F-contaminated bromophenols and wastes of chemical laboratories

Chemosphere, Vol. 29, No. 3, pp. 457-464, 1994

Pergamon

0(O5-6535(94)00179-0

Copyright O 1994 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0045-6535/94 $7.00+0.00

UV-PHOTOLYSIS OF PXDD/F-CONTAMINATED BROMOPHENOLS AND WASTES OF CHEMICAL LABORATORIES

J. Ritterbuseh, IL Vogt*, W. Lorenz, M. Bahadir 1) and H. Hopf2)

DInstitute of Ecological Chemistry and Waste Analysis, 2)Institute of Organic Chemistry, Technical University of Braunschweig, Hagenring 30, D-38106 Braunschweig, Germany. (Received in Germany 16 February 1994; accepted 2 May 1994)

Abstract PXDD/F-eontaminated solutions and chemicals from different sources have been irradiated with UV-light. The photochemical behaviour of PXDD/F standard solutions and laboratory wastes has been compared to that of dissolved bromophenols. In the first case the UV-photolysis caused a photolytic degradation >99% of PXDD/F to less toxic compounds. In contrast, the level of PBDD/F in irradiated solutions of bromophenols was up to three orders of magnitude higher after irradiation than in the starting material.

Keywords: Photolysis, PXDD/F, bromophenols, laboratory waste

Introduction

In earlier studies toxic compounds like polyhalogenated dibenzo-p-dioxins and .furans (PXDD/F; X = Br, C1) were detected in waste matrices of different origins. Recent research identified PXDD/F in wastes of a dioxin laboratory [1] and in products and wastes of organic teaching laboratories [2]. A typical experiment carried out in most laboratory courses of organic chemistry consists in the preparation of bromophenols from phenol and bromine by low temperature aromatic substitution. Its main products are 4-bromophenol, 2,4-dibromophenol and 2,4,6tribromophenol, but small amounts of polybrominated dibenzo-p-dioxins (PBDD) and -furans (PBDF) are formed as well. During distillation of the different bromophenols the PBDD/F accumulate in the distillation residues. Dioxin-contaminated laboratory wastes are problematic, they must not be mixed with other wastes during work-up but disposed of as hazardous waste. In this report the decontamination of h~7~_rdous substances in laboratory wastes I~yUV-photolysis has been examined. An advantage of this method is to reduce the risk of exposure. Since the early 1970s it has been known, that PCDD/F dissolved in organic H-donor solvents may be dechlorinated reductively by a radical mechanism on UV-photolysis [3]. In recent reports this photochemical degradation has also been applied for mixed brominated-chlorinated dibenzo-p-dioxins and -furans [4], which are decomposed to less toxic products by ultraviolet irradiation [1,4,5].

457

458 The bromophenols and laboratory wastes are either fiquid materials or easily soluble, thus their decontamination by photolysis seemed particularly attractive. In contrast to diluted waste solutions the bromophenols containing PXDD/F are accompanied by an excess of precursors. The PXDD/F are generated from these precursors by side reactions. It is conceivable that the presence of starting materials causes a different behaviour under UV-photolytic conditions.

Experimental A 100 ml photochemical reactor containing a middle-pressure mercury lamp (output 150 W) equipped with quartz glass cooling system was used for UV-irradiation [1,6]. To evaluate the effiency of the photolysis system used under optimal conditions, we carried out preliminary experiments with PCDD/F and PBDD/F mixed standards. Since the formation of other environmentally relevant chlorinated products during the photolysis is possible, OCDD and OCDF single standards were also irradiated. The solutions were investigated for formation of chlorinated biphenyls, chlorobenzenes and chlorophenols. The total irradiation time in all investigated solutions was 60 minutes. Three dioxin-contaminated waste solutions were photolyzed in n-hexane as solvent. The four solutions ofbromophenols were prepared as followed: Solution 1 (and 2):

75 mg (230 mg) distillation residue of4-bromophenol (2,4-dibromophenol) were dissolved in a small amount of acetone-methanol mixture (1:1). The yellow-brownish solution was diluted with n-hexane to a total volume of 100 ml.

Solution 3 (and 4):

5 g crude product of4-bromophenol (2,4-dibromophenol) was dissolved in 100 ml n-hexane

Deposition of dark polymeric products was observed at the walls of the photochemical reactor during irradiation of dissolved bromophenols. The colour intensity of solution 1 decreased, that of solution 2 increased during irradiation. Solution 3 showed a rich red colouring, solution 4 was pink coloured.

Clean upfor GC/MS.analysis a) Dioxin contaminated waste solutions and solutions of dioxin standards After UV-photolysis the clean up was performed using a basic aluminium oxide column as described by Hagenmaier et al. [7]. b)

Solutions ofbromophenols

For analysis of neutral compounds like PBDD/F, the acidic phenofic compounds were removed from the samples by alkaline extraction after irradiation. 30 ml of methanol was added to the solutions, followed by 10 ml of 5 N NaOH and 100 ml of distilled water. Extraction was carded out by vigorous shaking with 100 ml of n-hexane in a separating funnel for two minutes. The aqueous phase was drained and extracted twice again with 50 ml of n-hexane. The n-hexane phases were combined and washed twice with 100 ml of distilled water, followed by a wash with 100 ml of 0.1 N N a O H to remove remairun"g phenols. Finally it was washed twice with 100 ml of distilled water, the pH of the last step should be neutral. The n-hexane solution was dried over sodium sulfate. After concentration 13Clabelled internal 2,3,7,8-T4BDD/F standard was added. The clean up of the extract was performed using the usual basic aluminium oxide colunm [7]. Before GC/MS analysis a 13C-1,2,3,4-T4CDD standard was added.

459

GC/MS analysis The samples received fi'om the clean up were analyzed by HRGC/MS [GC system: HP 5890 H (Hewlett Packard) equipped with KAS 2 (Fa. G-erstel) and MSD 5970 B; capillary columns: DB-5 (J & W Scientific, 0.253 m m x 30 m, film thickness 0.25 ~m, PXDD/F group analysis) and CP-Sil 88 (Chrompack GmbH, 0.25 nun x 50 m, film thickness 0.25 I.tm, specific 2,3,7,8-PCDD/F isomer analysis)]. Quantification was carded out with the SIM-mode and related to the concentration of external PXDD/F standards. Other possible photochemical degradation products like polychlorinated biphenyls, chlorobenzenes and chiorophenols were investigated by H R ~ S

in the SIM-mode.

Results and discussion

The results of the photolysis of PCDD/F standards are shown in Tables 1 - 3. The test conditions chosen allowed effective photolytic degradation of PCDD/F. Five minutes a/~er starting the UV-photolysis 92.7% of the employed PCDD/F had been decomposed, the degradation was completed to more than 99% after 60 minutes of irradiation. The 2,3,7,8-isomers are more rapidly photolyzed than the other PCDD/F isomers of the same degree of haiogenation, as shown in Table 1.

Tab. 1:

Results of the UV-photolysis of PCDD/F in n-hexane PCDD/F-concentration at PCDD/F

start [ng/l]

2.5 rain [ng/l]

5 rain [ng/l]

10 min [ngl]

15 rain [ngl]

30 rain [ngl]

45 rain [ng/l]

60 rain [ng/l]

Z T4CDF Z 2,3,7,8-T4CDF

12 000 2800

19 000 2000

3 600 170

610 20

330 < 20

57 < 5

< 20 < 5

< 2.5 < 2.5

Z T4CDD Z 2,3,7,8-T4CDD

12 000 3000

6 300 400

1 400 22

1 300 < 20

240 < 20

23 <5

37 <5

< 2.5 < 2.5

Z P5CDF Z 2,3,7,8-PSCDF

26 000 53001

26 000 3100

1 600 200

250 33

120 < 20

32 < 15

< 20 <5

< 2.5 < 2.5

Z P5CDD Z 2,3,7,8-P5CDD

13 000[ 2 700

14 000 1 700

3 600 170

290 < 50

280 < 20

32 < 15

< 20 <5

< 2.5 < 2.5

Z H6CDF 5".2,3,7,8-H6CDF

51 000 9100

22 000 4800

1 000 390

210 70

94 47

70 < 15

< 20 <5

< 2.5 < 2.5

7. H6CDD 7. 2,3,7,8-H6CDD

40 000 ~ 11 000 8 300 3 700

2 800 420

440 85

130 < 10

40 <5

<5 <5

< 2.5 < 2.5

Z H7CDF 2,3,7,8-H7CDF

23 000. 11 000

8 900 3 314

500 350

110 81

42 < 50

< 15 < 15

<5 <5

< 2.5 < 2.5

~. H7CDD Z 2,3,7,8-H7CDD

11 000 1 800

8 700 680

710 80

130 < 50

36 < 20

< 15 < 20

<5 <5

<2.5 < 2.5

OCDF

12 000

1 600

120i

77

< 20

<5

<5

< 2.5

OCDD PCDD/F degradation

12 000

3 900

350

92

21

<5

<5

< 2.5

212 000

121 000

15 500

3 480

1 290

254

37

< 2.5

42.7 %

92.7 %

98.4 %

99.4 %

99.9 %

99.98% > 99.99%

460

Tables 2 and 3 show that no 2,3,7,8-isomers were enriched during photolysis of OCDD and OCDF. Only 2,3,7,8H7CDF and 2,3,7,8-H7CDD could be identified and quantified. The ratio of 2,3,7,8-substituted H7CDD/F to the not 2,3,7,8-substituted H7CDD/F was 1:9 for H7CDD and 1:3.5 for H7CDF. Durin8 the photolysis of OCDD- and OCDF-solutions no accumulation of other chlorinated pollutants was observed. The limit of determination for PCB, chlorophenols and chlorobenzenes was 40 ng/L. The concentrations of OCDD/F and T4-H7CDD/F are shown in Figure 1. The observed time dependence is an indication of the stepwise reductive photolytic dechlorination of dissolved PCDD/F. Other groups have published comparable results about PCDD/F photolysis in organic solvents [8-10].

Tab.2: Photolysis of OCDD in n-hexane (starting concentration: 87.5 pg/l) cone~tr~ion at PCDD/F

2.5 min

5 rain

7.5 min

10 rain

15 rain

20 min

30 win

45 rain

[ng/l]

[ng/l]

[ng/l]

[nWl]

[ng/l]

[ng/l]

[nWi]

[n~/1]

Z T4CDD

2 990

974

424

343

116

< 100

< 50

< 50

Y.P5CDD

6 080

985

383

255

< 100

< 100

< 50

< 50

Y.H6CDD

2 790

438

230

157

< 100

< 100

< 50

< 50

Z H7CDD

35 900

1 330

472

276

< 100

< 100

< 100

< 50

3 370

134

< 100

< 100

< 50

< 50

< 50

< 50

1,2,3,4,7,8,9-H7CDD OCDD

33 100

1 123

325

289

247

< 200

< 100

< 100

Z PCDD

80 860

4 850

1 830

1 220

363

< 100

< 100

< 100

OCDD-degradation

62.2 %

98.7 %

99.6 %

99.7 %

99.7 %

> 99.8% > 99.9°4

> 99.9%

100000 --~-80000 60000

OCDF

~

A

\\\\

° oooo

o

T4-H7CDF

4

7C

D

40000 C

8 20000

0

•

0

2,5

5

7,5

T

10

time [rain]

Fig. 1: Timedependence of the OCDD/F and T4-H7CDD/F-concentrations during UV-photolysis in n-hexane

461

Tab. 3: Photolysis of OCDF in n-hexane (starting concentration: 87.5 I~g/l) concentration at PCDD/F

2.5 rain [ng/l]

5 min [ng/l]

E T4CDF

4 780

3 070

E P5CDF

10 700

2 340

E H6CDF

4 980

440

E H7CDF

14 500

445

3 240

OCDF 7. PCDF

g 2,3,7,8-H7CDF

OCDF-degradation

7.5 rain [ng/l]

10 rain [ng/l]

20 rain [rig/l]

30 min [ng/l]

45 rain [rig/l]

200

< 100

< 100

< 50

< 50

1 000

180

< 100

< 100

< 50

< 50

< 200

< 100

< 100

< 50

< 50

< 50

< 200

< 200

< 100

< 100

< 50

< 50

< 200

< 100

< 100

< 50

< 50

< 50

< 50

6 390

< 200

< 200

< 100

< 100

< 50

< 50

< 50

41 350

4 850

2 210

380

< 100

< 100

< 100

< 50

92.7 %

98.7 %

1 210

15 rain [ng/l]

> 99.8% > 99.9% > 99.9°,6 > 99.9OA > 99.9OA > 99.9%

Results of the photolytic decomposition of PBDD/F mixed standards are listed in Table 4, the time dependence of the concentrations ofM1BDD, M1BDF, P5BDD and P5BDF is shown in Figure 2, The degradation of higher brominated PBDD/F is faster and an accumulation of lower brominated PBDD/F is observed. The concentration of lower brominated isomers decreases when most of the higher brominated PBDD/F have been decomposed hinting that stepwis¢ reductive debromination is the principal photolytic route for all PBDD/F.The difference in chemical behaviour of PBDD/F and PCDD/F, for which cleavage of the C-O-C-bonds is the dominant reaction [8] for M1-T4CDD/F, is due to the different bond energies of the C-Br and C-Cl-bonds [11]. C-Br bond cleavage is preferred over C-O-C-bond breaking, whereas C-Cl-bond breaking competes with C-O-Ccleavage.

Tab. 4: Results of the UV-photolysis of PBDD/F in n-hexane PBDD/F-concontrationat PBDD/F

start

10 s

30 s

45 s

90 s

120 s

300 s

[ne,/l]

[ns/I]

[n~]

[ns/l]

[n~]

[ns/l]

[n~]

Y.M1BDF

0

< 50

< 100

490

2 000

2 600

1 600

7. M1BDD

2 900

3 200

3 200

4 400

4 800

6 300

3 000

~. D2BDF

2 800

3 400

4 400

5 600

5 200

5 900

3 000

7. D2BDD

3 200

2 900

4 500

6 000

7 400

8 300

2 700

T. T3BDF

2 400

2 800

3 100

2 600

2 200

2 000

410

7. T3BDD T4BDF

2 400 1 300

2 700 1 300

3 100 l 500

3 500 960

3 800 l 100

4 100 900

l 200 280

~-T4BDD

1 300

1 200

1 300

1 200

1 600

1 600

460

7. P5BDF

2 000

2 100

1 900

1 500

640

610

97

7. P5BDD

2 000

2 100

2 300

1 400

890

910

200

20 300

21 700

25 300

27 700

29 600

33 200

11 900

7. PBDD/F

462

=

MIBDF

e

MIBDD

A

P5BDF

--x--P5BDD

7000 6000

5000

$

~

4000 3000

,/'°

2000 1000

0

50

100

150 time

200

250

300

~]

Fig. 2: Time dependence of the M1BDD/F and PSBDD/F-concentrations during UV-photolysis in n-hexane The results of the UV-irradiation of PBDD/F-contairdng laboratory wastes are presented in Table 5. The PBDD/F in the solvent wastes from a dioxin laboratory could be successfully degraded by UV-photolysis, more than 99% of PBDD/F were decomposed. Compared to the PBDD/F-standards the rate of photolytical degradation of waste solutions is slower. R is possible that other chemical substances in waste solutions reduce the photochemical reactivity of PBDD/F. The photolytic behaviour of PBDD/F-contaminated bromophenols in organic solvents differs significantly from that of "pure" PBDD/F solutions (Table 5). Larger amounts of PBDD/F were formed during the irradiation of solutions of the crude bromophenol products. The concentration of lower brominated PBDD/F increased more than that of higher brominated isomers. The irradiation of 2,4-dibromophanol produces much more pollutants than in the case of 4-bromophenol, their concentration increases up to three orders of magnitude in comparison to the nonirradiated samples. The toxicity equivalents (TEQ), calculated by u~ng the BGA/UBA-method for PCDD/F also were higher after UV-irradiation ( factor 2 for 4-bromophenol, factor 115 for 2,4-dibromophanol). The photolysis of dissolved distillation residues with high PBDD/F-concentration showed a different behaviour from the bromophenol solutions, the rate of increase for the total PBDD/F-concentration was smaller and the TEQs were lower in comparison to the starting materials. The reason was the lower amount of phenolic compounds as precursors. Finally, it should be noted that the contamination of bromophanol samples with brominated biphenyls and diphenylethers is important for the photoformation of PBDD/F. The irradiation of hromophenois generates phenoxy- and hydroxyphenyl radicals by breaking O-H- and C-Br-bonds. In subsequently reactions the radicals recombine and the concentration of biphenyls and diphenylethers increases, or they react to other intermediate radicals. The technically produced analogous chlorophenols contained impurities which, in addition to other isomeric chiorophenols, also include PCDD/F precursors like polychiorinated diphenylethers in the range of 100 ppm [17]. The photolytic behaviour of halogenated and unhalogenated phenols, diphenyls and diphenylethers is described in some earlier reports [18-21].

463

Table 5: Concentrations of PBDD/F and calculated TEQ-values in extracts of UV-irradiated solutions of solvent wastes, bromophenol crude products and distillation residues in comparison to extracts of not irradiated solutions [ng/kg] M1-

2,3,7,8-

M1-

2,3,7,8-

5~

I~

T3BDF T4BDF T4BDF P5BDF T3BDD T4BDD T4BDD P5BDD PBDD/F TE(~ ~olveatwastes

before UV

1560

3100

40

7400

520

300

10

250

13180

44

after UV

n.d.

n.d.

n.d.

n.d.

n.d.

n.d

n.d.

n.d.

n.d.

n.d

134(]

100

120

n.d.

400

n.d.l

n.d.

n.d.

1960

1"

2700

n.d.

n.d.

14200

n.d.[

n.d.

n.d.

329850

2~

120

150

n.d.

160

n.d.!

n.d.

n.d.

3480

1~

157000(] 179000

n,d.

1680 291000

10000

n.d.

n.d. 2051680 190~

39000

n.d.

n.d.

n.d.

417500

90~

n.d 453300

n.d.

n.d

n.d.

524400

n.d

15300

3500

n.d

n.d.

517900 105~

n.d 1023000

6500

n.d.

n.d. 2944400

*-bromopbenol before UV ~,rude product

2,4-dibromo-

after UV

31300(]

before UV

303(]

~henol :rude product

after UV

4-bromophenol ~before UV

36300(]

7200

8300

7110(

n.d.

n.d.

48500(

4300

9800

189390( 21000

n.d.

n.d.

distillation residue

afterUV

2,4.~libromo~hcnol

before UV

distillation

after UV

n.d

27:

residue

Most investigations are carded out with chlorinated species under different reaction conditions. In some cases chlorodibenzofurans (PCDF) are obtained in preparative yield by UV-irradiation of polychlorinated diphenylethers in n-hexane or more polar solvents like acetone or methanol [17,22,23]. Similiar reactions in water are possible. An important condition for PCDF production is a halogen atom in the ortho-position of the substrate molecule. In this case the chlorodiphenylcther formed the PCDF-ring system under loss of HX [ 16,17,22,23].

Summary PXDD/F are degraded rapidly by UV-photolysis in organic solvents when standard solutions or PXDD/Fcontaminated waste solutions (laboratory wastes, e.g. solvent wastes) with a low concentration of other photochemically active species are applied. In contrast, the PBDD/F-contamination of bromophenols could not be degraded by UV-photolysis in organic solvents. The amounts of lower brominated PBDD/F congeners in irradiated samples are very high in comparison to untreated samples. Reason for this behaviour is the great excess of bromophenols in solution, whereas the initial concentration of PBDD/F is low. Bromophenols are PBDD/F precursors and UV-irradiation induces condensation reactions. The rate of photochemical PBDD/F formation is greater than the rate of degradation. Acknowledgement Parts of these investigations were financially supported by the GSF Forschungszentrum fOr Umweit und Gesundheit, Munich, which we gratefully acknowledge.

464 References [1] J. Ritterbusch, Diplomarbeit, Technische Universitat Braunschweig, (1993). [2] R. Vogt, W. Lorenz, M. Bahadir, H. Hopf, LaborPraxis, 18. (1994), 30. [3] D. G. Crosby, A. S. Wong, J. R. Plimmer, E. A. Woolson, Photodecomposition of chlorinated dihenzo-pdioxins, Science, 173, (1971), 748. [4] H.oR. Buser, Rapid photolytic decomposition of brominated and brominated/chlorinated dibenzodioxins and dibenzofurans, Chemosphere, 1_7.7,(1988), 889. [5] D. Lenoir, K.-W. Schramm, O. Hutzinger, G. Schedel, Photochemical degradation of brominated dibenzo-pdioxins and -furans in organic solvents, Chemosphere, ~ (1991), 821. [6] Firmenschrift,Heraeus Instruments GmbH, (1989). [7] H. Hagenmaier, H. Brunner, R. Haag, H.-J. Kunzendorf, M. Kraft, K. Tichaczek, U. Weberrul3, Stand der Dioxinanalytik, VDI-Berichte 634: Dioxin - Eine technische, analytischeund toxikologische Herausforderung, VDI Verlag Dfisseldorf, (1987), 61. [8] G. G. Choudhry, O. Hutzinger, Photochemical formation and degradation ofpolychlorinated dibenzofuransand dibenzo-p-dioxins, Residue Rev., ~ (1982), 113. [9] H.-R. Buser, Preparation of qualitative standard mixtures of polychlorinated dihenzo-p-dioxins and dibenzofurans by ultraviolet and y-radiation of the octachloro compounds, J. Chromatogr., ~ (1976), 303. [10]H. Muto, Y. Takizawa, The liquid photolyses of tetra- and octa-CDDs and their CDFs in hexane solution, Chemistry Letters, (1991), 273. [1 l]J. T. Pinhey, R. D. G. Rigby, Photoreduction ofchloro- and bromoaromatic compounds, Tetrahedron Letters, 16, (1969), 1267. [12]D. Firestone, J. Ress, N. L. Brown, R. P. Barron, J. N. Damico, Determination of polychlorodibenzo-p-dioxin and related compounds in commercial chlorophenols,J. Assoc. OfficialAnal. Chemists, 55, (1972), 85. [13]E. C. Villanueve, V. W. Burse, R. W. Jennings, Chlorodibenzo-p-dioxincontamination of two commercially available pentachlorophenois, J. Agr. Food Chem., 2_1,(1973), 739. [14] C.-A. Nilsson, L. Renberg, Further studies on impurities in chlorophenols,J. Chromatogr., 89, (1974), 325. [15]H.-R. Buser, Analysis of polychlorinated dibenzo-p-dioxinsand dibenzofurans in chlorinated phenols by mass fragmentography, J. Chromatogr., 107, (1975), 295. [16] A. Norstr6m, K. Anderson, C. Rappe, Formation of chlorodibenzofuransby irradiation of chlorinated diphenyl ethers, Chemosphere, 5, (1976), 21. [17]A. NorstrOm, K. Anderson, C. Rappe, Studies on the formation of chlorodibenzofurans by irradiation or pyrolysis of chlorinated diphenylethers, Chemosphere, 6, (1977), 241. [ 18] K.-P. Zeller, H. Petersen, Photochemische Herstellung yon Dibenzofuranenund Dibenzothlophenen, Synthesis, (1975), 532. [19]J. A. Eiix, D. P. Murphy, Photocyclization of 2-methoxyphenyl phenyl ethers, Aust. J. Chem., ~ (1975), 1559. [20]H.-I. Joschek, S. I. Miller, Photocleavage of phenoxyphenols and bromophenols, J. Am. Chem. Soc., 88, (1966), 3269. [21]H-I. Joschek, S. I. Miller, Photooxidation of phenol, cresols and dihydruxybenzenes,J. Am. Chem. Soc., 88, (1966), 3273. [22]G. G. Choudhry, G. Sundstr6m, F. W. M. van der Widen, O. Hutzinger, Synthesis of chlorinated dibenzofurans by photolysis of chlorinated diphenylethers in acetone solution, Chemosphere, _6,(1977), 327. [23] G. G. Choudhry, G. Sundstr6m, L. O. Ruzo, O. Hutzinger, Photochemistry of chlorinated diphenyl ethers, J. Agr. Food Chem., ~ (1977), 1371.