Ordering of water in opals with different microstructures

Eckert, J.; Gourdon, Olivier; Jacob, Dorrit E.; Meral, Cagla; Monteiro, Paulo J.M.; Vogel, Sven C.; Wirth, Richard; Wenk, H. R.

doi:10.1127/ejm/2015/0027-2428

Cited by 26 publications

(31 citation statements)

References 54 publications

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“…FTIR spectra of 4A zeolite crystallized at 95°C for 0, 1, 3, 5 and 6 h are shown in Figure 5. Three bands at 475, 785, and 1090 cm −1 , ascribed to OWR (Eckert et al., 2015), can be obviously seen when crystallization time is 0 h. The bands at 785 and 1090 cm −1 are, respectively, ascribed to symmetrical and asymmetrical stretching vibration of the Si–O–Si, corresponding to amorphous silica (Jiang et al., 2012). All the 4A zeolite exhibit absorption bands at approximately 3435 and 1651 cm −1 both ascribed to O–H vibrations of the absorbed water (Su et al., 2016).…”

Section: Resultsmentioning

confidence: 99%

Preparation, characterization, and performance of 4A zeolite based on opal waste rock for removal of ammonium ion

Xie

Liu

et al. 2018

Adsorption Science & Technology

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In this study, 4A zeolite was prepared from opal waste rock by hydrothermal method and applied in ammonium ion adsorption. To optimize synthesis conditions, the effect of crystallization time (1-8 h), crystallization temperature (65-115 C), Na 2 O/SiO 2 (0.6-2.0), H 2 O/Na 2 O (20-70), and SiO 2 /Al 2 O 3 (1.0-3.5) was investigated. X-ray diffraction, scanning electron microscope imaging, cation exchange capacity, static water adsorption, Fourier transform infrared spectroscopy, and N 2 adsorption-desorption isotherm were used for assessing properties of 4A zeolite. Adsorption experiments were performed by 1.0 g l À1 4A zeolite with NH 4 þ solution (5-300 mg l À1) for 4 h at room temperature. The experiment results revealed with a crystallization time of 3 h, a crystallization temperature of 85 C, Na 2 O/SiO 2 ¼1.0, H 2 O/Na 2 O ¼ 40, and SiO 2 /Al 2 O 3 ¼2.0, the 4A zeolite synthesized had excellent performance with cation exchange capacity of 2.93 mmol (g dry zeolite) À1 and static water adsorption of 22.3%. The adsorption process was described by Freundlich model (R 2 >0.99) and the maximum adsorption capacity could reach to 53.11 mg g À1. The experimental results provided a novel approach for the utilization of opal waste rock, which is produced during the mining of opal-rich palygorskite, and for the synthesis of 4A zeolite and the removal of ammonium ion.

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Section: Resultsmentioning

confidence: 99%

Preparation, characterization, and performance of 4A zeolite based on opal waste rock for removal of ammonium ion

Xie

Liu

et al. 2018

Adsorption Science & Technology

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“…The 1100 cm −1 band is caused by the antisymmetric stretching vibration of Si-O (ν as (Si-O)), and the 780 cm −1 band is caused by the symmetric stretching vibration of Si-O (ν s (Si-O)). The 474 cm −1 band is related to O-Si-O bending vibration δ (O-Si-O) [5,[27][28][29][30][31][32][33]. The transition from the amorphous to the crystalline form is evident in the FTIR spectra.…”

Section: Ftir Spectroscopymentioning

confidence: 99%

Crystallinity and Play-of-Colour in Gem Opal with Digit Patterns from Wegel Tena, Ethiopia

Zhao

Bai

2020

Minerals

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A typical feature of Wegel Tena opal is the "digit pattern". This pattern consists of two parts, columns and matrix, with different colours, transparency or play-of-colour effect, which is still unexplained. This study aims at investigating the various parts of the digit pattern using different spectroscopic methods, and scanning and transmission electron microscopy (SEM and TEM). The band at 780 cm−1 on the Fourier transform infrared (FTIR) spectrum is correlated to the symmetric stretching vibration of Si–O. The bands at 1085, 895, 785 and 3600 cm−1 on Raman spectra indicate that Wegel Tena opal is opal-CT. Comparison of the relative intensity of the Raman signals around 360 cm−1 indicates that the microcrystalline opal on the top of the sample contains a higher amount of tridymite-like structural units, and the tridymite-type regions in the matrix contain a higher degree of structural defects. Silica spheres in the columns tend to be smaller and better ordered than in the matrix. The diameter of the silica spheres (d = 80–500 nm) or agglomerates (d = 200–580 nm) in Wegel Tena opal satisfies the conditions of diffraction of visible light, and the thickness of the silica layer (h = 120–200 nm) satisfies the conditions for film interference.

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“…Other techniques such as Raman spectroscopy [13,[19][20][21], 29 Si nuclear magnetic resonance (NMR) [22][23][24][25][26][27], near infra-red spectroscopy [28][29][30] and neutron scattering [31] have also been used to try to unravel the complex structural relationships between the types of opal. Trace chemical analysis both of opal and associated minerals [7,15,18,[32][33][34][35][36] may also provide evidence of provenance [37].…”

Section: Introductionmentioning

confidence: 99%

A Review of the Classification of Opal with Reference to Recent New Localities

et al. 2019

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Our examination of over 230 worldwide opal samples shows that X-ray diffraction (XRD) remains the best primary method for delineation and classification of opal-A, opal-CT and opal-C, though we found that mid-range infra-red spectroscopy provides an acceptable alternative. Raman, infra-red and nuclear magnetic resonance spectroscopy may also provide additional information to assist in classification and provenance. The corpus of results indicated that the opal-CT group covers a range of structural states and will benefit from further multi-technique analysis. At the one end are the opal-CTs that provide a simple XRD pattern (“simple” opal-CT) that includes Ethiopian play-of-colour samples, which are not opal-A. At the other end of the range are those opal-CTs that give a complex XRD pattern (“complex” opal-CT). The majority of opal-CT samples fall at this end of the range, though some show play-of-colour. Raman spectra provide some correlation. Specimens from new opal finds were examined. Those from Ethiopia, Kazakhstan, Madagascar, Peru, Tanzania and Turkey all proved to be opal-CT. Of the three specimens examined from Indonesian localities, one proved to be opal-A, while a second sample and the play-of-colour opal from West Java was a “simple” Opal-CT. Evidence for two transitional types having characteristics of opal-A and opal-CT, and “simple” opal-CT and opal-C are presented.

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Ordering of water in opals with different microstructures

Cited by 26 publications

References 54 publications

Preparation, characterization, and performance of 4A zeolite based on opal waste rock for removal of ammonium ion

Preparation, characterization, and performance of 4A zeolite based on opal waste rock for removal of ammonium ion

Crystallinity and Play-of-Colour in Gem Opal with Digit Patterns from Wegel Tena, Ethiopia

A Review of the Classification of Opal with Reference to Recent New Localities

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