Journal of Radioanalytical and Nuclear Chemistry

Journal of Radioanalytical and Nuclear Chemistry

Supplementary information

Sensing and extraction of uranium in polluted acid mine drainage by super-paramagnetic nanoparticles coated with carbon nanodots

Alexandre Loukanov1,2, Hibiki Udono1, Ryo Takakura1, Naritaka Kobayashi1, Ryuzo Kawamura1 and Seiichiro Nakabayashi1

1Graduate School of Science and Engineering, Saitama University, Shimo–Ohkubo 255, Sakura – Ku, Saitama 338-8570, Japan

2Laboratory of Engineering NanoBiotechnology, Department of Engineering geoecology, University of Mining and Geology “St. Ivan Rilski”, Bulgaria

Figure S1.(A) Composition of the model solution of acid mine drainage with pH = 4.5 used in batch experiments. The solution does not contains iron (III), because it precipitate at pH above 4.0.(B) Fluorescence response of aqeous solution of C-dots to addition of different metal ions with a concentration of 100 M. F and F0 correspond to the fluorescence intensity of the solution with the presence or absence of Mn+ ions, respectively.

Figure S2. Powder X-ray diffraction (XRD) pattern of the Fe3O4@C-dots nanoparticles. The characteristic peaks for magnetite (111), (220), (311), (400), (422), (511), (440) and (622) were identified by their indices.

Figure S3. Magnetization curve of the super-paramagnetic Fe3O4@C-dots core-shell nanoparticles.

Figure S4. Photoluminescence emission spectra of (A) and (B) super-paramagnetic Fe3O4@C-dots nanoparticles with progressively longer excitation wavelength from 300 to 400 nm in 20 nm increments; (C) and (D) control experiment of bare C-dots with the same progressive measurement of the excitation wavelength. The photoluminescence spectra in (B) and (D) are normalized.

Figure S5. Ninhyrdin test for detection of amine groups from the C-dots moiety: (A) control experiment with uncoated Fe3O4 nanoparticles, (B) positive reaction indicating the presence of immobilized C-dots on the surface of Fe3O4 nanoparticles.

Figure S6. (A) Topographical image of bare C-dots on a highly oriented pyrolytic graphite substrate taken by atomic force microscope. (B) Height profile in nanometers of the measured red line on AFM image.

The calculation of the obtained practical yield are described below:

The maximum adsorption capacity (qm) of Fe3O4@C-dots was obtained by Langmuir isotherm for uranium adsorption at ambient temperature. The used equation is:

Ce/qe = Ce/qm + 1/qmKL, where

Ce (mg L–1) is the equilibrium concentration, qe (mg g–1) is the equilibrium adsorption capacity, KL (L mg–1) is a constant related to the affinity of the binding sites.

lnqe = ln KF + 1/nlnCe, where

KF (mg g–1) is Freundlich constant indicating adsorption capacity and n is the intensity. The values qm, KL, KF and n were calculated from the slope and intercept of the linear plots of Ce/qe vs Ce:

Figure S7. Plots of Langmuir model for uranium acetate using super-paramagnetic Fe3O4@C-dots core-shell nanoparticles at various temperature (T = 25–45 °C, C0 = 10 – 100 mg L–1, pH = 4.4, R2 = 0.99). C0 is the initial concentration of U6+. The values of qm are 172 mg g–1 (at 25 °C), 161 mg g–1 (at 35 °C) and 141 mg g–1 (at 45 °C) at aerobic conditions.The maximum KL constant, calculated at 25 °C was 0.8 L mg–1.

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