Effects and mechanism of uranium(VI) removal by wood biochar loaded with MnFe2O4

Uranium (U) seriously threatens environmental health due to its chemical and radioactivity toxicity unless it is immobilized by adsorption materials. Here, MnFe2O4 was used to modify biochar derived from apple tree branches to obtain MnFe2O4-biochar (MFBC), which was used for U(VI) removal. The mechanisms were explored by advanced analytical techniques, including scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM-EDS), Brunauer-Emmett-Teller (BET), vibrating sample magnetometer (VSM), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The MFBC displayed a considerable adsorption rate of U(VI), with a maximum adsorption capacity of 83.00 mg/g at pH 6.0 and 313 K. The removal behavior was well described by the Freundlich and pseudo-second-order kinetic models. The dominant removal mechanism was complexation between the negatively charged O-containing groups on the MFBC and the positively charged U(VI). This work demonstrates the potential of MFBC to remediate U(VI)-contaminated wastewater.