Cations alkaline

Humic acids are alkaH-extractable materials and total humic acid content is a term that refers to the humic acid content of coal that has had its carboxylate cations removed with sodium pyrophosphate. Values for some typical AustraHan brown coals range from 24—92% (13). Treatment of lignitic coals with mineral acid to release the alkaH and alkaline cations may dissolve up to 20% of the coal. The naturally moist coals are slightly acidic and have a pH of 3.5—6.5. 

Fig. 2. Flow sheet for the acid circuit processing and recovery of mica from weathered granodiorite ore. An alkaline—cationic circuit may be used by inserting a second conditioner containing lignin sulfonate, adjusting the pH to 8.0, and adding NaOH and DRL (distilled tall oil) fatty acid to the first...

Krafft temperatures depend not only on chain length but on the cation. Eth-oxylation of the base alcohol reduces the Krafft temperature due to the higher solubility of the sulfate. Calcium and other earth alkaline metals produce an increase of the Krafft temperature that is significantly reduced by ethoxylation of the alcohol. The decrease is more significant for alkaline earth metals than for alkaline cations as shown in Table 6 [81,82], although it should be noted that, according to other workers, sodium dodecyl sulfate has a Krafft temperature of 16°C. 

The chemical compositions of the samples, obtained from chemical analyses are reported in Table 1. In order to check the chemical analyses, the mother and washing liquors were collected, analysed and their acidity was titrated. In all cases, the alkaline cations were detected only as traces. The acidimetric titration allowed us to determine the HPA amount remaining in the solution. On the other hand, the samples separated after precipitation and washings were weighted in order to calculate the precipitate yields. The results are reported in table 1 where the samples are designated as MxY (M being the alkaline or ammonium cation, Y the heteroatom, x the stoichiometry deduced from chemical analyses. 

Atomic ratio alkaline cation/central atom (P or Si). Molar ratio precipitate HPA/initial HPA. deduced from acidimetric titration of the mother solutions. 

Fig. 7. Ball and stick representations of (a) Na C Fee[N(CH2CH20)3]6 i and (b) Cs C Fe8[N(CH2CH20)3lg +, showing the template effect of the alkaline cation.

Cation-selective ionophores are the most successful in polymeric ISEs and selectivi-ties exceeding ten orders of magnitude became quite common. The cation-ionophore binding occurs dominantly due to Lewis interactions and could be understood in terms of hard and soft acid and bases theory (HSAB). While hard base oxygen atoms originate from ester, ether or carbonyl functionalities, and interact with hard acid alkaline cations, the softer sulfur or nitrogen atoms better bind with transition metal ions. Cation... 

Sorption depends on Sorption Sites. The sorption of alkaline and earth-alkaline cations on expandable three layer clays - smectites (montmorillonites) - can usually be interpreted as stoichiometric exchange of interlayer ions. Heavy metals however are sorbed by surface complex formation to the OH-functional groups of the outer surface (the so-called broken bonds). The non-swellable three-layer silicates, micas such as illite, can usually not exchange their interlayer ions but the outside of these minerals and the weathered crystal edges ("frayed edges") participate in ion exchange reactions. 

Table 12. Calculated and experimental polarizabit ities of some alkaline cations (values in A3)...

Influence of the Additives. Complexing agents like Kryptofix 222 and Kro-nenether are known to effect a dramatic change in the interactions of cations with their counter ions. The addition of these macrocycle compounds to a micellar Na(AOT) solution is supposed to gather alkaline cations (Na+) within macrocycle cavities near the interface. 

Ionophores, or polyether (PET) antibiotics, produced by various species of Streptomyces, possess broad spectrum anticoccidial activities. They are chemically characterized by several cyclic esters, a single terminal carboxylic acid group, and several hydroxyl groups. Representative members of this class include salinomycin (SAL), monensin (MON), lasalocid (LAS), narasin (NAR), maduramicin (MAD), and semduramicin (SEM). The main chemical properties of interest in the extraction methodology are their low polarities and instability under acidic conditions. They are able to form stable complexes with alkaline cations. All of these compounds, with the exception of LAS, bind monovalent cations (e.g., Na+ and K+). Lasalocid has a tendency to form dimers and can form complexes with divalent cations such as Mg2+ and Ca2+. The formation of metal complexes results in all of these compounds adopting a quasi-cyclic formation consequent to head-to-tail hydrogen bonding. No MRLs have yet been set by the EU for any of the carboxylic acid PETs (98). 

As calculations (Calle et al. 1992) show, the preferential approach of an alkaline cation to a 1,2-semidione is indeed in the middle of the two oxygen atoms. A cation-semid-... 

The X-ray structure of the L-Sr(Picrate)2 (L = p-tert-butyl-calix[4]arene-tetra(diethylamide)) is reported, as well as MD simulations on the L M2+ complexes in vacuo, in water, and in acetonitrile solutions for alkaline earth cations with a comparison of converging and diverging conformers.130 In the simulated and solid-state structures of the L M2+ complex, the ligand wraps around the complexed cations M2+ (more than it does with alkaline cations), which are completely encapsulated within the polar pseudo-cavity of L, without coordination to its counterion in the crystal or to solvent molecules in solution. In contrast to alkali cation complexes, which display conformational flexibility in solution, computations show that the alkaline earth cation complexes are of the converging type in water and in acetonitrile. Subtle structural changes from Mg2+ to Ba2+ are observed in the gas phase and in solution. Based on FBP calculations, a binding sequence of alkaline earth cations was determined Mg2+ displays the weakest affinity for L, while Ca2+ and Sr2+ are the most stable complexes, which is in agreement with the experiment. 

Various geometrical shapes have been observed upon addition of monovalent alkaline cations to the peptides.135,150 SEM and AFM studies revealed interwoven nanofibers... 

Minachev et al. [76] studied oxidative dehydrogenation of cyclohexane on zeolite cationic forms at 300-475 °C, the main reaction product of which is cyclohexene. Cyclohexadiene and C02 are also formed, and at long-term contacts benzene is detected. Cyclohexene yield and selectivity of the reaction depend on zeolite structure and composition, reaction temperature and oxygen cyclohexane ratio in the reaction mixture. Among alkaline cationic forms of zeolite, the highest cyclohexene yield (21%) is observed for NaA zeolite (66% selectivity). 

The impact of the type of earth alkaline cation on the shrinking mechanism is an interesting question by itself. Moreover, knowledge in this field is relevant for SAXS measurements. The earth alkaline cations with higher electron density might reflect the shape of the collapsing chains if they are bound to the very chains [77]. 

Clearly, the phase boundaries lie on top of each other. A closer look reveals a slight decrease in the slope r0 of Eq. (26) according to Ca2+>Sr2+>-Ba2+, which indicates that the larger the bivalent earth alkaline cation is, the smaller is the stoichiometric amount of M2+ necessary to precipitate NaPA. Although based on a different method, the present results suggest a comparison with data from Pochard et al. [73]. In doing so, we have to keep in mind that our own r0 values are of fair accuracy at best because they were evaluated from slopes based on a few data points only. Still, this trend in rQ is the opposite to the observation of Pochard et al. [73]. They found a decrease of the amount of M2+ per COO function at the precipitation threshold, if Ca2+... 

Fig. 27 Phase boundaries for three different earth alkaline cations in 0.01 M NaCl Ca2+ ( ) Sr2+ (A) Ba2+ ( ). The polymer sample is PA2...

Table 6 Parameters of Eq. 26 for phase boundaries of the system PA2 with M2+ denoting earth alkaline cations at T=25 °C...

Huang, M., Adnot, A. and Kaliaguine, S. Characterization of basicity in alkaline cation faujasite zeolites - An XPS study using pyrrole as aprobe molecule, J. Catal., 1992,137, 322-332. 

Moreover, pore and channel size and shape can be tuned by using different alkaline-earth cations (Mg2+, Ca2+, Sr2+, Ba2+) having different sizes and coordination numbers. The heat of water adsorption ranges from —46 to —52 kj mol-1, values similar to those of silica-containing zeolites. As recently reported, the properties of these materials can be further differentiated through the incorporation of transition (i.e. Co2+) or alkaline cations (i.e. K+) into the channels of barium-linked materials composed of metal-assembled cages. 

As previously described, the hydrothermal synthesis of aluminosilicate zeolites is carried out with highly reactive aluminosilicate gels in autogenous conditions. This kind of synthesis may involve the structure-directing role of alkaline cations in solution-mediated crystallization of the amorphous gel [55],... 

Sherry, in the last few years, has been generalizing all knowledge about selectivity during ion exchange in zeolites this author has summarized the selectivity rules as follows [21] every zeolite has preference for Na+ instead of Li+ and NH4 instead of Na+ zeolites with a low Si/Al ratio have preference for Ca2+ and zeolites with a high Si/Al ratio have preference for alkaline cations zeolites are selective for polarizable cations and the electroselectivity, molecular sieving, and space limitations rules are valid. 

A recent paper (6) reports an interesting case of a felspathoid, cancrinite, previously obtained in typically sodic environments with (7) or without added salts ( 8), synthesized in bicationic systems formed by lithium and a large alkaline cation (rubidium or cesium). Such syntheses suggest that cancrinite is a further phase, the... 

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