The kinetics of cation exchange of amorphized terskite

The kinetics of cation exchange between natural amorphized microporous zirconosilicate terskite Na4ZrSi6O15(OH)2 · H2O and aqueous solutions of cesium fluoride was studied calorimetrically under isothermal conditions, in the temperature range of 27.5 to 55.2°C, at CsF concentrations of 0.6–2.2 mol/l. The rate of the process was described by the first-order kinetic equation with the rate constant k, h−1 = 3.1 × 103CCsF0.92 exp(−(21 ± 8) × 103/RT). Upon replacing Na+ with Cs+, the first-order equilibrium was observed to shift abruptly toward the Cs-substituted sorbent form, where Cs2O content after saturation was 25.5–29.1 wt %. The average heat of ion exchange Q0 over the temperature range 27.5–32.4°C was shown to be ∼3.4 kJ per 1 mol of Na+ ions. We conclude that sorbents based on A-terskite are of practical interest for the processes of extracting 137Cs isotope from water.