The solubility of Li2CO3 in Na-K-Li-Cl brines was measured by isothermal dissolution method within the temperature range of 20 to 90 degrees C. It was found the solubility of Li2CO3 in all systems investigated decreased with increasing temperature. In NaCl and KCl solutions, the solubility of Li2CO3 initially increased to a maximum value and then decreased gradually with increasing solution concentration. However, the solubility of Li2CO3 in LiCl solutions decreased with increasing LiCl concentration due to the common ion effect of added Li+. New Pitzer activity coefficient model parameters for the Li+-CO32- ion pair were obtained by using experimental solubility data of Li2CO3 in pure water, and a new chemical model was built with the aid of Aspen Plus platform. The new model was shown to successfully predict the solubility of Li2CO3 in NaCl, KCl, LiCl and mixed NaCl-KCl solutions. Moreover, the new model could aid in analyzing the separation of lithium and magnesium in brines. (c) 2013 Elsevier Ltd. All rights reserved.