PCP can be photolytically reduced to isomeric tri- and

tetrachlorophenols, and, in dilute aqueous solutions exposed

to sunlight, PCP or its salts undergo the replacement of

ring chlorines by hydroxyl groups to form corresponding

chlorohydroquinones, which are subsequently oxidized to

chlorobenzoquinones and then dechlorinated and/or ring

cleaved. Pentachlorophenol is a moderately acidic compound

and thus will exist primarily as an anion in natural waters.

This is environmentally significant because the anion

absorbs well beyond 310 nm (sunlight spectrum) leading to

more effective photolytic reactions. Wong and Crosby (1978)

reported that the rate of photolysis of pentachlorophenolate

anion was much faster than that of the undissociated

compound.

 For the phenolic compounds in groundwater no photolysis

occurs naturally. However, this process can be useful in a

remedial action when spraying and recirculating is involved,

and needs to be considered as an option when performing a

feasibility study in a groundwater reclamation project.


3.3.2 Oxidation


 Phenol has been oxidized by passing molecular oxygen

into an aqueous solution at 250C and pH 9.5-13. This

suggests a possibility of nonphotolytic oxidation in highly

aerated waters. Little information is available pertaining

to the oxidation of chlorinated phenols but usually highly