The effect of temperature on the enthalpy of exchange of divalent - monovalent ions on a polymethacrylic cation exchange resin

Abstract

The influence of temperature on the selectivity and enthalpy of the exchange of Ni2+ - Na+
and Mg2+
- Na+
ions on the polymethacrylic cation exchange KB-4P2 in the range from 298 to 413 K was studied. It is
shown that when the temperature is raised simultaneously with a significant increase in the selectivity to the
doubly charged ion, the differential enthalpy increases linearly. The most strongly selectivity increases in the
region of "superheated" solutions with a temperature above 373 K. The differential enthalpy of the exchange
of Ni2+ - Na+
ions increases more significantly than in the case of the exchange of Ca2+ - Na+
ions. Thus, in
the exchange of calcium and sodium ions in the range from 273 K to 400 K, the differential enthalpy
increased from 4-6 kJ/eqv to 22-28 kJ/eqv, and in the exchange of Ni2+ - Na+
ions in the same temperature
range ranges from 4-6 kJ/eqv to 28-34 kJ/eqv. In the case of the exchange of Mg2+ - Na+
ions, the values of
the differential enthalpy were lower. The effect of the ionic composition of ion exchanger on the differential
enthalpy is much less than the effect of temperature. The discovered properties of polymethacrylic cation
exchanger can be of great importance for the development of ion-exchange separation processes, in
particular, they show the possibility of using "superheated" solutions with a temperature above 373 K in
dual-temperature reagentless processes.