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Ozonization of ethanolamine in aqueous medium
PII: S0043-1354(99)00245-6
Wat. Res. Vol. 34, No. 4, pp. 1340±1344, 2000 # 2000 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0043-1354/00/$ - see front matter
www.elsevier.com/locate/watres
OZONIZATION OF ETHANOLAMINE IN AQUEOUS MEDIUM Z. PARISHEVA* and A. DEMIREV Department of Chemistry, Technical University of Plovdiv, 8 Dustabanov St, Plovdiv, 4000, Bulgaria (First received 1 September 1998; accepted in revised form 1 May 1999) AbstractÐThe destruction of ethanolamine by ozonation in aqueous medium was studied. The eectiveness of ozonation was estimated by the degree of conversion a [%], and by the rate constant, k [minÿ1], which was calculated from a ®rst-order kinetic equation. The activation energy of the process was calculated from the rate constant vs temperature relationship according to the Arrhenius equation. The eect of pH of the medium and temperature, T, on the eectiveness of ozonation was investigated. It was established that ozonation of ethanolamine is most eective at T = 283 K and pH=11.0. Under these conditions the rate constant has its high value 0.118 minÿ1. At pH=11.0 the eect of the temperature on the rate constant is stronger which can be explained with the high value of the activation energy of the process. The amount of the residual ozone in gaseous phase was determined and the possibility of its decomposition on a catalyst of higher nickel oxide was studied. The eect of the amount of catalyst on the decomposition of the residual ozone was examined. The quantity of the catalyst needed for the complete decomposition of the residual gaseous ozone was estimated by the achieved degree of conversion of residual ozone a=100%. # 2000 Elsevier Science Ltd. All rights reserved Key wordsÐozone, ethanolamine, degree of conversion, residual ozone, catalytic decomposition, rate constant, activation energy
INTRODUCTION
The application of ozone for puri®cation of industrial waste waters from various manufactures is based on its high oxidation-reduction potential which determines its destructive action on a wide range of organic and inorganic compounds. The destruction of various organics and inorganics with ozone is extensively discussed in the literature. Beltran and Gonzalez (1992) studied the ozonation of two types of phenols at dierent pH values and proved that the ozonation reaction is fast of second order. Fehn and Heid (1994) examined the oxidation of cyanides with ozone mixed with hydrogen peroxide (H2O2) at pH values ranging from 4 to 11.5. They stated that in the presence of H2O2 and at increasing pH values the uptake rate of ozone increases. Investigating ozonation of cyanide in alkaline aqueous solutions buffered at pH=11.8 Zeevalkink et al. (1980) concluded that the reaction rate can be described by an equation which is of ®rst order in ozone and independent of the cyanide concentration. The ozonation of amines is investigated by *Author to whom all correspondence should be addressed. Tel.: +359-32-23-6515; e-mail: [email protected]
Hoigne and Bader (1983) under the assumption that the amino group is the only site for reaction with ozone. Elmghari-Tabib et al. (1982) studied the oxidation of a large group of fatty and aromatic amines with ozone and proposed a mechanism of their oxidation. Amines belong to the group of brighteners used in metal coating. After their release into the waste waters of galvanic manufactures they can be decomposed by ozonation. Even using the most modern systems for ozone dispersion into waste waters, the achieved amount of dissolved ozone is 92±97%. The quantity of unreacted ozone and ozone lost in the system (about 5%) ranges from 8 to 13% of the total amount of ozone produced. Given that ozone is a toxic gas, with a limiting allowable concentration (LAC) in a working environment of 0.20 mg mÿ3, the accumulation of ozone in the working environment is inadmissible. The amount of accumulated unreacted ozone (residual ozone) in the gaseous phase can be diminished through adsorption, thermal or catalytic decomposition (Orlov, 1984). The objective of the present work is to study the possibility of ethanolamine destruction in aqueous medium by ozonation and catalytic decomposition of residual gaseous ozone.
1340
Ozonization of ethanolamine
1341
Fig. 1. Scheme of the experimental set-up: 1=Control panel; 2=Ozonizer; 3=The solution studied; 4=Catalyst; 5=Ozone trap. MATERIALS AND METHODS
The choice of ethanolamine was determined by its use as a brightener used in various metal coatings. The experiments were carried out using model solution with initial concentration C0=145 mg dmÿ3, which corresponds to the average concentration of amines in industrial waste waters (Ministry of the Environment, 1996). The concentration of the amine before and during the oxidation was determined by spectrophotometry. The determination was based on the reaction of lower amines with bromcresol red and the formation of a coloured compound which was extracted with chloroform (Lurie and Ribnikova, 1977). The absorption maximum of the product obtained was at lmax=420 nm. The absorption was measured on a Perkin±Elmer l vis/uv. The relative standard deviation of the method is 26.0%. Ozone was obtained from a laboratory ozonizer described elsewhere (Parisheva and Demirev, 1995). The pre-treatment of the air for ozonation consisted of passing it through silicagel. The ozone concentration acquired from the generator was 5 mg lÿ1. The amount of ozone produced was regulated only by changing the voltage of the generator. The constant ozone-air ¯ow was applied to the solution through a porous glass plate of 20±30 mm pore diameter. All the experiments were executed at ozone-air ¯ow rate 20 ml minÿ1. The scheme of the experimental set-up is shown in Fig. 1. The amount of ozone before (produced ozone) and after treatment of the solution (residual gaseous ozone) was determined in liquid phase by iodimetry (Herch and Denkinger, 1963). The residual gaseous ozone was decomposed on a catalyst whose active phase was nickel oxide. The preparation and characterisation of the catalyst are described by Christoskova et al. (1995). The catalyst used was with a high content of total and surface active oxygen. The amount of active oxygen, total (O) and surface OS ), was determined by the procedures described by Kanungo (1979) and Nikagawa et al. (1962). The chemical analysis indicated that the content of total oxygen, O,
was approximately 7% and was basically on the surface of the oxide. The speci®c surface area of the catalyst (particle size 0.3±0.6 mm) determined by conventional low-temperature nitrogen adsorption according to the BET method was 30 m2 gÿ1. The catalytic decomposition of the residual ozone was carried out under the following conditions: volume of the catalyst layer 0.4 cm3, ¯ow rate of the ozone-air mixture 15 ml minÿ1, contact time 0.5 s, temperature of the catalyst layer 293 K. The eectiveness of ozonation was estimated by the degree of conversion, a [%], of ethanolamine, and by the rate constant k [minÿ1]. The rate constant k [minÿ1] was calculated from the following ®rst order kinetic equation: k
1 c0 In t c
The linear course of the ln c0/c vs time plot (Fig. 2) evidences that the oxidation runs according to a ®rst order reaction with respect to ethanolamine. For testing the ®rst order rate equation with respect to amine the experiments were carried out with an excess of ozone. Our preliminary experiments showed that 1 mmol ozone oxidizes 1.5 mmol amine. The activation energy of the process was calculated from the rate constant vs temperature relationship according to the Arrhenius equation: EA
RT1 T2 KT 1 ln DT KT 2
The eect of the pH of the medium on the eectiveness of the ozonation was studied. The eect of the catalyst amount on the eectiveness of the decomposition of the residual ozone in the gaseous phase was also examined. The working pH values were selected with the consideration that galvanic manufactures waste waters containing amines as brighteners are generally strongly alkaline.
Fig. 2. The relationship ln(Co/C)=f(t): pH=8.5; w T = 283 K; r T = 298 K.
1342
Z. Parisheva and A. Demirev
Fig. 3. Dependence of the concentration and degree of the conversion of ethanolamine on the time of ozonation: pH=8.5, solution volume 0.03 dm3; q,Q T = 283 K; r,R T = 298 K. RESULTS AND DISCUSSION
The results of ethanolamine ozonation in aqueous solution and of the catalytic decomposition of the residual ozone are presented in Figs 3 and 4, and 5 and in Tables 1 and 3. The kinetic curves in Fig. 3 show the decrease in the concentration of the amine as a result of ozonation at pH=8.5. The degree of conversion a [%], was calculated from the formula (c0ÿc)/c0. Thus the graphical relationship a [%], vs time contains information about turnover, [%] vs time. The data from Fig. 3 indicate that under the studied conditions the decrease in temperature from 298 to 283 K (which leads to an increase in the solubility of ozone) has practically no in¯uence on the eectiveness of ozonation. In order to ®nd conditions for the complete destruction of ethanolamine some experiments were
carried out at pH=11.0. The data presented in Fig. 4 indicate that ozonation of amine is more ecient at T = 283 K and pH of the solution of 11.0. The results concerning the eect of pH and temperature are summarised in Table 1. It can be seen that the eect of the temperature on the rate constant is stronger when the process is carried out at pH=11.0. The dierent rate constants re¯ect the impact of the amount of both molecular ozone and hydroxyl radicals. The highest concentrations of dissolved ozone corresponding to a negligible eect of hydroxyl radicals can be expected at pH 8.5 and T = 289 K. In this case the lowest rate constant re¯ects degradation processes of molecular ozone. In contrast, the formation of hydroxyl radicals will be favoured at pH 11.0 and T = 283 K and molecular ozone is of minor importance. The rate constant
Fig. 4. Dependence of the concentration and degree of the conversion of ethanolamine on the time of ozonation: pH=11.0, solution volume 0.03 dm3; q,Q T = 283 K; r,R T = 298 K.
Ozonization of ethanolamine
1343
Table 1. The in¯uence of pH and temperature on the degree of conversion a %, rate constant k [minÿ1] and activation energy E, kJ molÿ1. Initial ethanolamine concentration 145 mg dmÿ3 pH
8.5
11.0
Time of treatment (min)
T = 283 K
Activation energy (kJ molÿ1)
T = 298 K
C (mg dmÿ3)
a (%)
k a (minÿ1)
C (mg dmÿ3)
a (%)
k a (minÿ1)
145 93 79 57 43 33 25 145 67 29 21 18 18 17
± 35.9 45.5 60.7 70.3 77.2 82.8 ± 53.8 80.0 85.5 87.6 87.6 88.3
0.060
145 123 99 67 53 36 30 145 113 87 79 50 34 33
± 15.2 31.7 53.8 63.4 75.2 79.3 ± 22.1 40.0 45.5 65.5 76.5 77.2
0.045
13.46
0.051
39.22
0 5 10 15 20 25 30 0 5 10 15 20 25 30
0.118
a
Average value of the rate constant.
is highest indicating the occurrence of radical induced processes. The amounts of the ozone before passing through the solution of the amine (produced ozone) and afterwards (residual ozone) are given in Table 2. The quantity of the residual ozone increases with the increase in the degree of conversion of ethanolamine. That is why the possibility of a catalytic decomposition of the residual ozone on a catalyst, a higher nickel oxide, was studied. The eect of the catalyst quantity on the degree of decomposition of ozone was examined. The results are presented in Fig. 5 and in Table 3. Degree of conversion a=100% is only achieved at the beginning of ozonation for catalyst amounts of 0.1 and 0.3 g. The quantity of catalyst needed
for the complete decomposition of the residual ozone produced during the ozonation of the solution is 0.5 g. CONCLUSION
The obtained results indicate the possibility of decomposing ethanolamine in aqueous solution by ozonation. The eectiveness of the process estimated by the degree of conversion a [%], of ethanolamine is highest at pH 11.0 and T = 283 K. The results can be used as a base for developing a method for puri®cation of waste waters from galvanic manufactures where ethanolamine is used as a brightener. Some basic points of such a method are as follows:
Fig. 5. Dependence of residual ozone quantity on the quantity of catalyst: R without catalyst (see Table 2); q with 0.03 g catalyst; w with 0.06 g catalyst; Q with 0.1 g catalyst; r with 0.3 g catalyst; * with 0.5 g catalyst.
1344
Z. Parisheva and A. Demirev Table 2. Ozone amount (mmol lÿl)
Time of treatment, min Ozone amount, mmol lÿ1 Residual ozone, mmol lÿ1
5
10
15
20
25
30
0.325 0.158
0.625 0.420
0.913 0.613
1.050 0.992
1.366 1.038
1.679 1.330
Table 3. Decomposition of residual ozone (%) on increasing quantity of catalyst (g) Time of min
5 10 15 20 25 30
Residual ozone (mmol lÿ1)
Degree of decomposition of ozone (%)
0.3a
0.06a
0.10a
0.30a
0.50a
0.01 0.14 0.24 0.40 0.45 0.56
0.00 0.07 0.17 0.28 0.36 0.49
0.00 0.03 0.14 0.26 0.38 0.45
0.00 0.00 0.00 0.01 0.05 0.15
0.00 0.00 0.00 0.00 0.00 0.01
0.03a 88.6 66.7 60.1 59.5 56.2 57.9
0.06a 94.3 83.3 72.3 71.8 64.5 63.2
0.10a0.30a 100. 91.7 77.2 73.6 62.9 65.8
0.50a 100. 100. 100. 98.2 94.9 88.2
100. 100. 100. 100. 100. 98.6
a
Quantity of the catalyst (g).
1. Destruction by ozonation. 2. Decomposition of the residual ozone on a catalyst of a higher nickel oxide, until LAC is reached. 3. Catalyst recovery at regular intervals. For better understanding of the kinetics of the degradation process, the degradation pathway and the potential metabolites of ethanolamine will be investigated in our further studies. REFERENCES
Beltran F. and Gonzalez M. (1992) Study of ozonation of organics in water using unsteady state turbulent absorption theories. J.Environ. Sci. and Health 6, 1433±1452. Christoskova St, Danova N., Georgieva M., Argirov O. and Mehandjiev D. (1995) Investigation of nickel oxide system for heterogeneous oxidation of organic compounds. Appl. Catal. A General 128, 219±229. Elmghari-Tabib M., Laplanche A., Venien F. and Martin G. (1982) Ozonation of amines in aqueous solutions. Water Res. 16, 223±229. Fehn J. and Heid R. (1994) Oxidation of cyanide with
ozoneÐan alternative to the hypochlorite usage. Galvanotechnik 10, 3267±3273. Herch P. and Denkinger K. (1963) Galvanic monitoring of ozone in air. Anal. Chem. 35, 897±902. Hoigne J. and Bader H. (1983) Rate constants of reactions of ozone with organic and inorganic compounds. Water Res. 2, 185±189. Kanungo S. (1979) Physicochemical properties of MnO2 and MnO2±CuO and their relationship with the catalytic activity for H2O2. Decomposition and co-oxidation. J. Catal. 58, 419±435. Lurie M. and Ribnikova A. (1977) Chemical Analysis of Natural Waters. Himia, Moscow. Bulletin for the environment condition in Bulgaria (1996) ed. Ministry of the Environment, So®a. Nikagawa K., Konaka R. and Nakata T. (1962) Oxidation with nickel peroxide. Oxidation of alcohols. J. Org. Chem. 27, 1597±1601. Orlov V. (1984) Ozonation of Water. Stroyizdat, Moscow. Parisheva Z. and Demirev A. (1995) The eect of ozone on harmful oxidizable substances in industrial waste gases. Environ. Protec. Eng. 1, 137±144. Zeevalkink J., Visser D., Arnoldy P. and Boelhouwer C. (1980) Mechanism and kinetics of cyanide ozonation in water. Water Res. 10, 1375±1385.
Wat. Res. Vol. 34, No. 4, pp. 1340±1344, 2000 # 2000 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0043-1354/00/$ - see front matter
www.elsevier.com/locate/watres
OZONIZATION OF ETHANOLAMINE IN AQUEOUS MEDIUM Z. PARISHEVA* and A. DEMIREV Department of Chemistry, Technical University of Plovdiv, 8 Dustabanov St, Plovdiv, 4000, Bulgaria (First received 1 September 1998; accepted in revised form 1 May 1999) AbstractÐThe destruction of ethanolamine by ozonation in aqueous medium was studied. The eectiveness of ozonation was estimated by the degree of conversion a [%], and by the rate constant, k [minÿ1], which was calculated from a ®rst-order kinetic equation. The activation energy of the process was calculated from the rate constant vs temperature relationship according to the Arrhenius equation. The eect of pH of the medium and temperature, T, on the eectiveness of ozonation was investigated. It was established that ozonation of ethanolamine is most eective at T = 283 K and pH=11.0. Under these conditions the rate constant has its high value 0.118 minÿ1. At pH=11.0 the eect of the temperature on the rate constant is stronger which can be explained with the high value of the activation energy of the process. The amount of the residual ozone in gaseous phase was determined and the possibility of its decomposition on a catalyst of higher nickel oxide was studied. The eect of the amount of catalyst on the decomposition of the residual ozone was examined. The quantity of the catalyst needed for the complete decomposition of the residual gaseous ozone was estimated by the achieved degree of conversion of residual ozone a=100%. # 2000 Elsevier Science Ltd. All rights reserved Key wordsÐozone, ethanolamine, degree of conversion, residual ozone, catalytic decomposition, rate constant, activation energy
INTRODUCTION
The application of ozone for puri®cation of industrial waste waters from various manufactures is based on its high oxidation-reduction potential which determines its destructive action on a wide range of organic and inorganic compounds. The destruction of various organics and inorganics with ozone is extensively discussed in the literature. Beltran and Gonzalez (1992) studied the ozonation of two types of phenols at dierent pH values and proved that the ozonation reaction is fast of second order. Fehn and Heid (1994) examined the oxidation of cyanides with ozone mixed with hydrogen peroxide (H2O2) at pH values ranging from 4 to 11.5. They stated that in the presence of H2O2 and at increasing pH values the uptake rate of ozone increases. Investigating ozonation of cyanide in alkaline aqueous solutions buffered at pH=11.8 Zeevalkink et al. (1980) concluded that the reaction rate can be described by an equation which is of ®rst order in ozone and independent of the cyanide concentration. The ozonation of amines is investigated by *Author to whom all correspondence should be addressed. Tel.: +359-32-23-6515; e-mail: [email protected]
Hoigne and Bader (1983) under the assumption that the amino group is the only site for reaction with ozone. Elmghari-Tabib et al. (1982) studied the oxidation of a large group of fatty and aromatic amines with ozone and proposed a mechanism of their oxidation. Amines belong to the group of brighteners used in metal coating. After their release into the waste waters of galvanic manufactures they can be decomposed by ozonation. Even using the most modern systems for ozone dispersion into waste waters, the achieved amount of dissolved ozone is 92±97%. The quantity of unreacted ozone and ozone lost in the system (about 5%) ranges from 8 to 13% of the total amount of ozone produced. Given that ozone is a toxic gas, with a limiting allowable concentration (LAC) in a working environment of 0.20 mg mÿ3, the accumulation of ozone in the working environment is inadmissible. The amount of accumulated unreacted ozone (residual ozone) in the gaseous phase can be diminished through adsorption, thermal or catalytic decomposition (Orlov, 1984). The objective of the present work is to study the possibility of ethanolamine destruction in aqueous medium by ozonation and catalytic decomposition of residual gaseous ozone.
1340
Ozonization of ethanolamine
1341
Fig. 1. Scheme of the experimental set-up: 1=Control panel; 2=Ozonizer; 3=The solution studied; 4=Catalyst; 5=Ozone trap. MATERIALS AND METHODS
The choice of ethanolamine was determined by its use as a brightener used in various metal coatings. The experiments were carried out using model solution with initial concentration C0=145 mg dmÿ3, which corresponds to the average concentration of amines in industrial waste waters (Ministry of the Environment, 1996). The concentration of the amine before and during the oxidation was determined by spectrophotometry. The determination was based on the reaction of lower amines with bromcresol red and the formation of a coloured compound which was extracted with chloroform (Lurie and Ribnikova, 1977). The absorption maximum of the product obtained was at lmax=420 nm. The absorption was measured on a Perkin±Elmer l vis/uv. The relative standard deviation of the method is 26.0%. Ozone was obtained from a laboratory ozonizer described elsewhere (Parisheva and Demirev, 1995). The pre-treatment of the air for ozonation consisted of passing it through silicagel. The ozone concentration acquired from the generator was 5 mg lÿ1. The amount of ozone produced was regulated only by changing the voltage of the generator. The constant ozone-air ¯ow was applied to the solution through a porous glass plate of 20±30 mm pore diameter. All the experiments were executed at ozone-air ¯ow rate 20 ml minÿ1. The scheme of the experimental set-up is shown in Fig. 1. The amount of ozone before (produced ozone) and after treatment of the solution (residual gaseous ozone) was determined in liquid phase by iodimetry (Herch and Denkinger, 1963). The residual gaseous ozone was decomposed on a catalyst whose active phase was nickel oxide. The preparation and characterisation of the catalyst are described by Christoskova et al. (1995). The catalyst used was with a high content of total and surface active oxygen. The amount of active oxygen, total (O) and surface OS ), was determined by the procedures described by Kanungo (1979) and Nikagawa et al. (1962). The chemical analysis indicated that the content of total oxygen, O,
was approximately 7% and was basically on the surface of the oxide. The speci®c surface area of the catalyst (particle size 0.3±0.6 mm) determined by conventional low-temperature nitrogen adsorption according to the BET method was 30 m2 gÿ1. The catalytic decomposition of the residual ozone was carried out under the following conditions: volume of the catalyst layer 0.4 cm3, ¯ow rate of the ozone-air mixture 15 ml minÿ1, contact time 0.5 s, temperature of the catalyst layer 293 K. The eectiveness of ozonation was estimated by the degree of conversion, a [%], of ethanolamine, and by the rate constant k [minÿ1]. The rate constant k [minÿ1] was calculated from the following ®rst order kinetic equation: k
1 c0 In t c
The linear course of the ln c0/c vs time plot (Fig. 2) evidences that the oxidation runs according to a ®rst order reaction with respect to ethanolamine. For testing the ®rst order rate equation with respect to amine the experiments were carried out with an excess of ozone. Our preliminary experiments showed that 1 mmol ozone oxidizes 1.5 mmol amine. The activation energy of the process was calculated from the rate constant vs temperature relationship according to the Arrhenius equation: EA
RT1 T2 KT 1 ln DT KT 2
The eect of the pH of the medium on the eectiveness of the ozonation was studied. The eect of the catalyst amount on the eectiveness of the decomposition of the residual ozone in the gaseous phase was also examined. The working pH values were selected with the consideration that galvanic manufactures waste waters containing amines as brighteners are generally strongly alkaline.
Fig. 2. The relationship ln(Co/C)=f(t): pH=8.5; w T = 283 K; r T = 298 K.
1342
Z. Parisheva and A. Demirev
Fig. 3. Dependence of the concentration and degree of the conversion of ethanolamine on the time of ozonation: pH=8.5, solution volume 0.03 dm3; q,Q T = 283 K; r,R T = 298 K. RESULTS AND DISCUSSION
The results of ethanolamine ozonation in aqueous solution and of the catalytic decomposition of the residual ozone are presented in Figs 3 and 4, and 5 and in Tables 1 and 3. The kinetic curves in Fig. 3 show the decrease in the concentration of the amine as a result of ozonation at pH=8.5. The degree of conversion a [%], was calculated from the formula (c0ÿc)/c0. Thus the graphical relationship a [%], vs time contains information about turnover, [%] vs time. The data from Fig. 3 indicate that under the studied conditions the decrease in temperature from 298 to 283 K (which leads to an increase in the solubility of ozone) has practically no in¯uence on the eectiveness of ozonation. In order to ®nd conditions for the complete destruction of ethanolamine some experiments were
carried out at pH=11.0. The data presented in Fig. 4 indicate that ozonation of amine is more ecient at T = 283 K and pH of the solution of 11.0. The results concerning the eect of pH and temperature are summarised in Table 1. It can be seen that the eect of the temperature on the rate constant is stronger when the process is carried out at pH=11.0. The dierent rate constants re¯ect the impact of the amount of both molecular ozone and hydroxyl radicals. The highest concentrations of dissolved ozone corresponding to a negligible eect of hydroxyl radicals can be expected at pH 8.5 and T = 289 K. In this case the lowest rate constant re¯ects degradation processes of molecular ozone. In contrast, the formation of hydroxyl radicals will be favoured at pH 11.0 and T = 283 K and molecular ozone is of minor importance. The rate constant
Fig. 4. Dependence of the concentration and degree of the conversion of ethanolamine on the time of ozonation: pH=11.0, solution volume 0.03 dm3; q,Q T = 283 K; r,R T = 298 K.
Ozonization of ethanolamine
1343
Table 1. The in¯uence of pH and temperature on the degree of conversion a %, rate constant k [minÿ1] and activation energy E, kJ molÿ1. Initial ethanolamine concentration 145 mg dmÿ3 pH
8.5
11.0
Time of treatment (min)
T = 283 K
Activation energy (kJ molÿ1)
T = 298 K
C (mg dmÿ3)
a (%)
k a (minÿ1)
C (mg dmÿ3)
a (%)
k a (minÿ1)
145 93 79 57 43 33 25 145 67 29 21 18 18 17
± 35.9 45.5 60.7 70.3 77.2 82.8 ± 53.8 80.0 85.5 87.6 87.6 88.3
0.060
145 123 99 67 53 36 30 145 113 87 79 50 34 33
± 15.2 31.7 53.8 63.4 75.2 79.3 ± 22.1 40.0 45.5 65.5 76.5 77.2
0.045
13.46
0.051
39.22
0 5 10 15 20 25 30 0 5 10 15 20 25 30
0.118
a
Average value of the rate constant.
is highest indicating the occurrence of radical induced processes. The amounts of the ozone before passing through the solution of the amine (produced ozone) and afterwards (residual ozone) are given in Table 2. The quantity of the residual ozone increases with the increase in the degree of conversion of ethanolamine. That is why the possibility of a catalytic decomposition of the residual ozone on a catalyst, a higher nickel oxide, was studied. The eect of the catalyst quantity on the degree of decomposition of ozone was examined. The results are presented in Fig. 5 and in Table 3. Degree of conversion a=100% is only achieved at the beginning of ozonation for catalyst amounts of 0.1 and 0.3 g. The quantity of catalyst needed
for the complete decomposition of the residual ozone produced during the ozonation of the solution is 0.5 g. CONCLUSION
The obtained results indicate the possibility of decomposing ethanolamine in aqueous solution by ozonation. The eectiveness of the process estimated by the degree of conversion a [%], of ethanolamine is highest at pH 11.0 and T = 283 K. The results can be used as a base for developing a method for puri®cation of waste waters from galvanic manufactures where ethanolamine is used as a brightener. Some basic points of such a method are as follows:
Fig. 5. Dependence of residual ozone quantity on the quantity of catalyst: R without catalyst (see Table 2); q with 0.03 g catalyst; w with 0.06 g catalyst; Q with 0.1 g catalyst; r with 0.3 g catalyst; * with 0.5 g catalyst.
1344
Z. Parisheva and A. Demirev Table 2. Ozone amount (mmol lÿl)
Time of treatment, min Ozone amount, mmol lÿ1 Residual ozone, mmol lÿ1
5
10
15
20
25
30
0.325 0.158
0.625 0.420
0.913 0.613
1.050 0.992
1.366 1.038
1.679 1.330
Table 3. Decomposition of residual ozone (%) on increasing quantity of catalyst (g) Time of min
5 10 15 20 25 30
Residual ozone (mmol lÿ1)
Degree of decomposition of ozone (%)
0.3a
0.06a
0.10a
0.30a
0.50a
0.01 0.14 0.24 0.40 0.45 0.56
0.00 0.07 0.17 0.28 0.36 0.49
0.00 0.03 0.14 0.26 0.38 0.45
0.00 0.00 0.00 0.01 0.05 0.15
0.00 0.00 0.00 0.00 0.00 0.01
0.03a 88.6 66.7 60.1 59.5 56.2 57.9
0.06a 94.3 83.3 72.3 71.8 64.5 63.2
0.10a0.30a 100. 91.7 77.2 73.6 62.9 65.8
0.50a 100. 100. 100. 98.2 94.9 88.2
100. 100. 100. 100. 100. 98.6
a
Quantity of the catalyst (g).
1. Destruction by ozonation. 2. Decomposition of the residual ozone on a catalyst of a higher nickel oxide, until LAC is reached. 3. Catalyst recovery at regular intervals. For better understanding of the kinetics of the degradation process, the degradation pathway and the potential metabolites of ethanolamine will be investigated in our further studies. REFERENCES
Beltran F. and Gonzalez M. (1992) Study of ozonation of organics in water using unsteady state turbulent absorption theories. J.Environ. Sci. and Health 6, 1433±1452. Christoskova St, Danova N., Georgieva M., Argirov O. and Mehandjiev D. (1995) Investigation of nickel oxide system for heterogeneous oxidation of organic compounds. Appl. Catal. A General 128, 219±229. Elmghari-Tabib M., Laplanche A., Venien F. and Martin G. (1982) Ozonation of amines in aqueous solutions. Water Res. 16, 223±229. Fehn J. and Heid R. (1994) Oxidation of cyanide with
ozoneÐan alternative to the hypochlorite usage. Galvanotechnik 10, 3267±3273. Herch P. and Denkinger K. (1963) Galvanic monitoring of ozone in air. Anal. Chem. 35, 897±902. Hoigne J. and Bader H. (1983) Rate constants of reactions of ozone with organic and inorganic compounds. Water Res. 2, 185±189. Kanungo S. (1979) Physicochemical properties of MnO2 and MnO2±CuO and their relationship with the catalytic activity for H2O2. Decomposition and co-oxidation. J. Catal. 58, 419±435. Lurie M. and Ribnikova A. (1977) Chemical Analysis of Natural Waters. Himia, Moscow. Bulletin for the environment condition in Bulgaria (1996) ed. Ministry of the Environment, So®a. Nikagawa K., Konaka R. and Nakata T. (1962) Oxidation with nickel peroxide. Oxidation of alcohols. J. Org. Chem. 27, 1597±1601. Orlov V. (1984) Ozonation of Water. Stroyizdat, Moscow. Parisheva Z. and Demirev A. (1995) The eect of ozone on harmful oxidizable substances in industrial waste gases. Environ. Protec. Eng. 1, 137±144. Zeevalkink J., Visser D., Arnoldy P. and Boelhouwer C. (1980) Mechanism and kinetics of cyanide ozonation in water. Water Res. 10, 1375±1385.