Highly efficient uranium (VI) capture from aqueous solution by means of a hydroxyapatite-biochar nanocomposite: Adsorption behavior and mechanism

文献类型： 外文期刊

第一作者： Ahmed, Waqas

作者： Ahmed, Waqas;Chen, Di-Yun;Ahmed, Waqas;Chen, Di-Yun;Nunez-Delgado, Avelino;Mehmood, Sajid;Ali, Sehrish;Qaswar, Muhammad;Shakoor, Awais

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关键词： Adsorption; Biochar; Hydroxyapatite; Nanocomposite; Uranium; Wastewater treatment

期刊名称：ENVIRONMENTAL RESEARCH （ 影响因子：6.498； 五年影响因子：6.824 ）

ISSN： 0013-9351

年卷期： 2021 年 201 卷

页码：

收录情况： SCI

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 (q(e)) of 110.56 mg g(-1) (R-2 = 0.98) and 428.25 mg g(-1) (R-2 = 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 (R-2 = 0.97 and R-2 = 0.99). The thermodynamic results showed negative values for Delta G degrees, clearly indicating that the reaction was spontaneous, as well as positive values for Delta H degrees (11.04 kJ mol(-1) and 28.86 kJ mol(-1) , respectively) and Delta S degrees (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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