Purification Procedures Elimination of Pollutants

The resnlting sludge can be nsed to mannfactnre bnilding materials, road cover materials, and the like. Adsorptive pnrihcation is able to liberate the water from contaminants that cause its bad smell and taste. It is highly effective for the removal of xenobiota and of traces of petrolenm prodncts. In some cases it can even decolorize the water. 

Attempts to bnild electrochemical systems for oxidative purification of effluents have met a nnmber of problems  

Many substances are oxidized only at rather high anodic potentials, which narrows the available selection of corrosion-resistant anode materials. An alternative to platinnm metals are certain metals with an oxide coating (Pb02, Mn02, Sn02) which 

The anodic oxidation of organic substances is a complex multistep process. The question as to the depth of oxidation required (and sufficient) lias to be answered in each case. Where intermediate oxidation products pose no ecological risk, one can stop at incomplete oxidation. However, in the anodic oxidation of many aromatic substances, the corresponding quinones are formed in the first step, and these are more harmful than the original substances. Upon more profound oxidation, the benzene rings are broken and aliphatic substances are formed that are almost as harmless as carbon dioxide. 

In anodic processes conducted at high potentials, radical-type intermediates often are formed that lead to a polymerization (resin formation) of the organic substances and to passivation of the anodes. 

---