Article pubs.acs.org/jced
Solubility of 2,2′,6,6′-Tetrabromo-4,4′-isopropylidene Phenol in Aqueous Pollutant Solutions Jinhua Li, Jing Bai, Baoxue Zhou,* and Xiaofang Hu School of Environmental Science and Engineering, Shanghai Jiaotong University, Shanghai 200240, China ABSTRACT: The solubility of 2,2′,6,6′-tetrabromo-4,4′-isopropylidene phenol (TBBPA) in pure water, calcium chloride (CaCl2) + water and different surfactants (hexadecyltrimethylammonium bromide (CTAB), 1-hexadecylpyridinium chloride (CPC), sodium dodecylbenzenesulfonate (SDBS) and dodecyl sodium sulfate (SDS)) + water has been determined at (293.2, 298.2, 303.2, 308.2) K by the static equilibrium method. The solubility of TBBPA was determined by high performance liquid chromatography (HPLC). The relative standard deviations of the solubility data are all less than 2.6%.
■
INTRODUCTION 2,2′,6,6′-Tetrabromo-4,4′-isopropylidene phenol (TBBPA) is a type of brominated flame retardants (BFRs) that are widely used in a variety of commercial and industrial application for the purpose of fire prevention1 (see Figure 1 for its chemical
However, the solubility data of TBBPA reported are only concerned about the environment of pure water, and there is no report of the solubility of TBBPA at the presence of coexisting pollutants. The overall objective of this study was to investigate the solubility of TBBPA in the aqueous pollutant solutions (CaCl2, CTAB, CPC, SDBS, and SDS) in the temperature range of 293.2 K to 313.2 K. In addition, the effect of the solution pH on the solubility of TBBPA was also evaluated. By providing the basic solubility data, the results deepen our understanding of the TBBPA behavior in sediment-pore water systems, and facilitate more accurate assessment of its ecological risk.
■
EXPERIMENTAL SECTION Materials and Apparatus. The chemical formula, molar mass, supplier, and mass fraction purity of compounds used in this study are shown in Table 1. All materials were utilized without additional purification. The critical micelle concentration (CMC) of CTAB, CPC, SDBS, and SDS are 0.00099, 0.00090, 0.00143, and 0.0073 mol·kg−1, respectively. Doubled distilled water, treated with ion-exchange resin before distillation, was used and its conductivity was 1.18 × 10−4 S· m−1. Experimental Procedures. First, a series of concentrations were prepared for surfactant + water and CaCl2 + water. The surfactants or CaCl2 were measured by mass using an FA1240B analytical balance (Shanghai Precision & Scientific Instrument Co., China) with an uncertainty of ± 0.0001 g. The pH of aqueous solution was adjusted to a fixed value of 6.2 by the addition of HCl or NaOH and measured using a pHS-3C pH meter (Shanghai Precision &Scientific Instrument Co., China) with an uncertainty of ± 0.002. Then, a slight excess amount of TBBPA was added to the glass tubes, followed by equilibration in a DZK-2 thermostatted water bath (Shanghai Jinghong
Figure 1. Chemical structure for TBBPA.
structure). TBBPA is suspected to escape into rivers, streams, and surface waters during its processes of production, use, and disposal. Therefore, TBBPA has also been detected in fish, human plasma serum, and breast milk in women.2,3 Many studies suggested that exposure to TBBPA can affect the reproductive behavior, induce the vitellogenin yolk precursor, and even break the balance of ecosystems. Because of its extensive use, persistence, and toxicity, TBBPA may have the potential to be a source of endocrine disrupting chemical (EDC) and persistent organic pollutants (POPs).3−5 TBBPA is lipophilic and persistent with a relatively high hydrophobicity and a low solubility in water. TBBPA has two polar OH groups; hence, it can exist in three different states, that is, the molecular form (TBBPA) in acidic conditions and two dissociated forms (TBBPA− and TBBPA2−) in alkaline conditions.6,7 As a typical ionic compound, pH may have a significant influence on the solubility of TBBPA. Furthermore, the coexisting contaminants can also seriously affect the fate, transformation, and transportation of pollutants in the environment. Li et al found that the solubility of BPA could be affected significantly by the presence of other pollutants.8 © 2013 American Chemical Society
Received: June 26, 2013 Accepted: September 27, 2013 Published: October 11, 2013 3150
dx.doi.org/10.1021/je400602s | J. Chem. Eng. Data 2013, 58, 3150−3154
Journal of Chemical & Engineering Data
Article
Table 1. Properties of Compounds Used in the Study chemical name a
TBBPA CTABb CPCc SDBSd SDSe BAf calcium chloride sodium hydroxide hydrochloric acid a
chemical formula
source
M/g·molg
CAS registry no.
mass fraction purity
C15H12Br4O2 C19H42NBr C21H38NCl C18H29NaO3S C12H25SO4Na C7H6O2 CaCl2 NaOH HCl
Sigma Shanghai Shanghai Shanghai Shanghai Shanghai Shanghai Shanghai Shanghai
543.87 364.45 340.01 348.48 288.38 122.12 110.98 40 36.46
79-94-7 57-09-0 123-03-5 25155-30-0 151-21-3 65-85-0 17787-72-3 1310-73-2 7647-01-0
0.97 0.995 0.995 0.99 0.99 0.99 0.99 0.96 0.36−0.38
TBBPA, 2,2′,6,6′-tetrabromo 4,4′-isopropylidene phenol. bCTAB, hexadecyltrimethylammonium bromide. cCPC, 1-hexadecylpyridinium chloride. SDBS, sodium dodecylbenzenesulfonate. eSDS, dodecyl sodium sulfate. fBA, benzoic acid. gM, molar mass.
d
Table 3. Experimental Mole Fraction Solubilities x of TBBPA in Pure Water Under different pH at Varied Temperatures T and Pressure p = 0.1 MPaa
Experimental Instrument Co. Ltd.) at (293.2, 298.2, 303.2, 308.2) K at least for 72 h. The measured temperature was uncertain to ± 0.1 K. The saturated solutions were centrifuged with the speed of 10000 rpm for 5 min for further analysis. The following equation was used to calculate the mole fraction solubility (x): x=
m1/M1 m1/M1 + m2 /M 2 + m3 /M3
pH
T/K
106 x
pH
T/K
106 x
3
293.2 298.2 303.2 308.2 293.2 298.2 303.2 308.2 293.2 298.2 303.2 308.2 293.2 298.2 303.2 308.2
nd nd nd 0.0050 nd nd 0.0033 0.0083 nd 0.0056 0.0086 0.014 0.0076 0.014 0.21 0.26
7.2
293.2 298.2 303.2 308.2 293.2 298.2 303.2 308.2 293.2 298.2 303.2 308.2 293.2 298.2 303.2 308.2
0.21 0.26 0.31 0.36 0.64 0.68 0.73 0.77 0.73 0.81 0.88 0.94 0.83 0.86 0.92 0.95
(1) 4.7
8.1
where m1 represents the mass of TBBPA, m2 represents the mass of CaCl2 or surfactants, and m3 represents the mass of H2O. M1, M2, and M3 are the molecular weight of the TBBPA, CaCl2, or surfactants and H2O, respectively. Each experimental data point represents the average of at least three replicate measurements, and the relative standard deviations are less than 2.6%. Analysis. The concentrations of TBBPA were analyzed via HPLC equipped with a UV detector with a wavelength at 210 nm (waters, USA). The C18 reversed-phase column was 250 mm × 4.6 mm × 5 μm. The measurement for TBBPA was performed in an isocratic elution program with methanol/water = 80:20 (v/v) as the mobile phase. The flow rate was kept at 1 mL·min−1 and the injection volume was 20 μL.
The standard uncertainties u are u(T) = 0.1 K and u(pH) = 0.002, and the relative standard uncertainty ur for the solubilities is ur (x) = 0.026. nd indicates not detectable.
RESULTS AND DISCUSSION The Reliability and Accuracy of Experimental Method. Before the experiment, the accuracy about the equipment and
Table 4. Experimental Mole Fraction Solubilities x of TBBPA in Mass Fraction w CaCl2 + (1 − w) Water at Varied Temperatures T and Pressure p = 0.1 MPaa
6.2
6.7
Table 2. Experimental Mole Fraction Solubilities xexp and Literature Mole Fraction Solubilities xref of BA in Pure Water at Varied Temperatures T and Pressure p = 0.1 MPaa 103 xexp
103 xref
283.2 293.2 303.2 313.2 323.2
3.06 4.31 6.03 8.22 11.42
3.02 4.26 6.01 8.19 11.38
10.9
a
■
T/K
9.5
103 w = 0.56
103 w = 1.10
103 w = 5.47
103 w = 10.88
T/K
6
10 x
6
10 x
6
10 x
106 x
293.2 298.2 303.2 308.2
0.0050 0.016 0.023 0.037
nd 0.0070 0.011 0.028
nd nd nd nd
nd nd nd nd
a w is the mass fraction of CaCl2 in the (CaCl2 + water) solution. The standard uncertainties u are u(T) = 0.1 K and u(w) = 0.0001 and the relative standard uncertainty ur for the solubilities is ur (x) = 0.026. nd indicates not detectable.
a The standard uncertainties u are u(T) = 0.1 K and the relative standard uncertainty ur for the solubilities is ur(xexp) = 0.0098.
The Solubility of TBBPA in Pure Water under Different pH Values. The solubility of TBBPA was determined in a pH range from 3.0 to 12.0. The solubility of TBBPA under different pH values in pure water is summarized in Table 3. From Table 3, it can be clearly seen that an increase of TBBPA mole fraction solubility is caused by an increase of temperature and pH values. At lower pH values, the TBBPA solubility increases slowly. And then the TBBPA solubility increases significantly with the growth of the pH value. Similar
method was confirmed by comparing our solubility data of benzoic acid (BA) in water with those in the literature.9 All of the data are presented in Table 2. The result show that our experimental data are in good consistency with those in the literature, and the relative standard deviation is less than 0.98%. Therefore, the method used in this study is accurate and reliable. 3151
dx.doi.org/10.1021/je400602s | J. Chem. Eng. Data 2013, 58, 3150−3154
Journal of Chemical & Engineering Data
Article
Table 5. Experimental Mole Fraction Solubilities x of TBBPA in Mass Fraction w Cationic Surfactants + (1 − w) Water at Varied Temperatures T and Pressure p = 0.1 MPaa 103 w = 0.05
103 w = 0.10
103 w = 0.20
103 w = 0.40
103 w = 0.80
T/K
6
10 x
6
10 x
6
10 x
6
10 x
106 x
293.2 298.2 303.2 308.2
0.0082 0.014 0.020 0.028
0.012 0.023 0.029 0.040
0.024 0.034 0.047 0.061
0.038 0.056 0.072 0.096
0.056 0.074 0.10 0.14
293.2 298.2 303.2 308.2
0.010 0.015 0.023 0.030
0.014 0.022 0.034 0.048
0.027 0.039 0.052 0.074
0.037 0.060 0.074 0.11
0.056 0.092 0.12 0.17
CTAB
CPC
a
w is the mass fraction of cationic surfactants in the (cationic surfactants + water) solution. The standard uncertainties u are u(T) = 0.1 K and u(w) = 0.0001 and the relative standard uncertainty ur for the solubilities is ur (x) = 0.026.
Table 6. Experimental Mole Fraction Solubilities x of TBBPA in Mass Fraction w Anionic Surfactants + (1 − w) Water at Varied Temperatures T and Pressure p = 0.1 MPaa 103 w = 0.05
103 w = 0.10
103 w = 0.20
103 w = 0.40
103 w = 0.80
T/K
106 x
106 x
106 x
106 x
106 x
293.2 298.2 303.2 308.2
nd 0.0052 0.011 0.014
0.0053 0.0092 0.015 0.020
0.0060 0.011 0.017 0.027
0.012 0.017 0.029 0.049
0.047 0.075 0.98 0.12
293.2 298.2 303.2 308.2
nd nd 0.0096 0.015
0.0076 0.0096 0.014 0.022
0.011 0.014 0.024 0.032
0.017 0.022 0.030 0.38
0.028 0.034 0.42 0.58
SDBS
SDS
a w is the mass fraction of anionic surfactants in the (anionic surfactants + water) solution. The standard uncertainties u are u(T) = 0.1 K and u(w) = 0.0001 and the relative standard uncertainty ur for the solubilities is ur (x) = 0.026. nd indicates not detectable.
establish the hydrogen bond with water and hence increase the TBBPA solubility. The Solubility of TBBPA in CaCl2 Solution. The solubility of TBBPA in CaCl2 solution is illustrated in Table 4. It can be seen from Table 4 that the solubility of TBBPA increases with increasing CaCl2 concentration and then decreases with further addition of CaCl2. The decrease of the TBBPA solubility at the higher CaCl2 concentration may be due to the common salt out effect. The formation of hydration shells decreases the degrees of freedom of the water molecular and consequently leads to TBBPA solubility decrease. However, there have been relatively few reports on the increasing solubility of organic compound at lower concentrations of CaCl2. Although a clear explanation has never been made on this phenomenon so far, the structure of the TBBPA may be a possible cause. Further research may be conducted to clarify its inherent solubilization mechanism. The Solubility of TBBPA in Surfactants Solutions. The mole fraction solubility of TBBPA in cationic surfactant CTAB solutions are represented in Table 5. As shown in Table 5, the mole fraction solubility of TBBPA increases significantly within the whole ranges of CTAB. A similar trend is observed in the case of cationic surfactant CPC (Table 5). The solubility of TBBPA was determined in anionic surfactant SDBS solutions, and the values are presented in Table 6. It can be seen from Table 6 that the TBBPA solubility in anionic surfactant SDBS increases very slowly at lower concentration of SDBS, which is
Figure 2. Mass fraction w of different surfactant dependence of mole fraction solubilities x of TBBPA: □, CTAB; ○, CPC; △, SDBS; ▽, SDS.
results have been previously reported by Yu10 that the solubility of TBBPA in pure water at 298.2 K under the pH of 6.2 is close to the result of our study under the same condition. TBTBPA is a weak organic acid, which exists in both molecular and ionic forms due to the ionization within the pH range examined in this study. As the solution pH value increases, the deprotonated (anionic) form of TBBPA becomes more dominant, which can 3152
dx.doi.org/10.1021/je400602s | J. Chem. Eng. Data 2013, 58, 3150−3154
Journal of Chemical & Engineering Data
Article
Table 7. Experimental Mole Fraction Solubilities x of TBBPA in Mass Fraction w Surfactants + (1 − w) Water at Temperature 298.2 K and Pressure p = 0.1 MPaa surfactants
103 w
106 x
CTAB
0.05 0.10 0.20 0.40 0.80 0.05 0.10 0.20 0.40 0.80 0.05 0.10 0.20 0.40 0.80 0.05 0.10 0.20 0.40 0.80
0.0082 0.012 0.024 0.038 0.056 0.010 0.014 0.027 0.037 0.056 nd 0.0053 0.0060 0.012 0.047 nd 0.0076 0.011 0.017 0.028
CPC
SDBS
SDS
should be less significant on the mole fraction solubility of TBBPA.
■
CONCLUSIONS The mole fraction solubility of TBBPA in the aqueous pollutant solution increases progressively with the growth of the pH value. The presence of CaCl2 causes the TBBPA mole fraction solubility to increase at a lower CaCl2 concentration and then decrease when the CaCl2 concentration becomes higher. The mole fraction solubility of TBBPA in cationic surfactant CTAB and CPC increases linearly with the concentration of CTAB and CPC. The mole fraction solubility of TBBPA in the anionic surfactant SDBS and SDS solution increases slowly. On the basis of the obtained results, it is clear that the higher pH values, lower CaCl2 concentration, and the presence of surfactants increase the solubility of TBBPA, which can facilitate the release of TBBPA from sediment to water and increase the risk of exposure to TBBPA.
■
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Tel/Fax: +86-21-54747351. Notes
The authors declare no competing financial interest.
■
a
w is the mass fraction of surfactants in the (surfactants + water) solution. The standard uncertainties u are u(T) = 0.1 K and u(w) = 0.0001, and the relative standard uncertainty ur for the solubilities is ur (x) = 0.026. nd indicates not detectable.
REFERENCES
(1) Potvin, C. M.; Long, Z. B.; Zhou, H. D. Removal of tetrabromobisphenol A by conventional activated sludge, submerged membrane, and membrane aerated biofilm reactors. Chemosphere 2012, 89, 1183−1188. (2) Luo, S.; Yang, S. G.; Sun, C.; Wang, X. D. Feasibility of a twostage reduction/subsequent oxidation for treating Tetrabromobisphenol A in aqueous solutions. Water. Res. 2011, 45, 1519−1528. (3) Zhang, Y. H.; Tang, Y. L.; Li, S. Y.; Yu, S. L. Transformation of tetrabromobisphenol A in the presence of different solvents and metals. Chemosphere 2013, 222, 94−100. (4) Krishnan, A. V.; Starhis, P.; Permuth, S. F. Bisphenol A: An estrogenic substance is released from polycarbonate flasks during autoclaving. Endocrinology 1993, 132, 2279−2286. (5) Sun, W. L.; Ni, J. R.; Hao, P. P. Analysis of endocrine disruptors in water by solid phase extraction-liquid chromatography-ion trap mass/mass spectrometry. J. Chin. Soc. Mass Spectrosc. 2005, 26, 222− 226. (6) Sun, Z. H.; Li, M.; Xian, Q. M.; Yu, Y. J.; Li, H.; Yu, H. X. Effects of dissolved organic matter from sewage sludge on sorption of tetrabromobisphenol A by soils. J. Environ. Sci., China 2008, 20, 1075− 1081. (7) Li, R. Ro.; Liang, H. D.; Ge, C. H.; Lin, C. P.; You, Y. J.; Zhao, B. Equilibrium solubility of sodium 3-nitrobenzenesulfonate in binary NaCl + H2O, Na2SO4 + H2O, and C2H5OH + H2O solvent mixtures at elevated temperatures from (273.15 to 323.15) K. J. Chem. Eng. Data 2012, 57, 3434−3437. (8) Li, J. J.; Zhou, B. X.; Cai, W. M. W The solubility behavior of bisphenol A in the presence of surfactants. J. Chem. Eng. Data 2007, 52, 2511−2513. (9) Liu, G.Q.; Ma, L.X.; Liu, J. Manual of Chemical and Physical Properties: Organic Volume [M]; Beijing Chemical press: Beijing, 2002. (10) Mao, L.; Yu, Y. J.; Sun, Z. H. Water solubility and octanol/water partition behavior of tetrabromobisphenola. Environ. Chem. (China) 2010, 29, 583−587. (11) Zhou, X. Z.; Hao, J. C. Solubility of NaBr, NaCl, and KBr in surfactant aqueous solutions. J. Chem. Eng. Data 2011, 56, 951−955. (12) Liu, J. C.; Chang, P. S. Solubility and adsorption behaviors of chlorophenols in the presence of surfactant. Water Sci. Technol. 1997, 35, 123−130.
similar to that in pure water. The mole fraction solubility of TBBPA becomes high when the concentration of SDBS increases. The mole fraction solubility of TBBPA in SDS solutions also increases slowly. This is because TBBPA is highly lipophilic and is not very water-soluble. The surfactant monomer below the CMC has polar and nonpolar components in its structure, and the micelle above the CMC has a hydrophobic core and a hydrophilic mantle, both of which promote the aqueous solubility of TBBPA.11,12 Comparison of Solubility Data in Different Surfactants Solutions. The effects of various surfactants at 298.2 K on the mole fraction solubility of TBBPA are compared in Figure 2, and the solubility data are listed in Table 7. It is obvious that the solubility of TBBPA increases with the increase of surfactant concentration for all the surfactants. The order of increasing mole fraction solubility of TBBPA is CTAB ≈ CPC > SDBS ≈ SDS. The difference in solubilization capacity among the four surfactants could be attributed to the different CMC values and the alkyl chain length. As usual, the solubilization capacity of surfactant is related to the micelle core volume. The greater the micelle core volume is, the higher is the solubilization capacity. The surfactant with the lower CMC and longer alkyl chain can significantly increase micelle core volume, which hence enhances the solubility of a compound.12,13 Therefore, the solubility of TBBPA in a CTAB aqueous solution is similar to that in a CPC aqueous solution because of the closer CMC values and alkyl chain length. However, the solubility of TBBPA in anionic surfactant solutions (SDS and SDBS) is lower than that in cationic surfactants (CTAB and CPC). Compared with the CTAB and CPC, the SDS and SDBS have the higher CMC and shorter alkyl chain length. Therefore, the influence of SDS and SDBS 3153
dx.doi.org/10.1021/je400602s | J. Chem. Eng. Data 2013, 58, 3150−3154
Journal of Chemical & Engineering Data
Article
(13) Pennell, D. K.; Adinolfi, A, M.; Abriola, L. M.; Diallo, M. S. Solubilization of dodecane tetrachloroethylene, and 1,2-dichlorobenzene in micellar solutions of ethoxylated nonionic surfactants. Environ. Sci. Technol. 1997, 35, 1382−1389.
3154
dx.doi.org/10.1021/je400602s | J. Chem. Eng. Data 2013, 58, 3150−3154
