Triclosan Removal on a MgAl Hydrotalcite and its Calcined Product
2022
Macedo-Miranda, Guadalupe | Martínez-Gallegos, Sonia | Ordóñez Regil, Eduardo | Alvarez-García, Sonia | Valladares-Bernal, Angel A.
In this study, a hydrotalcite (HT MgAl) was synthesized by coprecipitation at a constant pH. Its mixed oxide (HTC MgAl) was obtained for the removal of triclosan (TCS). The two materials were characterized by Scanning Electron Microscopy (SEM), X-ray Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). Measurements of N₂ physisorption and Point of Zero Charge (pHPZC) were also analyzed. TCS removal was investigated in terms of pH, adsorption kinetics, adsorption isotherms, and temperature. The HT MgAl material presented the typical morphology and crystalline structure of a hydrotalcite composed of C, O, Al, and Mg. This material is classified as a mesoporous material with a specific surface area of 114.92 m²/g and a pHPZC of 8.82. On the other hand, HTC MgAl material is a MgAl oxide with a surface area of 140 m²/g and a pHPZC of 11.06. Adsorption results showed that the highest adsorption capacity was obtained at pH 9.0 and at an equilibrium time of 24 h in both materials. The experimental kinetic and isotherm data were well-adjusted to the pseudo-first order and Freundlich models, respectively. This indicates a physisorption mechanism on heterogeneous materials. Therefore, the adsorption of TCS into the HT MgAl material was by way of ion exchange. On the other hand, the adsorption of TCS into the HTC MgAl material was by way of ion exchange and TCS intercalation by the reconstruction of the material. The TCS adsorption process was exothermic, and not spontaneous; hence, randomness was reduced.
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