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Catalytic Wet Peroxide Oxidation (CWPO) Activated by Lanthanum-Perovskites

This study investigates the potential of iron, copper, and manganese lanthanum-perovskites for catalytic wet peroxide oxidation (CWPO). Results show promising catalytic performance in the degradation of organic compounds.

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Catalytic Wet Peroxide Oxidation (CWPO) Activated by Lanthanum-Perovskites

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  1. (SP-SEC-AOTs-1) Catalytic Wet Peroxide Oxidation (CWPO) activated by lanthanum-perovskites of iron copper or manganese L. A. Galeano*, J. C. Delgado E-mail*: alejandrogaleano@udenar.edu.co The First Latin American International Conference on Semiconductor Photocatalysis, Solar Energy Conversion, & Advanced Oxidation Technologies Cartagena, Colombia. May 28-31, 2013

  2. Outline • Introduction (AOPs; CWPO; Perovskites) • Materials and Methods • Results • Conclusions • Acknowledgments

  3. Introduction

  4. Phenol, substituted phenols, light carboxylic acids, azo-dyes, PCBs, organo-chlorinated compounds, pesticides, herbicides, VOCs, hormones, etc. Negative impact on surrounding ecosystems and humans even under trace concentrations Toxic and hazardous compounds. Biorefractory Natural water resources “Poorly defined mix of organic substances with variable properties in terms of acidity, MW and molecular structure” * Predominantly phenolic and carboxylic functionalities, plus alcohol, purine, amine and ketone groups DBPs precursors NOM Sharp et al. (2006), Sci. Total Environ. 363, 183 – 194.

  5. Martínez-Huitle et al. (2009), Appl. Catal. B: Environ. 87, 105 – 145.

  6. Advanced Oxidation Processes (AOPs) CWPO Fe,Cu, ¿Mn? – bearing solid catalysts H2O2/Fe2+ (Fenton) TiO2/hn/O2 Photocatalytic H2O2/Fe3+ (Fenton - like) H2O2/Fe2+ (Fe3+) /UV (Photoassisted Fenton) HO· Mn2+/Oxalic acid/O3 H2O2/Fe3+- oxalate H2O2/UV O3/UV O3/H2O2

  7. Catalytic Wet Peroxide Oxidation (CWPO) H2O2 HO.+ HO.2 CO2 + NO3- + SO42- + H2O Galeano et al. (2010), Appl. Catal. B: Environ. 100, 271 – 281.

  8. ABO3 Perovskites: structural aspects • A-substitutions • May lead to structural defects as anionic or cationic vacancies. • Change in the oxidation state of the B-sites • B-substitutions • Higher oxidation state leads to larger quantities of available oxygen at low temperature. • Vacancies of oxygen also favors catalytic oxidations because of oxygen mobility is enhanced into the lattice. Barbero et al. (2006), Appl. Catal. B: Environ. 65, 21 – 30.

  9. Materials and methods

  10. Experimental sketch LaMnO3 (LMO) LaFeO3 (LFO) LaCuO3 (LCO)

  11. Reagents and methods Reagents (Cer.) High purity oxides Fe2O3 (Aldrich), CuO (Aldrich), MnO2 (Merck) and La2O3 (Merck). Stoichiometricamounts. (Cit.)La(NO3)3•6H2O, Fe(NO3)3•9H2O, (Cu(NO3)2•3H2O), Mn(NO3)2•4H2O in stoichiometricamounts. C6H8O7•H2O (Merck) – 10% of stoichiometricexcess. Power XRD: Siemens D-500 diffractometer; 40 kV and 30mA. Scanning speed 2°/min, CuKα filtered radiation (λ = 1.5418Å). Database PCPDFWIN 2002. H2-TPR: Chembet 3000 (Quantachrome) – TCD. Samples 60 mesh, degasification 400 °C/1 h in Ar gas-flow. RT-1000 °C, ramp 10 °C/min, 10% (v/v) H2/Ar; 0.38 mL/s. Catalytic runs: Semi-batch reactor. Catalyst loading = 5.0 g/L; [MO]0 = 100 ppm; [PhO]0 = 5*10-4mol/L; [H2O2] = 0.1 mol/L; H2O2 addition flow rate = 2.0 mL/h; T = 18 ± 2.0 ºC; P = 0.7 atm.; Sampling = 1.5 mL/each time; treaction = 240 min; pH = 3.7. Analytical methods: MO: UV-Vis spectroscopy (λ = 467-486 nm as a f(pH)); PhO: HPLC-DAD – TOC. [Fe, Cu, Mn]240 min: AAS

  12. Results

  13. Powder-XRD analyses LMO LFO

  14. Powder-XRD analyses LCO – cit . LCO – cer.

  15. H2-TPR analyses Cu2+ Cu+ ¿ Cu3+ Cu2+ ? (275 °C) Cu+ Cu0 (520 °C) Mn4+ Mn3+ (346 °C) Fe3+ Fe2+ (450 – 560 °C) Mn2O3 Mn3+ (489 °C) Fe3+ Fe2+ (450 – 560 °C) Mn3+  Mn2+ (889 °C)

  16. Catalytic performance: MO removal [Mn]leached = 0.09 mg/L [Mn]leached = 8.01 mg/L. [Cu]leached = 1.0 mg/L [Cu]leached = 0.3 mg/L pH = 7.0 pH = 5.5 RT = 18 ºC; P = 0.7 atm; [MO]0 = 100 mg/L; [catal.] = 5.0 g/L; [H2O2]dose = 0.95 thestoichiometricfor full mineralization; [H2O2]flow-rate = 2.0 mL/h

  17. Catalytic performance: PhO removal [Fe]leached = 0.7 mg/L [Fe]leached = 0.3 mg/L. pH = 3.7 RT = 16 ºC; P = 0.7 atm; [PhO]0 = 36 mg C/L; [catal.] = 5.0 g/L; [H2O2]dose = 1.16 thestoichiometricfor full mineralization; [H2O2]flow-rate = 2.0 mL/h

  18. Conclusions • Mn and Fe-based La-perovskites can be prepared both pure and well crystallized by the citrate method at T as low as 600 °C. • Cu-based perovskites did not properly crystallized even under 1000 °C/24 h, probably because Cu3+ demands for higher P(O2) and T. • LaMnO3-(cit.) showed interesting catalytic behaviour in the CWPO-degradation of MO (73 % of decoulorization at t = 4 h; pH = 7.0). • LaFeO3 exhibited the higher catalytic potential in the CWPO-degradation of PhO (full depletion at t < 1 h; 65 % of TOC mineralized at t = 4 h), comparable to that usually displayed by Al/Fe-PILCs.

  19. Acknowledgement • Research Group ESCA, UNAL – Bogotá: H2-TPR and PhO degradation experiments. • Prof. M.A. Vicente, University of Salamanca, Spain. XRD analyses. ¡Thank you!

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