Corn Cob Biochar Filters Pull Ammonia and Micro and Nanoplastics From Water

Why It Matters

The dual‑contaminant removal addresses two emerging water quality threats with a single, inexpensive media, reducing treatment complexity and operating costs. Scaling this technology could enhance water safety while sequestering carbon from agricultural residues, supporting climate‑smart infrastructure.

Key Takeaways

• Corn‑cob biochar removes ~64% ammonia at 10 ppm
• Over 97% micro/nanoplastic removal across 0.1–2 µm sizes
• High‑temperature (700 °C) biochar shows best pore structure
• No PAH leaching detected, meeting safety standards
• Filters regenerate, retaining >55% ammonia removal after three cycles

Pulse Analysis

Ammonia runoff from fertilizers and livestock, together with the proliferation of micro‑ and nanoplastics, has become a dual crisis for freshwater ecosystems worldwide. Conventional treatment plants often rely on separate processes—biological nitrification for nitrogen and membrane filtration for plastics—each demanding significant capital and energy. The search for a single, low‑cost adsorbent has intensified as regulators tighten limits on both nutrients and emerging contaminants. Biochar, a carbon‑rich material produced by pyrolyzing biomass under limited oxygen, has long been explored for soil amendment, yet its porous structure also makes it a promising candidate for water purification.

The University of Delaware team demonstrated that corn‑cob biochar heated to 700 °C (CCB700) achieves a rare combination of high surface area and favorable surface charge, enabling it to capture up to 63.9% of ammonia at a 10 ppm feed and more than 97% of polystyrene particles from 0.1 µm to 2 µm. Scanning electron microscopy revealed particles lodged within the micro‑pores, while infrared spectroscopy confirmed electrostatic binding of ammonium ions to oxygen‑functional groups. Crucially, leaching tests showed no release of the 16 EPA‑listed PAHs, and the material retained over 55% ammonia removal after three regeneration cycles, underscoring its durability.

These results position corn‑cob biochar as a scalable, circular technology for decentralized water treatment in agricultural communities, livestock facilities, and small‑scale municipal systems. By converting locally available crop residues into reusable filters, operators can lower chemical procurement costs, reduce waste, and simultaneously sequester carbon in a stable form, aligning with climate‑smart agriculture goals. Commercial adsorbents such as activated carbon often carry higher price tags and generate spent media that require disposal; biochar offers a lower‑cost, regenerable alternative with comparable performance. Further work on reactor design, long‑term field trials, and integration with existing infrastructure could accelerate adoption across the water‑treatment sector.