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| Adsorption-reduction reaction between bagasse-prepared biochar and Cr(Ⅵ) |
| Received:December 16, 2022 |
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| KeyWord:bagasse biochar;Cr (Ⅵ);removal mechanism;adsorption;reduction |
| Author Name | Affiliation | E-mail | | LIN Chunling | College of Coastal Agricultural Science, Guangdong Ocean University, Zhanjiang 524088, China | | | ZHONG Laiyuan | Faculty of Chemistry and Environmental Science, Guangdong Ocean University, Zhanjiang 524088, China | zhly66@163.com | | ZHONG Xiaolan | Faculty of Chemistry and Environmental Science, Guangdong Ocean University, Zhanjiang 524088, China | | | WEI Biyu | Faculty of Chemistry and Environmental Science, Guangdong Ocean University, Zhanjiang 524088, China | | | YIN Junyong | Faculty of Chemistry and Environmental Science, Guangdong Ocean University, Zhanjiang 524088, China | |
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| Abstract: |
| With the strict exclusion of oxygen, two kinds of biochar(RC and HC)were prepared from bagasse by carbonization at 600℃ and 800℃, respectively. By combining several techniques, including scanning electron microscope-energy spectrum(SEM-EDS), surface area and pore analysis(BET), Fourier transform infrared spectroscopy(FTIR), X-ray photoelectron spectroscopy(XPS), and Raman spectroscopy(RS), the surface properties of these two biochars were well characterized. The Cr(Ⅵ)adsorption isotherm and kinetics of the biochars were examined, and the focus was placed on elucidating the underlying mechanisms thereof. The results showed that these two bagasse biochars had rich pore structures and surface active groups. The increase in carbonization temperature could increase the surface porosity and the degree of aromatization but decrease the relative contents of oxygen-containing functional groups such as OH and C O. The HC exhibited the highest efficiency for removing Cr(Ⅵ), with maximum removal amounts as high as 117.28 mg·g-1. By discriminating the relative contribution of adsorption and reduction from the Cr(Ⅵ)removal, the amounts of Cr(Ⅵ)removed by adsorption alone could be 76.00 mg·g-1, with 8.01 mg·g-1 for RC. With the increase in carbonization temperature, the degree of the defect was reduced, and the electron transport ability was enhanced. The reduction amounts of Cr(Ⅵ)by HC were 87.40 mg·g-1, which was 57.03 mg·g-1 higher than that for RC. Additionally, the kinetics of adsorption of Cr(Ⅵ)by bagasse biochar obeyed the pseudo-second-order kinetic model. The adsorption isotherm of Cr(Ⅵ)by HC was well described by the Langmuir model, with the Freundlich model more applicable for the Cr(Ⅵ)adsorption by RC. The XPS and FTIR analysis showed that the removal mechanisms of Cr(Ⅵ)by bagasse biochar involved three steps:the electrostatic adsorption of Cr(Ⅵ)by the surface, reduction of Cr(Ⅵ)to Cr(Ⅲ), and the complexation of Cr(Ⅲ). The relative contribution of adsorption reaction to Cr(Ⅵ)removal by RC and HC accounted for 22.98% and 64.80%, respectively, with 87.12% and 74.52% via the reduction reaction, respectively. The results indicate that the reduction reaction plays a major role in removing Cr(Ⅵ)from aqueous solutions using bagasse biochar. |
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