Journal
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
Volume 516, Issue -, Pages 362-374Publisher
ELSEVIER
DOI: 10.1016/j.colsurfa.2016.12.053
Keywords
Cr; Layered double hydroxides; Adsorption; Reduction
Categories
Funding
- Program for New Century Excellent Talents in University [NCET-12-0713]
- National Natural Science Foundation of China [51374157, 51504170]
- Nature Science Foundation of Hubei Province of China [2013CFA106, 2015CFB506]
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Chromium is highly toxic and readily soluble in water. Herein, Fe(II)-Al layered double hydroxides (LDH) with Fe:Al ratios of 2:1 (LDH-2) and 3:1 (LDH-3) were synthesized by a hydrothermal synthesis method. The resulted products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) measurements, scanning electron microscopy (SEM), thermogravimetric analysis coupled with differential scanning calorimetry (TG/DSC), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Highly crystalline forms with sheet structure were revealed by XRD and TEM results, while the BET surface area of the LDH-2 and LDH-3 materials were 46.85 and 53.22 m(2)/g, respectively. In addition, both products showed good performances in the removal of Cr(VI), although the removal efficiency of LDH-2 was higher than that of LDH-3. Based on the characterization results, two different removal mechanism involving both adsorption and reduction processes were proposed. The Fe2+ ions in LDH were involved in reducing Cr(VI) to Cr(III) while simultaneously being oxidized to Fe3+. pH was found to influence the adsorption of Cr(VI), with higher pH values being beneficial to the removal process. Common anions present in the environment such as SO42-, NO3-, and CO32- showed minor influence in the adsorption performance of the LDH materials. A competitive adsorption between Cr(VI) and humic acid (HA) was observed. The crystalline structure of LDH-2 collapsed after adsorption of very high concentrations of Cr(VI), thereby demonstrating once again that Fe involved in the lamination of LDH-2 was dissolved out to a large extent promoting the Cr(VI) to Cr(III) process. (C) 2016 Elsevier B.V. All rights reserved.
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