Treatment ofpolychlorinated biphenyl in water by ionizing radiation
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pentachlorophenate at a concentration of 1 ppb (3). Whether this confusion was due to
some error in experimental technique with very dilute solutions or whether these results
inconsistent with dilution are correct is not known but this question should be answered
by more careful experiments.
Effect ofpH
The former results were obtained with the water at pH 6.O. The solution became acidic
on irradiation, and this acid was identified as HCl, as described later. The production of
acid by irradiation could interfere with the determination by extraction with n-hexane.
Therefore, the influence of pH of the solution on the extraction efficiency was
investigated. The results obtained are shown in Table 2. This shows no dependence of
extracting efficiency on pH. Next, the influence of pH of the initial solution on the
reduction by irradiation was observed. The results obtained are shown in Table 3, which
shows no significant difference of reduction by irradiation of solutions at various pHs,
and refutes the suggestion that PCB in basic solution could be more easily destroyed than
in acidic solution because the HCl produced would be held by alkali and subsequently
lead to the production of HCl, i.e., destruction of PCB would be made easier.
Effect of atmosphere
To observe the influence of the atmosphere on the reduction of PCB by irradiation,
solutions saturated with nitrogen at 1 atm were irradiated. The results obtained are shown
in Table 4, in which no significant difference of reduction between solutions saturated
with air and solutions devoid of oxygen was found.
Analysis of irradiation products
It was noted that irradiated material became acidic. This acid was identified as HCl by
determination of chloride ions by titration with standard silver nitrate solution using
potassium chromate as indicator, followed by detection of HCl by paper
chromatography using Toyo filter paper No. 50, water or methanol as developing solvent,
bromophenol blue as developing agent, resulting in Rf value of 0.15 or 0.10, respectively.
Organic products soluble in n-hexane were analysed by paper chromatography and
TLC. In paper chromatography, Toyo filter paper No. 50, benzene and methanol (4 : 1)
as developing solvent, silver nitrate-hydrogen peroxide, o-toluidine, and fluoresceinrhodamine B-sodium carbonate as developing agent were used, in which biphenyl,
4:4'-dihydroxydiphenyl and phenylhydroquinone could not be identified. No production
of biphenyl was observed also by TLC, using "Spot Film" (Toyo Chem. Co.) as
the chromatogram sheet and n-hexane as developing solvent in the S-chamber and
formaldehyde in sulfuric acid as the developing agent.
Toxicity of irradiated PCB
Daily 0.5 ml of PCB of 100 ppb (i.e. 0.05 ßg a day) was administered intraperitoneally
for 50 days to each of a group of 20 mice, of ICR strain, 4 weeks old, 19 gm body weight
on average, but no significant differences were noted in the general appearance, appetite,
growth rate and urine examinations for protein, sugar, urobilinogen and porphyrin as
compared with a control group of 20 mice given 0.5 ml of distilled water daily. Thus, to
investigate whether irradiated PCB produced more toxic substances, an irradiated solution
of PCB of a dose of 10 Mrad was tested for toxicity to shrimps. The results obtained are
shown in Table 5, in which the irradiated solution is seen to be remarkably de toxicated. It
was noted that the irradiated solutions lost initial chlorine-like odour and became
odourless, but this does not mean that initial solutions had free chlorine, because no
chlorine could be detected in them by the o-tolidine method.
609
pentachlorophenate at a concentration of 1 ppb (3). Whether this confusion was due to
some error in experimental technique with very dilute solutions or whether these results
inconsistent with dilution are correct is not known but this question should be answered
by more careful experiments.
Effect ofpH
The former results were obtained with the water at pH 6.O. The solution became acidic
on irradiation, and this acid was identified as HCl, as described later. The production of
acid by irradiation could interfere with the determination by extraction with n-hexane.
Therefore, the influence of pH of the solution on the extraction efficiency was
investigated. The results obtained are shown in Table 2. This shows no dependence of
extracting efficiency on pH. Next, the influence of pH of the initial solution on the
reduction by irradiation was observed. The results obtained are shown in Table 3, which
shows no significant difference of reduction by irradiation of solutions at various pHs,
and refutes the suggestion that PCB in basic solution could be more easily destroyed than
in acidic solution because the HCl produced would be held by alkali and subsequently
lead to the production of HCl, i.e., destruction of PCB would be made easier.
Effect of atmosphere
To observe the influence of the atmosphere on the reduction of PCB by irradiation,
solutions saturated with nitrogen at 1 atm were irradiated. The results obtained are shown
in Table 4, in which no significant difference of reduction between solutions saturated
with air and solutions devoid of oxygen was found.
Analysis of irradiation products
It was noted that irradiated material became acidic. This acid was identified as HCl by
determination of chloride ions by titration with standard silver nitrate solution using
potassium chromate as indicator, followed by detection of HCl by paper
chromatography using Toyo filter paper No. 50, water or methanol as developing solvent,
bromophenol blue as developing agent, resulting in Rf value of 0.15 or 0.10, respectively.
Organic products soluble in n-hexane were analysed by paper chromatography and
TLC. In paper chromatography, Toyo filter paper No. 50, benzene and methanol (4 : 1)
as developing solvent, silver nitrate-hydrogen peroxide, o-toluidine, and fluoresceinrhodamine B-sodium carbonate as developing agent were used, in which biphenyl,
4:4'-dihydroxydiphenyl and phenylhydroquinone could not be identified. No production
of biphenyl was observed also by TLC, using "Spot Film" (Toyo Chem. Co.) as
the chromatogram sheet and n-hexane as developing solvent in the S-chamber and
formaldehyde in sulfuric acid as the developing agent.
Toxicity of irradiated PCB
Daily 0.5 ml of PCB of 100 ppb (i.e. 0.05 ßg a day) was administered intraperitoneally
for 50 days to each of a group of 20 mice, of ICR strain, 4 weeks old, 19 gm body weight
on average, but no significant differences were noted in the general appearance, appetite,
growth rate and urine examinations for protein, sugar, urobilinogen and porphyrin as
compared with a control group of 20 mice given 0.5 ml of distilled water daily. Thus, to
investigate whether irradiated PCB produced more toxic substances, an irradiated solution
of PCB of a dose of 10 Mrad was tested for toxicity to shrimps. The results obtained are
shown in Table 5, in which the irradiated solution is seen to be remarkably de toxicated. It
was noted that the irradiated solutions lost initial chlorine-like odour and became
odourless, but this does not mean that initial solutions had free chlorine, because no
chlorine could be detected in them by the o-tolidine method.