Electrochemical treatment of gases

Many processes involve the emission of acid gases, such as SO2, 

H2S and HCl, which clearly is of environmental concern throughout the world. These potential gaseous pollutants can be converted electro-chemically, in the liquid state, to species which are more environmentally acceptable and which may have some commercial value. Sulphur dioxide can be oxidised to sulphuric acid or reduced to sulphur, chlorine can be reduced to chloride ions, hydrogen sulphide can be oxidised to sulphur and nitrous oxides can be oxidised to nitric acid. 

All these electrochemical conversions are feasible in the aqueous phase. Consequently there have been several studies and proposals for electrochemical treatment of these gases. Alternative treatment processes have also been proposed which operate at high temperatures and which use molten salt electrolytes immobilised in membranes. 

In sulphur dioxide oxidation cells the prevention of deactivation of the cathode by sulphur formed by cathodic reduction of sulphite can be a problem. A solution to this is to use a cathode material less sensitive to sulphur (or H2S) formation such as tungsten carbide [49]. An alternative cathode material to be used in this context is Ebonex [50]. 

2 Flue gas desulphurisation (FGD) processes. A near commercial process (ISPRA) [51] is based on reaction of sulphur dioxide with electrochemically generated bromine  

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