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Zhou W, Li F, Su Y, Li J, Chen S, Xie L, Wei S, Meng X, Rajic L, Gao J, Alshawabkeh AN. O-doped Graphitic Granular Biochar Enables Pollutants Removal via Simultaneous H 2O 2 Generation and Activation in Neutral Fe-free Electro-Fenton Process. Sep Purif Technol 2021; 262. [PMID: 34366698 DOI: 10.1016/j.seppur.2021.118327] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
H2O2 generation by 2-electron oxygen electroreduction reaction (2eORR) has attracted great attention as an alternative to the industry-dominant anthraquinone process. Electro-Fenton (EF) process, which relies on the H2O2 electrogeneration, is regarded as an important environmental application of H2O2 generation by 2eORR. However, its application is hindered by the relatively expensive electrode materials. Proposing cathode materials with low cost and facile synthetic procedures are the priority to advance the EF process. In this work, a composite cathode structure that uses graphitic granular bamboo-based biochar (GB) and stainless steel (SS) mesh (GBSS) is proposed, where SS mesh functions as current distributor and GB supports synergistic H2O2 electrogeneration and activation. The graphitic carbon makes GB conductive and the oxygen-containing groups serve as active sites for H2O2 production. 11.3 mg/L H2O2 was produced from 2.0 g GB at 50 mA after 50 min under neutral pH without external O2/air supply. The O-doped biochar further increased the H2O2 yield to 18.3 mg/L under same conditions. The GBSS electrode is also effective for H2O2 activation to generate ·OH, especially under neutral pH. Ultimately, a neutral Fe-free EF process enabled by GBSS cathode is effective for removal of various model organic pollutants (reactive blue 19, orange II, 4-nitrophenol) within 120 min, and for their partial mineralization (48.4% to 63.5%). Long-term stability of the GBSS electrode for H2O2 electrogeneration, H2O2 activation, and pollutants degradation were also examined and analyzed. This work offers a promising application for biomass waste for removals of organic pollutants in neutral Fe-free EF process.
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Affiliation(s)
- Wei Zhou
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, 150001 P. R. China.,Department of Civil and Environmental Engineering, Northeastern University, Boston, MA, 02115 USA
| | - Feng Li
- School of Civil Engineering, South China University of Technology, Guangzhou, 510640, P. R.China
| | - Yanlin Su
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, 150001 P. R. China
| | - Junfeng Li
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, 150001 P. R. China
| | - Shuai Chen
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, 150001 P. R. China
| | - Liang Xie
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, 150001 P. R. China
| | - Siyu Wei
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, 150001 P. R. China
| | - Xiaoxiao Meng
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, 150001 P. R. China
| | - Ljiljana Rajic
- Pioneer Valley Coral & Natural Science Institute, 1 Mill Valley Road, Hadley, MA, 01035 USA
| | - Jihui Gao
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, 150001 P. R. China
| | - Akram N Alshawabkeh
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA, 02115 USA
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Zhou W, Rajic L, Meng X, Nazari R, Zhao Y, Wang Y, Gao J, Qin Y, Alshawabkeh AN. Efficient H 2O 2 electrogeneration at graphite felt modified via electrode polarity reversal: Utilization for organic pollutants degradation. Chem Eng J 2019; 364:428-439. [PMID: 32581640 PMCID: PMC7314056 DOI: 10.1016/j.cej.2019.01.175] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Electrochemical synthesis of H2O2 offers a great potential for water treatment. However, a significant challenge is the development of efficient cathode materials for the process. Herein, we implement a practical electrochemical cathode modification to support efficient H2O2 electrogeneration via the reduction of dissolved anodic O2. Graphite felt (GF) is in situ anodically modified by electrode polarity reversal technique in an acid-free, low-conductivity electrolyte. The modified GF exhibits a significantly higher activity towards O2 reduction. Up to 183.3% higher H2O2 yield is obtained by the anodized GF due to the increased concentrations of oxygen-containing groups and the hydrophilicity of the surface, which facilitates electron and mass transfer between GF and the electrolyte. Another significant finding is the ability to produce H2O2 at a high yield under neutral pH and low current intensity by the modified GF (35% of the charge need to produce the same amount by unmodified GF). Long-term stability testing of the modified GF showed a decay in the electrode's activity for H2O2 production after 30 consecutive applications. However, the electrode regained its optimal activity for H2O2 production after a secondary modification by electrode polarity reversal. Finally, in situ electrochemically modified GF is more effective for removal of reactive blue 19 (RB19, 20 mg/L) and ibuprofen (IBP, 10 mg/L) by the electro-Fenton process. The modified GF removed 62.7% of RB19 compared to only 28.1% by the unmodified GF in batch reactors after 50 min. Similarly, 75.3% IBP is removed by the modified GF compared to 57.6% by the unmodified GF in a flow-through reactor after 100 min.
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Affiliation(s)
- Wei Zhou
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
- Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Ljiljana Rajic
- Pioneer Valley Coral and Natural Science Institute, 1 Mill Valley Road, Hadley, MA 01035, USA
| | - Xiaoxiao Meng
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Roya Nazari
- Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Yuwei Zhao
- Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Yan Wang
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Jihui Gao
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
- Corresponding author: Prof. Jihui Gao, School of Energy Science and Engineering, Harbin Institute of Technology, 92, Dazhi Street, Nangang District, Harbin 150001, China, ; Akram N. Alshawabkeh, PhD, PE, Fellow ASCE, George A. Snell Professor of Engineering, Department of Civil and Environmental Engineering, Northeastern University, 360 Huntington Avenue, Boston, MA 02115,
| | - Yukun Qin
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Akram N. Alshawabkeh
- Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts 02115, United States
- Corresponding author: Prof. Jihui Gao, School of Energy Science and Engineering, Harbin Institute of Technology, 92, Dazhi Street, Nangang District, Harbin 150001, China, ; Akram N. Alshawabkeh, PhD, PE, Fellow ASCE, George A. Snell Professor of Engineering, Department of Civil and Environmental Engineering, Northeastern University, 360 Huntington Avenue, Boston, MA 02115,
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Kalhor K, Ghasemizadeh R, Rajic L, Alshawabkeh A. Assessment of groundwater quality and remediation in karst aquifers: A review. Groundw Sustain Dev 2019; 8:104-121. [PMID: 30555889 PMCID: PMC6291008 DOI: 10.1016/j.gsd.2018.10.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Karst aquifers, capable of storing and transmitting large amount of water, are the main source of drinking water in many regions worldwide. Their excessive permeability leads to an enhanced vulnerability to retain and spread the contamination accordingly. From sustainability perspective, the environmental, economic and social impacts of karst contamination on water resources management are gaining more attention. In this study, an overview of hydrogeological processes and concepts regarding groundwater flow and contaminant transport in karstic systems is presented, followed by a short discussion on surface water and groundwater interaction. Due to the complexity of karstic systems, different approaches have been developed by researchers for investigating and understanding hydrogeological processes and groundwater behavior in karst which are reviewed herein. Additionally, groundwater contamination issues and the most common and effective remediation techniques in karstic terrains are discussed. Lastly, modeling techniques and remote sensing methods, as beneficial and powerful tools for assessing groundwater flow and contaminant transport in karst terrains, are reviewed and evaluated. In each section, relevant research works conducted for Puerto Rico are discussed and some recommendations are presented to complement the ongoing hydrogeological investigations on this island.
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Affiliation(s)
| | - Reza Ghasemizadeh
- Department of Civil and Environmental Engineering, Northeastern University, 360 Huntington Ave, Boston, MA 02115, USA
| | - Ljiljana Rajic
- Department of Civil and Environmental Engineering, Northeastern University, 360 Huntington Ave, Boston, MA 02115, USA
| | - Akram Alshawabkeh
- Department of Civil and Environmental Engineering, Northeastern University, 360 Huntington Ave, Boston, MA 02115, USA
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Abstract
A low maintenance, "self-cleaning" electrochemical approach is evaluated for regeneration of dye-loaded granular activated carbon (GAC). To do so, batch experiments were conducted using a low-cost granular activated carbon/stainless steel mesh (GACSS) composite cathode and a stable Ti/mixed metal oxides (Ti/MMO) anode without the addition of oxidants or iron catalysts. The GACSS cathode supports simultaneous H2O2 electrogeneration via the in situ supplied O2 from Ti/MMO anode and the subsequent H2O2 activation for ·OH generation, thus enabling the cracking of dye molecules adsorbed on GAC and regenerating the GAC's sorption capacity. Results show that a prolonged electrochemical processing for 12h will achieve up to 88.7% regeneration efficiency (RE). While RE decreases with multi-cycle application, up to 52.3% could still be achieved after 10 adsorption-regeneration cycles. To identify the mechanism, experiments were conducted to measure H2O2 electrogeneration, H2O2 activation, and ·OH generation by various GAC samples. The dye-loaded GAC and GAC treated after 10 adsorption-regeneration cycles were still capable of ·OH generation, which contributes to effective "self-cleaning" and regeneration over multi-cycles.
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Affiliation(s)
- Wei Zhou
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
- Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Xiaoxiao Meng
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Yani Ding
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Ljiljana Rajic
- Pioneer Valley Coral and Natural Science Institute, Hadley, Massachusetts 01035, United States
| | - Jihui Gao
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Yukun Qin
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Akram N. Alshawabkeh
- Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts 02115, United States
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Zhou W, Rajic L, Chen L, Kou K, Ding Y, Meng X, Wang Y, Mulaw B, Gao J, Qin Y, Alshawabkeh AN. Activated carbon as effective cathode material in iron-free Electro-Fenton process: Integrated H 2O 2 electrogeneration, activation, and pollutants adsorption. Electrochim Acta 2019; 296:317-326. [PMID: 30631212 PMCID: PMC6322679 DOI: 10.1016/j.electacta.2018.11.052] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Major challenges for effective implementation of the Electro-Fenton (EF) water treatment process are that conventional efficient cathodes are relatively expensive, and H2O2 activation by Fe2+ may cause secondary pollution. Herein, we propose a low-cost activated carbon/stainless steel mesh (ACSS) composite cathode, where the SS mesh distributes the current and the AC simultaneously supports H2O2 electrogeneration, H2O2 activation, and organic compounds (OCs) adsorption. The oxygen-containing groups on the AC function as oxygen reduction reaction (ORR) sites for H2O2 electrogeneration; while the porous configuration supply sufficient reactive surface area for ORR. 8.9 mg/L H2O2 was obtained with 1.5 g AC at 100 mA under neutral pH without external O2 supply. The ACSS electrode is also effective for H2O2 activation to generate ‧OH, especially under neutral pH. Adsorption shows limited influence on both H2O2 electrogeneration and activation. The iron-free EF process enabled by the ACSS cathode is effective for reactive blue 19 (RB19) degradation. 61.5% RB19 was removed after 90 min and 74.3% TOC was removed after 720 min. Moreover, long-term stability test proved its relatively stable performance. Thus, the ACSS electrode configuration is promising for practical and cost-effective EF process for transformation of OCs in water.
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Affiliation(s)
- Wei Zhou
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA 02115, USA
| | - Ljiljana Rajic
- Pioneer Valley Coral and Natural Science Institute, 1 Mill Valley Road, Hadley, MA 01035, USA
| | - Long Chen
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA 02115, USA
| | - Kaikai Kou
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China
| | - Yani Ding
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China
| | - Xiaoxiao Meng
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China
| | - Yan Wang
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China
| | - Biruk Mulaw
- Department of Chemical Engineering, Northeastern University, Boston, MA 02115, USA
| | - Jihui Gao
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China
| | - Yukun Qin
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China
| | - Akram N Alshawabkeh
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA 02115, USA
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Zhou W, Meng X, Rajic L, Xue Y, Chen S, Ding Y, Kou K, Wang Y, Gao J, Qin Y, Alshawabkeh AN. "Floating" cathode for efficient H 2O 2 electrogeneration applied to degradation of ibuprofen as a model pollutant. Electrochem commun 2018; 96:37-41. [PMID: 30546268 PMCID: PMC6287755 DOI: 10.1016/j.elecom.2018.09.007] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The performance of the Electro-Fenton (EF) process for contaminant degradation depends on the rate of H2O2 production at the cathode via 2-electron dissolved O2 reduction. However, the low solubility of O2 (≈1×10-3 mol dm-3) limits H2O2 production. Herein, a novel and practical strategy that enables the synergistic utilization of O2 from the bulk electrolyte and ambient air for efficient H2O2 production is proposed. Compared with a conventional "submerged" cathode, the H2O2 concentration obtained using the "floating" cathode is 4.3 and 1.5 times higher using porous graphite felt (GF) and reticulated vitreous carbon (RVC) foam electrodes, respectively. This surprising enhancement results from the formation of a three-phase interface inside the porous cathode, where the O2 from ambient air is also utilized for H2O2 production. The contribution of O2 from ambient air varies depending on the cathode material and is calculated to be 76.7% for the GF cathode and 35.6% for the RVC foam cathode. The effects of pH, current, and mixing on H2O2 production are evaluated. Finally, the EF process enhanced by the "floating" cathode degraded 78.3% of the anti-inflammatory drug ibuprofen after 120 min compared to only 25.4% using a conventional "submerged" electrode, without any increase in the cost.
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Affiliation(s)
- Wei Zhou
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
- Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Xiaoxiao Meng
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
| | - Ljiljana Rajic
- Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Yunfei Xue
- Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Shuai Chen
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
| | - Yani Ding
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
| | - Kaikai Kou
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
| | - Yan Wang
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
| | - Jihui Gao
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
| | - Yukun Qin
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
| | - Akram N. Alshawabkeh
- Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts 02115, United States
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Hojabri S, Rajic L, Alshawabkeh AN. Transient reactive transport model for physico-chemical transformation by electrochemical reactive barriers. J Hazard Mater 2018; 358:171-177. [PMID: 29990804 PMCID: PMC6247793 DOI: 10.1016/j.jhazmat.2018.06.051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Revised: 06/22/2018] [Accepted: 06/23/2018] [Indexed: 05/12/2023]
Abstract
A comprehensive model that integrates coupled effects of chemical, physical, and electrochemical processes, is necessary for design, analysis, and implementation of the electro-remediation of groundwater under flow conditions. A coupled system of equations to solve for transport and multiple reactions in an electrochemical reactor is numerically intensive due to highly stiff nature of reaction model formulation. In this study, the focus is to develop an efficient model for reactions associated with the transport and physico-chemical transformation in an electrochemical reactor. The model incorporates effects of transport mechanisms as well as chemical and electrochemical reactions. Model verification is provided for pH profiles under different electrolyte compositions in two sets of reactors; a batch and a flow-through reactor. The model is able to predict the concentration of species during the electrochemical remediation process with a close correlation to experimental data (R2 = 0.99 for batch and R2 = 0.78 for flow-through reactor.) Imposing polarity reversal to the system will cause fluctuation of pH, however, the trend stays the same as if no polarity were applied. Ultimately, volumetric charge flow is introduced as a unique parameter characterizing the electroremediation reactor for operating purposes.
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Affiliation(s)
- Shirin Hojabri
- Civil and Environmental Engineering, Northeastern University, Boston, MA, 02115, USA
| | - Ljiljana Rajic
- Civil and Environmental Engineering, Northeastern University, Boston, MA, 02115, USA
| | - Akram N Alshawabkeh
- Civil and Environmental Engineering, Northeastern University, Boston, MA, 02115, USA.
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Zhou W, Rajic L, Zhao Y, Gao J, Qin Y, Alshawabkeh AN. Rates of H 2O 2 Electrogeneration by Reduction of Anodic O 2 at RVC Foam Cathodes in Batch and Flow-through Cells. Electrochim Acta 2018; 277:185-196. [PMID: 32153302 DOI: 10.1016/j.electacta.2018.04.174] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The Electro-Fenton process for in-situ H2O2 electrogeneration is impacted by low O2 utilization efficiency (<0.1%) and the need of acid for pH adjustment. An electrochemical flow-through cell can develop localized acidic conditions, coupled with simultaneous formation and utilization of O2 to enhance H2O2 formation. Multiple electrode configurations using reticulated vitreous carbon (RVC) foam and Ti/mixed metal oxides (MMO) are proposed to identify the optimum conditions for H2O2 formation in batch and flow-through cells. A pH of 2.75±0.25 is developed locally in the flow-through cell that supports effective O2 reduction. Up to 9.66 mg/L H2O2 is generated in a 180 mL batch cell under 100 mA, at pH 2, and mixing at 350 rpm. In flow-through conditions, both flow rate and current significantly influence H2O2 production. A current of 120 mA produced 2.27 mg/L H2O2 under a flow rate of 3 mL/min in a 3-electrode cell with one RVC foam cathode at 60 min. The low current of 60 mA does not enable effective H2O2 production, while the high current of 250 mA produced less H2O2 due to parasitic reactions competing with O2 reduction. Higher flow rates decrease the retention time, but also increase the O2 mass transfer. Furthermore, 3-electrode flow-through cell with two RVC foam cathodes was not effective for H2O2 production due to the limited O2 supply for the secondary cathode. Finally, a coupled process that uses both O2 and H2 from water electrolysis is proposed to improve the H2O2 yield further.
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Affiliation(s)
- Wei Zhou
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, P. R. China
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA, USA
| | - Ljiljana Rajic
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA, USA
| | - Yuwei Zhao
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA, USA
| | - Jihui Gao
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, P. R. China
| | - Yukun Qin
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, P. R. China
| | - Akram N Alshawabkeh
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA, USA
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Zhou W, Gao J, Rajic L, Ding Y, Zhao Y, Zhao H, Meng X, Wang Y, Kou K, Xu Y, Wu S, Qin Y, Alshawabkeh AN. Drastic Enhancement of H 2O 2 Electro-generation by Pulsed Current for Ibuprofen Degradation: Strategy Based on Decoupling Study on H 2O 2 Decomposition Pathways. Chem Eng J 2018; 338:709-718. [PMID: 32153347 PMCID: PMC7062375 DOI: 10.1016/j.cej.2017.12.152] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Efficient H2O2 electrogeneration from 2-electron oxygen reduction reaction (ORR) represents an important challenge for environmental remediation application. H2O2 production is determined by 2-electron ORR as well as H2O2 decomposition. In this work, a novel strategy based on the systematical investigation on H2O2 decomposition pathways was reported, presenting a drastically improved bulk H2O2 concentration. Results showed that bulk phase disproportion, cathodic reduction, and anodic oxidation all contributed to H2O2 depletion. To decrease the extent of H2O2 cathodic reduction, the pulsed current was applied and proved to be highly effective to lower the extent of H2O2 electroreduction. A systematic study of various pulsed current parameters showed that H2O2 concentration was significantly enhanced by 61.6% under pulsed current of "2s ON + 2s OFF" than constant current. A mechanism was proposed that under pulsed current, less H2O2 molecules were electroreduced when they diffused from the porous cathode to the bulk electrolyte. Further results demonstrated that a proper pulse frequency was necessary to achieve a higher H2O2 production. Finally, this strategy was applied to Electro-Fenton (EF) process with ibuprofen as model pollutant. 75.0% and 34.1% ibuprofen were removed under pulsed and constant current at 10 min, respectively. The result was in consistent with the higher H2O2 and ·OH production in EF under pulsed current. This work poses a potential approach to drastically enhance H2O2 production for improved EF performance on organic pollutants degradation without making any changes to the system except for power mode.
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Affiliation(s)
- Wei Zhou
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
- Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Jihui Gao
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
- Corresponding author: Prof. Jihui Gao, School of Energy Science and Engineering, Harbin Institute of Technology, 92, Dazhi Street, Nangang District, Harbin 150001, China, , Telephone: (86)-0451-8641 3231, Fax: (86)-0451-8641 2528
| | - Ljiljana Rajic
- Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Yani Ding
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Yuwei Zhao
- Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Haiqian Zhao
- School of Civil Engineering & Architecture, Northeast Petroleum University, Daqing 163318, P. R. China
| | - Xiaoxiao Meng
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Yan Wang
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Kaikai Kou
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Yiqun Xu
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Shaohua Wu
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Yukun Qin
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Akram N. Alshawabkeh
- Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts 02115, United States
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Shokri M, Vesper DJ, Herman EK, Rajic L, Hetrick KL, Padilla IY, Alshawabkeh AN. BULK CHEMISTRY OF KARST SEDIMENT DEPOSITS. Sinkholes Eng Environ Impacts Karst 2018; 2018:115-120. [PMID: 31435622 DOI: 10.5038/9780991000982.1043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Sediments are ubiquitous in karst systems and play a critical role in the fate and transport of contaminants. Sorbed contaminants may be stored on immobile sediments or rapidly dispersed on mobile sediments. Sediments may also influence remediation by either enhancing or interfering with the process. To better understand the potential effects of sediments on remediation, we conducted physical and chemical characterizations of 11 sediment samples from 7 cave and spring deposits from karst regions of Tennessee, Virginia, and West Virginia. The samples were analyzed for particle-size distribution using sieves and laser diffraction particle analysis. The sediment size fraction <2 mm (sand, silt, and clay) was analyzed for slurry pH and specific conductivity (SC) using electrodes and for bulk total carbon, organic carbon, nitrogen and sulfur on an ElementarTM Vario MAX Cube CNS. The same <2 mm fraction was subjected to a pseudo-total extraction using aqua regia with subsequent solution analysis by inductively coupled plasma-optical emission spectrometry (ICP-OES). Most of the samples were dominated by the <2 mm size fraction. Their slurry pHs ranged from 6.8 to 8.4 and their SCs ranged from 45 to 206 μS/cm with the exception of two high SC samples (726 and 8500 μS/cm). The fraction of organic carbon (Foc) in the sediments ranged from <0.1 to 2%. The sample from a saltpeter cave historically used for gunpowder production contained the highest concentrations of N and S (~3 g/kg) but lower total C than some of the spring samples. The pseudo-total extractions were analyzed for Al, Ca, Fe, Mg, and Mn. Of those elements, Mg was the most consistent across the locations (2.0-6.1 g/kg), and Ca was the most variable (1.4-52 g/kg). Given the importance of particle size and elemental concentrations in chemical reactions and remediation, more data of this type are needed to predict contaminant fate and transport and to plan successful remediation projects.
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Affiliation(s)
- Mohammad Shokri
- West Virginia University, Dept. of Geology and Geography, 98 Beechurst Ave., Morgantown, WV 26506, USA,
| | - Dorothy J Vesper
- West Virginia University, Dept. of Geology and Geography, 98 Beechurst Ave., Morgantown, WV 26506, USA,
| | - Ellen K Herman
- Bucknell University, Dept. of Geology and Environmental Geosciences, 1 Dent Drive, Lewisburg, PA, 17837, USA,
| | - Ljiljana Rajic
- Northeastern University, Dept. of Civil and Environmental Engineering, 360 Huntington Ave., Boston, MA, 02115, USA,
| | - Kimberly L Hetrick
- Northeastern University, Dept. of Civil and Environmental Engineering, 360 Huntington Ave., Boston, MA, 02115, USA,
| | - Ingrid Y Padilla
- University of Puerto Rico, Mayagüez, Dept, of Civil Engineering and Surveying, Calle Yagrumo, Mayagüez, PR, 00681, USA,
| | - Akram N Alshawabkeh
- Northeastern University, Dept. of Civil and Environmental Engineering, 360 Huntington Ave., Boston, MA, 02115, USA,
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Hetrick KL, Rajic L, Alshawabkeh AN, Shokri M, Vesper DJ. LABORATORY TESTING OF THE POTENTIAL FOR THE INFLUENCE OF SUSPENDED SEDIMENTS ON THE ELECTROCHEMICAL REMEDIATION OF KARST GROUNDWATER. Sinkholes Eng Environ Impacts Karst 2018; 2018:147-152. [PMID: 31435623 PMCID: PMC6703559 DOI: 10.5038/9780991000982.1017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Due to the complicated nature of karst aquifers, many groundwater treatment technologies are difficult to implement successfully. A particular challenge arises because sediments are ubiquitous and mobile in karst systems and may either facilitate contaminant transport or act as long-term substrates for storage via sorption. However, electrochemical remediation is a promising technology to be optimized for karst aquifers due to easy manipulation and control of groundwater chemistry as well as low cost, ability for in situ application, and performance under alternative power sources. This study investigates the effects of suspended karst sediments on the electrochemical remediation of groundwater via electro-Fenton (EF) mechanism. The EF mechanism relies on direct electrolysis (i.e., water electrolysis and ferrous iron release) and indirect, electrochemically-induced processes (i.e., Pd catalyzed H2O2 production). These processes can be optimized for H2O2 generation and support of its activation to hydroxyl radicals - a powerful oxidant capable of degrading and transforming a wide range of contaminants (e.g., chlorinated solvents). In this study, we tested sediments varying in concentrations of Fe, Mn and buffering capacities. When the sediments were introduced into the EF experiments, there were adverse effects on the H2O2 content: at steady state (120 min), Pd catalyzed formation of H2O2 decreased by 60%, 57%, and 75% in the presence of suspended sediment collected from three separate karst locations. Presented results imply that sediments' presence influences EF mechanism in electrochemical systems, but given the flexibility of the technology, it can be optimized in terms of electrode materials, current intensities and current regimes to address these challenges.
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Affiliation(s)
- Kimberly L Hetrick
- Northeastern University, Dept. of Civil and Environmental Engineering, 360 Huntington Ave., Boston, MA, 02115, USA,
| | - Ljiljana Rajic
- Northeastern University, Dept. of Civil and Environmental Engineering, 360 Huntington Ave., Boston, MA, 02115, USA,
| | - Akram N Alshawabkeh
- Northeastern University, Dept. of Civil and Environmental Engineering, 360 Huntington Ave., Boston, M.A, 02115, USA,
| | - Mohammad Shokri
- University of Central Florida, Civil, Environmental, and Construction Engineering Dept., 12800 Pegasus Drive, Orlando, FL, 32816, USA,
| | - Dorothy J Vesper
- West Virginia University, Dept. of Geology and Geography, 98 Beechurst Ave., Morgantown, WV 26506, USA,
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Taqieddin A, Nazari R, Rajic L, Alshawabkeh A. Review-Physicochemical hydrodynamics of gas bubbles in two phase electrochemical systems. J Electrochem Soc 2017; 164:E448-E459. [PMID: 29731515 PMCID: PMC5935447 DOI: 10.1149/2.1161713jes] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Electrochemical systems suffer from poor management of evolving gas bubbles. Improved understanding of bubbles behavior helps to reduce overpotential, save energy and enhance the mass transfer during chemical reactions. This work investigates and reviews the gas bubbles hydrodynamics, behavior, and management in electrochemical cells. Although the rate of bubble growth over the electrode surface is well understood, there is no reliable prediction of bubbles break-off diameter from the electrode surface because of the complexity of bubbles motion near the electrode surface. Particle Image Velocimetry (PIV) and Laser Doppler Anemometry (LDA) are the most common experimental techniques to measure bubble dynamics. Although the PIV is faster than LDA, both techniques are considered expensive and time-consuming. This encourages adapting Computational Fluid Dynamics (CFD) methods as an alternative to study bubbles behavior. However, further development of CFD methods is required to include coalescence and break-up of bubbles for better understanding and accuracy. The disadvantages of CFD methods can be overcome by using hybrid methods. The behavior of bubbles in electrochemical systems is still a complex challenging topic which requires a better understanding of the gas bubbles hydrodynamics and their interactions with the electrode surface and bulk liquid, as well as between the bubbles itself.
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Affiliation(s)
- Amir Taqieddin
- Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA
| | - Roya Nazari
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA 02115, USA
| | - Ljiljana Rajic
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA 02115, USA
| | - Akram Alshawabkeh
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA 02115, USA
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13
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Fallahpour N, Mao X, Rajic L, Yuan S, Alshawabkeh AN. Electrochemical dechlorination of trichloroethylene in the presence of natural organic matter, metal ions and nitrates in a simulated karst media. J Environ Chem Eng 2017; 5:240-245. [PMID: 29744302 PMCID: PMC5937535 DOI: 10.1016/j.jece.2016.11.046] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A small-scale flow-through limestone column was used to evaluate the effect of common coexisting organic and inorganic compounds on the electrochemical dechlorination of trichloroethylene (TCE) in karst media. Iron anode was used to produce ferrous ions and promote reducing conditions in the column. The reduction of TCE under 90 mA current, 1 mL min-1 flow rate, and 1 mg L-1 initial TCE concentration, was inhibited in the presence of humic acids due to competition for direct electron transfer and/or reaction with atomic hydrogen produced at the cathode surface by water electrolysis. Similarly, presence of 10 mg L-1 chromate decreased TCE reduction rate to 53%. The hexavalent chromium was completely reduced to trivalent chromium due to the ferrous species produced from iron anode. Presence of 5 mg L-1 selenate decreased the removal of TCE by 10%. Chromium and selenate complexation with dissolved iron results in formation of aggregates, which cover the electrodes surface and reduce TCE dechlorination rate. Presence of 40 mg L-1 nitrates caused reductive transformation of TCE up to 80%. Therefore, TCE removal is influenced by the presence of other contaminants that are present as a mixture in groundwater in the following order: humic acid, chromate, selenate, and nitrate.
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Affiliation(s)
- Noushin Fallahpour
- Civil and Environmental Engineering Department, Northeastern University, Boston, MA, 02115, USA
| | - Xuhui Mao
- Civil and Environmental Engineering Department, Northeastern University, Boston, MA, 02115, USA
- School of Resource and Environmental Science. Wuhan University, Wuhan City, 430072, P. R. China
| | - Ljiljana Rajic
- Civil and Environmental Engineering Department, Northeastern University, Boston, MA, 02115, USA
| | - Songhu Yuan
- Civil and Environmental Engineering Department, Northeastern University, Boston, MA, 02115, USA
- State Key Lab of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, 430074, P. R. China
| | - Akram N. Alshawabkeh
- Civil and Environmental Engineering Department, Northeastern University, Boston, MA, 02115, USA
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Rajic L, Nazari R, Fallahpour N, Alshawabkeh AN. Electrochemical degradation of trichloroethylene in aqueous solution by bipolar graphite electrodes. J Environ Chem Eng 2016; 4:197-202. [PMID: 26955517 PMCID: PMC4778262 DOI: 10.1016/j.jece.2015.10.030] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
In this study, we tested the use of the bipolar electrodes to enhance electrochemical degradation of trichloroethylene (TCE) in an undivided, flow-through electrochemical reactor. The bipolar electrode forms when an electrically conductive material polarizes between feeder electrodes that are connected to a direct current source and, therefore, creates an additional anode/cathode pair in the system. We hypothesize that bipolar electrodes will generate additional oxidation/reduction zones to enhance TCE degradation. The graphite cathode followed by graphite anode sequence were operated without a bipolar electrode as well as with one and two bipolar graphite electrodes. The system without bipolar electrodes degraded 29% of TCE while the system with one and two bipolar electrodes degraded 38% and 66% of TCE, respectively. It was found that the removal mechanism for TCE in bipolar mode includes hydrodechlorination at the feeder cathode, and oxidation through reaction with peroxide. The results show that the bipolar electrodes presence enhance TCE removal efficiency and rate and imply that they can be used to improve electrochemical treatment of contaminated groundwater.
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15
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Rajic L, Fallahpour N, Podlaha E, Alshawabkeh A. The influence of cathode material on electrochemical degradation of trichloroethylene in aqueous solution. Chemosphere 2016; 147:98-104. [PMID: 26761603 PMCID: PMC4742380 DOI: 10.1016/j.chemosphere.2015.12.095] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Revised: 12/22/2015] [Accepted: 12/23/2015] [Indexed: 05/11/2023]
Abstract
In this study, different cathode materials were evaluated for electrochemical degradation of aqueous phase trichloroethylene (TCE). A cathode followed by an anode electrode sequence was used to support reduction of TCE at the cathode via hydrodechlorination (HDC). The performance of iron (Fe), copper (Cu), nickel (Ni), aluminum (Al) and carbon (C) foam cathodes was evaluated. We tested commercially available foam materials, which provide large electrode surface area and important properties for field application of the technology. Ni foam cathode produced the highest TCE removal (68.4%) due to its high electrocatalytic activity for hydrogen generation and promotion of HDC. Different performances of the cathode materials originate from differences in the bond strength between atomic hydrogen and the material. With a higher electrocatalytic activity than Ni, Pd catalyst (used as cathode coating) increased TCE removal from 43.5% to 99.8% for Fe, from 56.2% to 79.6% for Cu, from 68.4% to 78.4% for Ni, from 42.0% to 63.6% for Al and from 64.9% to 86.2% for C cathode. The performance of the palladized Fe foam cathode was tested for degradation of TCE in the presence of nitrates, as another commonly found groundwater species. TCE removal decreased from 99% to 41.2% in presence of 100 mg L(-1) of nitrates due to the competition with TCE for HDC at the cathode. The results indicate that the cathode material affects TCE removal rate while the Pd catalyst significantly enhances cathode activity to degrade TCE via HDC.
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Affiliation(s)
- Ljiljana Rajic
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA 02115, USA
| | - Noushin Fallahpour
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA 02115, USA
| | - Elizabeth Podlaha
- Department of Chemical Engineering, Northeastern University, Boston, MA 02115, USA
| | - Akram Alshawabkeh
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA 02115, USA.
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Fallahpour N, Yuan S, Rajic L, Alshawabkeh AN. Hydrodechlorination of TCE in a circulated electrolytic column at high flow rate. Chemosphere 2016; 144:59-64. [PMID: 26344148 PMCID: PMC4695317 DOI: 10.1016/j.chemosphere.2015.08.037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 08/07/2015] [Accepted: 08/10/2015] [Indexed: 05/31/2023]
Abstract
Palladium-catalytic hydrodechlorination of trichloroethylene (TCE) by cathodic H2 produced from water electrolysis has been tested. For a field in-well application, the flow rate is generally high. In this study, the performance of Pd-catalytic hydrodechlorination of TCE using cathodic H2 is evaluated under high flow rate (1 L min(-1)) in a circulated column system, as expected to occur in practice. An iron anode supports reduction conditions and it is used to enhance TCE hydrodechlorination. However, the precipitation occurs and high flow rate was evaluated to minimize its adverse effects on the process (electrode coverage, clogging, etc.). Under the conditions of 1 L min(-1) flow, 500 mA current, and 5 mg L(-1) initial TCE concentration, removal efficacy using iron anodes (96%) is significantly higher than by mixed metal oxide (MMO) anodes (66%). Two types of cathodes (MMO and copper foam) in the presence of Pd/Al2O3 catalyst under various currents (250, 125, and 62 mA) were used to evaluate the effect of cathode materials on TCE removal efficacy. The similar removal efficiencies were achieved for both cathodes, but more precipitation generated with copper foam cathode (based on the experiments done by authors). In addition to the well-known parameters such as current density, electrode materials, and initial TCE concentration, the high velocities of groundwater flow can have important implications, practically in relation to the flush out of precipitates. For potential field application, a cost-effective and sustainable in situ electrochemical process using a solar panel as power supply is being evaluated.
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Affiliation(s)
- Noushin Fallahpour
- Civil and Environmental Engineering Department, Northeastern University, Boston, MA, 02115, USA
| | - Songhu Yuan
- Civil and Environmental Engineering Department, Northeastern University, Boston, MA, 02115, USA; State Key Lab of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, 430074, PR China
| | - Ljiljana Rajic
- Civil and Environmental Engineering Department, Northeastern University, Boston, MA, 02115, USA
| | - Akram N Alshawabkeh
- Civil and Environmental Engineering Department, Northeastern University, Boston, MA, 02115, USA.
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Abstract
In this study, we evaluate the use of different stainless steel (SS) materials as cost-effective cathode materials for electrochemical transformation of trichloroethylene (TCE) in contaminated groundwater. Ni, which is present in certain SS, has low hydrogen overpotential that promotes fast formation of atomic hydrogen and, therefore, its content can enhance hydrodechlorination (HDC). We a flow-through electrochemical reactor with a SS cathode followed by an anode. The performance of Ni containing foam cathodes (Fe/Ni and Ni foam) was also evaluated for electrochemical transformation of TCE in groundwater. SS type 316 (12% Ni) removed 61.7% of TCE compared to 52.6% removed by SS 304 (9.25% Ni) and 37.5% removed by SS 430 (0.75% Ni). Ni foam cathode produced the highest TCE removal rate (68.4%) compared with other cathodes. The slightly lower performance of SS type 316 mesh is balanced by the reduction in treatment costs for larger-scale systems. The results prove that Ni content in SS highly influences TCE removal rate.
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Affiliation(s)
- Ljiljana Rajic
- Civil and Environmental Engineering Department, Northeastern University, Boston, MA, 02115, USA
| | - Noushin Fallahpour
- Civil and Environmental Engineering Department, Northeastern University, Boston, MA, 02115, USA
| | - Emeka Oguzie
- Electrochemistry and Material Science Research Laboratory, Department of Chemistry, Federal University of Technology, PM B 1526, Owerri, Nigeria
| | - Akram Alshawabkeh
- Civil and Environmental Engineering Department, Northeastern University, Boston, MA, 02115, USA
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18
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Rajic L, Fallahpour N, Alshawabkeh AN. Impact of electrode sequence on electrochemical removal of trichloroethylene from aqueous solution. Appl Catal B 2015; 174-175:427-434. [PMID: 25931774 PMCID: PMC4410430 DOI: 10.1016/j.apcatb.2015.03.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The electrode sequence in a mixed flow-through electrochemical cell is evaluated to improve the hydrodechlorination (HDC) of trichloroethylene (TCE) in aqueous solutions. In a mixed (undivided) electrochemical cell, oxygen generated at the anode competes with the transformation of target contaminants at the cathode. In this study, we evaluate the effect of placing the anode downstream from the cathode and using multiple electrodes to promote TCE reduction. Experiments with a cathode followed by an anode (C→A) and an anode followed by a cathode (A→C) were conducted using mixed metal oxide (MMO) and iron as electrode materials. The TCE removal rates when the anode is placed downstream of the cathode (C→A) were 54% by MMO→MMO, 64% by MMO→Fe and 87% by Fe→MMO sequence. Removal rates when the anode is placed upstream of the cathode (A→C) were 38% by MMO→MMO, 58% by Fe→MMO and 69% by MMO→Fe sequence. Placing the anode downstream of the cathode positively improves (by 26%) the degradation of aqueous TCE in a mixed flow-through cell as it minimizes the influence of oxygen generated at the MMO anode on TCE reduction at the cathode. Furthermore, placing the MMO anode downstream of the cathode neutralizes pH and redox potential of the treated solution. Higher flow velocity under the C→A setup increases TCE mass flux reduction rate. Using multiple cathodes and an iron foam cathode up stream of the anode increase the removal rate by 1.6 and 2.4 times, respectively. More than 99% of TCE was removed in the presence of Pd catalyst on carbon and as an iron foam coating. Enhanced reaction rates found in this study imply that a mixed flow-through electrochemical cell with multiple cathodes up stream of an anode is an effective method to promote the reduction of TCE in groundwater.
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Affiliation(s)
- Ljiljana Rajic
- Department of Civil and Environmental Engineering, Northeastern University, 400 Snell Engineering, 360 Huntington Avenue, Boston, MA 02115, United States
| | - Noushin Fallahpour
- Department of Civil and Environmental Engineering, Northeastern University, 400 Snell Engineering, 360 Huntington Avenue, Boston, MA 02115, United States
| | - Akram N. Alshawabkeh
- Department of Civil and Environmental Engineering, Northeastern University, 400 Snell Engineering, 360 Huntington Avenue, Boston, MA 02115, United States
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Rajic L, Fallahpour N, Yuan S, Alshawabkeh AN. Electrochemical transformation of trichloroethylene in aqueous solution by electrode polarity reversal. Water Res 2014; 67:267-75. [PMID: 25282093 PMCID: PMC4262522 DOI: 10.1016/j.watres.2014.09.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 09/09/2014] [Accepted: 09/11/2014] [Indexed: 05/12/2023]
Abstract
Electrode polarity reversal is evaluated for electrochemical transformation of trichloroethylene (TCE) in aqueous solution using flow-through reactors with mixed metal oxide electrodes and Pd catalyst. The study tests the hypothesis that optimizing electrode polarity reversal will generate H2O2 in Pd presence in the system. The effect of polarity reversal frequency, duration of the polarity reversal intervals, current intensity and TCE concentration on TCE removal rate and removal mechanism were evaluated. TCE removal efficiencies under 6 cycles h(-1) were similar in the presence of Pd catalyst (50.3%) and without Pd catalyst (49.8%), indicating that Pd has limited impact on TCE degradation under these conditions. The overall removal efficacies after 60 min treatment under polarity reversal frequencies of 6, 10, 15, 30 and 90 cycles h(-1) were 50.3%, 56.3%, 69.3%, 34.7% and 23.4%, respectively. Increasing the frequency of polarity reversal increases TCE removal as long as sufficient charge is produced during each cycle for the reaction at the electrode. Electrode polarity reversal shifts oxidation/reduction and reduction/oxidation sequences in the system. The optimized polarity reversal frequency (15 cycles h(-1) at 60 mA) enables two reaction zones formation where reduction/oxidation occurs at each electrode surface.
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Affiliation(s)
- Ljiljana Rajic
- Civil and Environmental Engineering Department, Northeastern University, Boston, MA 02115, USA
| | - Noushin Fallahpour
- Civil and Environmental Engineering Department, Northeastern University, Boston, MA 02115, USA
| | - Songhu Yuan
- Civil and Environmental Engineering Department, Northeastern University, Boston, MA 02115, USA; State Key Lab of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR China
| | - Akram N Alshawabkeh
- Civil and Environmental Engineering Department, Northeastern University, Boston, MA 02115, USA.
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Cheney D, Rajic L, Sly E, Meric D, Sheahan T. Uptake of PCBs contained in marine sediments by the green macroalga Ulva rigida. Mar Pollut Bull 2014; 88:207-214. [PMID: 25261178 DOI: 10.1016/j.marpolbul.2014.09.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 09/03/2014] [Accepted: 09/06/2014] [Indexed: 06/03/2023]
Abstract
The uptake of PCBs contained in marine sediments by the green macroalga Ulva rigida was investigated in both laboratory and field experiments. Under laboratory conditions, total PCBs (tPCBs) uptake was significantly greater in live vs dead plants. The concentration of tPCB taken up in live plants was greatest in the first 24h (1580 μg kg(-1) dry weight), and then increased at a lower rate from day 2 to 14. Dead plants had a significantly lower tPCB concentration after 24h (609 μg kg(-1) dry weight) and lower uptake rate through day 14. Lesser chlorinated PCB congeners (below 123) made up the majority of PCBs taken up. Congener composition in both laboratory and field experiments was correlated to congener logKow value and sediment content. Field experiments showed that Ulva plants could concentrate PCBs to 3.9 mg kg(-1) in 24h. Thus, U. rigida is capable of removing PCBs in sediments at a rapid rate.
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Affiliation(s)
- Donald Cheney
- Marine Science Center, Northeastern University, Nahant, MA 01938, USA.
| | - Ljiljana Rajic
- Civil and Environmental Engineering, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA
| | - Elizabeth Sly
- Marine Science Center, Northeastern University, Nahant, MA 01938, USA
| | - Dogus Meric
- Civil and Environmental Engineering, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA
| | - Thomas Sheahan
- Civil and Environmental Engineering, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA
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