ABSTRACT
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 mgâg -1, which is 2.06 times higher than δ-MnO2 without template (370.0 mgâg -1), 4.53 times than tobacco stem-silks carbon (168.5 mgâg -1), and 10.39 times than commercial MnO2 (73.5 mgâg -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.
Subject(s)
Oxides , Water Pollutants, Chemical , Humans , Kinetics , Manganese Compounds , Spectroscopy, Fourier Transform Infrared , Water Pollutants, Chemical/analysis , AdsorptionABSTRACT
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.