Mechanism insights into enhanced Cr(VI) removal using nanoscale zerovalent iron supported on the pillared bentonite by macroscopic and spectroscopic studies.
NZVI was supported on a pillared bentonite (Al-bent) to enhance the reactivity of NZVI and prevent its aggregation. The performance and mechanisms of the combined NZVI/Al-bent on removing hexavalent chromium (Cr(VI)) was investigated by batch and XAFS experiments. The batch investigations indicated that Cr(VI) could be almost completely removed by NZVI/Al-bent after 120 min. The efficiency was not only much higher than that by NZVI (63.0%), but also superior to the sum of NZVI reduction and Al-bent adsorption (12.4%). Besides, NZVI/Al-bent exhibited good stability and reusability, and Al-bent could reduce the amount of iron ions released into the solution. XANES results provided evidence that NZVI/Al-bent could reduce Cr(VI) entirely into Cr(III), while NZVI reduced Cr(VI) partly into Cr(III) with a trace of Cr(VI) adsorbed on the corrosion products. The structure of Cr(VI)-treated NZVI/Al-bent determined with EXAFS revealed the formation of Cr-Al/Si bond, suggesting that some insoluble Cr(III) species might be transferred to the surface of Al-bent, therefore the precipitates on iron surface could be greatly reduced. The results demonstrated that Al-bent plays a significant role in enhanced reactivity and stability of NZVI, and may shed new light on design and fabrication of supported NZVI for environmental remediation.
College of Chemistry and Chemical Engineering, Shaoxing University, Zhejiang 312000, PR China. liym@usx.edu.cn
Yimin
Y
Li
Jianfa
J
Li
Yuling
Y
Zhang
D000327:Adsorption; D001546:Bentonite / Q000737:chemistry*; D002857:Chromium / Q000737:chemistry*; D052918:Environmental Restoration and Remediation; D007501:Iron / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
D014874:Water Pollutants, Chemical; D002857:Chromium; D001546:Bentonite; C074702:chromium hexavalent ion; D007501:Iron