In a recent study published in Scientific Reports, researchers Luiza Usevičiūtė, Artūras Kaklauskas, Vaidotas Danila, and Tomas Januševičius present a novel and effective solution to a pervasive environmental problem: phosphate pollution. The widespread use of phosphorus-containing products like detergents and fertilizers has led to an alarming rise in phosphate levels in water bodies, triggering eutrophication and threatening aquatic ecosystems. The European Union has regulations limiting total phosphorus concentration in treated wastewater to as low as 0.5 mg/L, but current removal methods often come with high costs, operational complexity, or the risk of secondary pollution. This new research introduces a cost-effective, sustainable adsorbent derived from used cork stoppers and modified with zirconium and chitosan. The key finding is that these composite beads can remove up to 95% of phosphate, demonstrating a significant advancement in water remediation technology.

The core of this innovative material is cork biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More, a porous, high-surface-area material produced from waste cork stoppers. While biochar is an excellent base, its negatively charged surface typically repels phosphate anions, making it inefficient for phosphate removal on its own. To overcome this limitation, the researchers modified the cork biochar with chitosan, a natural biopolymer that enhances adsorption, and zirconium (Zr(IV)) ions, which have a strong affinity for phosphate. The combination of these components created a powerful new composite material, Zr(IV)-loaded chitosan-modified used cork stopper biochar (CS-CBC-Zr) beads, that not only had a relatively large surface area (11.8 m²/g) but also a positive charge that actively attracts phosphate ions. The final beads were tested across various conditions to assess their efficacy and practical application.

The performance of the new composite beads was impressive, demonstrating superior phosphate removal compared to the original, unmodified materials. The study found that phosphate removal efficiency steadily increased with the dose of the adsorbent. When the CS-CBC-Zr dosage was increased from 0.025 to 0.45 g, the phosphate removal rate jumped from 15.8% to an outstanding 93.3%. The material also performed exceptionally well across a broad range of environmental conditions. It maintained excellent phosphate removal performance over a wide pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More range of 4–10, making it highly versatile for treating various water sources without needing extensive pH adjustments. This is a crucial finding, as many other adsorbents are limited to a narrow pH window, complicating their application.

In a competitive environment where other anions are present, such as in real wastewater, the CS-CBC-Zr beads showed excellent selectivity for phosphate. The presence of common co-anions like chloride, nitrate, and sulfate only caused a slight decrease in phosphate removal efficiency, which is a significant advantage for practical applications. The researchers determined that the adsorption mechanism was primarily a chemical process, specifically ion exchange, which explains the high selectivity and strong binding of phosphate to the zirconium on the bead’s surface. The Sips isotherm model provided the best fit for the experimental data, with a maximum adsorption capacity of 33.89 mg/g, a figure that closely matched the maximum experimental value of 34.2 mg/g. The kinetic data also fit well with a pseudo-second-order model, suggesting that the adsorption process was governed by chemisorption.

Beyond its high efficiency, the CS-CBC-Zr composite offers practical and sustainable benefits. It repurposes a waste material—used cork stoppers—into a valuable resource, reducing the overall cost and environmental footprint of water treatment. The beads also show promise for reusability, with the potential for regeneration. While the preparation process involves some additional steps like crosslinking and zirconium loading, the end result is a robust, efficient, and versatile adsorbent that can be a key player in the global effort to combat water pollution and eutrophication. The findings from this study suggest a promising, low-cost method for removing phosphate from water, offering a new tool for environmental managers and researchers in the face of escalating water quality challenges. The next step for this research is to validate the material’s performance in real-world wastewater treatment conditions.

Source: Usevičiūtė, L., Kaklauskas, A., Danila, V., & Januševičius, T. (2025). Enhanced aqueous phosphate removal using chitosan-modified zirconium-loaded cork biochar. Scientific Reports, 15(29240).