Mechanism of the fractionation of 7Li ions into aqueous solutions: ion-exchange with the six-membered oxygen ring of zeolite-A

Phase separation in hydrated LTA zeolite

“…6, the plot of the separation factor (α) for the lithium isotopes resembles a pseudo-α determined from column experiments [13]. In the range of 0.04 < x < 0.32, high α values were obtained (α = 1.017±0.003), whereas in the higher filling range of 0.56 < x < 0.71, low α values were obtained (α = 1.010±0.003).…”

“…The partition function product (Q = q trans q rot q vib ) ratio of the isotopic substitution (Q( 7 Li) / Q( 6 Li)) is simply expressed by normal mode frequencies and vibrational partition functions [15][16][17]. Accordingly, the lithium isotope separation factor (α) is defined using the frequencies and isotopic shifts of Li oscillations in both phases at room temperature [13].…”

“…The extent of the deviation of α is attributable to the isotopic fractionation occurring in the thermal ionization source of mass spectrometer [24][25][26]. The high α values in the range of 0.04 < x < 0.32 are attributable to the zeolite sites where the excess amount of 6 Li ions is left behind by the ion exchange with aqueous solutions that contain enriched 7 Li with strong hydration [13]. The low α values in the range of 0.56 < x < 0.71 indicate that the Li ions are distributed over the other ion-exchangeable sites that prefer 7 Li.…”

“…Previously calculated results [13] were used for the lithium tetrahydrate ion and a ring-molecule ion which represent the Li ion in aqueous solution and the local atomic arrangement around the Li ion of the six-membered oxygen ring, respectively.…”

“…10 µm) of NH 4 -A, which was prepared from Na-A (Tosoh) by ion-exchange [13]. At the final process of the ion-exchange, to remove the excess amount of NH 3 3 .…”