Regularity of Chemical Composition of Brine Produced by Ion Exchange Membrane Method

Abstract

In concentrating sea water for brine production by ion exchange membrane method, the permsele-tivity of each of the cations [Ti; {i cation in brine (N) /total cations in brine (N)} /{i cation in seawater (N) /total cations in sea water (N)}] was found to be expressed by linear equation of “thequivalent purity” of brine [P_Na; Na (N) /total cations (N)] independent of membranes, units andonditions of electrodialysis. Thus, the concentration ratios of cations in brine [Pi; i cation (N) /totalations (N)] were given by the following equations:
P_Mg=-0.8337 P_Na+0.8057
P_Ca=-0.1795 P_Na+0.1797
PK=0.01321 P_Na+0.01462
This regularity provided full suggestion as to the mechanism of permselectivity. For example, suggested the possibility of applying Stokes' law to the movement of ions within the membrane.In addition, three “purities” of brine generally used were termed here “the equivalent purity” P_Na; mentioned above,“the weight purity” [P_NaCl; NaCl (g/l) /total salts (g/l)] and “the convenienturity” [P°; {Cl-(Mg+Ca)} (N) /Cl (N)] of brine, respectively. These were correlated by theollowing equations:
P_Na=0.989P°-0.015 P_NaCl=0.871P°+0.095