3. Characterization

The X-ray Diffraction (XRD) methodology was used to determine the crystalline phases present in the natural and synthesized materials, together with the investigation of the nucleation and growth process during the synthesis of different materials to be used as adsorbents, ion exchangers and catalysts [29]. The XRD tests were carried out, at room temperature using a stage similar to an Anton Paar HTK-1200 N with an equipment similar to a Bruker D8 Advance system in a Bragg-Brentano vertical goniometer configuration, the angular measurements being made applying steps of 0.01° from 5 to 80°, using a Cu anode tube together with a Ni filter placed, prior to the detector, to eliminate Cu K<sup>α</sup> radiation the one-dimensional detector was employed [26].

#### 3.1 Thermo-gravimetric analysis (TGA)

The analytical test was carried out with an equipment similar to a TA, Q-500 instrument; the samples were placed onto a ceramic sample holder suspended from an analytical balance, suspended from an analytical balance; then the temperature was linearly scanned, from 25 to 300 C, at a heating rate of 5 C/min under a pure N2 flow of 100 mL/min. TGA testing process was carried out with a TA, Q-500 instrument, and the samples were placed onto a ceramic sample holder [27].

DRIFTS were gathered using equipment similar to a Thermo Scientific Nicolet iS10 FTIR spectrometer. The data of the hydrated and dehydrated samples were collected at a resolution of 4 cm�<sup>1</sup> employing 100 scans per sample; a background, with pure KBr, was in all cases collected before the collection of the spectra. Both the hydrated and dehydrated samples were gathered at room temperature while flowing N2 (Praxair, 99.99%) at a rate of 50 cc/min; while, the dehydration of the studied samples was performed at 100°C for 2 h in N2 flow of 50 mL/min while the sample under test was included in the finger-sample-holder of the IR high temperature cell [28].

Room-temperature Mossbauer Spectrometry measurements were made with a system similar to a SEECo supplied spectrometer operating at constant acceleration mode with a 50 mCi 57Co γ-ray source in a Rh matrix made by Rietverc GmbH. The 1024-point raw data were folded and analyzed using WMOSS, a public domain Mossbauer spectral analysis program; the calibration was made with reference to α-Fe metal [30].
