生物炭
吸附
朗缪尔吸附模型
水溶液
傅里叶变换红外光谱
X射线光电子能谱
核化学
化学
扫描电子显微镜
纳米复合材料
朗缪尔
吸附
化学工程
材料科学
分析化学(期刊)
物理化学
有机化学
纳米技术
热解
复合材料
工程类
作者
Waqas Ahmed,Avelino Núñez‐Delgado,Sajid Mehmood,Sehrish Ali,Muhammad Qaswar,Awais Shakoor,Diyun Chen
标识
DOI:10.1016/j.envres.2021.111518
摘要
The exploration and rational design of easily separable and highly efficient sorbents with the sufficient capability of retaining radioactive and toxic uranium U(VI) is paramount. In this study, a hydroxyapatite (HAP) biochar nanocomposite (BR/HAP) was successfully fabricated from rice straw biochar (BR), to be used as a new and efficient adsorbent for removing U(VI) from aqueous solution. Both BR and the BR/HAP composite were characterized via Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photo electron spectroscopy (XPS) techniques. Batch test results showed that BR/HAP exhibited remarkably higher adsorption capacity than the raw BR. A pseudo-second order kinetic model thoroughly explained the adsorption kinetics, providing the maximum U(VI) adsorption capacities (qe) of 110.56 mg g−1 (R2 = 0.98) and 428.25 mg g−1 (R2 = 0.99), for BR and BR/HAP, respectively, which was indicative of the rate-limited sorption via diffusion or surface complexation after rapid initial adsorption steps. The Langmuir isotherm model fitted the experimental data to accurately simulate the adsorption of U(VI) onto BR and BR/HAP (R2 = 0.97 and R2 = 0.99). The thermodynamic results showed negative values for ΔG°, clearly indicating that the reaction was spontaneous, as well as positive values for ΔH° (11.04 kJ mol−1 and 28.86 kJ mol−1, respectively) and ΔS° (88.97 kJ mol−1 K−1, and 183.42 kJ mol−1 K−1), making clear the endothermic nature of U(VI) adsorption onto both sorbents, with an increase in randomness at a molecular level. FTIR spectroscopy and XPS spectrum further confirmed that the primary mechanisms were ion exchange with UO22+ and surface complexion by –OH and –COOH. In addition, BR/HAP showed an excellent reusability, making it a promising candidate as a new sorbent for U(VI) removal from wastewater. In view of that, it would be interesting to perform future research to explore practical implications of this sorbent material regarding protection from environmental and public health issues related to that pollutant.
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