Department of Civil and Environmental Engineering, Old Dominion University, Norfolk, VA 23529, USA.
J Environ Manage. 2011 Oct;92(10):2504-12. doi: 10.1016/j.jenvman.2011.05.013. Epub 2011 Jun 12.
The ever-increasing growth of biorefineries is expected to produce huge amounts of lignocellulosic biochar as a byproduct. The hydrothermal carbonization (HTC) process to produce biochar from lignocellulosic biomass is getting more attention due to its inherent advantage of using wet biomass. In the present study, biochar was produced from switchgrass at 300 °C in subcritical water and characterized using X-ray diffraction, fourier transform infra-red spectroscopy, scanning electron micrcoscopy, and thermogravimetric analysis. The physiochemical properties indicated that biochar could serve as an excellent adsorbent to remove uranium from groundwater. A batch adsorption experiment at the natural pH (~3.9) of biochar indicated an H-type isotherm. The adsorption data was fitted using a Langmuir isotherm model and the sorption capacity was estimated to be ca. 2.12 mg of U g(-1) of biochar. The adsorption process was highly dependent on the pH of the system. An increase towards circumneutral pH resulted in the maximum adsorption of ca. 4 mg U g(-1) of biochar. The adsorption mechanism of U(VI) onto biochar was strongly related to its pH-dependent aqueous speciation. The results of the column study indicate that biochar could be used as an effective adsorbent for U(VI), as a reactive barrier medium. Overall, the biochar produced via HTC is environmentally benign, carbon neutral, and efficient in removing U(VI) from groundwater.
生物精炼厂的不断增长预计将产生大量的木质纤维素生物炭作为副产品。水热碳化（HTC）工艺由于其使用湿生物质的固有优势，越来越受到关注，用于从木质纤维素生物质生产生物炭。在本研究中，在亚临界水中于 300°C 下从柳枝稷生产生物炭，并使用 X 射线衍射、傅里叶变换红外光谱、扫描电子显微镜和热重分析进行了表征。物理化学性质表明，生物炭可以用作从地下水去除铀的优异吸附剂。在生物炭的自然 pH 值（约 3.9）下进行的批量吸附实验表明，吸附等温线呈 H 型。使用 Langmuir 等温线模型拟合吸附数据，估计吸附容量约为 2.12mg U g(-1) 的生物炭。吸附过程高度依赖于系统的 pH 值。向近中性 pH 值的增加导致最大吸附量约为 4mg U g(-1)的生物炭。U(VI)在生物炭上的吸附机制与其 pH 依赖的水相形态密切相关。柱研究的结果表明，生物炭可用作去除地下水 U(VI)的有效吸附剂，是一种反应性屏障介质。总体而言，通过 HTC 生产的生物炭在去除地下水 U(VI)方面是环境友好的、碳中和的和高效的。
