Oscar M González Díaz | Universidad de Las Palmas de Gran Canaria (original) (raw)
Papers by Oscar M González Díaz
Journal of Electroanalytical Chemistry
Journal of the Chemical Society, Faraday Transactions, 1991
ABSTRACT
Applied Catalysis B: Environmental, 2012
ABSTRACT Photocatalytic degradation of 3-chloropyridine in the homogeneous (photo-Fenton) and het... more ABSTRACT Photocatalytic degradation of 3-chloropyridine in the homogeneous (photo-Fenton) and heterogeneous (TiO 2) phase was studied using both UV and sun light. Complete mineralization was achieved in both cases though times required in photo-Fenton process were ca. 5 times shorter under our experimental conditions. Results found at lab scale (solar simulator) were successfully extrapolated to a larger scale (30L) thus evidencing the validity of the method for treatment of waters polluted with this kind of chemical. Toxicity tests (Vibrio fischeri) showed that some intermediates more toxic than 3-chloropyridine were formed as reaction proceeded. © 2012 Elsevier B.V.
Zeitschrift für Physikalische Chemie, 1967
International Journal of Legal Medicine, 2012
Gas embolism can arise from different causes (iatrogenic accidents, criminal interventions, or di... more Gas embolism can arise from different causes (iatrogenic accidents, criminal interventions, or diving related accidents). Gas analyses have been shown to be a valid technique to differentiate between putrefaction gases and gas embolism. In this study, we performed systematic necropsies at different postmortem times in three experimental New Zealand White Rabbits models: control or putrefaction, infused air embolism, and compression/decompression. The purpose of this study was to look for qualitative and quantitative differences among groups and to observe how putrefaction gases mask in vivo gas embolism. We found that the infused air embolism and compression/decompression models had a similar gas composition prior to 27h postmortem, being typically composed of around 70-80 % of N 2 and 20-30 % of CO 2 , although unexpected higher CO 2 concentrations were found in some decompressed animals, putting in question the role of CO 2 in decompression. All these samples were statistically and significantly different from more decomposed samples. Gas composition of samples from more decomposed animals and from the putrefaction model presented hydrogen, which was therefore considered as a putrefaction marker.
RSC Advances, 2020
Nanocrystalline titania was synthesized by a simple, innovative and eco-friendly gelation method ... more Nanocrystalline titania was synthesized by a simple, innovative and eco-friendly gelation method by using biopolymers (polysaccharides).
Chemical Engineering Journal, 2016
Effects of Ag and Pd on photocatalytic oxidation of pollutants were studied. The state of oxidati... more Effects of Ag and Pd on photocatalytic oxidation of pollutants were studied. The state of oxidation of metals affect photodegradation of the pollutants. The highest degradation rate for isoproturon was obtained with TiO 2-Pd. The highest degradation rate for diclofenac and phenol were obtained with TiO 2-Ag. The photodegradation of the byproducts of all pollutants were identified.
Optimisation of the photocatalytic activity of Ti02 and mixtures of TiOl + activated carbon throu... more Optimisation of the photocatalytic activity of Ti02 and mixtures of TiOl + activated carbon through dosage processes
Journal of the Chemical Society Faraday Transactions
Journal of Electroanalytical Chemistry
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1989
ABSTRACT
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1988
ABSTRACT Activity coeff. values for trichloroacetic acid (HTCA) at different acid concns. were de... more ABSTRACT Activity coeff. values for trichloroacetic acid (HTCA) at different acid concns. were detd. from a study of its aq. mixts. with HCl. The mixed system NaCl + NaTCA was also studied to det. the value of the mixing parameter, θCl-TCA, needed for substitution in the Pitzer equations. The γ± values are compared with those obtained in previous work in this lab. (E et al., 1987), in which the cell used to obtain the values included an uncancelled liq. junction potential, ΔEj, and the values were only apparent. Finally, an estn. of the liq. junction potential is obtained by combining the apparent values with the calcd. ones. The potentials thus obtained are compared with those calcd. from the Henderson equation. [on SciFinder(R)]
Berichte der Bunsengesellschaft für physikalische Chemie, 1993
F. Hernandez-Luis et al: Activity Coefficients of the Systems etc. ... Activity Coefficients of t... more F. Hernandez-Luis et al: Activity Coefficients of the Systems etc. ... Activity Coefficients of the Systems: NaBr + Na-Acetate + H 2 0 and NaBr + ... Na-Propionate + H20 at 25OC. Application of Scatchard's, Pitzer's and Lim's ... Felipe Hernandez-Luis, Luis Fernhndez-Mkrida, ...
Journal of Solution Chemistry, 1991
Activity coefficients for NaBr in the system NaBr+NaFormate+H2O at 25°C were determined from emf ... more Activity coefficients for NaBr in the system NaBr+NaFormate+H2O at 25°C were determined from emf measurements at different total ionic strengths. At each total ionic strength, the measurements were carried out at different Na-Formate/NaBr ionic strength ratios. The experimental activity coefficients were comparatively analyzed using Scatchard's, Pitzer's and Lim's methods. Although all these models can be successfully applied to the analysis
Journal of Solution Chemistry, 1995
Activity coefficients for NaBr in ethanol-water mixtures with O, 20, 40, 60, 70, 80, 90 and 99.8 ... more Activity coefficients for NaBr in ethanol-water mixtures with O, 20, 40, 60, 70, 80, 90 and 99.8 weight% of ethanol have been determined at 25 ~ from the emf measurements of the galvanic cells Na-glass / NaBr (m), tt20 (]00-Y), EtOH(Y), AgBr(s) [ Ag The results obtained were analyzed by using the Pitzer equation. Those for the mixtures with ethanol content higher than 60 wt% were also analyzed by using a chemical model and their ion pair formation constants
Journal of Hazardous Materials, 2007
Due to the toxicity effects and endocrine disrupting properties of phenolic compounds, their remo... more Due to the toxicity effects and endocrine disrupting properties of phenolic compounds, their removal from water and wastewater has gained widespread global attention. In this study, the photocatalytic degradation of phenolic compounds in the presence of titanium dioxide (TiO 2) nano-particles and UV light was investigated. A full factorial design consisting of three factors at three levels was used to examine the effect of particle size, temperature and reactant type on the apparent degradation rate constant. The individual effect of TiO 2 particle size (5, 10 and 32 nm), temperature (23, 30 and 37 °C) and reactant type (phenol, o-cresol and m-cresol) on the apparent degradation rate constant was determined. A regression model was developed to relate the apparent degradation constant to the various factors. The largest photocatalytic activity was observed at an optimum TiO 2 particle size of 10 nm for all reactants. The apparent degradation rate constant trend was as follows: o-cresol > m-cresol > phenol. The ANOVA data indicated no significant interaction between the experimental factors. The lowest activation energy was observed for o-cresol degradation using 5-nm TiO 2 particles. A maximum degradation rate constant of 0.0138 min −1 was recorded for o-cresol at 37 °C and a TiO 2 particle size of 13 nm at a D-optimality value of approximately 0.98. The response model adequately related the apparent degradation rate constant to the factors within the range of factors under consideration.
Journal of Electroanalytical Chemistry, 1992
... Activity coefficients for (sodium chloride + sodium hydrogen malonate + sodium malonate) (aq)... more ... Activity coefficients for (sodium chloride + sodium hydrogen malonate + sodium malonate) (aq) at 25 C. Application of Pitzer's equations Luis Fernandez-Merida, Felipe F. Hernandez-Luis, Oscar M. Gonzalez-Diaz and Miguel A ... 4 WJ Hamer, JO Burton and SF Acree, J. Res. Natl. ...
Journal of Chemical & Engineering Data, 1986
Transference numbers at 25 OC are measured for dlfferent concentratlons of NaBr by uslng both a f... more Transference numbers at 25 OC are measured for dlfferent concentratlons of NaBr by uslng both a falling and a rlslng sheared movlng-boundary cell. Both Ag/AgBr and Ag/AgCI electrodes are used with the rising cell, while only Ag/AgBr electrodes are used wlth the falling one. After different corrections are applled to the observed values, "best" transference numbers are calculated. I n all cases, these best values agree perfectly wlth one another and by applylng to them the Fuoss-Onsager and PMS equations, values at zero concentration, To, are obtalned. Moreover, electrolytic conductances at 25 OC for NaBr at different concentratlons are measured and later extrapolated to null lonlc strength by uslng the 1957 Fuoss-Onsager conductance equation. Indlvldual conductance values are obtalned by comblnlng both llmltlng parameters, T o and A'. I n the same manner, an adequate value for the adjustable parameter a , distance of the closest approach catlon-anion, Is obtalned from both experlmental techniques.
International Journal of Hydrogen Energy, 2013
A series of synthesised TiO 2-based and commercial photocatalysts were modified by Pt photodeposi... more A series of synthesised TiO 2-based and commercial photocatalysts were modified by Pt photodeposition and a study made of their photocatalytic activity in hydrogen production. The modified commercial photocatalysts were Evonik P25, Kronos vlp7000 and Hombikat UV-100, and the other modified photocatalysts were synthesised by our group using solegel and solegel hydrothermal processes (SG400, SG750 and HT). Pt weight percentages used in the study were 0.5, 1.0 and 2.1 wt.% (Pt/TiO 2). The photocatalysts were extensively characterised by X-ray diffraction (XRD), UVevis diffuse reflectance, BrunauereEmmetteTeller (BET) surface area measurement, transmission electron microscopy (TEM), scanning electron microscopy (SEMeEDX), Fourier transform infrared spectroscopy (FTIR) and laser light dispersion. Methanol (25% vol.) was used as sacrificial agent over the 8 h of the hydrogen production tests and measurements were taken of the final concentrations of formaldehyde and formic acid as well as initial and final TOC. Photoactivity of all photocatalysts increased in the presence of Pt. The most efficient of the synthesised photocatalysts was SG750 and of the commercial photocatalysts P25. Maximum production of SG750 was 1846 mmol h À1 at 1.0 wt.% Pt and its production per surface unit was notably higher than that of P25.
Journal of Electroanalytical Chemistry
Journal of the Chemical Society, Faraday Transactions, 1991
ABSTRACT
Applied Catalysis B: Environmental, 2012
ABSTRACT Photocatalytic degradation of 3-chloropyridine in the homogeneous (photo-Fenton) and het... more ABSTRACT Photocatalytic degradation of 3-chloropyridine in the homogeneous (photo-Fenton) and heterogeneous (TiO 2) phase was studied using both UV and sun light. Complete mineralization was achieved in both cases though times required in photo-Fenton process were ca. 5 times shorter under our experimental conditions. Results found at lab scale (solar simulator) were successfully extrapolated to a larger scale (30L) thus evidencing the validity of the method for treatment of waters polluted with this kind of chemical. Toxicity tests (Vibrio fischeri) showed that some intermediates more toxic than 3-chloropyridine were formed as reaction proceeded. © 2012 Elsevier B.V.
Zeitschrift für Physikalische Chemie, 1967
International Journal of Legal Medicine, 2012
Gas embolism can arise from different causes (iatrogenic accidents, criminal interventions, or di... more Gas embolism can arise from different causes (iatrogenic accidents, criminal interventions, or diving related accidents). Gas analyses have been shown to be a valid technique to differentiate between putrefaction gases and gas embolism. In this study, we performed systematic necropsies at different postmortem times in three experimental New Zealand White Rabbits models: control or putrefaction, infused air embolism, and compression/decompression. The purpose of this study was to look for qualitative and quantitative differences among groups and to observe how putrefaction gases mask in vivo gas embolism. We found that the infused air embolism and compression/decompression models had a similar gas composition prior to 27h postmortem, being typically composed of around 70-80 % of N 2 and 20-30 % of CO 2 , although unexpected higher CO 2 concentrations were found in some decompressed animals, putting in question the role of CO 2 in decompression. All these samples were statistically and significantly different from more decomposed samples. Gas composition of samples from more decomposed animals and from the putrefaction model presented hydrogen, which was therefore considered as a putrefaction marker.
RSC Advances, 2020
Nanocrystalline titania was synthesized by a simple, innovative and eco-friendly gelation method ... more Nanocrystalline titania was synthesized by a simple, innovative and eco-friendly gelation method by using biopolymers (polysaccharides).
Chemical Engineering Journal, 2016
Effects of Ag and Pd on photocatalytic oxidation of pollutants were studied. The state of oxidati... more Effects of Ag and Pd on photocatalytic oxidation of pollutants were studied. The state of oxidation of metals affect photodegradation of the pollutants. The highest degradation rate for isoproturon was obtained with TiO 2-Pd. The highest degradation rate for diclofenac and phenol were obtained with TiO 2-Ag. The photodegradation of the byproducts of all pollutants were identified.
Optimisation of the photocatalytic activity of Ti02 and mixtures of TiOl + activated carbon throu... more Optimisation of the photocatalytic activity of Ti02 and mixtures of TiOl + activated carbon through dosage processes
Journal of the Chemical Society Faraday Transactions
Journal of Electroanalytical Chemistry
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1989
ABSTRACT
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1988
ABSTRACT Activity coeff. values for trichloroacetic acid (HTCA) at different acid concns. were de... more ABSTRACT Activity coeff. values for trichloroacetic acid (HTCA) at different acid concns. were detd. from a study of its aq. mixts. with HCl. The mixed system NaCl + NaTCA was also studied to det. the value of the mixing parameter, θCl-TCA, needed for substitution in the Pitzer equations. The γ± values are compared with those obtained in previous work in this lab. (E et al., 1987), in which the cell used to obtain the values included an uncancelled liq. junction potential, ΔEj, and the values were only apparent. Finally, an estn. of the liq. junction potential is obtained by combining the apparent values with the calcd. ones. The potentials thus obtained are compared with those calcd. from the Henderson equation. [on SciFinder(R)]
Berichte der Bunsengesellschaft für physikalische Chemie, 1993
F. Hernandez-Luis et al: Activity Coefficients of the Systems etc. ... Activity Coefficients of t... more F. Hernandez-Luis et al: Activity Coefficients of the Systems etc. ... Activity Coefficients of the Systems: NaBr + Na-Acetate + H 2 0 and NaBr + ... Na-Propionate + H20 at 25OC. Application of Scatchard's, Pitzer's and Lim's ... Felipe Hernandez-Luis, Luis Fernhndez-Mkrida, ...
Journal of Solution Chemistry, 1991
Activity coefficients for NaBr in the system NaBr+NaFormate+H2O at 25°C were determined from emf ... more Activity coefficients for NaBr in the system NaBr+NaFormate+H2O at 25°C were determined from emf measurements at different total ionic strengths. At each total ionic strength, the measurements were carried out at different Na-Formate/NaBr ionic strength ratios. The experimental activity coefficients were comparatively analyzed using Scatchard's, Pitzer's and Lim's methods. Although all these models can be successfully applied to the analysis
Journal of Solution Chemistry, 1995
Activity coefficients for NaBr in ethanol-water mixtures with O, 20, 40, 60, 70, 80, 90 and 99.8 ... more Activity coefficients for NaBr in ethanol-water mixtures with O, 20, 40, 60, 70, 80, 90 and 99.8 weight% of ethanol have been determined at 25 ~ from the emf measurements of the galvanic cells Na-glass / NaBr (m), tt20 (]00-Y), EtOH(Y), AgBr(s) [ Ag The results obtained were analyzed by using the Pitzer equation. Those for the mixtures with ethanol content higher than 60 wt% were also analyzed by using a chemical model and their ion pair formation constants
Journal of Hazardous Materials, 2007
Due to the toxicity effects and endocrine disrupting properties of phenolic compounds, their remo... more Due to the toxicity effects and endocrine disrupting properties of phenolic compounds, their removal from water and wastewater has gained widespread global attention. In this study, the photocatalytic degradation of phenolic compounds in the presence of titanium dioxide (TiO 2) nano-particles and UV light was investigated. A full factorial design consisting of three factors at three levels was used to examine the effect of particle size, temperature and reactant type on the apparent degradation rate constant. The individual effect of TiO 2 particle size (5, 10 and 32 nm), temperature (23, 30 and 37 °C) and reactant type (phenol, o-cresol and m-cresol) on the apparent degradation rate constant was determined. A regression model was developed to relate the apparent degradation constant to the various factors. The largest photocatalytic activity was observed at an optimum TiO 2 particle size of 10 nm for all reactants. The apparent degradation rate constant trend was as follows: o-cresol > m-cresol > phenol. The ANOVA data indicated no significant interaction between the experimental factors. The lowest activation energy was observed for o-cresol degradation using 5-nm TiO 2 particles. A maximum degradation rate constant of 0.0138 min −1 was recorded for o-cresol at 37 °C and a TiO 2 particle size of 13 nm at a D-optimality value of approximately 0.98. The response model adequately related the apparent degradation rate constant to the factors within the range of factors under consideration.
Journal of Electroanalytical Chemistry, 1992
... Activity coefficients for (sodium chloride + sodium hydrogen malonate + sodium malonate) (aq)... more ... Activity coefficients for (sodium chloride + sodium hydrogen malonate + sodium malonate) (aq) at 25 C. Application of Pitzer's equations Luis Fernandez-Merida, Felipe F. Hernandez-Luis, Oscar M. Gonzalez-Diaz and Miguel A ... 4 WJ Hamer, JO Burton and SF Acree, J. Res. Natl. ...
Journal of Chemical & Engineering Data, 1986
Transference numbers at 25 OC are measured for dlfferent concentratlons of NaBr by uslng both a f... more Transference numbers at 25 OC are measured for dlfferent concentratlons of NaBr by uslng both a falling and a rlslng sheared movlng-boundary cell. Both Ag/AgBr and Ag/AgCI electrodes are used with the rising cell, while only Ag/AgBr electrodes are used wlth the falling one. After different corrections are applled to the observed values, "best" transference numbers are calculated. I n all cases, these best values agree perfectly wlth one another and by applylng to them the Fuoss-Onsager and PMS equations, values at zero concentration, To, are obtalned. Moreover, electrolytic conductances at 25 OC for NaBr at different concentratlons are measured and later extrapolated to null lonlc strength by uslng the 1957 Fuoss-Onsager conductance equation. Indlvldual conductance values are obtalned by comblnlng both llmltlng parameters, T o and A'. I n the same manner, an adequate value for the adjustable parameter a , distance of the closest approach catlon-anion, Is obtalned from both experlmental techniques.
International Journal of Hydrogen Energy, 2013
A series of synthesised TiO 2-based and commercial photocatalysts were modified by Pt photodeposi... more A series of synthesised TiO 2-based and commercial photocatalysts were modified by Pt photodeposition and a study made of their photocatalytic activity in hydrogen production. The modified commercial photocatalysts were Evonik P25, Kronos vlp7000 and Hombikat UV-100, and the other modified photocatalysts were synthesised by our group using solegel and solegel hydrothermal processes (SG400, SG750 and HT). Pt weight percentages used in the study were 0.5, 1.0 and 2.1 wt.% (Pt/TiO 2). The photocatalysts were extensively characterised by X-ray diffraction (XRD), UVevis diffuse reflectance, BrunauereEmmetteTeller (BET) surface area measurement, transmission electron microscopy (TEM), scanning electron microscopy (SEMeEDX), Fourier transform infrared spectroscopy (FTIR) and laser light dispersion. Methanol (25% vol.) was used as sacrificial agent over the 8 h of the hydrogen production tests and measurements were taken of the final concentrations of formaldehyde and formic acid as well as initial and final TOC. Photoactivity of all photocatalysts increased in the presence of Pt. The most efficient of the synthesised photocatalysts was SG750 and of the commercial photocatalysts P25. Maximum production of SG750 was 1846 mmol h À1 at 1.0 wt.% Pt and its production per surface unit was notably higher than that of P25.