Fig. 7 shows the effect of temperature on the distribution coefficient (Kd) for the ion exchange of metal ions onto resins. The distribution coefficient is defined as the ratio of metal ion concentration on the resin to that in the aqueous solution. The Kd values for Cu2+, Zn2+, Ni2+ Pb2+, and Cd2+ metal ions was very high and it increased with temperature and the reaction products are favored at high temperatures, as seen in Fig. 7. This is due to the endothermic ion exchange reactions of divalent cations. The equilibrium constants for such reaction increase with temperature and the reaction products are favored at high temperatures [18,19]. The working capacity of an ion exchanger depends on metal concentrations and temperatures. The surface energy of the Dowex 50W increases with temperature. Similar results obtained with the sorption studies completed with the Amberlite IR-120 [36].