Operating Principles and Plant Layout

In particular, for a NaCl solution, Na+ ions permeate through the cation exchange membrane in the direction of the cathode, and Cr ions permeate through the anion exchange membrane in the direction of the anode. 

Such a membrane stack terminates with electrodes at each end, which convert the ionic flux into an electric current by red-ox (reduction-oxidation) reactions occurring between the electrodes and a hexacyanoferrate aqueous solution in a bulk of NaCl (typically, K4Fe(CN)6 0.05mol/l, KjFelCNlg 0.05mol/l, NaCl 0.25mol/l [22]). As a result, an electron can be transferred from the anode to the cathode via an external electric circuit. This electrical current and the potential difference over the electrodes can be used to generate electrical power, when an external load is connected to the circuit. 

The key advantage of RED-based systems for power generation is its direct salinity gradient to electricity conversion, which makes the plant layout simpler in comparison with 

PRO-based systems, which entail intermediate conversions to pressure energy and then to mechanical work. 

Since Iz al = Izcil = 1 nd Ix al = l fcil = for N Cl solutions, Eq. 9 an reduce to the Nernst equation for an aqueous monovalent electrolyte  

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