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

Abstract

The utilization of Microcystis biomass is an urgent issue in the mitigation of cyanobacterial bloom. In this study, Microcystis-derived biochar (MB) and Fe₃O₄-modified biochar (Fe₃O₄/MB) were fabricated for the U(VI) elimination. The results showed that U(VI) sorption process by either MB or Fe₃O₄/MB was pH-dependent and ionic strength-independent. The maximum sorption capacity of MB was higher than that of Fe₃O₄/MB. According to the analysis of X-ray photoelectron spectroscopy, U(VI) sorption on both MB and Fe₃O₄/MB was mainly ascribed to the surface complexation between U(VI) and oxygen-containing functional groups on the surface of MB. Fe₃O₄ 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 Fe₃O₄/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.

Keywords: Magnetic biochar; Microcystis aeruginosa; Reusability; Sorption; Uranium.