Fabrication of δ-MnO2-modified algal biochar for efficient removal of U(VI) from aqueous solutions

Exploitation of algal biochar is a profitable opportunity for the utilization of filamentous green algae due to its sustainable growth and ease of harvest. In this study, Rhizoclonium -derived biochar (CB) and δ-MnO 2 -modified biochar (MnO 2 /CB) were fabricated for uranium (U(VI)) removal. The results showed that the δ-MnO 2 modification increased the BET surface area and decreased the isoelectric point. The maximum sorption amount of U(VI) by the MnO 2 /CB reached up to 100.2 mg/g (pH = 6.0, 289 K, and 0.01 M NaCl), which was two times higher than that of the CB. After five consecutive sorption/desorption cycles, the affinity of the MnO 2 /CB for U(VI) maintained in 94.8%. According to the analysis of X-ray photoelectron spectroscopy, it confirmed that the U(VI) sorption was mainly ascribed to the surface complexation between U(VI) and oxygen-containing functional groups on the surface of the MnO 2 /CB. Therefore, this investigation not only encourages the development of algal biochar derived from the filamentous green algae but also provides a novel adsorbent for U(VI) removal from aqueous solutions.