Self-Sustaining Processes of Water Softening and Desalination: Simple Two-Component Systems

Using the method of numerical experiment, the possibility of arranging steady-state self-sustaining processes for softening and desalinating salty water has been studied with use of two-component model solutions containing calcium and sodium ions as an example. In such processes, water softened by ion exchange is subjected to desalination, and the brine formed in this process—without any additional chemicals—is used to regenerate the cation-exchange resin in repeated sorption–desorption cycles. Interest in self-sustaining processes is associated with new technological capabilities for creating a new generation of water-treatment systems, for example, mobile independent units or systems with high degrees of freshwater extraction and brine concentration. The basic foundations of self-sustaining processes are discussed. The ion-exchange dynamics is calculated for many dozens of successive softening–desalination cycles under conditions of varying parameters, such as the ratio of components in the initial solution, the degree of mineralization of such solutions, the degree of concentration of brines, and the composition of desalinated water. The conditions under which the steady-state regimes are formed or not achieved are found.