Data on phase and chemical compositions of black sands from “El Ostional” beach situated in Mompiche, Ecuador

Data revealing the phase and chemical compositions of natural black sands from “El Ostional” beach, located in the northern Ecuadorian Pacific coast have been presented. The samples were collected from six points over the shore area of approximately 500 × 40 m2. The data on crystalline phases (iron titanium oxide, orthoclase feldspar and zircon) were determined by X-ray powder diffraction (XRPD), while semi-quantitative chemical analyses of major (Fe and Ti) and trace elements were obtained by X-ray fluorescence spectroscopy (XRF). The phase composition was verified by scanning electron microscopy (SEM), using backscattered electron (BSE) mode and energy dispersive spectroscopy (EDS). These comprehensive data are a contribution to valorize ilmenite-hematite solid solutions from natural resources towards the identification of novel technological applications.


Specifications
Materials Science Specific subject area Materials Chemistry  Type of data  Tables and Figures  How data were acquired • Sample collection points: global positioning system (GPS).

Data format
Raw and analyzed Parameters for data collection • GPS: Degrees, Minutes, Seconds (DMS) coordinates.
• XRF: X-ray tube with Rh anode and 50 kV accelerating voltage.

Description of data collection
• Black sand samples were collected from six points over the shore area in "El Ostional" beach. Their geographic coordinates were recorded by GPS and plotted with ArcGIS software. • XRPD: The phase composition was identified from the diffraction pattern profile refined with Le Bail method. • XRF: The chemical composition was determined by a semi-quantitative analysis.

Value of the Data
• These data present the first thorough characterization of "El Ostional" beach sands from Mompiche-Ecuador, which allows comparing these black sands locally or globally. • Dataset on phase and chemical compositions of Ecuadorian black sands could be useful as a benchmark for the identification of ilmenite-hematite solid solutions (0.6FeTiO 3 · 0.4Fe 2 O 3 ) from natural resources. • The data contribute to the valorization of Ecuadorian black sands as a low-cost raw material for novel technological applications of Fe 1.4 Ti 0.6 O 3 solid solution, different from the conventional manufacturing of TiO 2 pigment or the production of Portland cement clinker. • In addition to spintronic devices and photocatalysts, the new applications of these black sands could include their use as a precursor for the synthesis of Fe/Ti oxide nanostructures. Fig. 1 shows the geographic location of the prospected area that corresponds to "El Ostional" beach, situated in Mompiche-Ecuador, at the northern Ecuadorian Pacific coast. The six marks over the beach represent the collection points. The collected samples were denoted as S1 to S6. Fig. 2 shows the XRPD patterns of the collected samples. All patterns exhibit the same profile (positions and intensities). Iron titanium oxide was identified as the main phase, along with trace amounts of orthoclase feldspar and zircon ( Fig. 3 ). The phase composition was confirmed by Le Bail method [1] ( Fig. 4 ). In the case of iron titanium oxide (Fe 1.4 Ti 0.6 O 3 ), which corresponds to an ilmenite-hematite solid solution [2] , Le Bail fit to the rhombohedral ordered structure within space group R 3 and the unit-cell parameters are presented in Table 1 . In addition, TOPAS input and output data from Le Bail refinement of S1 sample are presented in Table 2 .     Table 3 presents the semi-quantitative chemical analysis of each collected sample. Iron and titanium were identified as the major elements.

Data from XRF
XRF data allowed verifying the chemical formula of Fe 1.4 Ti 0.6 O 3 . This solid solution belongs to Fe ( [3] . Based on the Fe/Ti mass ratio (2.8) computed from Table 3 , the following equation can be written: where, F e atomic weight = 55 . 8 g mol T i atomic weight = 47 . 9 g mol therefore, Fig. 5 shows BSE-SEM images of S1 sample. The particle size is between 50 and 200 μm ( Fig. 5 a). Irregular morphology appears to be due to weathering, which sometimes caused pullout of the embedded secondary particles ( Fig. 5 b). Besides, BSE signal distinguished three mineral phases which can be seen in Fig. 5 c.

Data from SEM
The chemical composition of the identified phases was confirmed by EDS analyses. The majority phase, observed through large gray particles, is composed of Fe, Ti and O, corresponding to iron titanium oxide ( Fig. 6 a). Small amounts of Mg and Al were also detected. Regarding to the dark color phase ( Fig. 6 b), it comprises K, Al, Si, Na and O. Therefore, this signal originates from orthoclase feldspar particles. Furthermore, small white particles embedded into the iron titanium oxide ( Fig. 6 c) correspond to zircon, due to the presence of Si, Zr and O. Low Fe and Ti contents in secondary phases come from the surrounding iron titanium oxide.
All samples presented the same phases and similar particle size and morphology, as illustrated in Fig. 7 .

Sample collection
"El Ostional" beach (see Fig. 1 ) has an extension area of approximately 500 × 40 m 2 . The entire beach contains black sands over shore and offshore. The samples were merely collected from the shore. To assure a whole beach coverage, a simple systematic sampling was carried out by drawing a rectangular grid pattern comprising six 83 × 40 m 2 cells. Thus, the black sands (5 kg) were taken from the rectangle centers at approximately 0.50 m depth. The sampling points were tracked by GPS and recorded in DMS coordinates.

Table 2
Input and output data from Le Bail refinement of S1 sample.  Prior to analysis, all the samples were washed several times with distillated water at 50 °C to eliminate residual salt. Afterwards, they were dried in a convection oven at 80 °C for 24 h.

XRPD
XRPD was carried out in a D8 Endeavor X-ray diffractometer from Bruker, operating with Cu K α radiation in a 2 θ range from 5 to 80 °and steps of 0.02 °. The current of 40 mA and accelerating voltage of 40 kV (1.6 kW) were used. The phase identification was performed with EVA software and PDF2 ICDD database, while Le Bail refinement was carried out using TOPAS software. The black sands were previously ground in a RETSCH PM 400 planetary mill, with a 20:1 ball to sand mass ratio, for 3 min. The resulting powder passed through a 400 mesh screen.

XRF
All the samples were analyzed in the form of pressed pads, which were prepared using a sample:binder mass ratio of 9:1. A Bruker S8 TIGER WDXRF spectrometer, equipped with an Xray tube with Rh anode, was used at 50 kV accelerating voltage. The data were analyzed by the semi-quantitative program Quant-Express of Spectra Pluss software.

BSE-SEM with EDS
A Vega 3 and TM30 0 0 scanning electron microscopes from Tescan and Hitachi, respectively, were used. The raw samples were sprinkled onto a conducting tape and used as prepared, without additional carbon or gold deposition. The accelerating voltages of 15 or 20 kV were used for SEM/EDS analyses.