The isotopic exchange kinetics of Zn2+ ions in hydrated Zn-A zeolite of composition Zn5·55Na0·90(AlO2)12(SiO2)12·aq were investigated by measuring the fractional attainment of isotopic equilibrium between a ZnCl2 solution and a 65Zn-labelled Zn-A zeolite (30 and 45μm particle radii) as a function of time, at 25 to 60C. The exchange mechanism was a two-step process which was resolved, using the Brown-Sherry-Krambeck model, into diffusion in the solid particles, with a Zn2+ diffusivity described by: D(m2/s) = 10-3.97exp[-67.1(kJ/mol)/RT], and an intracrystalline first-order exchange between bound and mobile Zn2+ ions in the network, with a rate constant given by k2(/s) = 103.05exp[-56.5(kJ/mol)/RT].

Isotopic Exchange Kinetics of Zinc Ions in Zn-A Zeolite. V.M.Radak, I.J.Gal, J.J.Salai: Journal of the Chemical Society - Faraday Transactions 1, 1976, 72, 1150-6

 

Table 9

Diffusion of Zn in NaA and NaX Zeolites

Zeolite

Temperature(K)

Coefficient

D(m2/s)

NaA

298

initial

9.55 x 10-16

NaA

298

final

3.95 x 10-15

NaA

303

initial

1.05 x 10-15

NaA

303

final

4.02 x 10-15

NaA

313

initial

1.16 x 10-15

NaA

313

final

4.12 x 10-15

NaA

323

initial

1.21 x 10-15

NaA

323

final

4.21 x 10-15

NaX

298

initial

6.53 x 10-16

NaX

298

final

1.73 x 10-15

NaX

303

initial

7.45 x 10-16

NaX

303

final

1.89 x 10-15

NaX

313

initial

8.00 x 10-16

NaX

313

final

2.04 x 10-15

NaX

323

initial

8.21 x 10-16

NaX

323

final

2.21 x 10-15