Engineering of phosphate-functionalized biochars with highly developed surface area and porosity for efficient and selective extraction of uranium

Abstract Properly engineering of surface functionality and structural porosity is critical to improve the sorption performance of biochars. Herein, we report a facile one-pot preparation of phosphate group-functionalized biochars (PBs) derived from bamboo sawdust by engineering with phytic acid prior to pyrolysis. High specific surface areas (629, 1298 and 1109 m2·g−1), large pore volumes (0.332, 0.919 and 0.789 cm3·g−1), and abundant phosphorous contents (1.14, 3.32 and 1.53 at.%) are achieved compatibly for the PBs pyrolyzed at given temperatures (i.e., 300, 450 and 600 °C) which are significantly higher than those of pristine biochars. Phytic acid not only releases hydrogen protons to tailor biochar matrixes to make micropores created and further developed, but also provides organic phosphorous-containing moiety to guarantee the surface phosphate functionality. PBs extract U(VI) from aqueous media efficiently, i.e., equilibrium achieved within 8 h, high sorption capacity of 229.2 mg·g−1 (at pH 4.0, T 298 K), and favorable selectivity towards U(VI) against the interference of coexisting metal ions. PBs can be regenerated by 0.1 mol·L−1 Na2CO3 and reused well after six recycles. This present work provides a path for the design and synthesis of advanced biochars with favorable potentials in the extraction of U(VI)-containing effluents.