Man Made Phenols and Drinking Water Quality

Phenols can impart unpleasant tastes and odors to water at concentrations lower than those considered to be of much toxicological significance, and phenols are not effectively removed from water by most conventional water treatment methods. Many simple phenols can be destroyed by strong oxidizing agents such as ozone. Phenolics can react with chlorine (such as that used to sanitize drinking water), thus creating more persistent chlorinated phenols. Trace concentrations of phenols generally can be removed from water by sorption to

Table 1 pKa values (i.e., ability of an ionizable group of an organic compound in aqueous media to donate a proton), water solubility, and toxicity (LD50 values; acute, oral, rats) for selected phenols differing in the type and position of several

substituents

Compound

PKa

Solubility (gl"1}

LD50 (mgkg " d "}

Phenol

9.82-10.0

86

317

o-Methoxyphenol

10.0

190

520

p-Methoxyphenol

10.2

40-41

1600

o-Methylphenol

10.3

26

121-1470

p-Methylphenol

10.3

22-25

207-242

o-Chlorophenol

8.6

28.5

40-670

p-Chlorophenol

9.4

27

660; 670; 20-100

o-Nitrophenol

7.2

2.1

334

m-Nitrophenol

8.4

13

328

p-Nitrophenol

7.08-7.2

12.4

250

2,4-Dinitrophenol

3.94-4.1

1.4

30

2,4,6-Trinitrophenol

0.4

12.8-14.0

200-290

Data from various sources.

Data from various sources.

granulated activated carbon. The adsorbed phenols can be removed as phenates by rinsing the activated carbon with a solution of NaOH. Many natural (plant-derived) complex phenols undergo at least partial oxidation with exposure to UV wavelengths in sunlight. Some chlorinated phenolics also are photosensitive.

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