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.

Enhancement of Visible-Light Photocatalytic Degradation of Tetracycline by Co-Doped TiO2 Templated by Waste Tobacco Stem Silk.

In this study, Co-doped TiO2 was synthesized using waste tobacco stem silk (TSS) as a template via a one-pot impregnation method. These samples were characterized using various physicochemical techniques such as N2 adsorption/desorption analysis, diffuse reflectance UV-visible spectroscopy, X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and electron paramagnetic resonance spectroscopy. The synthesized material was used for the photodegradation of tetracycline hydrochloride (TCH) under visible light (420-800 nm). No strong photodegradation activity was observed for mesoporous TiO2 synthesized using waste TSS as a template, mesoporous Co-doped TiO2, or TiO2. In contrast, Co-doped mesoporous TiO2 synthesized using waste TSS as a template exhibited significant photocatalytic degradation, with 86% removal of TCH. Moreover, owing to the unique chemical structure of Ti-O-Co, the energy gap of TiO2 decreased. The edge of the absorption band was redshifted, such that the photoexcitation energy for generating electron-hole pairs decreased. The electron-hole separation efficiency improved, rendering the microstructured biotemplated TiO2 a much more efficient catalyst for the visible-light degradation of TCH.