Simple one-pot synthesis of manganese dioxide modified bamboo-derived biochar composites for uranium(vi) removal

Exploitation of bamboo-derived biochar offers a lucrative opportunity for using moso bamboo due to its short growth cycle, large quantity and universality. Novel MnO2 modified bamboo-derived biochar composites (MnO2@BBC) were successfully fabricated via a facile one-pot solvothermal reaction, and uranium(vi) adsorption experiments of MnO2@BBC were systematically performed under different pH values, adsorbent dosages, contact times, initial uranium(vi) concentrations and temperatures. Characterization analysis via Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photo electron spectroscopy (XPS) techniques and batch experiments demonstrated that MnO2 decoration could promote uranium(vi) adsorption by MnO2@BBC because of the increasing BET surface area (from 10.56 m(2) g(-1) to 63.50 m(2) g(-1)) and more abundant oxygen-containing functional groups on the surface. The adsorption processes of uranium(vi) by MnO2@BBC were pH-dependent, endothermic (Delta H = 38.08 kJ mol(-1) for MnO2@BBC-1) and spontaneous (Delta G < 0) in nature, and fitted to pseudo-second-order and Langmuir models. The maximum adsorption capacity of uranium(vi) by MnO2@BBC-1 was 97.40 mg g(-1). As the primary mechanism of U(vi) adsorption by MnO2@BBC, inner-sphere surface complexation of U(vi) with the Mn-O in MnO2 or with the C-O and C=O on the biochar surface was considered. Low-cost feedstock, simple preparation route and competitive adsorption capacity further highlighted the feasibility of MnO2@BBC for treating uranium-containing wastewater in practical application.