Facile synthesis of δ-MnO₂ biotemplated by waste tobacco stem-silks for enhanced removal of Sb(III)

The elimination of antimony pollution has attracted increasing concerns because of its high toxicity to human health and the natural environment. In this work, biomimetic δ-MnO₂ was synthesized by using waste tobacco stem-silks as biotemplate (Bio-δ-MnO₂) and used in the capture of Sb(III)from aqueous solution. The tobacco stem-silks not only provided unique wrinkled morphologies but also contained carbon element self-doped into the resulting samples. The maximum Sb(III) adsorption capacity reached 763.4 mg∙g ⁻¹, which is 2.06 times higher than δ-MnO₂ without template (370.0 mg∙g ⁻¹), 4.53 times than tobacco stem-silks carbon (168.5 mg∙g ⁻¹), and 10.39 times than commercial MnO₂ (73.5 mg∙g ⁻¹), respectively. The isotherm and kinetic studies indicated that the adsorption behavior was consistent with the Langmuir isotherm model and the pseudo-second-order kinetic equation. As far as we are aware, the adsorption capacity of Bio-δ-MnO₂ is much higher than that of most Sb(III) adsorbents. FT-IR, XPS, SEM, XRD, and Zeta potential analyses showed that the main mechanism for the adsorption of Sb(III) by Bio-δ-MnO₂ includes electrostatic attraction, surface complexation, and redox. Overall, this study provides a new sustainable way to convert agricultural wastes to more valuable products such as biomimetic adsorbent for Sb(III) removal in addition to conventional activated carbon and biochar.