Thermal and spectroscopic studies of zeolites exchanged with metal cations

Castaldi, Paola; Santona, Laura; Cozza, C.; Giuliano, Veronica; Abbruzzese, C.; Nastro, Valentina; Melis, Pietro

doi:10.1016/j.molstruc.2004.09.009

Cited by 91 publications

(66 citation statements)

References 25 publications

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“…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%

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%

Thermal stability of Ag-exchanged clinoptilolite rich mineral

Akdeniz

Ülkü

2008

J Therm Anal Calorim

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“…They based this explanation on the observation that the evaporation of this water does not compromise the stability of the geopolymers when exposed to high temperatures. However, the water in zeolites comprises zeolite water as well as structural water, wherein the loss of structural water leads to the destruction of the zeolite's structure (Castaldi & Santona, 2005). Furthermore, Fernández-Jiménez, Palomo, Pastor, and Martin (2008) attribute the large amounts of weight lost at 100°C, which was observed in TGA, to the loss of adsorbed and some combined water in the N-A-S-H gel, which resembles weight loss of C-S-H in Portland cement cases.…”

Section: Introductionmentioning

confidence: 99%

Study on the Disposition of Water in Fly Ash-Based Geopolymers Using ATR–IR

Liu¹,

Yuan²,

Kayali³

2016

Proceedings of the 5th International Conference on the Durability of Concrete Structures

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This paper addresses the question of whether the main product of low calcium fly ash-based geopolymer is a hydrate, namely, sodium aluminosilicate hydrate (N-A-S-H). The answer to this question is important for understanding geopolymer characteristics. One of these is its fire resistance. In this study, fly ash-based geopolymers were synthesized using the combination of Na 2 CO 3 and Ca(OH) 2 . Samples were cured at ambient temperature for 7 days, then placed in the oven at 105°C for 24 h, and then calcined at 1050°C for 48 h. IR was used to examine the produced geopolymers at each stage so as to further knowledge on the following issues: the possibility of co-existence of calcium aluminosilicate hydrate (C-A-S-H) and N-A-S-H, the roles of cations as compensator and network modifier as well as the role of water. The results obtained suggest that the primary geopolymerization products, which are potentially good fire-resistant, are unlikely to contain hydrates. Even if there were hydrates, their amount must be very small such that the escaping of water does not compromise the structure's integrity.

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“…Finally, two distinct peaks at 738 and 607 cm −1 are related to Si-O(Si) and Si-O(Al) stretching bridges, respectively. 36 In the case of PQ/CL formulations, the peaks related to PQ molecule shows a slight shift in place after encapsulation in CL clays. These changes can be attributed to ionic interaction between the cationic PQ herbicide and anionic surface of CL.…”

Section: Ft-ir Spectramentioning

confidence: 97%

Controlled Release Systems Based on Intercalated Paraquat onto Montmorillonite and Clinoptilolite Clays Encapsulated with Sodium Alginate

2015

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As a model herbicide, paraquat (PQ) was intercalated into montmorillonite (MMT) and clinoptilolite (CL) clays at different concentrations. FT-IR, XRD, and SEM techniques were used to characterize the structures of the prepared formulations. The prepared PQ/clay samples were further encapsulated with alginate (Alg) polymer. After characterization, the potential application was verified through release of PQ from PQ/clay and PQ/clay/Alg formulations. According to the results, the release of PQ from PQ/MMT was slower than the release from the PQ/CL system. The presence of the alginate polymer in PQ/clay/Alg capsule beads caused the system to liberate PQ in a more controlled release manner than PQ/clay samples. Furthermore, the release data were fitted to empirical equations to estimate the kinetic parameters. The results suggested the feasibility of the use of clay/Alg formulations for controlled release of herbicides in agricultural applications. C 2015 Wiley Periodicals, Inc. Adv Polym Technol 2015, 0, 21597; View this article online at wileyonlinelibrary.com.

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Thermal and spectroscopic studies of zeolites exchanged with metal cations

Cited by 91 publications

References 25 publications

Thermal stability of Ag-exchanged clinoptilolite rich mineral

Thermal stability of Ag-exchanged clinoptilolite rich mineral

Study on the Disposition of Water in Fly Ash-Based Geopolymers Using ATR–IR

Controlled Release Systems Based on Intercalated Paraquat onto Montmorillonite and Clinoptilolite Clays Encapsulated with Sodium Alginate

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