Comparative study of natural and synthetic clinoptilolites containing silver in different states

Concepción-Rosabal, Beatriz; Rodrı́guez-Fuentes, G.; Bogdanchikova, Nina; Bosch, P.; Авалос, M.; Lara, V.H.

doi:10.1016/j.micromeso.2005.07.027

Cited by 72 publications

(55 citation statements)

References 28 publications

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“…The second class of vibrations; T-O double ring, pore opening, symmetry stretch, asymmetry stretch related to the linkages between the tetrahedral are observed at 650-500, 420-300, 750-820, 1150-1050 cm -1 wavelength, respectively. Additionally, H bonded H 2 O, H-O and isolated OH stretching are at 3400 and 3700 cm -1 wavelengths, respectively [5,13]. Ion exchange process causes formation of new bond and structure of zeolites which can change due which could be detected by FTIR [18].…”

Section: Introductionmentioning

confidence: 98%

“…This is due to the fact that bigger cations keep the rings open while smaller ones are very small that they cannot maintain expansion of the channels [4]. Concepcion et al, 2005, had studied the thermal behavior of Ag-exchanged natural and synthetic zeolites and they concluded that Ag-natural clinoptilolite samples were less thermally stable [5].…”

Section: Introductionmentioning

confidence: 99%

“…However in some zeolites irreversible changes in the framework structure occurs after complete dehydration; exchangeable cations initially located in the channels, may then become captured within the structure [5]. Vujakoviº et al, 2001, had studied the surfactant and anion adsorption of clinoptilolite.…”

Section: Introductionmentioning

confidence: 99%

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Thermal stability of Ag-exchanged clinoptilolite rich mineral

Akdeniz

Ülkü

2008

J Therm Anal Calorim

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Natural zeolites are formed mostly from the reaction of pore waters with volcanic glass and also by alteration of pre-existing feldspars, feldspathoids, poorly crystalline clay and biogenic silica. More than 50 different species of natural zeolites are known today but among them clinoptilolite is the most widespread one found in nature with high purity. It is available in many regions of Turkey for example; BalÏkesir, Bigadi¸; Emet, YukarÏaÈa¸; Izmir, Urla; Manisa, Gördes, KÏranköy, Avdaldere regions are available as sedimentary clinoptilolite and analcime deposits [1]. Natural zeolites have special value due to their characteristic properties, such as adsorption, catalytic and ion exchange property. These properties are enhanced in the dehydrated/calcined state thus the understanding of their behavior upon heating is important.Clinoptilolite, silica rich zeolite, is a member of heulandite group of natural zeolites. Clinoptilolite and heulandite are differing from each other with respect to their thermal stability, Si/Al ratio and preferential presence of Na + and K + in the exchangeable sites [2]. Clinoptilolite has Si/Al>4 and it survives its crystal structure an overnight heating at 450°C, while heulandite has Si/Al<4 and undergoes structural collapse below 450°C [3]. Thermal analyses techniques such as; thermogravimetric analysis (TG), differential thermal analysis (DTA), are used in order to differentiate clinoptilolite and heulandite, which are also good and straightforward methods used to determine the thermal stability of the minerals. Clinoptilolite structure consists of a two-dimensional system of the three types of channels. Two parallel channels, channel A (10 member ring) and channel B (8 member ring) which are perpendicularly intersected by channel C (8 member ring) with sizes 4.4×7.2, 4.1×4.7 and 4.0×5.4, respectively. The channels were filled with water and exchangeable cations, mainly Na, Ca, K, Mg and Ba. These exchangeable cations are located in the main sites of clinoptilolite coordinated with different number of water molecules and oxygen atom. Framework Si/Al ratio, ionic potential, size and composition of exchangeable cations, their coordination after water expulsion and framework topology are some of the factors which affect thermal behavior of zeolites. Cruciani (2006) stated that, as Si/Al ratio increases thermal stability will also increase because energy is required to break the Si-O bond compared to the Al-O bond is high. Thermal stability of zeolites are also described in terms Si/(Si+Al) ratio. Zeolites with high silica content having Si/(Si+Al) ratio higher than 0.79 (Si/Al³3.80) and zeolites with low silica having Si/(Si+Al) ratio lower than 0.56 (Si/Al£1.28) exhibit a large and poor thermal stability, respectively. The water-cation, water-water and water-oxygen atom interactions are differ from the zeolites having different cation content. In addition to that, zeolites Analysis and Calorimetry, Vol. 94 (2008) Thermal stability of clinoptilolite rich mineral from Western Anato...

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Thermal stability of Ag-exchanged clinoptilolite rich mineral

Akdeniz

Ülkü

2008

J Therm Anal Calorim

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“…Variations in the relative intensities of the clinoptilolite peaks (2 theta: 9.92º; 11.2º) were found in the XRD pattern of ZAg, after Ag ion exchange. These variations can be associated mainly with differences in the nature, amount and position of the extra-framework species in clinoptilolite channels [8]. The presence of new peaks (2 theta: 38º.1; 44.3º; 64.5º) can be attributed to the presence of metallic Ag, which confirmed the occurrence of reduction process of Ag ions [9].…”

Section: Photocatalytic Experimentsmentioning

confidence: 64%

“…2(c)). The first one, with asymmetric peak centered at 276 nm, is attributed to small Ag 4 δ+ clusters [8]. The other one, in visible region, with asymmetric peak centered at 400 nm, is assigned to silver particles [9].…”

Section: Druv-vis Spectroscopymentioning

confidence: 98%

Photocatalytic performance of Ag-modified natural zeolite catalyst for photocatalysis degradation of Methylene Blue (MB) under VIS irradiation

et al. 2012

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In this study, Ag-modified natural zeolite catalyst (Z-Ag red ) was synthesized by chemical activation prior to the ion exchange and followed by a silver reduction with sodium boron hydride. The surface characterization of Z-Ag red has been investigated by X-ray diffraction, FT-IR spectroscopy, SEM microscopy and EDX analysis. Also, UV-VIS diffuse reflectance (DRUV-VIS) spectroscopy was used to determine the light absorption properties of the catalyst. The effect of silver reduction was noticed by comparison with the characterization of silvermodified natural zeolite by ion-exchange without the reduction stage. The photocatalytic performance of Z-Ag red catalyst was proved by photocatalysis application for the decolorisation and degradation of Methylene Blue (MB) dye containing wastewater under visible irradiation. The optimum operating parameters were determined based on the assessment of the photocatalytic process efficiency as a function of the catalyst dose, the initial pH, and the initial concentration of dye. The good results regarding the photocatalytic degradation of MB dye using Z-Ag red catalyst claim it as a potential for the real photocatalysis application in MB-containing wastewater under solar light.

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Crystallization field study for the formation of single phase sodium clinoptilolite: Batch composition, seed and temperature effects

Güvenir

Kalıpçılar

Çulfaz³

2009

Cryst. Res. Technol.

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Although clinoptilolite is the most abundant zeolite mineral in nature, its synthesis under laboratory conditions has been difficult. A partial crystallization field study was done for the synthesis of clinoptilolite based on a nominal batch composition of 2.1Na 2 O:Al 2 O 3 :10Si 2 O:110H 2 O to delineate the limits of composition and temperature within which sodium clinoptilolite can be produced as a single phase in high yields. Effects of temperature, SiO 2 /Al 2 O 3 molar ratio in the batch composition, and the use of different raw materials in batch preparation were studied. The need for the use of seed crystals for reproducible synthesis of clinoptilolite was established.

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Comparative study of natural and synthetic clinoptilolites containing silver in different states

Cited by 72 publications

References 28 publications

Thermal stability of Ag-exchanged clinoptilolite rich mineral

Thermal stability of Ag-exchanged clinoptilolite rich mineral

Photocatalytic performance of Ag-modified natural zeolite catalyst for photocatalysis degradation of Methylene Blue (MB) under VIS irradiation

Crystallization field study for the formation of single phase sodium clinoptilolite: Batch composition, seed and temperature effects

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