RESUMO
Cr(VI) is of great concern to public health and environmental safety due to its high toxicity. Here, we report a low-cost yet highly efficient method to prepare a novel LDH, ultra-thin layered meixnerite, which performed superiorly in treatment of aqueous Cr(VI) with little secondary pollution being induced. The produced ultra-thin layered meixnerite was composed of nanoparticles with a thickness of around 7 nm, less than 9 times the thickness of a single LDH layer. The XRD patterns of the ultra-thin layered meixnerite, in which the characteristic diffraction peaks of a typical LDH were weakened or even disappeared, confirmed the successful delamination. This special morphology of the ultra-thin layered meixnerite was not only helpful to its full dispersion in the Cr(VI)-bearing solutions but also facilitated the formation of more active sorption sites on its external surface. As a result, the maximum sorption capacity of UTLM for Cr(VI) removal was 480.9 mg g-1, far higher than that of OM (196.9 mg g-1). In addition to electrostatic attraction and anion exchange, the ultra-thin layered meixnerite could also become restacked during removal of aqueous Cr(VI) to generate inner-sphere complexation, finally inducing an enhanced Cr(VI) uptake. Furthermore, XPS analysis characterized the promotion of the break of Al-OH bond with the increase in temperature, and the Cr-O peak increased correspondingly from 29.69% at 25 °C to 48.77% at 85 °C, resulting that the ultra-thin layered meixnerite could remove Cr(VI) more effectively at higher reaction temperatures. Therefore, ultra-thin layered meixnerite is very suitable for future application in treatment of industrial wastewaters with elevated temperatures.
