Why Lead Dioxide Anode is Used in Effluent Treatment?

Why Lead Dioxide Anode is Used in Effluent Treatment?

With increasing legislative regulation, effluents should be fully treated before discharge into rivers, lakes, or the sea, there have been extensive studies of the electrolytic mineralisation of organic compounds with a particular focus on compounds that are toxic or resistant to biological treatments. It is widely believed that complete mineralisation occurs by mechanisms dominated by oxygen transfer and adsorbed or free OH radicals rather than direct electron transfer from the organics to the anode.

This requires anodes that are stable at very positive potentials; lead dioxide and B-doped diamond have proved the most suitable materials. In general, B-doped diamond gives the highest rate of mineralisation but such anodes are expensive and doubts remain about their long term stability. This presents opportunities for lead dioxide. Particularly in water and effluent treatment, the absence of Pb(II) contamination of the medium must clearly be demonstrated.

There have been many studies of the mechanisms for the degradation of organics at lead dioxide anodes using electrochemical, spectroscopic and intermediate product identification. The most compelling evidence for a role for OH radicals comes from the use of spin trapping agents but many of the steps in the complex reaction sequences remain speculation. There is also good evidence that doping the electrodeposited PbO2 layer with elements such as Bi(III), Fe(III) and F accelerates oxidation, leads to more complete mineralisation and/or enhances the stability of the coating.