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Efficient removal of U(VI) from mine radioactive wastewater is important for environmental remediation and radiation protection. In this work, a new series of polyamidoxime/polydopamine-decorated graphene oxide (GO/PDA/PAO) composites were obtained by one-pot synthesis and used for the removal of U(VI) from mine radioactive wastewater. The as-synthesized GO/PDA/PAO composites (GO/PDA/PAO-0.2, GO/PDA/PAO-0.5, and GO/PDA/PAO-1) were examined by transmission electron microscopy, Fourier transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS). The effects of pH, ionic strength, contact time, initial U(VI) concentration, and temperature on the adsorption behavior of U(VI) by GO/PDA/PAO were investigated. The maximum adsorption capacity of GO/PDA/PAO-0.2 was 502.5 mg/g at pH 6.0 and 298 K. The adsorption kinetics and isotherms can be well illustrated by the pseudo-second-order kinetics model and Langmuir isotherm model. The thermodynamic study indicated that the removal of U(VI) by GO/PDA/PAO-0.2 was an endothermic and spontaneous process. The interactions between GO/PDA/PAO-0.2 and U(VI) were explained based on the FT-IR and XPS analyses. Furthermore, GO/PDA/PAO was applied for U(VI) removal from mine radioactive wastewater. The concentration of U(VI) in the wastewater can be reduced to 7.28 μg/L, which is below the allowable uranium concentration for drinking water stipulated in the standard by the World Health Organization (30 μg/L).

Highly efficient removal of U­(VI) from mine radioactive wastewater has received a lot of attention. Herein, the polyamidoxime/polyethyleneimine magnetic graphene oxide (mGO-PP) adsorbent was successfully prepared by in situ polymerization of acrylonitrile on magnetic GO (mGO) covalently modified with polyethylenimine (PEI). The mGO-PP was characterized by Fourier transform infrared (FT-IR), scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometer, and X-ray photoelectron spectroscopy (XPS). The maximum adsorption capacity of mGO-PP toward U­(VI) was 606.06 mg/g at 298 K and pH 6.0. The removal of U­(VI) by mGO-PP for U­(VI) was a monolayer chemisorption based on the study of the batch experiment. The calculated thermodynamic parameters indicated that the removal of U­(VI) by mGO-PP was a spontaneous and endothermic process. The adsorption mechanism of mGO-PP toward U­(VI) was explored by FT-IR and XPS analyses. Furthermore, the removal rate of U­(VI) by mGO-PP is 93.68% and the K d value for U­(VI) is 444.73 L/g in actual mine radioactive wastewater, and the residual U­(VI) concentration (6.37 μg/L) in wastewater was lower than the maximum permissible concentration of uranium in drinking water (30 μg/L) (World Health Organization). This indicated that the mGO-PP composite is a promising adsorbent for efficient removal of U­(VI) from practical mine radioactive wastewater.

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