You Know That an Ion Exchange Reaction Has Taken Place if the Products Include

Ion Exchange Reaction

The ion-exchange reaction is the nearly widely used method replacing the pre-occupied ions inside interlayer space of host with desired invitee species [three].

From: Progress in Polymer Science , 2013

Challenges, novel applications, and future prospects of chalcogenides and chalcogenide-based nanomaterials for photocatalysis

Mehmet Ates , ... Mehmet Kayra Tanaydın , in Chalcogenide-Based Nanomaterials every bit Photocatalysts, 2021

3.ii.1.vii Ion-substitution and Kirkendall-consequence-induced method

Ion exchange reactions are a method of converting 1 textile into another in a liquid medium. The ion substitution reaction is based on the large difference in the solubility production (Ksp) between the original nanocrystals and the final production. The case as to whether the ion substitution reaction can take place is very complex. Due to phase change, the bodily ion concentrations in the solution, the solvent upshot and the activation free energy of the surface energy depend on many factors. Nevertheless, although the clearer criterion is the divergence in solubility of the reagents and the production, it can exist judged roughly by looking at the solubility of the product.

The cation exchange reaction is used to replace the existing ionic nanocrystalline construction with a dissimilar metal ion. It is particularly effective in transformation of metal chalcogenide nanocrystals. In the cation commutation method, the morphology of the production is controlled by the properties of the original reactant nanocrystals and the crystal structures of the production. If the size of the nanocrystals is below a critical value, the morphology of the final product that is obtained is controlled by the structure to be formed. If the size of the nanocrystals is much larger than this critical value, the product will retain the original morphology of the reagents.

The anion exchange reaction is based on the solubility difference of reagents and products such as cation exchange. Many MC materials can be effectively prepared past the anion exchange reaction. In MCs, since the anions are usually much larger than the cations, they are circuitous in comparison to the cation commutation and generally the anions grade the framework of the crystal construction. Therefore, the exchange procedure, which is usually based on improvidence of ions, is slower than the cation exchange procedure and requires more energy. Since the anion exchange reaction is mostly carried out under more hard atmospheric condition, the morphology of the production is different from those of the reactants [53,54].

The ion exchange reaction is carried out in engraved nanoparticles, nanotubes, nanocages and similar materials. Information technology tin also pb to formation of carved structures. This is related to the Kirkendall effect, a classical phenomenon in metallurgy. Since the ion exchange reaction is carried out by diffusion of ions, hollow structures will exist formed past the Kirkendall result. The ion substitution reaction, alloying from a nanostructured chalcogen (such every bit Te nanowires) or metal source (such as Co nanoparticles), may also induce the Kirkendall issue. However, if nanostructured chalcogens are used as the reagents, the hollow construction cannot be formed since the internet diffusion of atoms will be inward considering of the large anions. The fact that Se and Te are reactive to different metals, even at room temperature, makes them perfect molds for synthesis of different metal chalcogenides. For example, Ag₂Te nanowires are obtained from Te nanowires [55].

A wide range of copper-based ternary and quaternary chalcogenide nanosheets with inclusion of CuInS_two, CuInxGa1 − xS_two and Cu₂ZnSnS_iv were successfully synthesized via the cation-substitution method [56].

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THE REMOVAL AND SOLIDIFICATION OF IODIDE ION USING A NEW INORGANIC ANION EXCHANGER

Hiroshi Kodama , in Progress in Ion Exchange, 1997

3.2 Ion Exchange Reaction

The ion substitution reaction of BiPbO _iiNO_iii with iodide ion was studied in 0.05 and 0.005 mol dm^−three NaI solutions which were previously adjusted pH to 1 and xiii. Powder BiPbO₂NO₃ (2.00 g) was placed in 10 ml of solutions at 25 °C for 24 hours.

Table iii gives the experimental results. Iodide (iodate) ion was removed from the all solutions and it was removed very well from the solution of pH = 13 more from the solution of pH = 1. In the case of the former, subsequently the reaction, iodide ion of most 99.nine % was removed and, in the case of later, iodide ion of nearly 98 % was removed.

Table 3. The results of the ion exchange reaction

The concentration of iodide ion in solution /mol dm−3
earlier reaction	afterwards reaction
	in solution of pH = i	in solution of pH = 13
5 × ten−ii (6345 ppm)	vi.537 × ten−four (82.95 ppm)	1.590 × 10−5 (two.02 ppm)
5 × 10−three (634.v ppm)	0.881 × 10−4 (eleven.17 ppm)	two.85 × 10−6 (0.36 ppm)

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BIOMOLECULES, BIOINTERFACES, AND APPLICATIONS

Rolando Roque-Malherbe , in Handbook of Surfaces and Interfaces of Materials, 2001

3.2.ane Ion Exchange Reaction

The ion commutation reaction in zeolites is represented by [ 117, 125]

(three.1) $z_{\text{B}}\text{A}\{z_{\text{A}}+\}+\text{BZ}\rightleftarrows \text{AZ}+z_{\text{A}}\text{B}\{z_{\text{B}}+\}$

where z _A+ and z _B+ are the charges of cations A and B, respectively, A{z _A+} and B{z _B+} depict the cations A and B in solution, and finally, AZ and BZ are the cations A and B in the zeolite.

Ion commutation equilibrium data are reported in the grade of isotherms with the help of the equivalent ionic fraction [117]: in solution (Fig. 9a),

Fig. 9. (a) Graph of an ionic exchange isotherm; (b) the kinetics of ionic commutation [117].

(iii.2) $X_{\text{A}}=z_{\text{A}}{m}_{\text{A}}/(z_{\text{A}}{m}_{\text{A}}+z_{\text{B}}{m}_{\text{B}})$

and in the zeolite,

(three.3) ${\overline{X}}_{\text{A}}=z_{\text{A}}{\overline{m}}_{\text{A}}/(z_{\text{A}}{\overline{\mathrm{yard}}}_{\text{A}}+z_{\text{B}}{\overline{m}}_{\text{B}})$

where m _A and m _B are the molalties of A and B in solution, whereas ${\bar{m}}_{\text{A}}$ and ${\bar{m}}_{\text{B}}$ are the numbers of moles of A and B per gram of zeolite.

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Functions Containing Two or Ane Chalcogens (and No Halogens)

W. Petz , in Reference Module in Chemistry, Molecular Sciences and Chemical Applied science, 2015

Compounds with the SCNCu₂ core

Room-temperature condensation and ion-commutation reaction of molar equivalents of CuO ^t Bu and North-allylbenzothiazolium iodide in THF led to the isolation of [(AllBzThzylid)Cu(μ-I)_ii(μ-AllBzThzylid)Cu(AllBz-Thzylid)] (36) containing a bridging carbene ligand (AllBzThzylid   = Northward-allylbenzothiazolin-ii-ylidene), which crystallizes along with the isomer [(AllBzThzylid)Cu(μ-I)₂Cu(AllBzThzylid)₂] with 3 terminal carbene ligands as shown in Scheme 27 ; the molecular structure of 36 is presented. ²¹

Scheme 27. SCNCu_two cadre for 36.

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ION EXCHANGE | Inorganic Ion Exchangers

E.Northward. Coker , in Encyclopedia of Separation Science, 2000

Zeolites

Zeolites are microporous crystalline aluminosilicate minerals which occur naturally and may be synthesized easily in the laboratory. An introduction to the structures and properties of zeolites is given in the commodity by Dyer. Zeolites are used on a large scale as ion exchangers in many fields; most notable are their use as 'builders' or water softeners for laundry detergents, and their use in the decontamination of various types of waste streams. Typical applications of zeolites as ion exchangers are given in Tabular array 1. Additionally, the ion commutation capability of zeolites can be used equally a tool to modify their catalytic and sorptive properties. Some attention volition exist paid to structural parameters which influence the ion exchange backdrop of zeolites in the following paragraphs.

Tabular array one. Master applications of zeolites as ion exchangers

Application	Blazon of zeolite oft used	Ion exchange procedure
Detergent building	A (synthetic)	Removal of Ca2+ and Mgii+ from solution
	MAP (synthetic)
	X (synthetic)
Wastewater treatment	Clinoptilolite (natural)	Uptake of ${\text{NH}}_{\text{four}}^{+}$ and heavy metals from waste material streams
	Chabazite (natural)
	Mordenite (natural)
	Phillipsite (natural)
Radioactive waste treatment	Clinoptilolite (natural)	Uptake of 137 Cs +, 90 Sr 2+ and other radionuclides
	Chabazite (natural)
	Phillipsite (natural)
	Mordenite (natural)
	Mordenite (constructed)
	Ionsiv IE-96 (synthetic)
	Ionsiv A-51 (synthetic)
Animal food supplement	Various (natural)	Regulation of ${\text{NH}}_{\text{4}}^{+}$ and NHiii levels in tum
Animal nutrient supplement	Diverse (natural)	Scavenging of radionuclides following contamination of livestock
Fertilizer	Various ${\text{NH}}_{\text{iv}}^{+}$ forms (natural), oft those used to remove ${\text{NH}}_{\text{four}}^{+}$ from wastewater	Tiresome release of ${\text{NH}}_{\text{4}}^{+}$ (and other cations)

Besides the conditions under which an ion exchange reaction is performed, a number of factors may influence the ion substitution properties of zeolites, including:

•

the construction of the zeolite, particularly the diameters of the windows allowing access to the pores and cavities

•

the location of the ion commutation sites; unlike cation environments atomic number 82 to different ion commutation properties. The number of charge-balancing cations required for an electroneutral textile is often less than the number of bachelor ion exchange sites, thus partial occupancy of sites is common. Some of the possible cation positions in zeolites A and X (2 of the near widely used synthetic zeolite ion exchangers) are indicated in Figure two

Effigy 2. A representation of some of the possible positions of exchangeable cations in the structures of zeolites A (A) and X (B). Note: the two structures are not shown on the aforementioned scale. Reproduced with permission from Stucky GD and Dwyer FG (eds) (1983) Intrazeolite Chemistry. ACS Symposium Series, vol. 218, p. 288. Washington, DC: American Chemical Society.

•

the composition of the zeolite framework; varying the Si:Al ratio or irresolute the framework substituent elements may change, for example, the density of exchange sites, the electric field strength or the hydrophobicity of the sample as a whole

The empirical structural formula for an aluminosilicate zeolite may be given as

$K_{\text{x}/\text{due north}}^{(\text{northward})}\left[{\left({\text{AlO}}_{\text{2}}\right)}_{\text{x}}{\left({\text{SiO}}_{\text{two}}\right)}_{\text{y}}\right]\cdot \mathrm{westward}{\text{H}}_{\text{2}}\text{O}$

where the framework is constructed from the entities within the square brackets and the water molecules and charge-balancing cations (Grand) occupy the interstitial space. The x/northward M ^north+ cations are present to counterbalance the x units of negative accuse on the framework due to the presence of x AlO_two groups. In many cases, ion exchange reactions in zeolites may achieve completion, that is, all of the accuse-balancing cations (M) initially present are capable of being replaced by the ingoing cation.

Incomplete ion exchange reactions

In some cases, some of the cations are constrained within the structure and are nonexchangeable. Such cations are introduced into small cavities in the structure during growth of the zeolite crystal. This situation is common with feldspars and feldspathoids, which are like in composition to zeolites, but possess more limited porosity. Fifty-fifty in instances when all charge-balancing cations in the zeolite are physically exchangeable, the total theoretical commutation capacity might not be obtained practically.

There are several reasons for incomplete ion exchange; the iii most of import of these are given below and illustrated schematically in Figure three.

Figure 3. The principal reasons for limitations to ion exchange reactions found in zeolites. (A) Ion-sieving; (B) book exclusion; (C) low charge density (with multivalent cations). The lightly shaded regions stand for an excerpt of the zeolite framework. For clarity, simply ingoing cations are shown.

1.

The most obvious cause of partial or nonexistent exchange is ion-sieving, where the cation to be exchanged into the zeolite is too large, or has a hydration sphere which is too large and robust for information technology to have unrestricted access to the pores of the zeolite. Univalent cations will typically reach 100% commutation, except in limiting cases such equally large cations combined with pocket-sized-pore zeolites. Ion-sieving is more than commonly observed with multiply charged cations, which tend to accept larger hydration spheres on account of their higher charge densities. Zeolites which possess more than i ion exchange site (see Effigy two) may brandish ion-sieving properties depending on the thermodynamics of the substitution reactions occurring at the various sites. The sites which offering the greatest thermodynamic advantage are exchanged beginning, while the less favourable sites may non substitution at all.

ii.

Volumetric exclusion may occur if beefy (organic) cations are exchanged into zeolites of loftier accuse density. Here, the volume occupied by the cations may reach that available in the pores of the crystal before consummate exchange has occurred.

3.

A third reason for limited substitution to be observed is when multivalent cations are exchanged into zeolites of low charge density. As the density of ion commutation sites decreases, the hateful separation between next sites increases, until a point is reached where multivalent cations are unable to satisfy two or more cation commutation sites because of the distance between them. Tabular array two illustrates this point past list the maximum exchange limits observed for several multivalent cations in samples of zeolites ZSM-5 and EU-1 possessing a range of Si/Al ratios.

Table ii. Ion commutation limits (mole fraction) for diverse multivalent cations and temperatures in samples of zeolites ZSM-five and EU-1 with varying numbers of aluminium atoms in the framework. In all cases, the ingoing cation replaces sodium

Zeolite type	Al per u.c. a	Ca ii+ (25°C)	Sr ii+ (25°C)	Ba 2+ (25°C)	La three+ (25°C)	Ca 2+ (65°C)	Sr 2+ (65°C)	Ba 2+ (65°C)	La iii+ (65°C)
ZSM-5	1.i	0.28	0.31	0.36		0.50	0.51	0.52
ZSM-5	ii.0	0.31	0.36	0.56		0.54	0.64	0.76
ZSM-five	2.4	0.36	0.48	0.67	0.39	0.50	0.67	0.77	0.48
ZSM-5	4.2	0.37	0.42	0.90		0.62	0.85	0.93
EU-1	i.2	0.54	0.56	0.56
EU-1	ii.1	0.62	0.67	0.67		0.85	0.89	0.89
European union-1	3.viii	0.86	0.93	0.93		0.96	0.97	0.97

a

Number of aluminium atoms in framework per unit cell.

It is easy to visualize the limiting factors of ion exchange under equilibrium conditions; however, practical ion substitution may take also kinetic limitations. A particular instance of when the desired ion exchange is kinetically express simply still capable of reaching 100% of the theoretical capacity is the softening of water.

Zeolites are used in vast quantities in the detergent industry every bit a water-softening additive for laundry detergents – up to 30% by weight of virtually mod washing powders is zeolite. The zeolite is added principally to remove calcium and magnesium and thus forbid their precipitation with surfactant molecules. Zeolite A is most unremarkably used, due to its high ion substitution capacity, which is a consequence of the framework possessing the maximum possible number of aluminium atoms (Si:Al=1:ane). Recently, zeolite MAP (Maximum Aluminium P), also with Si:Al=one:i, has been introduced into some detergents. Although the Mgⁱⁱ⁺ ion (radius 0.07   nm) is considerably smaller than the Caⁱⁱ⁺ ion (radius 0.1   nm), its exchange into the zeolite is far less facile than that of Ca²⁺, due to its large, tight hydration sphere (the radii of the hydrated Ca²⁺ and Mg²⁺ cations are estimated to be 0.42 and 0.44   nm, respectively). Figure 4 shows the kinetics of exchange of Caⁱⁱ⁺ and Mg²⁺ into Na-A zeolite. The major restriction to the hydrated Mg²⁺ cation is the 0.42   nm window in zeolite A through which information technology must pass to proceeds access to the exchange sites within the construction. In society for the ion exchanger to be effective as a water softener for detergents, it must reduce water hardness inside a few minutes of beginning the launder cycle. While zeolites A and MAP perform well at removing calcium from hard water quickly, their functioning towards magnesium is generally poor. Despite the kinetic limitations, Ca^two+ and Mg²⁺ are fully exchangeable into zeolite A, although selectivity is greater for Ca²⁺ (Effigy 5). Detergent-class zeolites possess small crystallite sizes in gild to provide adequate kinetics of Ca²⁺ exchange.

Figure 4. Kinetics of exchange of Ca²⁺ and Mg²⁺ for 2Na⁺ in zeolite A. Circles, Ca²⁺ exchange; triangles, Mgⁱⁱ⁺ exchange. Data were determined at 25°C, pH 10 and at a solution concentration of 0.05   mol equiv. L^−ane.

Figure 5. Isotherms for Caⁱⁱ⁺/2Na⁺ and Mg²⁺/2Na⁺ substitution in zeolite A. Circles, Caⁱⁱ⁺ exchange; triangles, Mg^two+ substitution. Data were determined at 25°C, pH 10 and at a solution concentration of 0.05   mol equiv. 50⁻¹.

Materials closely related to zeolites

Semicrystalline zeolites

Some involvement has been shown in the ion commutation properties of zeolite precursors, which are obtained by quenching a zeolite synthesis mixture before it has fully crystallized. In these semicrystalline materials, some larger windows and pores are nowadays than in the crystalline counterpart considering the structure has not fully formed. This leads to ion exchange selectivities which are dissimilar from the crystalline textile. Also, their ion commutation capacities are lower than the respective crystalline zeolites. The materials typically show weak zeolite Ten-ray diffraction patterns, and are thus not totally baggy, but possess some brusque-to-medium range club. Semicrystalline precursors to zeolites accept been investigated every bit potential h2o softeners with enhanced magnesium performance for detergent apply. The materials testify slightly limited capacities for both calcium and magnesium, but the selectivity ratio of Mg:Ca is college than that in the fully crystalline counterpart. In the kinetics of exchange, 1 sees the influence of the population of larger windows and pores. The charge per unit of Mg²⁺ exchange approaches that of Ca²⁺ commutation, since the openness of the semicrystalline structure presents less limitation to the diffusion of large hydrated cations (see Figure 6 and compare with Figure iv). Despite the improvement in Mg²⁺ exchange properties relative to Ca²⁺, the performance of such zeolite precursors is probably also poor for detergent applications.

Figure 6. Kinetics of substitution of Ca^two+ and Mg^two+ for 2Na⁺ in the semicrystalline forerunner to zeolite A. Circles, Ca²⁺ exchange; triangles, Mg^two+ exchange. Data were determined at 25°C, pH 10 and at a solution concentration of 0.05   mol equiv. L^−ane.

Materials with nonaluminosilicate frameworks

Zeolite-like structures composed partially or wholly of oxides other than those of Al and Si such as silicoaluminophosphates (SAPOs), metal aluminophosphates (MeAPOs), stannosilicates, zincosilicates, titanosilicates and beryllophosphates are expected to possess ion exchange properties, although few data exist in the literature. Of these materials, the titanosilicates take received the most attention. Recently, the titanosilicate TAM-five has been adult; this exhibits high selectivity for Cs⁺ in the presence of loftier concentrations of other alkali cations and over a pH range from below 1 to above 14. Also, high selectivity of this material for Srⁱⁱ⁺ in basic media has been observed. These loftier selectivities, and its stability to solutions roofing this pH range, has led to commercialization of the material by UOP as Ionsiv IE-910 (powder) and Ionsiv IE-911 (granules) for apply in nuclear waste product treatment.

Particularly interesting ion exchange properties are shown past materials possessing high electrical field strengths, which may arise with frameworks composed of oxides of elements with valencies differing from each other past more than i unit. An example is the beryllophosphate Na₈[(BeO₂)_eight(PO₂)₈]·5H₂O, which has the same construction as the aluminosilicate zeolite gismondine (or constructed zeolite P). Beryllium and phosphorus are strictly alternating in the structure and have valencies of +two and +5 respectively, giving rise to a framework with alternating −2 and +i nominal charges (on Be and P), equally opposed to −1 and 0 for Al and Si in the aluminosilicate analogue. Due to the high electric field slope, hard cations tend to exist favoured over soft ones. Thus, magnesium is favoured kinetically over calcium; the diffusion coefficient for commutation of Mg²⁺ into Na_eight[(BeO₂)₈(PO₂)₈]·5H₂O is more than than three times higher than that of Ca²⁺ under the same conditions (Figure 7), which is a reversal of the situation seen in the aluminosilicate zeolites (compare Effigy seven Figure four). The relatively tedious kinetics of exchange may be attributed to the small window size of the beryllophosphate fabric (the beryllophosphate unit of measurement cell is smaller than the aluminosilicate one). Univalent cations besides exhibit unusual exchange characteristics with Na₈[(BeO₂)_eight(PO₂)₈]·5H₂O, due in function to the relatively brusque Be–O and P–O bonds and the rigidity of the structure. High resistance is experienced past ingoing cations and large hysteresis loops are seen in, for instance, the exchange of K⁺ for Na⁺, while the same reactions in the aluminosilicate analogue do not showroom hysteresis (compare Effigy 8 Figure 9). Hysteresis occurs when the ii cease-members of exchange (in this case, the pure K and Na forms) are mutually immiscible, and grade separate phases which tin usually exist differentiated by Ten-ray diffraction. The two phases will be present simultaneously over a range of cation compositions (in intermediate Na/1000 forms), depending on the caste of immiscibility of the two cease-members.

Effigy 7. Kinetics of exchange of Caⁱⁱ⁺ and Mg²⁺ for 2Na⁺ in Na₈[(BeO_ii)_viii(PO_two)_eight]·5H₂O. Circles, Ca²⁺ exchange; triangles, Mg²⁺ substitution. Data were adamant at 25°C, pH x and at a solution concentration of 0.05   mol equiv. Fifty⁻¹. Interdiffusion coefficients (D): D _(Ca)=2.0×10⁻¹⁸ mⁱⁱ s⁻¹; D _(mg)=half-dozen.v×10⁻¹⁸ m^two due south⁻¹. (Reproduced with permission from Coker EN and Rees LVC (1992) Ion substitution in beryllophosphate G. Office 2. Ion exchange kinetics. Journal of the Chemic Society, Faraday Transactions 88: 273–276.)

Figure viii. Isotherm for Chiliad⁺/Na⁺ exchange in Na₈[(BeO₂)_viii(PO₂)₈]·5H₂O. Circles, forward commutation; triangles, reverse exchange. Data were determined at 25°C, pH 10 and at a solution concentration of 0.05   mol L⁻¹. (Reproduced with permission from Coker EN and Rees LVC (1992) Ion exchange in beryllophosphate One thousand. Office 1. Ion substitution equilibria. Journal of the Chemic Club, Faraday Transactions 88: 263–272.)

Figure 9. Isotherm for K⁺/Na⁺ exchange in zeolite P. Circles, forrad exchange; triangles, reverse commutation; K _{due south}, cation fraction in solution; K _z, cation fraction in the solid. Data were adamant at 25°C and at a solution concentration of 0.1   mol 50^−ane. (Reproduced with permission from Barrer RM and Munday BM (1971) Cation commutation reactions of zeolite NaP. Journal of the Chemical Society A 2909–2914.)

Solid-state ion commutation in zeolites

The exchange of cations from one solid to another, probably mediated by the presence of minor quantities of water, is referred to as solid-state ion exchange. This is a technique which is useful for the preparation of catalysts, that is, the introduction of cations which are only sparingly soluble, or which process hydration spheres which are too big to permit easy diffusion into the cavities of the zeolite from solution. The technique may involve thermal handling (at temperatures upwardly to 500°C) of an intimate mixture of the zeolite and the salt containing the cation to be exchanged (or some other zeolite) although, in some instances, exchange has been observed to occur nether ambient conditions. Some other advantage of the solid-state approach to preparing catalysts is the avoidance of generating large quantities of waste exchange solution.

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Ion-Exchange and Extraction Chromatography Separation of Rare Earth Elements

Dezhi Qi , in Hydrometallurgy of Rare Earths, 2018

six.3.i.i Ion Exchange Reaction

In the course of elution, the ion-exchange reactions occur on the ion-exchange bed and are described as the following reactions. In order to explain easily, supposing that the rare world elements captivated on exchange bed are RE₁ and RE₂, EDTA is used as eluting agent, and Cu^{ii   +} is used equally the retardant. When the elution starts, the following reaction takes place:

(vi.19) ${\overline{\mathrm{RE}}}^{3+}+3{{\mathrm{NH}}_4}^{+}+{\mathrm{Ch}}^{4-}=\mathrm{three}{{\overline{\mathrm{NH}}}_4}^{+}+{\text{RECh}}^{-}$

When the elution continuously carries out, RECh⁻ deabsorbed from the column bed in eluting solution reacts with retardant Cu^{2   +} on the column bed, Cu^{two   +} is eluted, and rare earth ion is absorbed on the column bed again:

(vi.20) ${\text{RECh}}^{-}+{\overline{\mathrm{Cu}}}^{2+}+{\mathrm{H}}^{+}={\overline{\mathrm{RE}}}^{3+}+{\text{CuHCh}}^{-}$

Because rare world band consists two next rare globe elements, the chelating constants of these two rare earth elements with EDTA are different (that of RE₁ is bigger, and that of RE₂ is smaller); therefore, when the elution starts, the rare earth ions deabsorbed behind the band move forward with the eluting solution and move cantankerous rare earth ring; the substitution reactions take identify for the different rare earth elements; the rare earth element RE_two with smaller chelating constants in eluting solution replaces that RE_one with bigger chelating constants on the cavalcade and is captivated on the column:

(vi.21) ${\overline{\mathrm{RE}}}_1^{3+}+{\mathrm{RE}}_2{\mathrm{Ch}}^{-}={\overline{\mathrm{RE}}}_{\mathrm{ii}}^{\mathrm{iii}+}+{\mathrm{RE}}_{\mathrm{one}}{\mathrm{Ch}}^{-}$

Reaction equilibrium abiding:

(vi.22) $K=\frac{\left[{\overline{\mathrm{RE}}}_2^{\mathrm{three}+}\right]\left[{\mathrm{RE}}_1{\mathrm{Ch}}^{-}\right]}{\left[{\overline{\mathrm{RE}}}_1^{\mathrm{iii}+}\right]\left[{\mathrm{RE}}_2{\mathrm{Ch}}^{-}\right]}$

The retarding function of Cu^{2   +} makes the above reaction constantly occurs until the original composition of rare earth is totally inverse. At last, RE₁ is enriched in the front of the band, and its concentration decreases progressively from the front to the rear of the rare world band; RE₂ is enriched in the rear of the ring, and its concentration increases from the front to the rear of the band; RE_one and RE₂ are separated by this way, but a mixed zone for RE_ane and RE₂ would occur betwixt pure RE₁ and pure RE₂ zones; this zone is called transposition section.

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Science and Engineering in Catalysis 2006

Hideki Kurokawa , ... Hiroshi Miura , in Studies in Surface Science and Catalysis, 2007

2 Experimental

The Thousand^{n   +} -mont activator was prepared by ion-exchange reaction of Na⁺-mont and metallic nitrate in aqueous media, drying at 130 °C, calcination at 400 °C, and evacuation at 400 °C. The resulting Thou^{n   +}-mont was treated with a toluene solution of TIBA and then washed with toluene to remove backlog TIBA. Slurry of the supported catalyst was prepared by reaction of Cp₂ZrCl_ii and M^{north   +}-mont in a toluene solution. In the catalysts slurry, as well the montmorillonite-supported Cp₂ZrCl_ii, unsupported Cp_twoZrCl₂ was contained. The catalyst slurry (13 mg of M^{n   +}-mont, Zr-ii.vii μmol), hexane (solvent, 50 ml), and TIBA (0.eight mmol, Al/Zr = 300) were charged into a 100 ml autoclave equipped with a magnetic stirrer. Ethylene was polymerized at 0.7 MPa and threescore °C for 1.5 h. The amount of Cp₂ZrCl_ii supported on G^{northward   +}-mont was calculated on the footing of unsupported Cp_iiZrCl_ii amount determined by ICP-AES measurement of the solution recovered from the catalyst slurry.

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Oxide-based Systems at the Crossroads of Chemistry

A. Colella , B. de Gennaro , in Studies in Surface Science and Catalysis, 2001

two.1 Materials

Both materials used for studying equilibrium and kinetics of the ion-exchange reactions came from the huge formation of Neapolitan yellow tuff [10]. One of them, collected from a tuff quarry in Marano (Naples), was rich in phillipsite, whereas the other, coming from a drilling core in Parco Margherita (Naples), was rich in chabazite. Rock mineralogy was investigated by 10-ray pulverisation diffraction using a Philips PW1730, equipped with a Philips 3710 count unit. Zeolite grade was obtained through the Reference Intensity Ratio (RIR) procedure [eleven].

Enriched phillipsite and chabazite samples, practically free from other cation exchanger phases, were obtained from the parent rocks by enrichment processes (grinding and sieving, separation by heavy liquids or magnetic table, etc.), based on the greater friability and lower density of zeolite relative to other rock constituents [12]. Chemical analysis of the ii zeolites in the enriched products was performed past electron microprobe analysis (CAMECA SX50). Water content was measured by thermogravimetry (Netzsch STA 409 thermoanalyzer).

The two zeolite-rich samples, in their original form or after pre-exchange in Na⁺ form, were stored for long time (at least one calendar week) at room temperature over saturated Ca(NO_iii)₂ solution (relative humidity near fifty%) earlier using them for ion-substitution runs.

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Porous Materials and Nanomaterials

J.A. Brant , ... J.A. Aitken , in Comprehensive Inorganic Chemical science Two (2d Edition), 2013

five.09.4.ii.3 Post-synthesis ion-substitution reactions

Since the surfactants are spring to the inorganic framework through weak surface interactions, ion-exchange reactions can be used to farther tune these materials postal service synthesis. This holding is prominently shown in the example of the C₁₂PyPtSnSe, which has hexagonal packing when direct synthesized. However, when cubic packed C₂₀PyPtSnSe is exchanged with C₁₂Py a cubic variation of C₁₂PyPtSnSe with a remarkable pore contraction of 11   Å tin can exist accessed. This process can fifty-fifty be reversed with nearly full recovery of the C_xxPyPtSnSe starting material. ²²⁹ Another example of this process is the system of C_sixteenPyInSbSe, which possesses cubic pore packing that converts to hexagonal packing when exchanged with C₁₄Py. When the exchanged is reversed and C₁₆Py is added the resulting textile does non return to cubic packing simply adapts a disordered wormhole packing arrangement. Similar alterations to C₁₆Py(Zn,Cd)SbSe did not display alterations in pore packing demonstrating the influence of the linking amanuensis on pore ordering. ²¹²

Ion–exchange reactions in these materials are not limited to surfactants of varying tail grouping lengths. For example, samples of C₁₈PyPtGeSe can be reversibly exchanged with C₁₂Py and irreversibly exchanged with NH₄ ⁺. The exchange for NH_iv ⁺ resulted in a large contraction of the pores and a noted deterioration of the long-range pore ordering. ²⁴⁰ Further studies on mesoporous binary compounds NU-MGe-2 where Thou   =   Sb, In, Sn, Lead, Cd also demonstrated the power to supplant the N-eicosane-North,N-dimethyl-Due north-(ii-hydroxyethyl) ammonium bromide (EDMHEAB) surfactant with NH_four ⁺. In this case, the materials were found to have 6–7% of the initial amount of surfactant left with the pore structure retained after one ion-exchange stride. However, when a second ion commutation pace is carried out the remaining surfactant is removed and pore guild suffers significant degradation. ²⁴¹ A more encouraging example is that of cubic C₂₀PyPtSnSe which tin undergo an ion commutation for H⁺ from strong acids without decomposition or oxidation. In this case, the farthermost flexibility of the inorganic framework is demonstrated past an amazing 55% reversible contraction of the pore structure with no loss of local structure or morphology. ²⁴² To the other extreme, the hexagonal example of C₁₈PyReSeBr can undergo proton ion exchange with lilliputian to no contraction of the pores, demonstrating the rigidity of this particular framework. ²⁴³ The ability to exchange bulky surfactant molecules with smaller, more easily removed ions is the beginning step in making the pores of these mesostructured materials attainable.

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Applications III: Functional Materials, Environmental and Biological Applications

E. Monflier , ... D. O'Hare , in Comprehensive Organometallic Chemistry III, 2007

12.16.2.2.2 Synthesis and structural aspects

Redox active organometallic compounds tin be intercalated into the metal dichalcogenides by either straight reaction, ion exchange, or by electrochemical routes. This observation was initially reported in 1975 when Dines described the intercalation of [Co(Cp)_ii] and [Cr(Cp)_two] into a range of metal disulfides (MS₂: M   =   Ti, Zr, Nb, Ta, and Sn). ³¹⁰ Today, the range of organometallic guests which tin be intercalated into these hosts is now quite extensive (Table 4), including metal π-complexes, ³¹¹ metallic clusters, ³¹² and metal phosphine complexes. ³¹³

Tabular array 4. Selected examples of intercalation compounds formed past layered metal dichalcogenides with unlike organometallic guests

Host	Guest a	Guest occupancy/ten host {Grand}x	Interlayer spacing (c)   (Å)	Lattice expansion (Δc)   (Å)	References
ZrS ii			5.83	None
	Cr(Cp)2	0.25	eleven.64	5.81	309
	Co(CpMe)ii	0.25	eleven.17	5.34	310
	Co(CpPri)2	0.15	xi.57	5.74	310
	Co(CpBun)two	0.13	xi.17	v.34	310
	Cr(Bz)2	0.16	11.73	v.90	309
	Mo(Bz)2	0.xvi	11.64	5.81	309
	Mo(Tol)two	0.13	11.63	5.80	309
	Mo(Mes)two	0.08, 0.20	11.61, xiii.6	5.78, vii.78	309
	Ti(Cp)(COT)	0.23	12.23	6.4	309
	Cr(Cp)(CHT)	0.25	12.0	6.17	309
	Cr(Cp)(Bz)	0.24	11.nine	6.07	309
1T TaS two			vi.04	None
	[Co(Cp)2]	0.25	eleven.45	5.41	310
	Co(CpMe)ii	0.21	eleven.59	5.68	310
	Co(CpPri)2	0.17	12.05	half dozen.eighteen	310
	Co(CpBunorthward)two	0.13	11.44	v.53	310
	[Fe6Seight(PEtiii)]	0.05	17.49	eleven.45	312
SnSe 2
	Co(Cp)2	0.33	eleven.51	v.38	315
NbSe 2			6.00	None
	Co(Cp)2	0.31		v.53	310
	Cr(Cp)2	0.20		v.56	310
MoS 2			6.fourteen	None
	Co(Cp)ii	0.31	11.68	5.53	318
(PbS)ane.xviii(TiSii)2	Co(Cp)2	0.15	11.21	v.52	287
(PbSe)1.12(NbSetwo)ii	Co(Cp)2	0.15	xi.58	5.59	287

a

Bz   =   η-C₆H₆, CHT   =   η-C_sevenH₇, COT   =   η-C₈H₈.

The electron-transfer mechanism from guest to host is the ascendant process for these reactions. Every bit a consequence there is the correlation betwixt the reducing ability of the organometallic guest and its power to intercalate into a given host lattice. For example, ferrocene does non announced to intercalate into MS₂ (Chiliad   =   Ti, Nb, Sn) compounds whereas cobaltocene readily intercalates into a broad range of the dichalcogenides. The magnetic susceptibilities of TaS_two{Co(Cp)_ii}_0.25 and TaS₂{Cr(Cp)₂}_0.25 are consistent with complete electron transfer from the metallocenes to the hosts. However, 10-ray photoelectron studies on SnS₂{Co(Cp)₂}_0.three point that this may non always occur and complex mixed-valence behavior may issue. ³¹⁴ The orientation of the unsubstituted metallocenes with respect to the host layers has been subject area to much argue since Dines' initial report. ³¹⁰ The complication arises from the fact that the lattice expansion of ca. 5.31 Å observed for all uncomplicated metallocene intercalates does non immediately reveal the orientation of the guest. These molecules have virtually a spherical van der Waals' surface of approx. half dozen.v Å diameter. For SnS₂{Co(Cp)_ii}_0.3 the debate has been resolved by a combined 10-ray and neutron diffraction report, which shows that the cobaltocene molecules are ordered inside the van der Waals' gap with their primary axes parallel to the layer planes (Tabular array iv). ³¹⁵ In addition, variable-temperature solid-state ²H NMR tin can exist used to great consequence to written report the metallocene orientations within these layers. ^316,316a More recently, a study of a series of π-bonded sandwich complexes [K(η ⁿ -C _n H _n )(η ^m -C _m H _thousand )] intercalated in ZrS₂ shows that for any ring size (C₅–C₈) the principal axis of the circuitous lies parallel to the host layers (Figure 61). ³¹⁷

Figure 61. Schematic representation of a sandwich molecule intercalated in a metal dichalcogenide host. Two orientations of the sandwich molecule are illustrated; C _north molecular axis either parallel or perpendicular to the host layers.

The evolution of significant intercalation chemistry of MoS_two is relatively recent. The fabric is chemically more inert and this tin can be traced back to the coordination of the molybdenum every bit well as the ligand field backdrop of the d ^two ion divers in the interlaminar region. MoS_ii avoids direct intercalation, except for lithium. However, syntheses of single-layer suspensions of MoS₂ in h2o have been developed past rapid hydrolysis of Li _x MoS₂ producing molecular H₂ causing the exfoliation of the sulfide. ³¹⁸

Ferrocene and a number of other non-electron donor ferrocenes have been intercalated into MoS₂ by treating a saturated CCl₄ solution of the guest with a intermission of exfoliated MoS₂. The interlayer spacings for the substituted ferrocene intercalates indicate the germination of a bilayer of guest molecules. ³¹⁹ Direct reaction of metallocene cations [G(Cp)₂]⁺Cl⁻ (G   =   Fe, Co) with exfoliated MoS_ii yields a material with alternating layers of metallocenium invitee and partially negatively charged MoS₂ layers. Intercalation of [(η-arene)Ru(H_iiO)₂]²⁺ (arene   =   C_half-dozenH_{half dozen}, 1,two,4,5-C₆H₂Me₄) gives two phases, depending on the pH of the reaction. At pH 3.2, the ruthenium complex is inserted every bit a monomer, while at pH eight.5, the ruthenium species is binuclear. ³²⁰

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