- Email: [email protected]
water partition coefficient and its application
Fluid Phase Equilibria 161 Ž1999. 295–304
A rapid determination method of the airrwater partition coefficient and its application Seon-Ah Ryu, So-Jin Park
)
Department of the Chemical Engineering, College of Engineering, Chungnam National UniÕersity, Taejon, 305-764, South Korea Received 1 September 1998; accepted 23 February 1999
Abstract The airrwater partition coefficient Ž K aw . and Henry’s constant Ž H . were measured by our own modified EPICS ŽEquilibrium Partitioning in Closed System. method, which uses two bubble columns. This method gives accurate K aw data much more rapidly than other methods. In order to establish this method, the influence of airflow rate and the volume ratios of water in two columns to partition coefficient were carefully examined. Then we have measured K aw for some n-alkanes, aromatic and chlorinated compounds. The experimental results of our modified EPICS method agreed very well with literature values. Besides the relationships between K aw and molar volume, vapor pressure and water solubility were also analyzed. q 1999 Elsevier Science B.V. All rights reserved. Keywords: Modified EPICS; K aw partition coefficient; Henry’s constant; Molar volume; Vapor pressure; Solubility
1. Introduction Recently, one tends to emphasize the contamination of livings and environments which relate to accident connected with hazardous waste management and chronic contamination of the environment due to the use of chemicals. The toxic chemicals, which were introduced in environment, disappear through transport and mixing phenomena and alteration of the structure of a compound. Among them, transport through the environment, while reasonably well understood, is quite complex and has not yet been quantified. The solubility, vapor pressure, and mass-transfer coefficient of individual
)
Corresponding author. Tel.: q82-42-821-5684; fax: q82-42-822-8995; e-mail: [email protected]
0378-3812r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 3 8 1 2 Ž 9 9 . 0 0 1 9 3 - 4
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
296
compounds in mixtures control the transport phenomena. The major problem is how to get the value of these properties, which are either known or not known with sufficient accuracy w1–3x. Without these information, fugacity of each compound in different phases, and the direction and magnitude of the transport between phases, which is crucial for an understanding of their environmental behavior, cannot be calculated. Recently, transport phenomena was usually predicted with partition coefficient as an environmental parameter w4x. The partition coefficient K aw , relating air and aqueous concentrations of a volatile substance, is commonly referred to as Henry’s constant Ž H . w5x. Knowledge of the Henry’s law constant is essential in calculating the direction of the transfer. If the solute concentrations in the air and water are determined, it immediately gives the direction of the transfer. In cases where the solute is close to equilibrium, an accurate value of H is more essential. In this work, we suggest a simple and rapid method of determining K aw as well as H for ordinary organic compounds at environmental concentrations.
2. Theory The airrwater partition ratio is used not only to characterize the airrwater equilibrium distribution of a compound, but also to describe the rate expressions of air–water systems relate to equilibrium. The Henry’s constant Ž H . may be thought as simply the ratio of a compound’s abundance in the gas phase to that of aqueous phase at equilibrium. If we express the abundance of a compound in air and water as Ca and C w , respectively, we can obtain then so-called dimensionless Henry’s constant Ž Hc .. The H and Hc may be related to one another by adopting the ideal gas law. Hc can be expressed as described below: K aw s
Ca Cw
s Hc s
H
Ž1.
RT
The total moles Ž M . of a volatile solute added to a bubble column will be partitioned at equilibrium according to Eq. Ž2.: M s C wVw q CgVg s Cg
Vw Hc
q Vg
Ž2.
where C w s concentration of solute in water Žmolrl., Cg s concentration of the solute in gas Žmolrl., Vw s volume of water in the column, Vg s volume of headspace in the column. If two columns are prepared with different liquid volumes Vw1 and Vw2 , we may write Eqs. Ž 3. and Ž4. from Eq. Ž2.: M1 s Cg1
M2 s Cg 2
Vw1 Hc Vw 2 Hc
q Vg1
Ž3.
q Vg 2
Ž4.
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
297
We can divide Eq. Ž3. by M1 and Eq. Ž4. by M2 . The left side of each equation will be unified and then combined as:
Ž Cg1rM1 . Ž Vw1rHc . q Vg1
s Ž Cg 2rM2 . Ž Vw 2rHc . q Vg 2
Ž5.
Solving for Hc then yields: Hc s
Vw 2 y Ž Cg1rM1 . r Ž Cg 2rM2 . Vw1
Ž Cg1rM1 . r Ž Cg 2rM2 .
Vg1 y Vg 2
Ž6.
or Hc s
Vw 2 y g Vw1
g Vg1 y Vg 2
where
g s Ž Cg1rM1 . r Ž Cg 2rM2 . To avoid the injection problem of insoluble or solid solutes, all the solutes were prepared as methanol solution because most of the solutes dissolved in methanol completely. If the different mass of solute, which was prepared as methanol solution Ž stock solution. , was injected to two columns, the concentrations of headspace Ž gas phase. will be different in two columns at the equilibrium between the gas and liquid phases. Such difference allows the calculation of Hc with Eq. Ž6.. 3. Experiment 3.1. Apparatus The modified EPICS measuring system is illustrated in Fig. 1. This system was used in a controlled room temperature Ž 258C.. The air was introduced into the column by a Cole–Parmer Model
Fig. 1. Schematic diagram of experimental system.
298
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
Masterflex LrS peristaltic pump. The injection and sampling port were sealed with a screw cap and silicone-rubber septum. The thermostated water at an accuracy of 25 " 0.18C was circulated in a water jacket of column using the MONO-TECH Model MRC-213D thermostat. After the equilibrium was reached between two phases, the concentration of solute in the head space were analyzed by Hewlett Packard 5890 ser. II gas chromatography. 3.2. Materials Commercial grade organic compounds used in this experiment were supplied from Aldrich and Merck. They were dried before use, using a 3A molecular sieve. The purity of each chemical was more than 99.8 wt.% by gas chromatographic analysis. 3.3. Procedure Distilled water Ž15 ml or 30 ml. was introduced to each bubble column by using a motor-driven burette at an accuracy of "0.01 ml. Methanol was used to prepare the stock solution as a solvent. It did not affect partitioning of solute between air and water phase because only very small amounts of stock solution will be injected to water phase in columns. It is explained well in Ref. w5x. The prepared stock solutions were injected into each column with a 0.1 ml gas-tight syringe. Quantitatively precise determination of injected mixture was made gravimetrically; the 0.1 ml syringe used was weighed before and after injection to the column. Air was then circulated in isolated bubble columns until equilibrium was reached at the programmed time Žabout 1 h.. The concentrations of headspace Ž gas phase. of solute compounds in equilibrated columns were analyzed two times by gas chromatography. Then K aw and Henry’s constant were calculated with Eq. Ž6.. 4. Results The accuracy of this method is primarily dependent on how real the approach is to the true equilibrium state. In order to evaluate it, the dependence of airflow rate and the ratio of water volume
Table 1 Comparison of experimental log K aw with reference and EPICS values Compounds n-alkane n-hexane n-heptane n-octane n-nonane a
Ref. w6x. Ref. w7x. c Ref. w8x. b
Exp. value
1.8201 1.9498 2.0799 2.2682
EPICS value c
Ref. value 1a
2b
1.7515 1.9115 2.0815 2.3132
1.8362 1.9675 2.0829 2.3047
1.7391 1.8692 2.0815 2.3281
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
299
Table 2 K aw and Henry’s constantŽ H . for n-alkanes at 258C Compounds
Molar volume Žcm3rmol.
K aw
H ŽkPa m3rmol.
n-alkane n-hexane n-heptane n-octane n-nonane
86.17 100.21 114.23 128.26
66.0846 89.0841 120.1987 185.4385
163.8118 220.8251 297.9508 459.6685
in two columns were carefully analyzed. As a result of the experiment with p-xylene and some alkanes, the optimal condition of the airflow rate was 200 mlrmin, and it needs only about 1 h for equilibrium partitioning of experimented chemicals between two phases. It reduced measuring time by at least one-third as compared to conventional EPICS method which needs about 3 to 24 h for experimental systems. Because conventional EPICS method is a static method in which equilibrium partitioning will be reached by stirring the water phase with a magnetic bar in a serum bottle. However, our modified EPICS method is a dynamic method which helps solute reach equilibrium state between air and water phase more rapidly by circulating air through water in bubble columns. Since water volume ratio between two columns had no significant meaning, the volume ratio of 1:2 Žcolumn 1:column 2. was therefore arbitrarily selected in this work. The accuracy and reproducibility of this method were reliable since measured K aw data agreed very well with literature values Ž within 1% average deviation for some n-alkanes, as shown in
Table 3 The K aw and Henry’s constant Ž H . for aromatic and chlorinated compounds at 258C Compounds
Molar volume Žcm3rmol.
K aw
H ŽkPa m3rmol.
Aromatic compound Benzene1 Toluene 2 p-xylene 3 Ethylbenzene 4 n-buthylbenzene5 n-penthylbenzene6 Chlorobenzene7 o-dichlorobenzene8 1,2,4-trichlorobenzene9 1,2,3,4-tetrachlorobenzene10
89.41 106.85 123.93 140.4 184.8 207 102.24 113.05 125.1 127
0.2345 0.2721 0.2818 0.3277 0.5485 0.6568 0.2175 0.0874 0.1513 0.1165
0.5806 0.6748 0.6991 0.9432 1.3578 1.6282 0.5370 0.2127 0.3752 0.2890
Chlorinated compound Dichloromethane11 Trichloromethane12 Tetrachloromethane13 cis-Dichloroethylene14 trans-Dichloroethylene15 Trichloroethylene16 Tetrachloroethylene17
64.1 90.67 97.09 75.1 76.6 90.01 102.71
0.0985 0.1496 1.0540 0.2721 0.2561 0.4256 0.7582
0.2441 0.3708 2.6120 0.6745 0.6348 1.0550 1.8794
300
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
Fig. 2. K aw values for alkyl benzene at 258C ŽArabic numerals refer to chemicals in Table 2..
Table 1.. The K aw and H for n-alkanes, aromatic and chlorinated compounds were measured and listed in Tables 2 and 3. The superscripted numbers indicating compounds in Table 3 are also valid in the following figures. The relationships between K aw Ž H . and molar volume, vapor pressure and water solubility of solute were also analyzed. The K aw and H were linearly proportional to molar
Fig. 3. K aw for chlorinated compounds at 258C ŽArabic numerals refer to chemicals in Table 2..
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
301
Fig. 4. K aw for n-alkane at 258C.
volume except cis and trans dichloroethylene, as shown in Figs. 2–4 and they were inversely proportional to vapor pressure and water solubility except Cl substituted benzenes, as shown in Figs. 5–7. Cl substituted benzenes did not show any dependency to molar volume, vapor pressure and water solubility. The K aw was changed by the difference in molecular structure.
Fig. 5. Henry’s constant vs. vapor pressure and solubility for n-alkane at 258C.
302
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
Fig. 6. Henry’s constant vs. vapor pressure for aromatic and chlorinated compounds at 258C ŽArabic numerals refer to chemicals in Table 2..
Fig. 7. Henry’s constant vs. solubility for aromatic and chlorinated compounds at 258C ŽArabic numerals refer to chemicals in Table 2..
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
303
5. Conclusion Our modified EPICS method gives accurate and much more rapid K aw data than conventional EPICS method. In the experimented systems, the K aw were linearly proportional to molar volume and inversely proportional to vapor pressure and water solubility except Cl substituted benzenes. The Cl substituted benzenes did not show any special relationships with molar volume, vapor pressure and water solubility. It may have been caused by the difference of intermolecular forces.
6. List of symbols A, B, C Ci Cs fi H Hc n Mw P Pis pi R T Vi Õi xi yi
Antoine constant concentration of solute in i phase solubility in water fugacity in i phase Henry’s constant dimensionless Henry’s constant total amount of solute molecular weight total pressure saturated vapor pressure of component i partial pressure of component i gas constant absolute temperature volume of i phase molar volume of chemical in i phase liquid phase mole fraction of the component i vapor phase mole fraction of the component i
Acknowledgements The authors appreciate the Korea Science and Engineering Foundation for the financial support ŽGrant No. KOSEF 961-1109-053-2. .
References w1x A.W. Andren, in: D. Mackey, S. Paterson, S.J. Eisenreich, M.S. Simmons ŽEds.., Physical Behavior of PCBs in the Great Lakes, Ann Arbor Science, Ann Arbor, MI, 1983, 127–140. w2x P.V. Doskey, A.W. Andren, Environ. Sci. Technol. 15 Ž1981. 705–711. w3x W.B. Neely, Gas transfer at water surface, Sci. Total Environ. Ž1977. 117–129. w4x D. Mackay, Multimedia Environmental Model; The Fugacity Approach, Lewis Pub., 1991.
304
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
w5x J.M. Gossett, Measurement of Henry’s law constant for C 1 and C 2 chlorinated hydrocarbon, Environ. Sci. Technol. 21 Ž1987. 202–208. w6x R.P. Schwarzenbach, P.M. Gschwend, D.M. Imboden Environmental Organic Chemistry, Wiley, 1993. w7x D. Mackay, W.Y. Shiu, A critical review of Henry’s law constants for chemicals of environmental interest, J. Phys. Chem. Ref. Data 10 Ž1981. 4–30. w8x S.J. Park, S.D. Hann, S.A. Ryu, Measurement of airrwater partition coefficient ŽHenry’s law constant. by using EPICS method and their relationship with vapor pressure and water solubility, J. Kor. Inst. Chem. Eng. 35 Ž1997. 915–920.
A rapid determination method of the airrwater partition coefficient and its application Seon-Ah Ryu, So-Jin Park
)
Department of the Chemical Engineering, College of Engineering, Chungnam National UniÕersity, Taejon, 305-764, South Korea Received 1 September 1998; accepted 23 February 1999
Abstract The airrwater partition coefficient Ž K aw . and Henry’s constant Ž H . were measured by our own modified EPICS ŽEquilibrium Partitioning in Closed System. method, which uses two bubble columns. This method gives accurate K aw data much more rapidly than other methods. In order to establish this method, the influence of airflow rate and the volume ratios of water in two columns to partition coefficient were carefully examined. Then we have measured K aw for some n-alkanes, aromatic and chlorinated compounds. The experimental results of our modified EPICS method agreed very well with literature values. Besides the relationships between K aw and molar volume, vapor pressure and water solubility were also analyzed. q 1999 Elsevier Science B.V. All rights reserved. Keywords: Modified EPICS; K aw partition coefficient; Henry’s constant; Molar volume; Vapor pressure; Solubility
1. Introduction Recently, one tends to emphasize the contamination of livings and environments which relate to accident connected with hazardous waste management and chronic contamination of the environment due to the use of chemicals. The toxic chemicals, which were introduced in environment, disappear through transport and mixing phenomena and alteration of the structure of a compound. Among them, transport through the environment, while reasonably well understood, is quite complex and has not yet been quantified. The solubility, vapor pressure, and mass-transfer coefficient of individual
)
Corresponding author. Tel.: q82-42-821-5684; fax: q82-42-822-8995; e-mail: [email protected]
0378-3812r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 3 8 1 2 Ž 9 9 . 0 0 1 9 3 - 4
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
296
compounds in mixtures control the transport phenomena. The major problem is how to get the value of these properties, which are either known or not known with sufficient accuracy w1–3x. Without these information, fugacity of each compound in different phases, and the direction and magnitude of the transport between phases, which is crucial for an understanding of their environmental behavior, cannot be calculated. Recently, transport phenomena was usually predicted with partition coefficient as an environmental parameter w4x. The partition coefficient K aw , relating air and aqueous concentrations of a volatile substance, is commonly referred to as Henry’s constant Ž H . w5x. Knowledge of the Henry’s law constant is essential in calculating the direction of the transfer. If the solute concentrations in the air and water are determined, it immediately gives the direction of the transfer. In cases where the solute is close to equilibrium, an accurate value of H is more essential. In this work, we suggest a simple and rapid method of determining K aw as well as H for ordinary organic compounds at environmental concentrations.
2. Theory The airrwater partition ratio is used not only to characterize the airrwater equilibrium distribution of a compound, but also to describe the rate expressions of air–water systems relate to equilibrium. The Henry’s constant Ž H . may be thought as simply the ratio of a compound’s abundance in the gas phase to that of aqueous phase at equilibrium. If we express the abundance of a compound in air and water as Ca and C w , respectively, we can obtain then so-called dimensionless Henry’s constant Ž Hc .. The H and Hc may be related to one another by adopting the ideal gas law. Hc can be expressed as described below: K aw s
Ca Cw
s Hc s
H
Ž1.
RT
The total moles Ž M . of a volatile solute added to a bubble column will be partitioned at equilibrium according to Eq. Ž2.: M s C wVw q CgVg s Cg
Vw Hc
q Vg
Ž2.
where C w s concentration of solute in water Žmolrl., Cg s concentration of the solute in gas Žmolrl., Vw s volume of water in the column, Vg s volume of headspace in the column. If two columns are prepared with different liquid volumes Vw1 and Vw2 , we may write Eqs. Ž 3. and Ž4. from Eq. Ž2.: M1 s Cg1
M2 s Cg 2
Vw1 Hc Vw 2 Hc
q Vg1
Ž3.
q Vg 2
Ž4.
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
297
We can divide Eq. Ž3. by M1 and Eq. Ž4. by M2 . The left side of each equation will be unified and then combined as:
Ž Cg1rM1 . Ž Vw1rHc . q Vg1
s Ž Cg 2rM2 . Ž Vw 2rHc . q Vg 2
Ž5.
Solving for Hc then yields: Hc s
Vw 2 y Ž Cg1rM1 . r Ž Cg 2rM2 . Vw1
Ž Cg1rM1 . r Ž Cg 2rM2 .
Vg1 y Vg 2
Ž6.
or Hc s
Vw 2 y g Vw1
g Vg1 y Vg 2
where
g s Ž Cg1rM1 . r Ž Cg 2rM2 . To avoid the injection problem of insoluble or solid solutes, all the solutes were prepared as methanol solution because most of the solutes dissolved in methanol completely. If the different mass of solute, which was prepared as methanol solution Ž stock solution. , was injected to two columns, the concentrations of headspace Ž gas phase. will be different in two columns at the equilibrium between the gas and liquid phases. Such difference allows the calculation of Hc with Eq. Ž6.. 3. Experiment 3.1. Apparatus The modified EPICS measuring system is illustrated in Fig. 1. This system was used in a controlled room temperature Ž 258C.. The air was introduced into the column by a Cole–Parmer Model
Fig. 1. Schematic diagram of experimental system.
298
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
Masterflex LrS peristaltic pump. The injection and sampling port were sealed with a screw cap and silicone-rubber septum. The thermostated water at an accuracy of 25 " 0.18C was circulated in a water jacket of column using the MONO-TECH Model MRC-213D thermostat. After the equilibrium was reached between two phases, the concentration of solute in the head space were analyzed by Hewlett Packard 5890 ser. II gas chromatography. 3.2. Materials Commercial grade organic compounds used in this experiment were supplied from Aldrich and Merck. They were dried before use, using a 3A molecular sieve. The purity of each chemical was more than 99.8 wt.% by gas chromatographic analysis. 3.3. Procedure Distilled water Ž15 ml or 30 ml. was introduced to each bubble column by using a motor-driven burette at an accuracy of "0.01 ml. Methanol was used to prepare the stock solution as a solvent. It did not affect partitioning of solute between air and water phase because only very small amounts of stock solution will be injected to water phase in columns. It is explained well in Ref. w5x. The prepared stock solutions were injected into each column with a 0.1 ml gas-tight syringe. Quantitatively precise determination of injected mixture was made gravimetrically; the 0.1 ml syringe used was weighed before and after injection to the column. Air was then circulated in isolated bubble columns until equilibrium was reached at the programmed time Žabout 1 h.. The concentrations of headspace Ž gas phase. of solute compounds in equilibrated columns were analyzed two times by gas chromatography. Then K aw and Henry’s constant were calculated with Eq. Ž6.. 4. Results The accuracy of this method is primarily dependent on how real the approach is to the true equilibrium state. In order to evaluate it, the dependence of airflow rate and the ratio of water volume
Table 1 Comparison of experimental log K aw with reference and EPICS values Compounds n-alkane n-hexane n-heptane n-octane n-nonane a
Ref. w6x. Ref. w7x. c Ref. w8x. b
Exp. value
1.8201 1.9498 2.0799 2.2682
EPICS value c
Ref. value 1a
2b
1.7515 1.9115 2.0815 2.3132
1.8362 1.9675 2.0829 2.3047
1.7391 1.8692 2.0815 2.3281
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
299
Table 2 K aw and Henry’s constantŽ H . for n-alkanes at 258C Compounds
Molar volume Žcm3rmol.
K aw
H ŽkPa m3rmol.
n-alkane n-hexane n-heptane n-octane n-nonane
86.17 100.21 114.23 128.26
66.0846 89.0841 120.1987 185.4385
163.8118 220.8251 297.9508 459.6685
in two columns were carefully analyzed. As a result of the experiment with p-xylene and some alkanes, the optimal condition of the airflow rate was 200 mlrmin, and it needs only about 1 h for equilibrium partitioning of experimented chemicals between two phases. It reduced measuring time by at least one-third as compared to conventional EPICS method which needs about 3 to 24 h for experimental systems. Because conventional EPICS method is a static method in which equilibrium partitioning will be reached by stirring the water phase with a magnetic bar in a serum bottle. However, our modified EPICS method is a dynamic method which helps solute reach equilibrium state between air and water phase more rapidly by circulating air through water in bubble columns. Since water volume ratio between two columns had no significant meaning, the volume ratio of 1:2 Žcolumn 1:column 2. was therefore arbitrarily selected in this work. The accuracy and reproducibility of this method were reliable since measured K aw data agreed very well with literature values Ž within 1% average deviation for some n-alkanes, as shown in
Table 3 The K aw and Henry’s constant Ž H . for aromatic and chlorinated compounds at 258C Compounds
Molar volume Žcm3rmol.
K aw
H ŽkPa m3rmol.
Aromatic compound Benzene1 Toluene 2 p-xylene 3 Ethylbenzene 4 n-buthylbenzene5 n-penthylbenzene6 Chlorobenzene7 o-dichlorobenzene8 1,2,4-trichlorobenzene9 1,2,3,4-tetrachlorobenzene10
89.41 106.85 123.93 140.4 184.8 207 102.24 113.05 125.1 127
0.2345 0.2721 0.2818 0.3277 0.5485 0.6568 0.2175 0.0874 0.1513 0.1165
0.5806 0.6748 0.6991 0.9432 1.3578 1.6282 0.5370 0.2127 0.3752 0.2890
Chlorinated compound Dichloromethane11 Trichloromethane12 Tetrachloromethane13 cis-Dichloroethylene14 trans-Dichloroethylene15 Trichloroethylene16 Tetrachloroethylene17
64.1 90.67 97.09 75.1 76.6 90.01 102.71
0.0985 0.1496 1.0540 0.2721 0.2561 0.4256 0.7582
0.2441 0.3708 2.6120 0.6745 0.6348 1.0550 1.8794
300
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
Fig. 2. K aw values for alkyl benzene at 258C ŽArabic numerals refer to chemicals in Table 2..
Table 1.. The K aw and H for n-alkanes, aromatic and chlorinated compounds were measured and listed in Tables 2 and 3. The superscripted numbers indicating compounds in Table 3 are also valid in the following figures. The relationships between K aw Ž H . and molar volume, vapor pressure and water solubility of solute were also analyzed. The K aw and H were linearly proportional to molar
Fig. 3. K aw for chlorinated compounds at 258C ŽArabic numerals refer to chemicals in Table 2..
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
301
Fig. 4. K aw for n-alkane at 258C.
volume except cis and trans dichloroethylene, as shown in Figs. 2–4 and they were inversely proportional to vapor pressure and water solubility except Cl substituted benzenes, as shown in Figs. 5–7. Cl substituted benzenes did not show any dependency to molar volume, vapor pressure and water solubility. The K aw was changed by the difference in molecular structure.
Fig. 5. Henry’s constant vs. vapor pressure and solubility for n-alkane at 258C.
302
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
Fig. 6. Henry’s constant vs. vapor pressure for aromatic and chlorinated compounds at 258C ŽArabic numerals refer to chemicals in Table 2..
Fig. 7. Henry’s constant vs. solubility for aromatic and chlorinated compounds at 258C ŽArabic numerals refer to chemicals in Table 2..
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
303
5. Conclusion Our modified EPICS method gives accurate and much more rapid K aw data than conventional EPICS method. In the experimented systems, the K aw were linearly proportional to molar volume and inversely proportional to vapor pressure and water solubility except Cl substituted benzenes. The Cl substituted benzenes did not show any special relationships with molar volume, vapor pressure and water solubility. It may have been caused by the difference of intermolecular forces.
6. List of symbols A, B, C Ci Cs fi H Hc n Mw P Pis pi R T Vi Õi xi yi
Antoine constant concentration of solute in i phase solubility in water fugacity in i phase Henry’s constant dimensionless Henry’s constant total amount of solute molecular weight total pressure saturated vapor pressure of component i partial pressure of component i gas constant absolute temperature volume of i phase molar volume of chemical in i phase liquid phase mole fraction of the component i vapor phase mole fraction of the component i
Acknowledgements The authors appreciate the Korea Science and Engineering Foundation for the financial support ŽGrant No. KOSEF 961-1109-053-2. .
References w1x A.W. Andren, in: D. Mackey, S. Paterson, S.J. Eisenreich, M.S. Simmons ŽEds.., Physical Behavior of PCBs in the Great Lakes, Ann Arbor Science, Ann Arbor, MI, 1983, 127–140. w2x P.V. Doskey, A.W. Andren, Environ. Sci. Technol. 15 Ž1981. 705–711. w3x W.B. Neely, Gas transfer at water surface, Sci. Total Environ. Ž1977. 117–129. w4x D. Mackay, Multimedia Environmental Model; The Fugacity Approach, Lewis Pub., 1991.
304
S.-A. Ryu, S.-J. Park r Fluid Phase Equilibria 161 (1999) 295–304
w5x J.M. Gossett, Measurement of Henry’s law constant for C 1 and C 2 chlorinated hydrocarbon, Environ. Sci. Technol. 21 Ž1987. 202–208. w6x R.P. Schwarzenbach, P.M. Gschwend, D.M. Imboden Environmental Organic Chemistry, Wiley, 1993. w7x D. Mackay, W.Y. Shiu, A critical review of Henry’s law constants for chemicals of environmental interest, J. Phys. Chem. Ref. Data 10 Ž1981. 4–30. w8x S.J. Park, S.D. Hann, S.A. Ryu, Measurement of airrwater partition coefficient ŽHenry’s law constant. by using EPICS method and their relationship with vapor pressure and water solubility, J. Kor. Inst. Chem. Eng. 35 Ž1997. 915–920.