ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

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

E-mail: teresa.olguin@inin.gob.mx

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 (HT_c), as well as its calcined form (CHT_c), 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 (pH_PZC), 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 CHT_c), and this thermal process is accompanied by an increase in the surface fractal dimension D_f. After contact with H₂O or a (NH₄)₂CO₃ aqueous solution, the original CBP and CHT_c 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 ; pH_pzc 

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-018-0602-8

Chemical Papers 73 (2) 415–424 (2019)