Laboratory of Chemical & Electrochemical Processes

Department of Chemical Engineering – University of Patras

Project Page

Electrochemical Promotion of aerobic-catalytic treatment of toxic pollutants in aqueous phase

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This project is implemented under the "ARISTEIA ΙI" Action ( 3073) of the  "OPERATIONAL PROGRAMME EDUCATION AND LIFELONG LEARNING" and is co-funded by the European Social Fund (ESF) and National Resources.


Project goals and Objectives
The development and expansion of various industries (textile, leather, paper production, food technology, agricultural, photoelectrochemical cells, hair coloring etc.) that use various organic and inorganic compounds (which are often very toxic) is remarkable during the last decades. The quantity of wastewaters produced from these activities is continuously increasing. Regardless the contaminant concentration, these wastewaters are often highly colored and turbid. In addition, many organics and their breakdown products are toxic and/or mutagenic to life. Due to their highly polluting nature, the treatment of such wastewaters has attracted significantly attention for several years. Although biological degradation methods are between the most economic processes for wastewater treatment, they are usually ineffective to degrade molecules of refractive nature, like phenolic, carboxylic acids and nitrogen-containing compounds. Furthermore, the survival of anaerobic biomass in the presence of high concentration of specific organics (such as azo dyes) is a difficult task. Therefore, for the treatment of this type of wastewaters alternative methods have been proposed. The majority concern advanced oxidation processes (AOPs) [1-5], like electrooxidation, catalytic wet oxidation (CWO), Fenton, photocatalysis or even combinations of them. The application range of each AOP varies according to the flow rate and organic content of effluent to be treated.
The catalytic treatment of organic and inorganic compounds in aqueous phase is a very promising technique for wastewater treatment. Most catalytic procedures in aqueous phase concern oxidation of organic compounds via gaseous oxygen supplied in the solution. This process called Wet air oxidation (WAO), proposed and developed by Zimmermann [6], is one of the most economically and technologically viable AOPs for wastewater treatment, since it has a great potential for the treatment of effluent, which contains high concentration of organic matter (about 10–100 g/L of COD) and/or toxic contaminants for which direct biological treatment is not feasible. In WAO, the organic pollutants are either partially oxidized into biodegradable intermediates or mineralized to carbon dioxide, water and innocuous end products at high temperature (125–320◦C) and pressure (0.5–20 MPa), using a gaseous source of oxygen (either pure oxygen or air) as the oxidant [7]. WAO is not only eco-friendly but also economically efficient compared to other AOPs, where harmful and expensive oxidizing agents, like ozone and hydrogen peroxide are used.
Application of a proper catalyst, in the WAO process, i.e. catalytic wet air oxidation (CWAO), not only reduces the severity of reaction conditions but also, favors the decomposition of even refractory pollutants, resulting in significant reduction of the capital and operational cost [7-10]. Accounting for a variation according to the type of wastewater, the operating cost of a CWAO process is about half that of a conventional non-catalytic WAO due to milder operation conditions and shorter residence times [11]. Although the homogenous catalysts, e.g. dissolved copper salts, are effective, an additional separation step is required to remove or recover the metal ions from the treated effluent due to their toxicity, which increases the operational cost. Thus, the development of highly active heterogeneous catalysts has received great attention, since no additional separation step is necessary. Various solid catalysts including noble metals, metal oxides, and mixed oxides have been widely studied for the CWAO of aqueous pollutants. Worthnoting is that there are several reports in literature where a catalytic treatment in aqueous phase process was used for the hydrogenation of several unsaturated organic compounds [12-15]. In this case the catalytic hydrogenation takes place via gaseous hydrogen at ambient pressure and temperature.
The activity of the catalyst is of great importance and affects both the performance and the cost of the process. In common catalytic and electrocatalytic devices the properties of the catalyst can hardly be changed and/or improved in situ, while very often catalyst deactivation takes place due to undesirable side reactions and deposition of poisonous byproducts. To overcome these drawbacks the catalyst should be regenerated or replaced periodically rising the cost of the process. As it has been already mentioned, expensive materials (such as noble metals) are usually selected due to their stability and high activity.
 
In the past it has been shown (by the group of Professor Costas Vayenas) that the catalytic activity and selectivity of conductive catalysts deposited on solid electrolytes can be altered in a very pronounced, reversible and, to some extent, predictable manner by applying electrical currents or potentials (typically up to ±2 V) between the catalyst and a second electronic conductor (counter electrode) also deposited on solid electrolyte [16]. The term Electrochemical Promotion of Catalysis (EPOC) is used to describe the very pronounced changes observed in the catalytic properties. Numerous different catalytic reactions (oxidations, reductions, hydrogenations, dehydrogenations, isomerizations, decompositions) have been electrochemically promoted on Pt, Pd, Rh, Ag, Au, Ni, Cu, Fe, IrO2, RuO2 catalysts deposited on O2- (YSZ), Na+ or K+ (b”-Al2O3), H+ (CaZr0.9In0.1O3-a, Nafion), F- (CaF2), mixed ionic-electronic (TiO2) and CeO2 conductors [16,17]. EPOC seems to be not limited to any particular class of conductive catalyst, catalytic reaction or ionic support. It can be used in order to affect the rate and selectivity of heterogeneous catalytic reactions in a reversible and very pronounced manner.
Although the majority of the studies concerns gaseous heterogeneous catalytic reactions using solid electrolytes there are a few reports suggesting the utilization of EPOC in aqueous media using liquid electrolytes [18-21]. These studies reported the catalytic reaction of gaseous hydrogen and oxygen on Pt electrodes immersed in a liquid electrolyte and reported the enhancement of the catalytic rates under anode polarization.
The first objective of the current proposal is the application of EPOC in aqueous phase catalytic processes. The catalytic reaction could be either an oxidation or a reduction of a specific light hydrocarbons and alcohols, phenolic, carboxylic acids and nitrogen-containing compounds which are dissolved in the liquid phase. The final products of the treatment could be CO2 and H2O in the case of full oxidation processes and/or even useful products such hydrogen or valuable hydrocarbons in the case of partial oxidation or hydrogenation processes. The novelty of the proposal concerns the combination of the phenomenon of EPOC with aqueous phase catalytic oxidations/hydrogenations and the development of an effective, low cost and controllable electrocatalytic procedure operating in atmospheric conditions for chemical treatment and high value products synthesis. Both conventional and novel catalysts will be developed and studied under electropromoted conditions.
The second aim of the project will be the investigation of the origin of EPOC in aqueous media using the technique of the Differential Mass Spectrometry (DMS). It should be noted that although DMS has been successively employed in electrocatalytic cells [22] the purpose was not neither on the EPOC effect nor on the mechanism and origin of electropromotion.
As a result, the successful application of EPOC in aqueous phase catalytic oxidations/hydrogenations will lead to a novel process substantially more productive and efficient than current technologies.


References
1. Zhou M, He J (2007). Electrochimica Acta 53:1902
2. Koparal A, Yavuz Y, Gurel C, Ogutveren U (2007). Journal of Hazardous Materials 145:100
3. Sanroman M, Pazos M, C C (2004). Journal of Chemical Technology and Biotechnology 79:1349
4. Xiong Y, Strunk P, Xia H, Zhu X, Karisson H (2001). Water Research 35:4226
5. Comninellis C (1994) Electrochimica Acta 39 (11-12):1857
6. Zimmermann F (1958) Chemical Engineering Journal 65:117
7. Mishra V, Mahajani V, JB J (1995). Industrial and Engineering Chemistry Researsh 34:2
8. Luck F (1996). Catalysis Today 27:195
9. Imamura S (1999). Ind Eng Chem Res 38:1743
10. Kim K, Ihm S (2011). Journal of Hazardous Materials 186:16
11. Levec J (1997). Chemical and Biochemical Engineering Q 11:47
12. Pardillos-Guindet J, Metais S, Vidal S, Court J, Fouilloux P (1995). Applied Catalysis A: General 132:61
13. Wagnar C (1970). Advanced Catalysis 21:323
14. Lamy-Pitara E, Bencharif L, Barbier J (1985). Applied Catalysis B: Environmental 18:117
15. Lamy-Pitara E, Belegridi I, El Ouazzani L, Barbier J (1993). Catalysis Letters 19:87
16. Vayenas CG, Bebelis S, Pliangos C, Brosda S, Tsiplakides D (2001) Electrochemical Activation of Catalysis: Promotion, Electrochemical Promotion and Metal-Support Interactions. Kluwer Academic/Plenum Publishers, New York
17. Katsaounis A (2010) Journal of Applied Electrochemistry 40 (5):885
18. Labou D, Neophytides SG (2007) Topics in Catalysis 44 (3):451
19. Tsiplakides D, Neophytides SG, Enea O, Jaksic M, Vayenas CG (1997) Journal of the Electrochemical Society 144 (6):2072
20. Neophytides SG, Tsiplakides D, Stonehart P, Jaksic M, Vayenas CG (1996) The Journal of Physical Chemistry 100 (35):14803
21. Neophytides SG, Tsiplakides D, Stonehart P, Jaksic MM, Vayenas CG (1994) Nature 370 (6484):45
22. Anastasijevic NA, Baltruschat H, Heitbaum J (1993) Electrochimica Acta 38 (8):1067

 

Reports

Title Description File
Open Meeting for the Presentation of Project Achievements, 26/10/2015 Oral Presentations and Agenda
 
Electrochemical CO2 reduction: Product Distribution Screeening on Cu-Co Thin Film Composition Spread Samples by Coupling of a Scanning Flow Cell to OLEMS Invited Talk of Ian-Philipp Grote, Max Planck Institute for Iron Research, Duesseldorf, Germany, 26/10/2015
Differential Electrochemical Mass Spectroscopy (DEMS): New Insights Oral Presentation Abd-El-Aziz And -El-Latif, 26/10/2015
Differential Electrochemical Mass Spectroscopy (DEMS) as a toll for reactions study. The cas of hydrogen oxidation and methanol reforming. Oral Presentation J. Vakros, University of Patras, 26/10/2015
Ηλεκτροχημική οξείδωση αλκοολών σε κυψελίδες καυσίμου χαμηλών θερμοκρασιών Oral Presentation at the 10th Panhellenic Meeting of Chemical Engineering, Patras, 04 – 06/05 2015, B. Hasa, E. Kalamaras, E.I. Papaioannou, J. Vakros, and A. Katsaounis
Hydrophobically Modified Porous Anodic Alumina Membranes Oral Presentation Nikolaos Spiliopoulos, University of Patras, 26/10/2015
Study of methanol reforming using Differential Electrochemical Mass Spectroscopy (DEMS). Oral Presentation at the 4th European Conference on Environmental Application of Advanced Oxidation Processes, Athens, Greece, 21 - 24/10 2015, J. Vakros, B. Hasa and A. Katsaounis
Study of hydrogen oxidation using Differential Electrochemical Mass Spectroscopy (DEMS) Poster Presentation at the 4th European Conference on Environmental Application of Advanced Oxidation Processes, Athens, Greece, 21 - 24/10 2015, J. Vakros, B. Hasa and A. Katsaounis
Ανοδικά ηλεκτρόδια Pt-RuO2-TiO2 για την ηλεκτροχημική οξείδωση αλκοολών σε κυψελίδες καυσίμου χαμηλών θερμοκρασιών Oral Presentation at the 4th Symposium of Green Chemistry and Sustainable development, Ioannina, Greece, 30/10 – 01/11 2014, J. Vakros, B. Hasa, A. Katsaounis.

Main Results/Publications

PUBLICATIONS
1.  "Effect of TiO2 loading on Pt-Ru Catalysts During Alcohol Electrooxidation", B. Hasa, E. Kalamaras, E.I. Papaioannou, J. Vakros, L. Sygellou and A. Katsaounis, Electrochim. Acta 179 (2015) 578-587.
2.  "Ηλεκτροχημική οξείδωση αλκοολών σε κυψελίδες καυσίμου χαμηλών θερμοκρασιών",  B. Hasa, E. Kalamaras, E.I. Papaioannou, J. Vakros, and A. Katsaounis, Proceedings of the 10th Panhellenic Meeting of Chemical Engineering, Patras, 04 – 06/05 2015


ORAL PRESENTATIONS
10th Panhellenic Meeting of Chemical Engineering, Patras, 04 – 06/05 2015
“Anodic electrodes Pt-Ru-TiO2 for electrochemical oxidation of alcohols in low temperature fuel cells” (Ηλεκτροχημική οξείδωση αλκοολών σε κυψελίδες καυσίμου χαμηλών θερμοκρασιών), B. Hasa, E. Kalamaras, J. Vakros, A. Katsaounis.

4th European Conference on Environmental Applications of Advanced Oxidation Processes, Athens, Greece, 21 – 24/10 2015
“Study of methanol reforming using Differential Electrochemical Mass Spectrometry (DEMS) ”, J. Vakros, B. Hasa, A. Katsaounis.

4th Symposium of Green Chemistry and Sustainable development, Ioannina, Greece, 30/10 – 01/11 2014
"Ανοδικά ηλεκτρόδια Pt-RuO2-TiO2 για την ηλεκτροχημική οξείδωση αλκοολών σε κυψελίδες καυσίμου χαμηλών θερμοκρασιών" (Electrochemical oxidation of alcohols in a low temperature fuel cell), J. Vakros, B. Hasa, A. Katsaounis.
 

POSTER PRESENTATIONS
4th European Conference on Environmental Applications of Advanced Oxidation Processes, Athens, Greece, 21 – 24/10 2015
“Study of hydrogen oxidation using Differential Electrochemical Mass Spectrometry (DEMS) ”, J. Vakros, A. Katsaounis.

Collaborations

Department of Physical and Theoretical Chemistry, University of Bonn, Germany
Department of Physics, University of Patras, Greece

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