Clinoptilolite: the distribution of potassium atoms and its role in thermal stability

K, Koyama; Takéuchi, Yoshio

doi:10.1524/zkri.1977.145.16.216

Cited by 67 publications

(84 citation statements)

References 9 publications

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“…The capacity in run 5 is observed to be less than that for run 4, which might be on account of some degradation of the zeolite by the acid. Clinoptilolite is likely only to suffer a minor capacity loss due to its high silica to aluminium ratio, unlike other zeolites with higher aluminium ratios, which can be totally degraded 15–17…”

Section: Resultsmentioning

confidence: 99%

Continuous removal of ammonium ion by ion exchange in the presence of organic compounds in packed columns

Jorgensen

Weatherley

2006

J of Chemical Tech & Biotech

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The removal of ammonia from wastewaters after secondary biological treatment can successfully be achieved by ion exchange. However, the presence of residual organic compounds can impart significant influence on the uptake and their presence may need to be considered during the design of a treatment system. The aim of this work was to determine the effect of the presence of certain organic compounds upon the uptake of ammonium ion and column breakthrough. Two organic contaminants were considered, including citric acid and protein (as whey protein isolate). Three cationic exchangers were used and included the natural zeolite clinoptilolite, the gel resin Dowex 50w-x8, and a macronet resin, Purolite MN-500. The influence of regeneration upon column breakthrough behaviour was also determined. The results showed that the presence of organic compounds had variable effects on ammonium ion uptake. In the case of clinoptilolite the presence of protein appeared to have very little effect upon breakthrough capacity. In the case of the clinoptilolite and the MN500 a substantial reduction of breakthrough capacity was observed in the presence of citric acid. In the case of clinoptilolite a very significant increase in column breakthrough performance was observed after cycles of exhaustion and regeneration. This was not observed in the case of the synthetic resins, which showed a more consistent performance from run to run. Overall the Dowex50w-x8 gave the highest breakthrough capacity for ammonium ion removal of 700 bed volumes. Regenerated clinoptilolite showed a maximum breakthrough capacity of 450 bed volumes, and MN-500 a consistent breakthrough capacity of 300 bed volumes.

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Section: Resultsmentioning

confidence: 99%

Continuous removal of ammonium ion by ion exchange in the presence of organic compounds in packed columns

Jorgensen

Weatherley

2006

J of Chemical Tech & Biotech

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“…Such effects are frequently observed in framework structures like those of zeolite (Mortier et al, 1975;Koyama and Takeuchi, 1977;Takeuchi et al, 1979). This is thought to be the consequence of conpensating for weaker Na -Ο bonds introduced to the C 3 A structure to give the CII type.…”

Section: Characteristic Features Of the CII Structure Typementioning

confidence: 93%

Crystal-chemical characterization of the 3CaO·Al₂O₃—Na₂O solid-solution series

Takéuchi¹,

Nishi²

1980

Zeitschrift Für Kristallographie - Crystalline Materials

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The 3 CaO · AI 2 0 3 (=C 3 A)-Na z O solid solutions (Ca 9 _ x/2 Na I -[A1 2 0 18 ]), have been crystal-chemically characterized based on four new structures:(i) 2.4wt% Na 2 0 (x = 0.625), a = 15.248(2)Ä, Ρ2^, Ζ = 8. (ii) 3.3% Na z O, a = 10.879(1), b = 10.845(2), c = 15.106(2), Pbca, Ζ = 4. (iii) 5.7 wt% Na 2 0 {x = 1.5), a = 10.877 (6), b = 10.854(13), c = 15.135(13), y = 90.1(1)°, P2Ja, Ζ = 4. (iv) 6.6 wt% Na 2 0, a = 10.844(2), 6 = 10.855(2), c= 15.122(4), y = 90.38(1)°, P2 1 /a, Ζ = 4. Among these, (ii) contains 0.45 Fe and 0.375 Si, and (iv) 0.465 Si per 18 oxygen atoms. The structures have been refined to R = 3.5 ~ 4.9%.The structure (i) represents the structure type of a hitherto unreported cubic phase, which is here denoted by CII (the C 3 A is then denoted by CI); the compositional range of the new phase possibly extends from around 1.0 to 2.4 in wt % of Na 2 0. The Na atoms in the structure substitute for Ca at Ca3B and Ca4B which respectively correspond to the Ca(3) and Ca(4) sites in C 3 A, and excess Na atoms, resulting from the replacement in the Ca/Na ratio of 1/2, go to the centers of the six-membered rings. The substitution gives rise to an expansion of the polyhedra particularly about Ca4B; such an effect would presumably limit the CII structure type at the Na z O content of around 2.4%. With increasing Na 2 0 content, the cubic arrangement of the sixmembered rings undergoes a drastic change to yield an orthorhombic arrangement. In the orthorhombic structure type, Na substitutes for Ca only at the Ca5 site, and the Na occupancy in the rings is increased compared to the cubic cases; the rings are more contracted compared to those in CII. When Si is present in the orthorhombic solid solution, it gives an effect of reducing the Na occupancy in the rings and thus extends the solid-solution Brought to you by | New York University Bobst Library Technical Service Authenticated Download Date | 8/2/15 4:08 AM Y. Takeuchi et al.: 3 CaO • A1 2 0 3 -Na 2 0 solid-solution series range towards the compositions of Na-poor range. As the content of Na increases further, the Ca5 site splits into two nonequivalent sites, Ca5A and Ca5B, which accommodate Na in different amounts, thus distorting the orthorhombic structure to monoclinic; the arrangement of rings is essentially the same as that for the orthorhombic structure type. When Si is present in the monoclinic solid solution, it permits the Na occupancy of 100 % at Ca5B and reduces the Na occupancy in the rings; as the total effect, the Na content in the structure increases and the solid-solution range is extended to a region which is richer in Na.The X-ray, single-crystal study at high temperatures have confirmed that the monoclinic structure type is transformed to orthorhombic in a transition which is reversible. The transition is caused by an order-disorder of Na and Ca in the Ca5A and Ca5B sites. The inversion twins that occur in monoclinic crystals, and the growth twins that commonly occur in non-cubic crystals, can be structurally interpreted.* In cement...

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“…in the form of anatase (Alfa-Aesar). The adsorbent agents used were a natural zeolite, clinoptilolite [62][63][64][65][66], and carbon nanotubes [67,68]. The latter were used both as adsorbents and as reinforcing nano-fibers [69][70][71][72].…”

Section: Methodsmentioning

confidence: 99%

Preparation and Characterization of Plasters with Photodegradative Action

Luca

Candamano

et al. 2018

Buildings

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The aim of this project is to investigate the behaviour of several special types plasters specifically designed to degrade the most common pollutants which are present in the atmosphere. In particular, specific additives have been added to these plasters, in order to obtain a broad spectrum of active and synergic response, each of which have peculiar functions: - microporous materials, such as clinoptilolite, a natural zeolite, that promotes the adsorption of air pollutants thanks to its porous nature; - nano-fillers, such as carbon nanotubes, that behave both as reinforcing agents as well as adsorbent materials; - photochemical agents, such as titanium oxide, that degrade air pollutants, previously adsorbed on carbon nanotubes and zeolites, thanks to the action of light that activates photodegradation reactions. All the samples were also characterized in terms of mechanical properties, adhesion to supports and water absorption. Furthermore, photodegradation tests were carried out by exposing plaster surfaces, wetted with a Rodamine solution, to Ultraviolet rays (UV) for different times. Plasters photodegradative capacity was evaluated and the results highlighted the fact that the designed admixtures showed an important photodegradative action, strictly dependent on the types and specific ratios of the selected additives.

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Clinoptilolite: the distribution of potassium atoms and its role in thermal stability

Cited by 67 publications

References 9 publications

Continuous removal of ammonium ion by ion exchange in the presence of organic compounds in packed columns

Continuous removal of ammonium ion by ion exchange in the presence of organic compounds in packed columns

Crystal-chemical characterization of the 3CaO·Al₂O₃—Na₂O solid-solution series

Preparation and Characterization of Plasters with Photodegradative Action

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Clinoptilolite: the distribution of potassium atoms and its role in thermal stability

Cited by 67 publications

References 9 publications

Continuous removal of ammonium ion by ion exchange in the presence of organic compounds in packed columns

Continuous removal of ammonium ion by ion exchange in the presence of organic compounds in packed columns

Crystal-chemical characterization of the 3CaO·Al2O3—Na2O solid-solution series

Preparation and Characterization of Plasters with Photodegradative Action

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Crystal-chemical characterization of the 3CaO·Al₂O₃—Na₂O solid-solution series