Efficient removal of U(VI) from aqueous solutions using the magnetic biochar derived from the biomass of a bloom-forming cyanobacterium (Microcystis aeruginosa)

The utilization of Microcystis biomass is an urgent issue in the mitigation of cyanobacterial bloom. In this study, Microcystis -derived biochar (MB) and Fe 3 O 4 -modified biochar (Fe 3 O 4 /MB) were fabricated for the U(VI) elimination. The results showed that U(VI) sorption process by either MB or Fe 3 O 4 /MB was pH-dependent and ionic strength-independent. The maximum sorption capacity of MB was higher than that of Fe 3 O 4 /MB. According to the analysis of X-ray photoelectron spectroscopy, U(VI) sorption on both MB and Fe 3 O 4 /MB was mainly ascribed to the surface complexation between U(VI) and oxygen-containing functional groups on the surface of MB. Fe 3 O 4 particles on the surface of MB didn’t provide extra active sites for the sorption of U(VI), but it enabled the adsorbent to be magnetically separated. Five consecutive sorption/desorption cycles verified the good reusability of Fe 3 O 4 /MB in this study. Therefore, the investigation is not only meaningful for the utilization of nuisance biomass from cyanobacterial blooms, but also provides novel adsorbents for the U(VI) removal from aqueous solutions.