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Physicochemical properties of layered double hydroxides by-product obtained from Al–MgO mechanochemical process to produce hydrogen

B. E. López-Muñoz, J. L. Iturbe-García, and M. T. Olguin

Instituto Nacional de Investigaciones Nucleares, Mexico, Mexico



Abstract: The characteristics of a by-product, both untreated (BP) and thermally treated (CBP), obtained from an Al-MgO mechanochemical process to produce hydrogen, is presented in this work. Commercial hydrotalcite (HTc), as well as its calcined form (CHTc), is included for comparison purposes. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FT-IR), pH of the point of zero charge (pHPZC), thermogravimetry analysis (TGA), BET analysis, and fractal dimension, to characterize the by-product were considered. The results showed that the by-product corresponded to Mg–Al-layered double hydroxide with structural characteristics similar to the hydrotalcite. The surface area and pore volume of the materials notably increased after the thermal treatment (CBP and CHTc), and this thermal process is accompanied by an increase in the surface fractal dimension Df. After contact with H2O or a (NH4)2CO3 aqueous solution, the original CBP and CHTc crystalline structure was regenerated by the memory effect, showing that BP has a similar structure to a hydrotalcite compound. The mechanism of the by-product formation is also proposed in this work.

Keywords: By-product ; Hydrotalcites ; Memory effect ; Mg–Al-layered double hydroxide ; Al–MgO ; Fractal dimension ; pHpzc 

Full paper is available at

DOI: 10.1007/s11696-018-0602-8


Chemical Papers 73 (2) 415–424 (2019)

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