Water eutrophication, driven by excess ammonium and phosphate from agricultural runoff and wastewater, is a growing environmental concern. Researchers from Shaanxi, China, investigated an innovative approach to address this issue using iron-modified biochar (Fe-HBC). This material, derived from agricultural waste and treated with ferric chloride (FeCl3), was shown to efficiently adsorb both ammonium and phosphate from water.

The study found that Fe-HBC, compared to unmodified biochar, exhibited an enhanced surface area, improved pore structure, and increased functional groups. The iron oxides on the biochar’s surface (Fe2O3 and Fe3O4) facilitated effective co-adsorption through mechanisms like electrostatic attraction, ion exchange, and coprecipitation. Batch experiments revealed ammonium adsorption capacities of 7.59-10.59 mg/g and phosphate capacities of 10.46-15.22 mg/g, depending on biochar composition.

Optimal adsorption was observed with a biochar concentration of 1% and a flow rate of 1 mL/min in column experiments. These results highlight the potential of Fe-HBC for practical wastewater treatment applications. By recovering nitrogen and phosphorus, the process not only helps prevent eutrophication but also offers a sustainable way to manage agricultural and industrial wastewater. This research underscores the value of using modified biochar as a cost-effective, eco-friendly solution to water pollution.