Calcium ammonium exchange

Table 8.5. A comparison of exchange coefficients for several cation exchange equations, as calculated from the ammonium-calcium exchange data of Table 8.2...

Table 8.5 compares different exchange coefficients calculated from the data for ammonium-calcium exchange in Table 8.2. The simple Gapon equation (8.10) yields the most uniform exchange coefficient for this set of data the Eriksson equation s predictions also agree well with the measured values. Bond and Verburg (1997) applied the various ion equations to the more complicated case of ternary (Ca-K-Na). Their slight modifications of the 1918 work by Rothmund and Kornfeld yielded the most consistent exchange coefficients in their study. Snyder and Cavallaro (1997) applied a single-phase mixture approach to NH -Ba2+-La3+ exchange on clays.

Chung, J.B., Zasoski, R.J., 1994. Ammonium-potassium and ammonium-calcium exchange equilibria in bulk and rhizosphere sod. Soil Sci. Soc. Am. J. 58, 1368-1375. 

The formation of heavy carbonaceous compounds in 5A calcium exchanged zeolites depends on the calcium content. These zeolites are able to protonated ammonia molecules in ammonium ions. This Bronsted acidity results from the presence of CaOH+ species which are formed by water dissociation on Ca2+ ions and have an IR signature at 3515 cm"1. 

The work discussed here compares the relative site occupancies for three series of hydrated Y zeolites ammonium, calcium and lanthanum exchanged. The data for these same three series of samples in the dehydrated forms are also presented and the assignment of the observed resonances is discussed. 

Figure 2. Comparison of sodium-23 MASNMR spectra of hydrated Na-Y and partially ammonium, calcium, or lanthanum exchanged Na-Y zeolites at 96 MHz.

Synthesized zeolites can be modified by ion exchange. Exchange of. sodium by pota.ssium, ammonium, calcium, barium, rare earth and transition metal elements is industrially important... 

In studying the mechanism of action of bisquatemary ammonium compounds upon mediator exchange in the vegetative nerve system, most attention has been concentrated on the part played by thiamine and panthothenic acid. The results obtained from these studies have shown that thiamine and calcium pantheonate as antidotes exert a certain positive effect in acute poisonings by one of the bisquatemary ammonium compounds, such as hexamethylen-bis-(4-nitrobenzene) chlorine ammonium. Calcium pantheonate has shown a high antidote activity. 

Ammonium ion exchange Clinoptilolite, a natural zeolite, selectively removes ammonium ion by ion exchange Na clinoptilolite + -> clinoptilolite + Na. The ion exchanger is regenerated with sodium or calcium salts. 

Addition of a salt can transform the shale by cation exchange to a less sensitive form of clay, or reduce the osmotic swelling effect by reducing the water activity in the mud below that which occurs in the shale. These effects depend on the salt concentration and the nature of the cation. Salts containing sodium, potassium, calcium, magnesium, and ammonium ions ate used to varying degrees. 

The modern history of ion exchange began in about 1850 when two English chemists, Thompson(4) and Way(5), studied the exchange between ammonium ions in fertilisers and calcium ions in soil. The materials responsible for the exchange were shown later to be naturally occurring alumino-silicates 6. History records very much earlier observations of the phenomenon and, for example, Aristotle(7), in 330 BC, noted that sea-water loses some of its salt when allowed to percolate through some sands. Those who claim priority for Moses(8) should note however that the process described may have been adsorption ... 

The TEB value may be obtained by either the sum of the individually measured cations or by evaporating and igniting a portion of the ammonium ethanoate leachate to convert the metallic cations to oxides and carbonates, followed by addition of excess acid (to convert carbonates to chlorides) and back-titration with alkali. The latter method is difficult if the soil is insufficiently base-rich to provide an adequate amount of bases for the titration. On the other hand, the calcium carbonate in calcareous soils may be partially leached by the ammonium ethanoate at pH 7.0 in addition to the exchangeable bases and thus give an exaggerated TEB value and a percentage base saturation in excess of 100%. The TEB by ignition/titration can serve as a check on the values from the summation method. 

Radium in hydrochloric acid solution may be separated effectively by ion exchange methods using cation exchange-resin columns. A weak HCl solution is passed through the column. The absorbed metals on the ion-exchange column are eluted with ethylenediaminetetraacetic acid (EDTA) at pH 6.25 or with ammonium citrate at pH 7.8. With either eluant, radium is eluted last, after removing barium and then lanthanum, calcium, magnesium, and other metals. 

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