Gaston G. Fouga - Academia.edu (original) (raw)

Papers by Gaston G. Fouga

Biochar has emerged as an attractive electrode material due to its biocompatibility, low cost and... more Biochar has emerged as an attractive electrode material due to its biocompatibility, low cost and reduced environmental impact. The temperature at which biochar is produced greatly affects its physicochemical properties and its environmental performance. Despite that, only biochar obtained at relatively high temperatures (800 to 1000°C) has been applied in microbial electrochemical technologies (METs) so far. In this work, the physicochemical and electrical properties of biochar electrodes obtained at several temperatures (500°C to 1000°C) are explored and compared to those of graphite which is the most commonly used electrode material in METs. Besides, the associated carbon emissions and energy input of the production process at each temperature are estimated and compared to those of graphite. Results indicate that low-temperature (600°C) biochar electrodes generate about half of the electric current obtained with high-temperature biochar or graphite electrodes. Furthermore, carbon emissions and energetic inputs for the production of low-temperature biochar are much lower than those of graphite production, with the 600°C electrodes having a net positive carbon footprint and also a lower production cost. Nevertheless, further research is needed to optimize biochar conductivity and mechanical performance in order to allow its integration into large scale METs. Sustainability spotlight As stated in the UN's Sustainable Development Goals (SDG12 and SDG13) the application of sustainable patterns of production including the reduction of material footprint and greenhouse gas emissions is essential for mitigating climate change and lowering biodiversity loss and pollution. Electrochemical grade graphite production is based on the extraction of mineral ores and fossil fuels and is associated with high energy inputs and carbon emissions. In this work we study the use of biochar obtained from pruning residues as an alternative to graphite in bioelectrochemical systems showing that this material has an acceptable performance and, more importantly, requires low energy input for its production and can have a net positive carbon footprint.

Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, Oct 23, 2007

The kinetics of the chlorination of zinc oxide has been studied by thermogravimetry between 723 a... more The kinetics of the chlorination of zinc oxide has been studied by thermogravimetry between 723 and 973 K. The starting temperature for the reaction of ZnO with chlorine is determined at about 498 K. The influence of gaseous flow rate, sample mass, temperature, and chlorine partial pressure in the reaction rate is analyzed. It is established that the reaction occurs under mixed control, being pore diffusion coupled with chemical reaction as the rate controlling step. An apparent reaction order of 0.5 with respect to chlorine partial pressure was determined. A kinetic model for the chlorination reaction of porous solids under mixed control determined an intrinsic reaction order of zero with respect to partial pressure of chlorine and an intrinsic activation energy of 249 kJ mol-1 .

Mineral Processing and Extractive Metallurgy, Dec 1, 2007

The kinetics of the ilmenite chlorination was studied between 600 and 850uC. The ilmenite chlorin... more The kinetics of the ilmenite chlorination was studied between 600 and 850uC. The ilmenite chlorination rate was determined by monitoring the mass changes using a thermogravimetric system of high resolution. Non-isothermal and isothermal runs were performed. The influence of temperature, chlorine flow and sample mass in the reaction rate was established. The thermal decomposition of ilmenite previous to the chlorination was taken into account. The formation of intermediate titanates during the chlorination reactions was found. The dependence of the reaction rate with temperature was analysed, and apparent activation energy of 186 kJ mol 21 was obtained for the chlorination process. A global mechanism was proposed involving: rupture of the ilmenite structure, formation and subsequent decomposition of pseudorutile and chlorination of hematite.

Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, Oct 15, 2014

The europium oxide (Eu 2 O 3 (s)) chlorination reaction with sucrose carbon was studied by thermo... more The europium oxide (Eu 2 O 3 (s)) chlorination reaction with sucrose carbon was studied by thermogravimetry between room temperature and 1223 K (950°C). The nonisothermal thermogravimetry showed that the reaction consists of three stages, and their stoichiometries were studied. The product of the first stage was europium oxychloride, and it showed independence of the reaction kinetics with the carbon content. Subsequently, in the second stage, the Eu-OCl(s) was carbochlorinated with formation of EuCl 3 (l) and its evaporation is observed in the third stage. The analysis by Fourier transform infrared spectroscopy of gaseous species showed that the reaction at second stage occurs with the formation of CO 2 (g) and CO(g). Both reactants and products were analyzed by X-ray diffraction, scanning electron microscopy and wavelengthdispersive X-ray fluorescence spectroscopy. The influence of carbon content, total flow rate, sample initial mass, chlorine partial pressure, and temperature were evaluated. The second stage kinetics was analyzed, which showed an anomalous behavior caused by generation of chlorine radicals during interaction of Cl 2 (g) and carbon. It was found that the reaction rate at 933 K (660°C) was proportional to a potential function of the chlorine partial pressure whose exponent is 0.56. The conversion curves were analyzed with the Avrami-Erofeev model and it was obtained an activation energy of 154 ± 5 kJ mol-1 .

Thermochimica Acta, Oct 1, 2009

In this work the reaction between several manganese oxides and chlorine is investigated. The reac... more In this work the reaction between several manganese oxides and chlorine is investigated. The reaction path for the chlorination of the oxides is established, which involves recrystallization of high valence manganese oxides: Mn 3 O 4 and Mn 2 O 3 during the chlorination of MnO, and Mn 2 O 3 during the chlorination of Mn 3 O 4 and Mn 2 O 3. The starting temperature for the reaction of the oxides is determined by non-isothermal thermogravimetric measurements. Analysis of the samples at different reaction degrees reveals that three simultaneous processes are taking place during the whole reaction: chlorination, volatilization of manganese chloride and recrystallization of manganese oxides. The effect of temperature in the reaction rate is analyzed. The activation energies obtained for the reaction of the three oxides with chlorine, which are in accordance with the vaporization enthalpy of MnCl 2 , suggest that although during the mass loss three processes occur (chlorination, recrystallization and volatilization), volatilization of manganese chloride has a strong influence in the rate observed.

InTech eBooks, Oct 24, 2012

Journal of Alloys and Compounds, Mar 1, 2023

Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, Aug 22, 2013

The kinetics of europium oxide (Eu 2 O 3) chlorination using gaseous chlorine as a chlorination a... more The kinetics of europium oxide (Eu 2 O 3) chlorination using gaseous chlorine as a chlorination agent was studied between 523 K and 1223 K (250°C and 950°C). The relative mass change during the chlorination reaction was continuously monitored using a high resolution thermogravimetric system. The starting temperature for the reaction of Eu 2 O 3 (s) with chlorine was determined at about 523 K (250°C) with the formation of solid europium oxychloride (EuOCl). For temperatures above 1123 K (850°C), the EuOCl(s) is chlorinated producing EuCl 3 (l). The influence of gaseous flow rate, sample mass, chlorine partial pressure, and temperature on the reaction rate was analyzed. The results showed that for 673 K (400°C) and temperatures below, the system is under chemical control. Concerning the influence of chlorine partial pressure, it was determined that pressures greater than 50 kPa do not modify the kinetic regime. For the experiment at 673 K (400°C), it was found that the chlorination rate was proportional to a potential function of the partial pressure of chlorine whose exponent is 0.54. The conversion curves were analyzed with the Johnson-Mehl-Avrami description. Intrinsic activation energy of 115 kJ mol À1 was obtained for the temperature range of 573 K to 673 K (300°C to 400°C). Finally, a global rate equation that includes these parameters was developed.

Fuel, Oct 1, 2016

Abstract As gasification reactivity of carbonaceous solid material chars is known to be strongly ... more Abstract As gasification reactivity of carbonaceous solid material chars is known to be strongly dependent on their formation conditions, a comprehensive study was carried out on the effects of pyrolysis conditions on structure of chars prepared from an Argentine asphaltite. The study comprised qualitative and quantitative analyses of char structures by X-ray diffraction, complemented with the characterization of physical morphology of char particles by scanning electronic microscopy and high-resolution transmission electronic microscopy. Effects of pyrolysis temperature, heating rate and holding time at the peak temperature were investigated separately in a fixed bed tubular reactor. Additionally, the overall effect of variations in time-temperature history of individual char particles was evaluated using a drop tube furnace reactor. Experimental results have shown that pyrolysis conditions have a strong influence on the asphaltite-derived char structure, producing a significant reordering of the carbonaceous matrix at high heat treatment temperatures that is evidenced by increments in aromaticity and crystalline carbon fraction. The resulting physical morphology of asphaltite-derived char particles was found to be profoundly influenced by the heating rate at which the volatile matter is released, due to the appearance of a liquid phase during the heating process.

International Journal of Hydrogen Energy, Jun 1, 2010

ABSTRACT The kinetics of the gasification of an Argentinean coal char with carbon dioxide has bee... more ABSTRACT The kinetics of the gasification of an Argentinean coal char with carbon dioxide has been studied by thermogravimetry between 1073 and 1223 K. The starting temperature for the reaction of the char with carbon dioxide is determined at about 873 K. The influence of gaseous flow rate, sample mass, temperature and carbon dioxide partial pressure in the reaction rate is analyzed. The conditions under which the progress of reaction is controlled by chemical reaction are established. In those conditions, an activation energy of 45.6 kcal mol−1 was obtained with an isoconversional method. Regarding the effect of partial pressure of CO2, the gasifications were found to be of first order reaction for CO2 for partial pressures of CO2 up to 61 kPa. In addition, a Langmuir–Hinshelwood type equation fits the experimental data for whole range of pressures to a certain extent.

Journal of Alloys and Compounds, Mar 1, 2019

The reactions of Pr 2 O 3 and Pr 6 O 11 with Cl 2 (g) were studied thermodynamically and experime... more The reactions of Pr 2 O 3 and Pr 6 O 11 with Cl 2 (g) were studied thermodynamically and experimentally, and proposed in the systems Pr 2 O 3 /Cl 2 (g) and Pr 6 O 11 /Cl 2 (g). A kinetic analysis was performed on Pr 6 O 11 chlorination, which differs from with other light rare earth oxide chlorinations. The praseodymium oxychlorides obtained by full chlorination of Pr 6 O 11 at 425 °C and 800 °C are different, being well charact erized by X-ray diffraction, scanning electron microscopy, magnetic susceptibility measurements and X-ray photoelectron spectroscopy. The crystal structures of the oxychlorides were refined with the Rietveld method. The comparison between the theoretical magnetic moment of Pr 3+ and the estimated magnetic moment in the praseodymium oxychloride obtained at 425 °C revealed the presence of Pr 3+ and Pr 4+ , whereas no significant difference was observed between the theoretical and the experimental values of Pr 3+ obtained for the praseodymium oxychloride prepared at 800 °C. These observations are consiste nt with the analyses in the X-ray photoelectron spectra for both oxychlorides. Finally, a general formula of PrO 1+x Cl is proposed for the oxychlorides synthesized at T<800 °C.

Energy Conversion and Management, Nov 1, 2022

Fuel, Feb 1, 2011

The kinetics of Argentinean asphaltite char gasification using carbon dioxide as gasifying agent ... more The kinetics of Argentinean asphaltite char gasification using carbon dioxide as gasifying agent was studied between 1048 and 1223 K. The chars were obtained by pyrolysis of an asphaltite in a fixed bed reactor. The relative mass change during the gasification reaction was continuously monitored using a high resolution thermogravimetric system. The starting temperature for the reaction of the char with carbon dioxide was determined at about 800 K. The influence of gaseous flow rate, sample mass, carbon dioxide partial pressure and temperature in the reaction rate was analyzed. The experimental condition under which the progress of gasification reaction is chemically controlled was established. In those conditions, an activation energy of 185 kJ mol À1 was obtained with an isoconversional method. Concerning the influence of carbon dioxide partial pressure, it was determined that pressures greater than 50 kPa do not alter the kinetics regime. Finally a reaction order of 0.5 for carbon dioxide partial pressure was determined and a global rate equation that includes these parameters was developed. Rate ¼ da dt ¼ ð1 À aÞ 2=3 Á 1:1 Â 10 5 exp À

Energy Conversion and Management, 2022

La reactividad de los halógenos puede ser estudiada mediante reacciones químicas de desplazamient... more La reactividad de los halógenos puede ser estudiada mediante reacciones químicas de desplazamiento. La enseñanza de estas reacciones demanda prácticas de laboratorio que implementen dispositivos experimentales seguros, interesantes y conceptualmente enriquecedores. En este trabajo, se presenta el diseño de un dispositivo experimental que muestra las reacciones de desplazamiento que se producen en reactores conectados en serie. También se compara este diseño con otros publicados anteriormente. Se discuten alcances para distintos niveles educativos.

Journal of Thermal Analysis and Calorimetry, May 28, 2015

The reaction between Gd2O3(s) and Cl2(g) was studied in a high-resolution thermogravimetric syste... more The reaction between Gd2O3(s) and Cl2(g) was studied in a high-resolution thermogravimetric system. The reaction product was GdOCl, which was the unique solid phase produced in all the temperature range studied. The GdOCl is subsequently chlorinated producing GdCl3 for temperatures above 1123 K. The system is under chemical control for temperatures below 723 K. It was found that the reaction order with respect to the chorine partial pressure is 0.77 and the activation energy is 132 kJ mol−1 for the temperature range of 623–723 K. The global rate equation was developed. The GdOCl obtained was characterized by X-ray diffraction, scanning electron microscopy and magnetic measurements. The structure of GdOCl was refined with the Rietveld method, and it crystallized in a tetragonal form of REOX possessing the Matlockite-type (PbFCl) structure. The magnetic measurements indicated that the sample is paramagnetic at all the measurement ranges. The parameters of the Curie–Weiss law obtained were as follows: θ = −12.0 K, C = 7.9592 emu K mol−1 and µeff = 7.98µB.

Thermochimica Acta, May 1, 2012

ABSTRACT The kinetics of Argentinean Hubnerite (MnWO4) chlorination using gaseous chlorine as chl... more ABSTRACT The kinetics of Argentinean Hubnerite (MnWO4) chlorination using gaseous chlorine as chlorination agent was studied between 750 and 950 °C. The relative mass change during the chlorination reaction was continuously monitored using a high resolution thermogravimetric system. The starting temperature for the reaction of the manganese tungstate with chlorine was determined at about 650 °C. The influence of gaseous flow rate, sample mass, chlorine partial pressure, and temperature on the reaction rate was analyzed. The dependence of the reaction rate with sample mass clearly indicates that the reaction is not occurring under chemical control, so the reaction proceeds under mixed control for sample masses greater than 0.5 mg. In those conditions, an apparent activation energy of 198 ± 9 kJ mol−1 was obtained with an isoconversional method. Concerning the influence of chlorine partial pressure, it was determined that pressures greater than 35 kPa do not modify the kinetic regime. For the experiment at 850 °C, it was found that the chlorination rate was proportional to a potential function of the partial pressure of chlorine whose exponent is around 0.85. Finally, a global rate equation that includes these parameters was developed.

Mining, Metallurgy & Exploration, 2021

Metallurgical and Materials Transactions B, 2014