A recent study published in the journal Environmental Science and Pollution Research by Sepideh Ansari, Ricardo Bello-Mendoza, and Aisling O’Sullivan explores the use of iron-modified barley straw biochar as a sustainable solution for water treatment. The research team focused on addressing the global issue of water quality degradation caused by excessive nutrients, specifically nitrate and phosphate, which enter water bodies through inadequately treated runoff and wastewater. These pollutants pose significant risks to both the environment and human health, with high nitrate levels linked to conditions like “blue baby syndrome” and various cancers, while excessive phosphate leads to eutrophication and oxygen depletion in aquatic ecosystems.

The primary challenge addressed in this manuscript is the inherent limitation of standard biochar, which typically carries a net negative surface charge. Because both nitrate and phosphate are anionic (negatively charged) pollutants, they are naturally repelled by raw biochar, resulting in poor removal efficiency. Furthermore, while agricultural residues like barley straw are abundant, they often lack the mechanical stability and chemical surface area required for effective large-scale water filtration in their raw state.

To solve this, the researchers synthesized an iron-treated barley straw biochar, referred to as Fe-BSBC. The production involved pyrolyzing barley straw at 600°C before immersing it in a ferric chloride solution and treating it with ammonium hydroxide to form iron hydroxide deposits on the surface. This modification successfully incorporated iron onto the biochar, creating a layer of iron oxides that significantly increased the positive surface charge of the material. The researchers verified this using scanning electron microscopy, which showed iron oxide particles uniformly distributed across the porous biochar structure.

The outcomes of the batch experiments demonstrated that Fe-BSBC is a highly effective adsorbent, particularly for phosphate removal. Under optimal conditions, the material achieved an experimental adsorption capacity of 13.7 milligrams per gram for phosphate and 2.0 milligrams per gram for nitrate, outperforming many previously reported biochar-based adsorbents. Statistical modeling further predicted maximum potential capacities as high as 22.0 milligrams per gram for phosphate and 4.07 milligrams per gram for nitrate. The study identified that while nitrate removal is primarily driven by electrostatic attraction, phosphate removal involves both electrostatic forces and ligand exchange, forming stable iron-phosphate complexes.

This research highlights that utilizing local agricultural by-products like barley straw to create nutrient-trapping biochar is not only economically viable but also aligns with circular economy principles. By converting waste into a value-added water treatment tool, this method helps reduce environmental pollution from common practices such as stubble burning while providing a low-cost technology for regions with limited access to advanced filtration systems. These findings support global sustainable development goals by offering a scalable and efficient means to protect drinking water security and aquatic biodiversity.

Source: Ansari, S., Bello-Mendoza, R., & O’Sullivan, A. (2026). Iron-modified barley straw biochar for nitrate and phosphate removal from water. Environmental Science and Pollution Research.