In the present work the rates of absorption of carbon dioxide into aqueous hydroxides (0.01-2.0 kmol.m (3)) and blends of hydroxides and carbonates with mixed counter ions (1-3 kmol.m (3)) containing Li+, Na+ and K+ as cations were studied in a String of Discs Contactor (SDC). The temperature range was 25-64 degrees C and the conditions were such that the reaction of CO2 could be assumed pseudo-first-order. The dependence of the reaction rate constant on temperature and concentration/ionic strength and the effect of counter ions were verified for the reaction of CO2 with hydroxyl ions in these aqueous electrolyte solutions. The infinite dilution second order rate constant k(OH-)(infinity) was derived as an Arrhenius temperature function and the ionic strength dependency of the second order rate constant, k(OH-), was validated by the widely used Pohorecki and Moniuk model (Pullorecki and Moniuk, 1988) with refitted parameters. The contribution of ions to the ionic strength and the model itself, was extended to the given concentration and temperature ranges. The model with refitted parameters represents the experimental data with less than 12% AARD. (C) 2014 Elsevier Ltd. All rights reserved.