  This paper presents a thermodynamically consistent model for multicomponent
electrolyte solutions. The first part of this paper derives the general
governing equations for nonequilibrium systems within the theory of
nonequilibrium thermodynamics. Here, we consider electrolyte solutions as
general mixtures of charged constituents. Furthermore, in this part of the
paper we combine the general theory of nonequilibrium thermodynamics with the
well-known splittings of the entropy and the energy into a pure substance part
and a part due to mixing. Thereby, we successfully establish evolution
equations for both parts. Furthermore, we derive for both parts explicit
expressions of the respective entropy production rates. Hence, we provide an
approach that allows to study the entropy of mixing independently of the pure
substance entropy and vice versa. This is of great value, in particular for a
better understanding of the complex phenomena due to mixing in multicomponent
systems. In the second part of this paper, we close the system of general
balance equations by applying constitutive laws. This is the crucial step in
the modeling procedure. ...
