Boosted charge transfer in a naturally formed Ca(Al 2 Si 2 O 8 )/Fe 2 O 3 heterojunction for piezocatalytical formation of H 2 O 2 and solidification of U(VI).

Energy and environmental issues make the generation of H2 O2 and the separation of U(VI) from water very important topics. In this work, we disclosed a low-cost, high-efficiency method for separating U(VI) from water based on the naturally formed catalyst (red volcanic stone powders, RVSP) of Ca(Al2 Si2 O8 )/Fe2 O3 heterojunction through a piezocatalytic pathway induced by ultrasonication. The charges were found to be elevatedly separated due to the formation of the heterojunction. It is found that under ultrasonication, charges were effectively separated and then reacted with water to form H2 O2 with a high yield of 196.7 μmol·g-1 in 4 h, which further solidifies U(VI) to form a solid of UO2 O2 . The removal rate of U(VI) in water reached 96 % (50 ppm) within 150 min. Furthermore, the results calculated by VASP show that the cyclic variation of the conduction bands under a cyclic force field facilitates the charge separation, and thus may promote piezocatalysis. Most importantly, the application study in real seawater indicates that U(VI) piezocatalysis based on natural minerals has great potential. This work presents a comprehensive investigation of U(VI) piezocatalysis by Ca(Al2 Si2 O8 )/Fe2 O3 and provides a new idea for piezocatalytic extraction of uranium.