Volume 7, Issue 2 (June 2022)
J Environ Health Sustain Dev 2022, 7(2): 1676-1683 |
Back to browse issues page
Download citation:
BibTeX | RIS | EndNote | Medlars | ProCite | Reference Manager | RefWorks
Send citation to:
BibTeX | RIS | EndNote | Medlars | ProCite | Reference Manager | RefWorks
Send citation to:
Dolatabadi M, Ghorbanian A, Ahmadzadeh S. Degradation of High-Concentration of Perchloroethylene from Aqueous Solution Using Electro-Fenton Process. J Environ Health Sustain Dev 2022; 7 (2) :1676-1683
URL: http://jehsd.ssu.ac.ir/article-1-442-en.html
URL: http://jehsd.ssu.ac.ir/article-1-442-en.html
Pharmaceutics Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran.
Keywords: Aqueous Solution, Degradation, Electro-Fenton Process, Hydroxyl Radical, Perchloroethylene.
Full-Text [PDF 333 kb]
(253 Downloads)
| Abstract (HTML) (691 Views)
.PNG)
Figure 1: Effect of solution pH on PCE degradation (Conditions: PCE concentration of 5 mg L-1, the current density of 6 mA cm-2, and H2O2 concentration of 30 µL)
.PNG)
Figure 2: Effect of current density on PCE degradation (Conditions: PCE concentration of 5 mg L-1, solution pH of 5, and H2O2 concentration of 30 µL)
.PNG)
Figure 3: Effect of H2O2 concentration on PCE degradation (Conditions: PCE concentration of 5 mg L-1, solution pH of 5, and current density of 8 mA cm-2)
.PNG)
Figure 4: Effect of PCE concentration on PCE degradation (Conditions: solution pH of 5, current density of 8 mA cm-2, and H2O2 concentration of 50 µL)
.PNG)
Figure 5: PCE degradation using EF process in the presence of different radical scavengers
Full-Text: (216 Views)
Degradation of High-Concentration of Perchloroethylene from Aqueous Solution Using Electro-Fenton Process
Maryam Dolatabadi 1, 2, Akram Ghorbanian 3, Saeid Ahmadzadeh 4, 5*
1 Student Research Committee, Kerman University of Medical Sciences, Kerman, Iran.
2 Environmental Science and Technology Research Center, Department of Environmental Health Engineering, School of Public Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.
3 Department of Environmental Health Engineering, Faculty of Health and Research Center for Health Sciences, Hamadan University of Medical Sciences, Hamadan, Iran.
4 Pharmaceutics Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran.
5 Pharmaceutical Sciences and Cosmetic Products Research Center, Kerman University of Medical Sciences, Kerman, Iran.
Maryam Dolatabadi 1, 2, Akram Ghorbanian 3, Saeid Ahmadzadeh 4, 5*
1 Student Research Committee, Kerman University of Medical Sciences, Kerman, Iran.
2 Environmental Science and Technology Research Center, Department of Environmental Health Engineering, School of Public Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.
3 Department of Environmental Health Engineering, Faculty of Health and Research Center for Health Sciences, Hamadan University of Medical Sciences, Hamadan, Iran.
4 Pharmaceutics Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran.
5 Pharmaceutical Sciences and Cosmetic Products Research Center, Kerman University of Medical Sciences, Kerman, Iran.
| A R T I C L E I N F O | ABSTRACT | |
| ORIGINAL ARTICLE | Introduction: Perchloroethylene (PCE) is one of the most well-known chlorinated organic compounds recently detected in aqueous environments. The presence of PCE in aquatic ecosystems has caused many health problems and environmental challenges. Therefore, its removal and treatment from aqueous environments are essential. Materials and Methods: The electro-Fenton (EF) process was carried out in a cylindrical reactor containing 250 mL contaminated water with PCE. The effects of parameters, including solution pH (3-12), current density (2-10 mA cm-2), H2O2 concentration (20-70 µL H2O2 per 250 mL sample.), PCE concentration (5-50 mg L-1), and electrolysis time (1-15 min) on PCE degradation were investigated. The kinetics and radical’s scavenger of the EF process were examined to detect the exact mechanism of PCE degradation. Results: The degradation of the PCE of 98.1% was obtained in the optimum condition, including solution pH of 5, the current density of 8 mA cm-2, H2O2 concentration of 50 µL per 250 mL sample, PCE concentration of 15 mg L-1, and electrolysis time of 10 min. The kinetics studies of the EF process indicated that the obtained results were in satisfactory agreement with the first-order model (R2 = 0.9858, Kapp = 0.2822). Also, the addition of ethanol and tertiary butanol caused an inhibiting effect. Conclusion: The EF process was effectively applied to degrade PCE from polluted water as an efficient technique. The obtained results indicated that the generation of •OH throughout the EF process was the key mechanism that controlled the EF process. |
|
Article History: Received: 05 March 2022 Accepted: 20 May 2022 |
||
*Corresponding Author: Saeid Ahmadzadeh Email: chem_ahmadzadeh@yahoo.com Tel: +983431325241 |
||
Keywords: Aqueous Solution, Degradation, Electro-Fenton Process, Hydroxyl Radical, Perchloroethylene |
Citation: Dolatabadi M, Ghorbanian A, Ahmadzadeh S. Degradation of High-Concentration of Perchloroethylene from Aqueous Solution Using Electro-Fenton Process. J Environ Health Sustain Dev. 2022; 7(2): 1676-83.
Introduction
Chlorinated organic compounds (COCs) are the important group of organic compounds that are persistent and resistant to decomposition in the environment. They have caused many health problems and environmental challenges. Among COCs, perchloroethylene (PCE) is one of the most frequently found COCs in environment 1, 2. More than 520,000 tons of PCE are used annually worldwide. Among the various industries, the laundry industry and dry-cleaning activity have the highest consumption of PCE. Of the total PCE, 50% was used for the dry-cleaning activity, 30% for chemical polymerization, 15% for metal cleaning and degreasing, and 5% for other activities 3. Many toxicological and epidemiological studies have shown that PCE is toxic and carcinogenic. PCE exposure is related to various cancers, including cervical, kidney, esophageal cancer, and non-Hodgkin's lymphoma. NIOSH recognizes PCE as a carcinogen for humans, and also IARC grouped this compound in carcinogenic substances of the A-2 group (probable carcinogens) 4. The United States Environmental Protection Agency has issued its maximum contaminant level at 5 μg L-1 by the Safe Drinking Water Act 5. Many researchers in water and wastewater treatment have conducted considerable and extensive studies to remove and treat PCE from water sources. Conventional water and wastewater treatment processes have not been effective in removing PCE. Among different water and wastewater treatment processes, reverse osmosis, adsorption, and advanced oxidation processes (AOPs)have shown suitable performance for the degradation of PCE from contaminated water 3, 6.
AOP processes have a special place in water and wastewater treatment among the mentioned techniques. AOPs can effectively degrade and mineralize the resistant organic pollutants by generating strong oxidants, such as hydroxyl radicals (E0 = 2.80 V/SHE) 7. Furthermore, recently AOPs as an environmentally friendly method received extraordinary attention because of their high efficiency for removing non-biodegradable organic pollutants from aquatic environments, such as wastewater, ground, and surface water by the in-situ generation of the •OH as the oxidizing agent. Among the AOPs, the Fenton reagent (mixture of H2O2 and Fe2+ ion) has attracted significant attention due to its strong oxidative capacity on organic contaminants 8, 9. The main disadvantages of using the electro-Fenton (EF) process in water and wastewater treatment are, on the one hand, dependence on electrical energy and, on the other hand, the management of the produced sludge and also the neutralization of the treated effluent after the process. The EF process is the electrochemically assisted Fenton’s reaction (reaction 1) 10, 11.
Fe2+ + H2O2→ Fe3+ + •OH + OH- (1)
This study evaluated the effective parameters, such as pH, current density, H2O2 concentration, and reaction time for PCE degradation using the EF process. According to the author's search strategy, this is the first report based on the EF treatment process using iron electrodes to remove PCE from the aqueous solution. Most of the studies for degradation of PCE are based on platinum electrodes, diamond electrodes, and lead dioxide electrodes and are not cost-effective treatment processes.
Materials and Methods
Chemical
PCE (C2Cl4, assay ≥ 99.9%), sodium hydroxide (NaOH, assay ≥ 98%), tert-butanol (C4H10O, assay ≥ 99.5%), sodium sulfate (Na2SO4, assay ≥ 98.5%), sulfuric acid (H2SO4, assay ≥ 95%), hydrogen peroxide (H2O2, assay 30%), methanol (MeOH, assay ≥ 99.9%), and ethanol (C2H6O, assay ≥ 99%) were purchased from Merck Co. All stock solutions were prepared using distilled water.
Experimental procedure and apparatus
The experiments were done in the batch mode using a cylindrical Pyrex cell with a working volume of0.25 L as the reactor. The stock solution of PCE was prepared in methanol, then, sample solutions were prepared in distilled water by diluting this stock solution in the range of 5–50 mg L-1. The EF process unit was equipped with two iron electrodes with dimensions of 2.5 cm × 1 cm × 0.1 cm, which was placed parallel to each other, and the distance between electrodes of 3 cm and the constant concentration of 50 mM Na2SO4 was used in all the experiments. The solution pH was determined using a Metrohm 827 pH meter. A DC power supply was used to adjust the desired current density. At the end of each test, two ml of the sample were taken from the reactor, filtered using PTFE syringe filters, and finally used for analysis. The PCE concentration in the aqueous phase was determined using a high-performance liquid chromatography (HPLC) system. The HPLC column was an ODS-C18, and the detection wavelength of the UV detector was set at 210 nm. The eluent was a methanol/water mixture (65/35, %v/v) 12.
Ethical issues
The current work was done in the autumn 2020, after receiving approval from the ethics committee of Kerman University of Medical Sciences [IR.KMU.REC. 1398.680].
Results
Effect of solution pH on the degradation of PCE
As a fundamental parameter, the solution pH affects the PCE degradation during the EF process. Therefore, the effect of solution pH in the range of 3 to 12 on the PCE degradation was investigated in the stable condition, including PCE concentration of 5 mg L-1, the current density of 6 mA cm-2, and H2O2 concentration of 30 µL (Figure 1). In the lowest pH value of 3, the degradation efficiency of 73.2% was achieved. Moreover, by increasing the solution pH to 5, 7, 9, and 12, a decrease in PCE degradation of 65.7%, 41.3%, 35.5%, and 9.8% was observed. According to the observed results, the PCE degradation at pH 3 is close to pH 5 (less than 8%) due to the issue that pH 3 is a harsh condition (equipment corrosion, high acid consumption, etc.). Therefore, solution pH of 5 was chosen as the optimum pH value.
Chlorinated organic compounds (COCs) are the important group of organic compounds that are persistent and resistant to decomposition in the environment. They have caused many health problems and environmental challenges. Among COCs, perchloroethylene (PCE) is one of the most frequently found COCs in environment 1, 2. More than 520,000 tons of PCE are used annually worldwide. Among the various industries, the laundry industry and dry-cleaning activity have the highest consumption of PCE. Of the total PCE, 50% was used for the dry-cleaning activity, 30% for chemical polymerization, 15% for metal cleaning and degreasing, and 5% for other activities 3. Many toxicological and epidemiological studies have shown that PCE is toxic and carcinogenic. PCE exposure is related to various cancers, including cervical, kidney, esophageal cancer, and non-Hodgkin's lymphoma. NIOSH recognizes PCE as a carcinogen for humans, and also IARC grouped this compound in carcinogenic substances of the A-2 group (probable carcinogens) 4. The United States Environmental Protection Agency has issued its maximum contaminant level at 5 μg L-1 by the Safe Drinking Water Act 5. Many researchers in water and wastewater treatment have conducted considerable and extensive studies to remove and treat PCE from water sources. Conventional water and wastewater treatment processes have not been effective in removing PCE. Among different water and wastewater treatment processes, reverse osmosis, adsorption, and advanced oxidation processes (AOPs)have shown suitable performance for the degradation of PCE from contaminated water 3, 6.
AOP processes have a special place in water and wastewater treatment among the mentioned techniques. AOPs can effectively degrade and mineralize the resistant organic pollutants by generating strong oxidants, such as hydroxyl radicals (E0 = 2.80 V/SHE) 7. Furthermore, recently AOPs as an environmentally friendly method received extraordinary attention because of their high efficiency for removing non-biodegradable organic pollutants from aquatic environments, such as wastewater, ground, and surface water by the in-situ generation of the •OH as the oxidizing agent. Among the AOPs, the Fenton reagent (mixture of H2O2 and Fe2+ ion) has attracted significant attention due to its strong oxidative capacity on organic contaminants 8, 9. The main disadvantages of using the electro-Fenton (EF) process in water and wastewater treatment are, on the one hand, dependence on electrical energy and, on the other hand, the management of the produced sludge and also the neutralization of the treated effluent after the process. The EF process is the electrochemically assisted Fenton’s reaction (reaction 1) 10, 11.
Fe2+ + H2O2→ Fe3+ + •OH + OH- (1)
This study evaluated the effective parameters, such as pH, current density, H2O2 concentration, and reaction time for PCE degradation using the EF process. According to the author's search strategy, this is the first report based on the EF treatment process using iron electrodes to remove PCE from the aqueous solution. Most of the studies for degradation of PCE are based on platinum electrodes, diamond electrodes, and lead dioxide electrodes and are not cost-effective treatment processes.
Materials and Methods
Chemical
PCE (C2Cl4, assay ≥ 99.9%), sodium hydroxide (NaOH, assay ≥ 98%), tert-butanol (C4H10O, assay ≥ 99.5%), sodium sulfate (Na2SO4, assay ≥ 98.5%), sulfuric acid (H2SO4, assay ≥ 95%), hydrogen peroxide (H2O2, assay 30%), methanol (MeOH, assay ≥ 99.9%), and ethanol (C2H6O, assay ≥ 99%) were purchased from Merck Co. All stock solutions were prepared using distilled water.
Experimental procedure and apparatus
The experiments were done in the batch mode using a cylindrical Pyrex cell with a working volume of
Ethical issues
The current work was done in the autumn 2020, after receiving approval from the ethics committee of Kerman University of Medical Sciences [IR.KMU.REC. 1398.680].
Results
Effect of solution pH on the degradation of PCE
As a fundamental parameter, the solution pH affects the PCE degradation during the EF process. Therefore, the effect of solution pH in the range of 3 to 12 on the PCE degradation was investigated in the stable condition, including PCE concentration of 5 mg L-1, the current density of 6 mA cm-2, and H2O2 concentration of 30 µL (Figure 1). In the lowest pH value of 3, the degradation efficiency of 73.2% was achieved. Moreover, by increasing the solution pH to 5, 7, 9, and 12, a decrease in PCE degradation of 65.7%, 41.3%, 35.5%, and 9.8% was observed. According to the observed results, the PCE degradation at pH 3 is close to pH 5 (less than 8%) due to the issue that pH 3 is a harsh condition (equipment corrosion, high acid consumption, etc.). Therefore, solution pH of 5 was chosen as the optimum pH value.
Figure 1: Effect of solution pH on PCE degradation (Conditions: PCE concentration of 5 mg L-1, the current density of 6 mA cm-2, and H2O2 concentration of 30 µL)
Effect of current density on the degradation of PCE
The effect of current density on the PCE degradation in the range of 2 to 10 mA cm-2 was investigated. The obtained result of PCE degradation during the EF process is presented in Figure 2. The PCE degradation increased by increasing the current density. Under the constant condition, including PCE concentration of 5 mg L-1, pH solution of 5, and H2O2 concentration of 30 µL, after 15 min of electrolysis time, when the current density increased to 2, 4, 6, 8, and 10 mA PCE degradation reached 33.5%, 53.6%, 65.7%, 78.1%, and 82.6%, respectively. According to the observed result, the PCE degradation at the current density of 10 mA cm-2 is close to 8 mA cm-2 (less than 5%). Therefore, the current density of 8 mA cm-2 was chosen as the optimum current density.
The effect of current density on the PCE degradation in the range of 2 to 10 mA cm-2 was investigated. The obtained result of PCE degradation during the EF process is presented in Figure 2. The PCE degradation increased by increasing the current density. Under the constant condition, including PCE concentration of 5 mg L-1, pH solution of 5, and H2O2 concentration of 30 µL, after 15 min of electrolysis time, when the current density increased to 2, 4, 6, 8, and 10 mA PCE degradation reached 33.5%, 53.6%, 65.7%, 78.1%, and 82.6%, respectively. According to the observed result, the PCE degradation at the current density of 10 mA cm-2 is close to 8 mA cm-2 (less than 5%). Therefore, the current density of 8 mA cm-2 was chosen as the optimum current density.
Figure 2: Effect of current density on PCE degradation (Conditions: PCE concentration of 5 mg L-1, solution pH of 5, and H2O2 concentration of 30 µL)
Effect of H2O2 concentration on the degradation of PCE
The effect of H2O2 concentration (v/v%) on PCE degradation was investigated over a range of 20-70 µL per 250 mL sample, at pH 5, PCE concentration of 5 mg L-1, and current density of 8 mA cm-2. The effect of H2O2 concentration on PCE degradation is shown in Figure 3. According to the observed results, the concentration of H2O2 had a direct effect on the degradation efficiency, and by increasing the concentration of H2O2, the degradation efficiency was increased. The obtained result demonstrated that at low H2O2 concentrations of 20 µL and 30 µL, the PCE degradation rates were very slow and equal 62.5% and 78.1%, respectively. By increasing the H2O2 concentration to 40 µL and 50 µL, the PCE degradation enhanced to 88.6% and 98.4%, respectively. However, at higher concentration (70 µL), no significant improvement was observed for PCE degradation (99.1%). Hence, the maximum H2O2 concentration of 50 µL for the effective PCE degradation was considered.
The effect of H2O2 concentration (v/v%) on PCE degradation was investigated over a range of 20-70 µL per 250 mL sample, at pH 5, PCE concentration of 5 mg L-1, and current density of 8 mA cm-2. The effect of H2O2 concentration on PCE degradation is shown in Figure 3. According to the observed results, the concentration of H2O2 had a direct effect on the degradation efficiency, and by increasing the concentration of H2O2, the degradation efficiency was increased. The obtained result demonstrated that at low H2O2 concentrations of 20 µL and 30 µL, the PCE degradation rates were very slow and equal 62.5% and 78.1%, respectively. By increasing the H2O2 concentration to 40 µL and 50 µL, the PCE degradation enhanced to 88.6% and 98.4%, respectively. However, at higher concentration (70 µL), no significant improvement was observed for PCE degradation (99.1%). Hence, the maximum H2O2 concentration of 50 µL for the effective PCE degradation was considered.
Figure 3: Effect of H2O2 concentration on PCE degradation (Conditions: PCE concentration of 5 mg L-1, solution pH of 5, and current density of 8 mA cm-2)
Effect of PCE concentration on the degradation of PCE
The PCE concentration effect in the range of 5 to 50 mg L-1 was investigated in the constant condition, including solution pH of 5, the current density of 8 mA cm-2, and the H2O2 concentration of 50 µL. The obtained result displayed that the degradation of the PCE is highly concentration-dependent. The observed results are presented in Figure 4. According the figure, the degradation of PCE decreased to 98.4%, 98.2%, 98.1%, 90.5%, and 79.4% when the concentration of the PCE was increased to 5, 10, 15, 30, and 50 mg L-1, respectively. PCE degradation was insignificant after applying 10 min electrolysis time, and the obtained curve seems smooth. Therefore, a PCE concentration of 15 mg L-1 was chosen as the optimum concentration.
The PCE concentration effect in the range of 5 to 50 mg L-1 was investigated in the constant condition, including solution pH of 5, the current density of 8 mA cm-2, and the H2O2 concentration of 50 µL. The obtained result displayed that the degradation of the PCE is highly concentration-dependent. The observed results are presented in Figure 4. According the figure, the degradation of PCE decreased to 98.4%, 98.2%, 98.1%, 90.5%, and 79.4% when the concentration of the PCE was increased to 5, 10, 15, 30, and 50 mg L-1, respectively. PCE degradation was insignificant after applying 10 min electrolysis time, and the obtained curve seems smooth. Therefore, a PCE concentration of 15 mg L-1 was chosen as the optimum concentration.
Figure 4: Effect of PCE concentration on PCE degradation (Conditions: solution pH of 5, current density of 8 mA cm-2, and H2O2 concentration of 50 µL)
Kinetics
The first and second-order kinetic model studies of PCE degradation using EF process were performed in optimum conditions, including solution pH of 5, the current density of 8 mA cm-2, H2O2 concentration of 50 µL, and PCE concentration of 15 mg L-1. The obtained results are shown in Table 1 13-15.
The first and second-order kinetic model studies of PCE degradation using EF process were performed in optimum conditions, including solution pH of 5, the current density of 8 mA cm-2, H2O2 concentration of 50 µL, and PCE concentration of 15 mg L-1. The obtained results are shown in Table 1 13-15.
Table 1: Kinetics models parameter for the PCE degradation using EF process
| Kinetics model | Equation | kapp | R2 |
| First-order | 0.2822 | 0.9858 | |
| Second-order | 0.2199 | 0.8395 |
Radical scavenger
Radical scavenger experiments were carried out to better elucidate the mechanism of PCE degradation and identify the dominant radicals in the EF process. Radical scavengers studies with the constant concentration of0.5 M were conducted under optimum treatment conditions (the optimum condition, including solution pH of 5, the current density of 8 mA cm-2, H2O2 concentration of 50 µL, PCE concentration of 15 mg L-1, and electrolysis time of 10 min); the results are provided in Figure 5. The figure reveals that there was a significant decrease in PCE degradation in the presence of ethanol (EtOH) and tertiary butanol (TBA ). Without adding any scavenging agent (control), 98.1% of PCE was removed after 10 min; however, the degradation was inhibited when EtOH and TBA were separately added to the solution. The degradation yield was only 56.5% and 43.7% for EtOH and TBA , respectively.
Radical scavenger experiments were carried out to better elucidate the mechanism of PCE degradation and identify the dominant radicals in the EF process. Radical scavengers studies with the constant concentration of
Figure 5: PCE degradation using EF process in the presence of different radical scavengers
Discussion
The optimum solution pH for the EF process should be < 5.0. Several studies have showed that the optimum pH for degradation is 3 and the extent of degradation decreases by increasing pH for pH > 3.0. In contrast, Fe2+ ions are unstable at pH > 5.0, and they quickly form Fe3+ ions, which tend to produce Fe(OH)n complexes. These complexes would form further [Fe(OH)4]- when the pH value was > 9.0. Besides, H2O2 is also unstable in basic solution and may decompose to give oxygen and water and lose its oxidation ability 16, 17. The current density is the most critical parameter, affecting the reaction rate of electrochemical processes. As expected, PCE degradation increased with an increase in the current density.
These results accelerate the anodic scarification process, increasing the generated Fe2+ ions concentration 18-20. Consequently, according to the Fenton reaction expressed by Eq. 1, generation of Fe2+ ions results in increased •OH generation, and consequently, the PCE degradation increases. The effect of H2O2 concentration on PCE degradation was investigated over a range of 20-70 µL. At low H2O2 concentrations, the PCE degradation rates were very slow due to the insufficient •OH in an aqueous solution. As the H2O2 concentration increased to 50 µL, the PCE degradation enhanced due to the generation of more radicals. However, for a higher concentration (70 µL), no significant additional improvement was observed due to the scavenging effect of •OH and the inhibition of iron corrosion by hydrogen peroxide 21, 22. As expressed by reaction (2), although other radicals (HO2• and O2•-) are generated, they are much less reactive that may be neglected 23-25.
OH + H2O2 → HO2•+ H2O (2)
The results showed that increasing PCE concentration led to a decrease in PCE degradation, which is in accordance with the characteristics of the EF process. The observed phenomena can be interpreted, since a particular amount of active intermediates are produced. At the same time, the PCE concentration increased by increasing the PCE concentration. Consequently, the amount of •OH was not enough for effective degradation of high concentration of a contaminant, which results in degradation reduction 26, 27.
Based on the obtained results of kinetic studies, the coefficient of correlation (R2) of the applied model was over 0.98, confirming the increased ability of the model to fit the kinetic data of PCE degradation by EF process. The PCE degradation of 98.1% significantly decreased in the presence of EtOH and TBA as radical scavengers, indicating that the generated •OH species controlled the primary mechanism of the degradation path throughout the EF process.
Conclusion
The present study was focused on the PCE degradation from an aqueous solution using the EF process.
The EF process is a promising approach for the degradation of PCE and other persistent pollutants, in the EF process, Fe2+ ions released from the anode electrode in the presence of H2O2 are produced to produce •OH.
The maximum PCE degradation was 98.1% under optimal conditions. The PCE degradation by EF process fitted well the first-order kinetic models. The key mechanism responsible for the PCE degradation was the •OH.
Acknowledgment
The authors would like to express their appreciation to the Student Research Committee of Kerman University of Medical Sciences for supporting the current study.
Funding
This work received a grant from the Kerman University of Medical Sciences [Grant number 98000942].
Conflict of interest
The authors declare that they have no conflict of interest regarding the publication of the current paper.
This is an Open-Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt, and build upon this work for commercial use.
References
1. Miao Z, Gu X, Lu S, et al. Perchloroethylene (PCE) oxidation by percarbonate in Fe2+ catalyzed aqueous solution: PCE performance and its removal mechanism. Chemosphere. 2015;119:1120-5.
2. Jamali‐Behnam F, Najafpoor AA, Davoudi M, et al. Adsorptive removal of arsenic from aqueous solutions using magnetite nanoparticles and silica‐coated magnetite nanoparticles. Environ Prog Sustain Energy. 2018;37(3):951-60.
3. Karimaei M, Nabizadeh R, Shokri B, et al. Dielectric barrier discharge plasma as excellent method for Perchloroethylene removal from aqueous environments: Degradation kinetic and parameters modeling. J Mol Liq. 2017;248:177-83.
4. Karimaei M, Shokri B, Khani MR, et al. Comparative investigation of argon and argon/oxygen plasma performance for Perchloroethylene (PCE) removal from aqueous solution: optimization and kinetic study. J Environ Health Sci and Eng. 2018;16(2):277-87.
5. Muñoz‐Morales M, Sáez C, Cañizares P, et al. Anodic oxidation for the remediation of soils polluted with perchloroethylene. J Chem Technol Biotechnol. 2019;94(1):288-94.
6. Ahmadzadeh S, Kassim A, Rezayi M, et al. Thermodynamic study of the complexation of p-isopropylcalix [6] arene with Cs+ cation in dimethylsulfoxide-acetonitrile binary media. Molecules. 2011;16(9):8130-42.
7. Poza-Nogueiras V, Rosales E, Pazos M, et al. Current advances and trends in electro-Fenton process using heterogeneous catalysts–a review. Chemosphere. 2018;201:399-416.
8. Ammar S, Oturan MA, Labiadh L, et al. Degradation of tyrosol by a novel electro-Fenton process using pyrite as heterogeneous source of iron catalyst. Water Research. 2015;74:77-87.
9. Dolatabadi M, Ghaneian MT, Wang C, et al. Electro-Fenton approach for highly efficient degradation of the herbicide 2, 4-dichlorophenoxyacetic acid from agricultural wastewater: Process optimization, kinetic and mechanism. J Mol Liq. 2021;334:116116.
10. Oturan N, Aravindakumar CT, Olvera-Vargas H, et al. Electro-Fenton oxidation of para-aminosalicylic acid: degradation kinetics and mineralization pathway using Pt/carbon-felt and BDD/carbon-felt cells. Environ Sci Pollut Res. 2018;25(21):20363-73.
11. Dolatabadi M, Świergosz T, Ahmadzadeh S. Electro-Fenton approach in oxidative degradation of dimethyl phthalate-The treatment of aqueous leachate from landfills. Sci Total Environ. 2021;772:145323.
12. Saez V, Esclapez MD, Bonete P, et al. Sonochemical degradation of perchloroethylene: the influence of ultrasonic variables, and the identification of products. Ultrasonics sonochemistry. 2011;18(1):104-13.
13. An T, Yang H, Li G, et al. Kinetics and mechanism of advanced oxidation processes (AOPs) in degradation of ciprofloxacin in water. Appl Catal B: Environ. 2010;94(3):288-94.
14. Najafpoor A, Alidadi H, Esmaeili H, et al. Optimization of anionic dye adsorption onto Melia azedarach sawdust in aqueous solutions: effect of calcium cations. Asia-Pac J Chem Eng. 2016;11(2):258-70.
15. Fouladgar M, Ahmadzadeh S. Application of a nanostructured sensor based on NiO nanoparticles modified carbon paste electrode for determination of methyldopa in the presence of folic acid. Appl Surf Sci. 2016;379:150-5.
16. Mirzaei S, Farzadkia M, Jonidi Jafari A, et al. Removal of Paraquat from Aqueous Solution Using Fenton and Fenton-like Processes. Journal of Mazandaran University of Medical Sciences. 2017;27(149):151-66.
17. Nidheesh PV, Gandhimathi R, Ramesh ST. Degradation of dyes from aqueous solution by Fenton processes: a review. Environ Sci Pollut Res. 2013;20(4):2099-132.
18. Yang Z, Chen H, Wang J, et al. Efficient degradation of diisobutyl phthalate in aqueous solution through electro-Fenton process with sacrificial anode. J Environ Chem Eng. 2020;8(5):104057.
19. Ganzenko O, Oturan N, Sirés I, et al. Fast and complete removal of the 5-fluorouracil drug from water by electro-Fenton oxidation. Environ Chem Lett. 2018;16(1):281-6.
20. Cheng W, Yang M, Xie Y, et al. Enhancement of mineralization of metronidazole by the electro-Fenton process with a Ce/SnO2–Sb coated titanium anode. Chem Eng J. 2013;220:214-20.
21. Kamaraj R, Vasudevan S. Sulfur‐Doped Carbon Chain Network as High‐Performance Electrocatalyst for Electro‐Fenton System. ChemistrySelect. 2019;4(8):2428-35.
22. Jiang WL, Xia X, Han JL, et al. Graphene modified electro-Fenton catalytic membrane for in situ degradation of antibiotic florfenicol. Environ Sci Technol. 2018;52(17):9972-82.
23. Yu F, Chen Y, Pan Y, et al. A cost-effective production of hydrogen peroxide via improved mass transfer of oxygen for electro-Fenton process using the vertical flow reactor. Sep Purif Technol. 2020;241:116695.
24. Moraleda I, Oturan N, Saez C, et al. A comparison between flow-through cathode and mixed tank cells for the electro-Fenton process with conductive diamond anode. Chemosphere. 2020;238:124854.
25. Li D, Yang T, Li Y, et al. Facile and green synthesis of highly dispersed tar-based heterogeneous Fenton catalytic nanoparticles for the degradation of methylene blue. J Clean Prod. 2020;246:119033.
26. Guo W, Yang Z, Zhou Xj, et al., editors. Degradation and mineralization of dyes with advanced oxidation processes (AOPs): A brief review. 2015 International Forum on Energy, Environ. Sci and . Mater; 2015: Atlantis Press.
27. Moradi M, Elahinia A, Vasseghian Y, et al. A review on pollutants removal by Sono-photo-Fenton processes. J Environ Chem Eng. 2020;8(5):104330.
The optimum solution pH for the EF process should be < 5.0. Several studies have showed that the optimum pH for degradation is 3 and the extent of degradation decreases by increasing pH for pH > 3.0. In contrast, Fe2+ ions are unstable at pH > 5.0, and they quickly form Fe3+ ions, which tend to produce Fe(OH)n complexes. These complexes would form further [Fe(OH)4]- when the pH value was > 9.0. Besides, H2O2 is also unstable in basic solution and may decompose to give oxygen and water and lose its oxidation ability 16, 17. The current density is the most critical parameter, affecting the reaction rate of electrochemical processes. As expected, PCE degradation increased with an increase in the current density.
These results accelerate the anodic scarification process, increasing the generated Fe2+ ions concentration 18-20. Consequently, according to the Fenton reaction expressed by Eq. 1, generation of Fe2+ ions results in increased •OH generation, and consequently, the PCE degradation increases. The effect of H2O2 concentration on PCE degradation was investigated over a range of 20-70 µL. At low H2O2 concentrations, the PCE degradation rates were very slow due to the insufficient •OH in an aqueous solution. As the H2O2 concentration increased to 50 µL, the PCE degradation enhanced due to the generation of more radicals. However, for a higher concentration (70 µL), no significant additional improvement was observed due to the scavenging effect of •OH and the inhibition of iron corrosion by hydrogen peroxide 21, 22. As expressed by reaction (2), although other radicals (HO2• and O2•-) are generated, they are much less reactive that may be neglected 23-25.
OH + H2O2 → HO2•+ H2O (2)
The results showed that increasing PCE concentration led to a decrease in PCE degradation, which is in accordance with the characteristics of the EF process. The observed phenomena can be interpreted, since a particular amount of active intermediates are produced. At the same time, the PCE concentration increased by increasing the PCE concentration. Consequently, the amount of •OH was not enough for effective degradation of high concentration of a contaminant, which results in degradation reduction 26, 27.
Based on the obtained results of kinetic studies, the coefficient of correlation (R2) of the applied model was over 0.98, confirming the increased ability of the model to fit the kinetic data of PCE degradation by EF process. The PCE degradation of 98.1% significantly decreased in the presence of EtOH and TBA as radical scavengers, indicating that the generated •OH species controlled the primary mechanism of the degradation path throughout the EF process.
Conclusion
The present study was focused on the PCE degradation from an aqueous solution using the EF process.
The EF process is a promising approach for the degradation of PCE and other persistent pollutants, in the EF process, Fe2+ ions released from the anode electrode in the presence of H2O2 are produced to produce •OH.
The maximum PCE degradation was 98.1% under optimal conditions. The PCE degradation by EF process fitted well the first-order kinetic models. The key mechanism responsible for the PCE degradation was the •OH.
Acknowledgment
The authors would like to express their appreciation to the Student Research Committee of Kerman University of Medical Sciences for supporting the current study.
Funding
This work received a grant from the Kerman University of Medical Sciences [Grant number 98000942].
Conflict of interest
The authors declare that they have no conflict of interest regarding the publication of the current paper.
This is an Open-Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt, and build upon this work for commercial use.
References
1. Miao Z, Gu X, Lu S, et al. Perchloroethylene (PCE) oxidation by percarbonate in Fe2+ catalyzed aqueous solution: PCE performance and its removal mechanism. Chemosphere. 2015;119:1120-5.
2. Jamali‐Behnam F, Najafpoor AA, Davoudi M, et al. Adsorptive removal of arsenic from aqueous solutions using magnetite nanoparticles and silica‐coated magnetite nanoparticles. Environ Prog Sustain Energy. 2018;37(3):951-60.
3. Karimaei M, Nabizadeh R, Shokri B, et al. Dielectric barrier discharge plasma as excellent method for Perchloroethylene removal from aqueous environments: Degradation kinetic and parameters modeling. J Mol Liq. 2017;248:177-83.
4. Karimaei M, Shokri B, Khani MR, et al. Comparative investigation of argon and argon/oxygen plasma performance for Perchloroethylene (PCE) removal from aqueous solution: optimization and kinetic study. J Environ Health Sci and Eng. 2018;16(2):277-87.
5. Muñoz‐Morales M, Sáez C, Cañizares P, et al. Anodic oxidation for the remediation of soils polluted with perchloroethylene. J Chem Technol Biotechnol. 2019;94(1):288-94.
6. Ahmadzadeh S, Kassim A, Rezayi M, et al. Thermodynamic study of the complexation of p-isopropylcalix [6] arene with Cs+ cation in dimethylsulfoxide-acetonitrile binary media. Molecules. 2011;16(9):8130-42.
7. Poza-Nogueiras V, Rosales E, Pazos M, et al. Current advances and trends in electro-Fenton process using heterogeneous catalysts–a review. Chemosphere. 2018;201:399-416.
8. Ammar S, Oturan MA, Labiadh L, et al. Degradation of tyrosol by a novel electro-Fenton process using pyrite as heterogeneous source of iron catalyst. Water Research. 2015;74:77-87.
9. Dolatabadi M, Ghaneian MT, Wang C, et al. Electro-Fenton approach for highly efficient degradation of the herbicide 2, 4-dichlorophenoxyacetic acid from agricultural wastewater: Process optimization, kinetic and mechanism. J Mol Liq. 2021;334:116116.
10. Oturan N, Aravindakumar CT, Olvera-Vargas H, et al. Electro-Fenton oxidation of para-aminosalicylic acid: degradation kinetics and mineralization pathway using Pt/carbon-felt and BDD/carbon-felt cells. Environ Sci Pollut Res. 2018;25(21):20363-73.
11. Dolatabadi M, Świergosz T, Ahmadzadeh S. Electro-Fenton approach in oxidative degradation of dimethyl phthalate-The treatment of aqueous leachate from landfills. Sci Total Environ. 2021;772:145323.
12. Saez V, Esclapez MD, Bonete P, et al. Sonochemical degradation of perchloroethylene: the influence of ultrasonic variables, and the identification of products. Ultrasonics sonochemistry. 2011;18(1):104-13.
13. An T, Yang H, Li G, et al. Kinetics and mechanism of advanced oxidation processes (AOPs) in degradation of ciprofloxacin in water. Appl Catal B: Environ. 2010;94(3):288-94.
14. Najafpoor A, Alidadi H, Esmaeili H, et al. Optimization of anionic dye adsorption onto Melia azedarach sawdust in aqueous solutions: effect of calcium cations. Asia-Pac J Chem Eng. 2016;11(2):258-70.
15. Fouladgar M, Ahmadzadeh S. Application of a nanostructured sensor based on NiO nanoparticles modified carbon paste electrode for determination of methyldopa in the presence of folic acid. Appl Surf Sci. 2016;379:150-5.
16. Mirzaei S, Farzadkia M, Jonidi Jafari A, et al. Removal of Paraquat from Aqueous Solution Using Fenton and Fenton-like Processes. Journal of Mazandaran University of Medical Sciences. 2017;27(149):151-66.
17. Nidheesh PV, Gandhimathi R, Ramesh ST. Degradation of dyes from aqueous solution by Fenton processes: a review. Environ Sci Pollut Res. 2013;20(4):2099-132.
18. Yang Z, Chen H, Wang J, et al. Efficient degradation of diisobutyl phthalate in aqueous solution through electro-Fenton process with sacrificial anode. J Environ Chem Eng. 2020;8(5):104057.
19. Ganzenko O, Oturan N, Sirés I, et al. Fast and complete removal of the 5-fluorouracil drug from water by electro-Fenton oxidation. Environ Chem Lett. 2018;16(1):281-6.
20. Cheng W, Yang M, Xie Y, et al. Enhancement of mineralization of metronidazole by the electro-Fenton process with a Ce/SnO2–Sb coated titanium anode. Chem Eng J. 2013;220:214-20.
21. Kamaraj R, Vasudevan S. Sulfur‐Doped Carbon Chain Network as High‐Performance Electrocatalyst for Electro‐Fenton System. ChemistrySelect. 2019;4(8):2428-35.
22. Jiang WL, Xia X, Han JL, et al. Graphene modified electro-Fenton catalytic membrane for in situ degradation of antibiotic florfenicol. Environ Sci Technol. 2018;52(17):9972-82.
23. Yu F, Chen Y, Pan Y, et al. A cost-effective production of hydrogen peroxide via improved mass transfer of oxygen for electro-Fenton process using the vertical flow reactor. Sep Purif Technol. 2020;241:116695.
24. Moraleda I, Oturan N, Saez C, et al. A comparison between flow-through cathode and mixed tank cells for the electro-Fenton process with conductive diamond anode. Chemosphere. 2020;238:124854.
25. Li D, Yang T, Li Y, et al. Facile and green synthesis of highly dispersed tar-based heterogeneous Fenton catalytic nanoparticles for the degradation of methylene blue. J Clean Prod. 2020;246:119033.
26. Guo W, Yang Z, Zhou Xj, et al., editors. Degradation and mineralization of dyes with advanced oxidation processes (AOPs): A brief review. 2015 International Forum on Energy, Environ. Sci and . Mater; 2015: Atlantis Press.
27. Moradi M, Elahinia A, Vasseghian Y, et al. A review on pollutants removal by Sono-photo-Fenton processes. J Environ Chem Eng. 2020;8(5):104330.
Type of Study: Original articles |
Subject:
Water quality and wastewater treatment and reuse
Received: 2022/03/5 | Accepted: 2022/05/20 | Published: 2022/06/20
Received: 2022/03/5 | Accepted: 2022/05/20 | Published: 2022/06/20
Send email to the article author
| Rights and permissions | |
 |
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. |
