Download Versión PowerPoint
Document related concepts
no text concepts found
Transcript
Proyectos de Investigación Jorge Ibáñez Cornejo (JIC) • Procesos electroquímicos para: • Eficientar el uso de energía • Tratamiento de contaminantes • Electrogeneración de luz PROCESOS SIMULTÁNEOS • En electroquímica es frecuente que se use sólo una de las dos reacciones de la celda para producir una sustancia de interés. • Por ello estamos trabajando en procesos en donde se usa la electricidad en ambos electrodos para llevar a cabo una reacción útil Electrocoagulation - + OHFe2+ OH- Ibanez, J. G.; Singh, M. M.; Szafran, Z.; Pike, R. M. “Laboratory Experiments On Electrochemical Remediation Of The Environment. Part 4. Color Removal of Simulated Wastewater by Electrocoagulation-Electroflotation”. J. Chem. Educ. 75 (8) 1040-1041 (1998). Electrocoagulación asistida por un campo magnético Fuente de poder VOLTAJE - + Ánodo (Fe) Cátodo + - Fe(OH)2 Fe(OH)3 Fe2+ [Ar]3d6 diamagnético Fe3+ [Ar]3d5 paramagnético Electrocoagulación asistida por un campo magnético Fe concentration, mg/L Average Fe(II/III) production as a function of the applied potential, in N 2 5 4 3 Avg. mg/L Fe2+ 2 Avg. mg/L Fe3+ 1 0 3 4.5 6 7.5 Voltage, volts 9 12 Producción y uso de Ag3+ para oxidación de contaminantes AgAg3+ + 3e3H2O + 3e- 3/2 H2 + 3OH- Removal of insoluble MX(s) by chelation and regeneration of M + L CuCO3·Cu(OH)2 - surrogate pollutant MX(s) + H2O MX(s) + EDTA Cu 2+ Cu2CO3(OH)2 (s) CuO(s) 1.0 Fraction 0.8 0.6 0.4 0.2 0.0 0 2 4 6 8 10 12 14 pH Ibanez, Jorge; Balderas-Hernández, Patricia; Garcia-Pintor, Elizabeth; Barba-Gonzalez, Sandy; Doria-Serrano, Maria; Hernaiz-Arce, Lorena; Diaz-Perez, Armando; Lozano-Cusi, Ana. Laboratory Experim. on the Electrochem. Remediation of Cu pH = 3.5 H4 EDTA ELECTROLUMINISCENCIA SIMULTÁNEA ClO2 H2O 2e ClO 2OH ClO H2O e Paired Electrochemical Processes Biaani Sotomayor Martínez-Barranco, Daniel Zavala Araiza, Jorge G. Ibanez Depto. Ing. y C. Químicas. Mexican Microscale & Green Chemistry Center. U. Iberoamericana – México Luminol (2,3-aminophthalohydrazide) can be oxidized in basic conditions to yield a relatively longlived excited state from which it emits blue light. A co reactant (H2O2) was used to increase light emission. Paired electrochemical processes: - Avoid the need for a “sacrificial reaction” - Reduce the generation of waste and the consumption of energy + Both electrodic reactions can be used for ELECTROLUMINISCENCE (ECL) FIRST EXAMPLE OF SIMULTANEOUS ELECTROLUMINISCENCE Study of individual processses (i.e., conditions for ECL in cathode and anode) Characterization of luminol and ClO- (LSV) (Figures 1a – 1c) Couple both processes and attempt simultaneous ECL Obtain ECL separately Cathodic ECL is more sensitive; the cathodic potenial is fixed at -200 mV -1.05 Current ( m A) Current ( m A) 300 250 200 -6.05 Reduction signal at -450 mV (should NOT occur at the cathode) 0 -11.05 150 100 -16.05 50 0 0 200 400 600 800 1000 -21.05 -800 Potential (mV vs. Ag/AgCl) -600 -500 -400 -300 -200 Potential (mV vs. Ag/AgCl) -100 Reduction signal. Starts at -200 mV (should occur at cathode). -20 -30 -40 -50 -60 -1000 -700 * Figure 2 shows the cell arrangement used for the simultaneous process. -10 Current (m A) Oxidation signal at 300 mV (should occur at anode) 350 Blue ECL is produced in both compartments (constant in the anodic side, intermittent in the cathodic side). -800 -600 -400 -200 0 200 400 0 Potential (mV vs. Ag/AgCl) Figure 1 – (a) Anodic LSV for luminol in basic medium, (b) cathodic LSV for luminol in basic medium, (c) cathodic LSV for ClO2-. Pt gauze Reference electrode (Ag / AgCl) Reference electrode (Ag/AgCl) Pt flag Catholyte: 1 M NaClO2 (5 mL) Anolyte: 5.6 x 10-6 M luminol solution made basic with NaOH. H2O2 was added as coreactant (30 μL of 10 % *As electrochemical reduction initiated, 2 mL of luminol/H2O2 solution (same as anolyte) was added dropwise on top of the Pt gauze. H2O2 in 5 mL of test solution) Cationic Exchange membrane Figure 2 – Experimental cell used for simultaneous ECL. LITERATURE REFERENCES 1. Paddon, C.A.; Atobe, M.; Fuchigami, T.; He, P.; Watts, P.; Hasswel, S.J.; Pritchard, G.J.; Bull, S.D.; Marken, F. Towards Paired and Coupled Electrode Reactions for Clean Organic Microreactor Electrosyntheses, J. Appl Electrochem, 2005, 36, 617-634. 2. Rajeshwar, K.; Ibanez, J. G. Environmental Electrochemistry: Fundamentals and Applications in Pollution Abatement. Academic Press, San Diego, 1997. 3. Gomez-Gonzalez, A.;. Ibanez, J. G.; Vasquez-Medrano, R. C.; Paramo-Garcia, U.; Zavala-Araiza, D. Cathodic Production of ClO2 from NaClO3, J. Electrochem. Soc. 2009, 156 (7), E113-E117. 4. Mena-Brito, R.; Terrazas-Moreno, S.; Ibanez, J. G. Towards A Green Production Of Chlorine Dioxide By Convergent Paired Electrosynthesis. (In press, Fresenius Environmental Bulletin, Germany). 5. Liu, X.; Jiang, H.; Lei, J.; Ju, H. Anodic Electrochemiluminescence of CdTe Quantum Dots and its Energy Transfer for Detection of Catechol Derivatives, Anal. Chem. 2007, 79, 8055 - 8060. 6. Bolton, E.; Richter, M.; Light Emission at Electrodes: An Electrochemiluminescence Demonstration”, J. Chem. Ed., 2001, 78, 641 – 643. 7. Kumala, S.; Ala – Kleme, T.; Papkovsky, D.; Loikas, K. Cathodic Electrogenerated Chemiluminescence of Luminol at Disposable Oxide – covered Aluminum Electrodes”, Anal. Chem. 1998, 70, 1112 – 1118. (7) (8) (9) Luminol in NaOH + H2O2 The equilibrium between ClO2- and ClO- at a cathode could allow for the use of this last species to provoke the oxidation of the luminophore to produce an excited state. EXAMPLE: We developed a small–scale process for the production of ClO2. (An environmentallyfriendly alternative to Cl2 for disinfection, water treatment, pulp bleaching) + Reduction of ClO3-, oxidation of ClO2- Cl2 2OH LH Cl2 AP2* AP2* AP2 hν (6) Gases: Indirect Oxidation, Outer-Cell Process Electrochemical treatments of H2S Lab experiment with H2S Ibanez, J. G. “Laboratory Experiments On Electrochemical Remediation Of The Environment. Part 5. Indirect H2S removal”. J. Chem. Educ. 2001 (6) 78, 778-779. Oxidation of Sulfide Ions by Iodine Iodine Regeneration by Electrolysis Frost diagram of Cl species 11 10 9 8 7 -nE 6 pH 0 pH 14 5 4 3 2 1 0 -1 -2 -1 0 1 2 3 4 5 Oxidation number 6 7 8 Electrochemical Production of Chlorine Dioxide Paired production of ClO2 NaClO3, 1 M NaClO2, 1 M Identification UV-Vis Spectrum of gaseous chlorine dioxide Ibanez, Jorge G.; Navarro-Monsivais, Carlos; Terrazas-Moreno, Sebastian; Mena-Brito, Rodrigo; Pedraza-Segura, Lorena; Mattson, Bruce; Anderson, Michael P.; Fujita, Jiro; Hoette, Trisha. “Microscale Environmental Chemistry, Part 5. Production of ClO2, an Environmentally-Friendly Oxidizer and Disinfectant”, Chem. Educator 2006, 11, 174-177. Photocatalysis eCB VB Ox 1 Red 1 Cu2+ Cu1+ or Cu Red 1 Ox 1 Org CO2 h+ Coupled oxidation and reduction Cu(II) removal and organic oxidation by photocatalysis before To power sourc e UV lamp quartz tubes TiO2 + Cu(II) + org Ba(OH)2 Side view Optional CO test 2 Top view after At/Ao Cu (II) concentration change 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 10 20 30 40 50 60 70 t/min Ibanez, Jorge G.; Mena-Brito, Rodrigo; Fregoso-Infante, Arturo. “Laboratory Experiments on the Electrochemical Remediation of the Environment. Part 8. Microscale Photocatalysis”, J. Chem. Educ. 2005, 82, 1549-1551.
Related documents