Chloride and chlorinated compounds

The anodic dehalogenation of 1,2 dichloroethane has been demonstrated [80] at a smooth platinum electrode. The major products of this are CO2 (60% current efficiency), HCIO4 (20%) and chlorine. The smooth platinum anode was found to be superior to electrode made of RUO2, Ti02, PtO c and Pb02 coated materials. 

1 Direct electrochemical reduction. The direct electrochemical reduction of organic species can be used to detoxify the wide range of chlorinated compounds on the EC list of priority compounds [81]  

Transformer washings can contain PCBs at concentrations up to 1000 ppm in mineral oils. These oils are inappropriate for direct electrolysis and thus a process for treatment has been developed in which the PCBs are solvent extracted, e.g. in propylene carbonate containing tetra-ethylammonium chloride, which is suitable for the electroreduction [83]. 

There are several waste water treatment applications which involve electrochemically generated oxidants. Suitable oxidants include ozone, hydrogen peroxide and notably hypochlorite, which is widely used. 

Hypochlorite can be produced by the reaction of chlorine gas with sodium hydroxide solution. On-site generation of hypochlorite avoids storage and transport difficulties associated with chlorine gas, and is convenient for many applications, including sewage treatment, sterilisation of water, disinfection, biological growth prevention and enhanced oxidation of, for example, cyanide wastes. The electrochemical generation of hypochlorite has been the subject of several reviews (see [84]). 

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