Adsorption mechanism of phosphorus in eutrophic waters by KOH modified hydrochar from corn stover

Solid waste generated during agricultural production, as a potential resource, has shown great promise in removing environmental pollutants, particularly in mitigating eutrophication caused by phosphorus pollution.In this work, corn stover hydrochar was synthesized using agricultural solid waste as the feedstock, with the synergistic combination of in-situ KOH modification and surface impregnation KOH modification employed for its preparation. On this basis, an innovative comparative framework was employed to systematically and comprehensively analyze the intrinsic relationship between the structural properties and phosphorus adsorption performance of hydrochars under different modification conditions, thereby achieving a more holistic understanding of how modification conditions regulate the adsorption behavior of hydrochars. We found that the specific surface area, total pore volume, microporous volume and average pore diameter of the modified hydrochar increased with rising the modified pH value, thereby enhancing its adsorption capacity, with the optimal performance achieved at pH 13. The phosphorus adsorption capacities of HCO13 and HCE13 reached 7.58 mg/g and 8.83 mg/g, respectively, at 45 °C, demonstrating excellent adsorption performance. KOH modification improved the specific surface area，pore distribution and oxygen-containing functional groups on the surface of the hydrochar, which provided abundant active sites for the adsorption of phosphorus, and enhanced the adsorption capacity. This revealed the underlying mechanism of phosphate adsorption by modified hydrochar. Furthermore, the practical performance of this adsorbent in removing phosphorus from eutrophic waters was validated, and phosphorus mass balance calculations confirmed its recycling potential. The demonstrated synthesis strategy of KOH-modified novel hydrochar, offers a robust theoretical foundation and practical guidance for the development of environmentally friendly technologies for phosphorus pollution control.