A novel effect of combining microorganisms and graphene oxide for solidifying simulated nuclides strontium

Highlights: • Propose a new strategy for microbial solidification of strontium. • Mineralization of strontium can be realized in a wide range. • The presence of GO stabilizes the large-scale rock-like SrCO₃ minerals. Inspired by microbial diagenesis and mounding, microbial mineralization technology has been widely used in the treatment of heavy metal and radionuclide contamination. S. pasteurii can decompose urea as a source of energy to produce CO₃²⁻ in the microbial mineralization system. Therefore, strontium-contaminated radioactive wastewater can be effectively treated by combining CO₃²⁻ with surrounding strontium ions (Sr²⁺) to form strontium carbonate (SrCO₃). Herein, we investigated how the concentration of graphene oxide (GO) and mineralization time influence the morphology of SrCO₃ and the mineralization efficiency. GO was used as a crystal regulator to solidify the radionuclide strontium in the microbial mineralization system to obtain large-scale rock-like SrCO₃ minerals. The results showed that GO can adsorb the surrounding Sr²⁺ with oxygen-containing functional groups on its surface to form SrCO₃ complexes, directly influencing the morphology and consolidation percentage of SrCO₃. Considering the leaching behaviour of nuclides, we further studied the stability of consolidated SrCO₃ minerals. The results indicated that the presence of GO improved the stability of the mineralized samples obtained in the microbial mineralization system.