Engineered phosphorous-functionalized biochar with enhanced porosity using phytic acid-assisted ball milling for efficient and selective uptake of aquatic uranium

Abstract The efficient extraction of uranium is challenging for radioactive wastewater treatment. Concerning to the specific coordination of functional groups with radionuclides, the development of ideal sorbents with high surface area, enhanced porosity and abundant functional groups compatibly to uptake uranium selectively is of great significance. Biochar, an attractive material to concentration aquatic targets, exhibits a positive correlation of surface area and pore volume of biochars with pyrolysis temperature, whereas a negative relation of surface functionality with thermolysis temperature. Here we applied a facile and environmental-friendly ball-milling technique to engineer raw biochars in the presence of phytic acid. Ball-milling treatment increased the external surface area of biochars by reducing grain sizes, as well as enhanced the micropore surface area by exposing blocked micropore networks. P-containing moiety was grafted to the surface of biochar matrix successfully. The physicochemical characteristics of biochars enabled a high uptake capacity (128.5 mg/g) and favorable selectivity of U(VI). It suggested that ball-milling of raw biochars with activating solvents could achieve an excellent performance for the efficient concentration of aquatic uranium.