Salt Splitting

Definition - What does Salt Splitting mean?

Salt splitting is the process of decomposing the salts of carboxylic acids into their corresponding acid and base compounds.

An electrochemical reaction occurs when the salt is passed through an anion- or cation-exchange membrane. The membranes serve to separate the metallic and acidic ions. For example, in the salt splitting of sodium chloride, the separation is between the sodium and chloride ions.

Corrosionpedia explains Salt Splitting

Salt splitting is achieved by the use of bipolar membranes. These are comprised of two ion exchange membranes, an anionic and a cationic, which are capable of splitting water into hydroxyl ions and protons in an electrochemical cell. A two-compartment electrolysis cell uses a salt solution as the anolyte and a base solution as the catholyte in a cation-exchange membrane. In the anion-exchange membrane the acid solution is used as an anolyte while the salt is used as catholyte.

The salt is passed through the compartment under the influence of a potential field. In the case of a sodium sulfate salt, the sodium ions pass through the cation-permeable membrane into the catholyte and the sulfate is transported through the anion-permeable membrane into the anolyte. The cathode reaction generates the hydroxide that results in the accumulation of caustic soda in the catholyte while the anode reaction produces protons, resulting in sulfuric acid in the anolyte.

The factors that affect salt splitting include:

  • Type of salt and base solutions
  • Current density
  • Initial concentrations
  • Flow rate
  • Type of bipolar membrane used

The process is applicable to both organic and inorganic salts. Salt splitting is widely used in electrochemical industry processes and provides an environmentally friendly solution when used in:

  • Production of caustic soda, since there is no coproduction of chlorine
  • Decomposition of heavily laden salt solutions for disposal
  • Recovering water, nitric acid and hydrofluoric acid from the rinse water in the pickling baths of steel

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