Remediation of arsenic contamination is of great importance given the high toxicity and easy mobility of arsenic species in water and soil. This work reports a new and stable adsorbent for efficient elimination of arsenic by coating polyethyleneimine (PEI) molecules onto the surface of iron-doped birnessite (Fe-Bir). Characterization results of surface microstructure and crystalline feature (scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR) and X-ray photoelectron spectroscopy (XPS), etc.) suggest that Fe-Bir/PEI possesses a fine particle structure, inhibiting the agglomeration of birnessite-typed MnO2 and offering abundant active sites for arsenic adsorption. Fe-Bir/PEI is capable of working in a wide pH range from 3 to 11, with an efficient removal capacity of 53.86 mg/g at initial pH (pH0) of 7. Meanwhile, commonly coexisting anions (NO3-, SO42-, and Cl-) and cations (Na+, K+, Ca2+ and Mg2+) pose no effect on the arsenic removal performance of Bir/PEI. Fe-Bir/PEI exhibits a good reusability for arsenic removal with low Mn and Fe ions leaching after 5 cycles. Besides, Fe-Bir/PEI possesses efficient remediation capability in simulated As-contaminated soil. The modification of PEI in Fe-Bir/PEI can adsorb newly formed As(V), which is impossible for the adsorbent without PEI. Further, the arsenic removal mechanism of Fe-Bir/PEI is revealed with redox effect, electrostatic attraction and hydrogen bonding.
Keywords: Arsenic removal; Iron-doped birnessite; PEI modification; Removal mechanism; Reusability.
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