Environ. Sci. Technol. $990, 2 4 , 903-908
Identification of Novel Chlorinated Monoterpenes Formed during Kraft Pulp Bleaching of Pinus radiata Trevor R. Stuthrldge," Allstalr L. Wllklns, and Alan G. Langdon
Chemistry Department, University of Waikato, Hamilton, New Zealand
Keith L. Mackle and Paul N. McFarlane
Forest Research Institute, Rotorua, New Zealand
w The chlorination stage bleaching effluents of a New Zealand kraft pulp and paper mill processing the softwood Pinus radiata contained a group of novel chlorinated monoterpenes. Fourteen compounds were isolated from the effluents by a combination of liquid-liquid extraction, column chromatography, and preparative gas chromatography. Mass spectral and 'H and NMR data showed these compounds to be chlorinated and/or hydroxylated derivatives of P. radiata monoterpenes. The major compounds were a dichlorobornane and four dichloro-p-menthane-l&diols. The chlorinated monoterpenes were detected in total concentrations of 1400-12300 pg/L [70-600 g/air-dried tonne (ADT) bleached pulp] and they were the major class of low molecular weight extractable organic compounds present in the chlorination stage effluent. The principal factor determining their formation appears to be the high concentration of monoterpenes remaining in the P. radiata brown stock produced in the mill's continuous digester. Introduction The use of chlorine to bleach kraft pulp leads to the formation of a wide range of high and low molecular weight chlorinated and nonchlorinated organic compounds, many of which are subsequently discharged to the kraft mill effluent treatment system. To date, more than 300 low molecular weight compounds have been identified in bleach plant wastewaters (I). These low molecular weight chlorinated organic compounds are of particular concern because of their established toxicity, mutagenicity, and potential for bioaccumulation (2). As part of an on-going study at one of New Zealand's two kraft pulp and paper mills we have sought to identify and quantify the low molecular weight extractable organic compounds present in effluents from the mill's two bleach plants. The use of conventional gas chromatography and gas chromatography/mass spectrometry (GC/MS) techniques has lead to the identification of over 200 low molecular weight compounds from chlorination and alkali extraction stage effluents (3). Many of these compounds correspond to those previously detected in the wastewaters from North American or Scandinavian pulp mills. However, high concentrations of a group of chlorinated compounds of unknown structure were also observed. This paper describes the structural characterization of these compounds. Experimental Methods Chlorination Effluent. Effluent was obtained from the chlorination stage of the mill's (D/C)EoDED sequence kraft pulp bleaching plant. Typical bleaching conditions during the course of sampling are presented in Table I. Isolation of Compounds. A bulk chlorination stage effluent sample (100 L) was extracted without pH adjustment (pH 1.96) for 48 h with redistilled dichloromethane in 10-L continuous liquid-liquid extractors. The 0013-936X/90/0924-0903$02.50/0
Table I. Chlorination Stage Bleaching Conditions brown stock incoming P no. pulp consistency, % total applied chlorine (active Clz), % sequential replacement, % reaction time, min temperature, OC final pH extracted P no.
kraft P. radiata 24 4.3 6.67 30.2 36 26.5 1.6 1.1
extracts were dried with anhydrous magnesium sulfate and the solvent was removed on a rotary evaporator; the extracts were combined to afford 6.1 g of extractives. The combined extract was dissolved in diethyl ether and highly polar material was removed by precipitation/centrifugation following the addition of an equal volume of n-hexane. The concentrated supernatant was then introduced onto a 100 cm X 25 mm column of silica gel 60. Thirty 50-mL fractions were collected with hexane/diethyl ether/methanol(5050:1) and a further 20 50-mL fractions were collected with hexane/diethyl ether/methanol(5:5:1) as the eluting solvent. Compound V, the major chlorinated monoterpene hydrocarbon was present in 95% purity in fraction 8; other chlorinated monoterpene hydrocarbons were present in fractions 4-10. The chlorinated monoterpene alcohols were present in fractions 37-50. Fractions 37-50 were combined and further separated by preparative gas chromatography [ 10 m X 6 mm column, 5% SE-30 on Chrompak GW, helium carrier gas (400 kPa), temperature programmed from 150 to 222 "C at 2 "C/min]. The preparative GC effluent was split 1OO:l to collector and FID detector, respectively. Effluent fractions from 70 5-pL injections were combined to variously afford between 0.05 and 2 mg each of compounds VIII-XIV, or their dehydro analogues. Quantitation of Compounds. Effluent samples (125 mL) were acidified to pH 3 and extracted for 4 h with dichloromethane in 125-mL liquid-liquid extractors using n-octadecane as internal standard. Extracts were dried with anhydrous magnesium sulfate and concentrated to ca. 1 mL on a rotary evaporator at 25 "C. An ethereal solution of diazomethane was added to the concentrated extracts to derivatize acidic and chlorophenolic compounds present in the extracts. The derivatized samples were analyzed on a Hewlett-Packard 5890 gas chromatograph, fitted with a 25-m HP-1 fused-silica capillary column. Helium was employed as carrier gas (linear velocity 30 cm/s); the injector and flame ionization detector temperatures were maintained at 225 and 250 "C, respectively. After a Grob splitless injection (30-9 load), the gas chromatograph was programmed from 40 (2-min hold) to 250 "C (16-min hold) at 5 "C/min. Concentrations were calculated from the octadecane internal standard (equivalent to 500 pg/L) by using purified compound XI11 as the response factor standard.
0 1990 American Chemical Society
Environ. Sci. Technol., Vol. 24, No. 6, 1990 903
Table 11. E1 Mass Spectral Data for Compounds I-XIV mass fragment m / z (relative intensity)
compound monoterpene hydrocarbons I I1 111 IV V VI VI1 monoterpene alcohols VI11 IX X XI XI1 XI11 XIV v
I
55 (loo), 81 (88.0), 95 (19.6), 105 (21.7), 121 (9.8), 135 (21.7), 171 (18.5) 55 (loo), 67 (80.4), 81 (18.5), 109 (59.2), 121 (16.3), 135 (25.0), 171 (23.9) 93 (23.9), 108 (loo), 129 (7.6), 135 (23.9), 171 (7.1) 81 (loo), 93 (38.0), 108 (44.6), 121 (18.5), 135 (53.3), 157 (9.8), 171 (47.3) 93 (loo), 129 (64.0), 135 (55.9), 170 (13.0), 171 (5.0), 191 (0.5), 206 (0.7) 81 (12.0), 95 (15.2), 108 (loo), 129 (5.4), 135 (16.8), 171 (16.3) 55 (loo), 93 (43.5), 107 (50.5), 121 (53.3), 135 (52.2), 170 (8.71, 171 (6.0) 59 (loo), 95 (58.0), 110 (58.2), 135 (3.61, 150 (12.4) 69 (43.4), 93 (loo), 111 (71.3), 160 (36.9), 207 (7.0), 222 (17.6) 59 (loo), 93 (26.3), 128 (4.3), 129 (7.1), 171 (1.8), 187 (3.4), 207 (4.3), 225 (1.4) 59 (loo), 93 (17.6), 128 (8.0), 129 (7.5), 173 (3.4), 187 (1.7), 207 (2.9), 225 (0.8) 59 (loo), 93 (19.0), 128 (5.7), 129 (5.6), 173 (13.3), 189 (1.9), 207 (2.3), 225 (1.3) 59 (loo), 93 (15.0), 128 (7.6), 129 (12.7), 171 (2.1), 187 (4.8), 207 (4.0), 225 (1.9) 59 (loo), 127 (7.0), 177 (2.3), 185 (2.6), 221 (2.9), 241 (5.3), 259 (1.3) X X I Xlll
I1 I
Table 111. Quantity of Chlorinated Monoterpenes Found in Chlorination Stage Bleaching Effluentso compound
Figure 1. Gas chromatogram of chlorination stage effluent extract showing posffion of compounds I-XIV and octadecane internal standard (IS,500 pglL).
Mass Spectrometry. EI-GC/MS and CI-GC/MS data were obtained on a Hewlett-Packard 5985 mass spectrometer using the GC conditions given above. EI-MS were obtained at 70 eV, 300-PA ionization energy. CI-MS were obtained by use of hydrogen, ammonia, methane, or isobutane as ionizing gases. Accurate mass data were obtained by GC/MS (EI) on a Kratos MS80 RFA instrument operated at 3000 RP and 1 s/decade scan rate. 'H and 13CNuclear Magnetic Resonance Spectroscopy. 'H and 13CNMR spectra were recorded in CDC1, on a Bruker AM400 NMR spectrometer with deuteriochloroform as solvent and trimethylsilane as reference. Results GC/MS analysis revealed the presence in chlorination stage effluents of a series of nonaromatic chlorinated monoterpenes (Figure l),the CI-MS and EI-MS of which served to subdivide the substances into two groups; namely, dichlorinated monoterpene hydrocarbons of molecular weight 206 amu (compounds I-VII) and chlorinated monoterpene alcohols of molecular weight 222 amu and above (compounds VIII-XIV) (Table 11). Analysis of chlorination stage effluents collected daily over a 4-week period showed that compounds I-XIV were the dominant low molecular weight extractable organic compounds occurring in this effluent (Table 111;levels of trichlorocatechol are included for comparison). In order to obtain sufficient quantities of some of the compounds for structural elucidation and biological studies, 100 L of spent chlorination effluent was extracted with dichloromethane. The isolation procedure gave two fractions. The less polar of the two fractions contained the predominant chlorinated monoterpene hydrocarbon, 904
Environ. Sci. Technol., Vol. 24,
No. 6, 1990
monoterpene hydrocarbons I I1 I11 IV V VI VI1 total monoterpene alcohols VI11 IX
x
XI XI1 XI11 XIV total trichlorocatechol
range, g/ADT av, g/ADT
SD
0.9-2.3 1.3-7.1 0.5-8.5 0.8-21.0 4.0-48.5 3.9-19.8 8.1-38.3 28.7-149.1
1.4 4.6 5.3 6.0 17.9 10.3 22.7 72.7
0.4 1.7 2.6 4.9 14.4 5.4 10.0 39.0
0.3-10.2
