The review considers thermodynamics and kinetics of isotope exchange in the
H2O-H2S system. The temperature dependences of separation factor a are con
sidered for all binary H-T, H-D, and DT mixtures. The effect of equilibrium
constants of homo-molecular exchange reactions involving water and hydroge
n sulfide on concentration dependence of a is demonstrated. Distribution of
tritium between the liquid and the gas phases has been studied as a functi
on of the HID ratio in each phase. The differential equations describing th
e steady-state interdiffusion of dissolved hydrogen sulfide and water accom
panied by chemical reaction of isotope exchange have been solved. It has be
en shown that solution to the mass-transfer problem allows for calculation
of the HTU (height of transfer unit) value in a packed separation column. T
he HTU dependences on the flowrate in a packed column and on the compositio
n of liquid-phase in the H2O-H2S and D2O-D2S systems are presented. A mathe
matical model of isotope separation by the dual-temperature method is discu
ssed. The model is used to analyze the basic features of the method and the
effects associated with mutual solubility of phases. Optimization of the G
irdler-Spevack process by varying the operation parameters in the column ar
e discussed. The results of testing a modified dual-temperature set-up demo
nstrate a high efficiency of separation of hydrogen isotopes by the propose
d technique.