TY - JOUR
T1 - Highly efficient uranium (VI) capture from aqueous solution by means of a hydroxyapatite-biochar nanocomposite : adsorption behavior and mechanism
AU - Ahmed, Waqas
AU - Núñez-Delgado, Avelino
AU - Mehmood, Sajid
AU - Ali, Sehrish
AU - Qaswar, Muhammad
AU - Shakoor, Awais
AU - Chen, Di-Yun
PY - 2021
Y1 - 2021
N2 - 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.
AB - 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.
UR - https://hdl.handle.net/1959.7/uws:71434
U2 - 10.1016/j.envres.2021.111518
DO - 10.1016/j.envres.2021.111518
M3 - Article
SN - 0013-9351
VL - 201
JO - Environmental Research
JF - Environmental Research
M1 - 111518
ER -
