The sorption and transport processes in electromembrane systems containing aqueous solutions of sodium chloride and mercury(II) chloride and MC-40, MA-40, and MA-41 ion-exchange membranes have been studied. The concentrations of complex species present in the contacting solutions have been calculated. It has been found that mercury is absorbed as a constituent of neutral and negatively charged complex particles by the anion-exchange membranes only. The specific interaction of mercury with the functional groups of the MA-40 anion-exchange membrane has been confirmed by IR spectroscopy, conductometry, and the measurements of the hydration properties of the membranes.