Modus Operandi of Regenesys

The ionically bonded sodium bromide receives two electrons, and loses two +ve sodium cations to form sodium tri-bromide (see Porterfield, 1993). An alternative homogeneous reaction route to tri-bromide is to bubble bromine (Br2) through aqueous sodium bromide. Accordingly, the electrochemically formed tri-bromide has an associated atmosphere of bromine from homogeneous dissociation. Such bromine is corrosive, but is contained by the fluorinated plastic tanks and by one side of the (Na ) Nafion perm-selective membrane. Nafion is itself a compound with many fluorine atoms. Bromine is very much lower than fluorine in chemical reactivity, so that the bromine containment strategy is complete, and the selection of the bromide electrolyte seen to be a well-considered choice. 

The —ve cell half reaction, polysulphide oxidation or electron removal, with i = 2 as in Eqn (2.1), is illustrated simply as 

But clearly, although the poly-4-sulphide may predominate, the other polymers will form an equilibrium mixture (Giggenbach, 1974 ) in the storage tank. 

The illustrative aqueous overall cell reaction showing polymer rearrangement is 

The reaction proceeds, with charge or power input, from left to right. As there is no valency change between Na2S4 and Na2S2, the polymerised sulphur is referred to as zero-valent . 

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