modified material yielded compelling results in swine manure treatment. When incorporated at 20% into manure, it reduced ammonia emissions by 64.89% . Simultaneously, it significantly lowered the bioavailability of copper by 57.82% and zinc by 48.50%. This capability means that farmers can not only control harmful gases but also transform manure into safer, nutrient-rich compost, supporting circular agriculture principles.
Beyond its environmental benefits, this approach offers substantial economic advantages. By repurposing low-value coal tailings, the method avoids expensive primary resource extraction and energy-intensive processes often required for commercial adsorbents. The estimated economic savings range from $425 to $1700 per ton compared to commercial activated carbon, making it a viable and attractive option for large-scale agricultural operations.
Advancing Sustainable Solutions
Researchers are actively exploring ways to further enhance the material's scalability and cost-effectiveness. Future work focuses on substituting silver with more earth-abundant elements in the catalyst and optimizing spray coating techniques for catalyst immobilization within reactors. These advancements aim to prevent catalyst depletion, reduce operational costs, and minimize any potential introduction of catalytic elements into agricultural systems, paving the way for even more sustainable and widespread adoption.
Suggested author quote for approval:
"Our goal was to create a solution that not only tackles the pressing environmental issues of agricultural waste but also offers clear economic benefits," said Professor Jing Hu from The University of Melbourne . "By transforming coal tailings into a high-performance, multifunctional adsorbent, we are opening new pathways for resource recovery, pollution control, and the production of safer, slow-release fertilizers for a truly circular economy."
Corresponding Authors:
Jing Hu, School of Agriculture, Food and Ecosystem Sciences, The University of Melbourne, Parkville, VIC, 3010, Australia.
Deli Chen, School of Agriculture, Food and Ecosystem Sciences, The University of Melbourne, Parkville, VIC, 3010, Australia.
Original Source: https://doi.org/10.1007/s44246-026-00276-2
Contributions: All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Jing Hu, Bing Han, and Clayton Butterly. The first draft of the manuscript was written by Jing Hu and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
Carbon Research
Experimental study
Not applicable
Interface-activated coal tailings for coupled ammonia adsorption and potentially toxic metal complexation via Ag/TiO₂ catalysis
1-Jul-2026
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.