Jara-Munoz, P., Guzman-Fierro, V., Arriagada, C., Campos, V., Campos, J. L., Gallardo-Rodriguez, J. J., et al. (2019). Low oxygen start-up of partial nitrification-anammox process: mechanical or gas agitation? J. Chem. Technol. Biotechnol., 94(2), 475–483.
Abstract: BACKGROUND Partial nitrification-anammox (PN-A) is a widely recognized technology to remove nitrogen from different types of wastewater. Low oxygen concentration is the most used strategy for PN-A start-up, but stability problems arise during the operation; thus, in the present study the effects of the type of agitation, oxygenation and shear stress on the sensitivity, energy consumption and performance were evaluated. Recognition of these parameters allows considered choice of the design of an industrial process for nitrogen abatement. RESULTS A mechanically agitated reactor (MAR) was compared to a stable, long-term operation period bubble column reactor (BCR), both started under low dissolved oxygen concentration conditions. MAR microbial assays confirmed the destruction of the nitrifying layer and an imbalance of the entire process when the oxygen to nitrogen loading ratio (O-2:N) decreased by 25%. The granule sedimentation rate and specific anammox activity were 17% and 87% higher (respectively) in BCR. Economic analysis determined that the cost of aeration for the MAR and for the BCR were 23.8% and 1% of the total PN-A energy consumption, respectively. CONCLUSIONS The BCR showed better results than the MAR. This study highlights the importance of type of agitation, oxygenation and shear stress for industrial-scale PN-A designs. (c) 2018 Society of Chemical Industry
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Rendon, R. C., Salvo, C., Sepulveda, E., Arulraj, A., Sanhueza, F., Rodriguez, J. J., et al. (2022). Evaluation of Structural and Functional Properties of La0.6Sr0.4MnO3 Perovskite Prepared by the Fast Solution Combustion Approach. Catalysts, 12(12), 1636.
Abstract: A series of La0.6Sr0.4MnO3 (LSM) perovskite was made using the rapid solution combustion method, which was calcined by varying the temperatures. In order to determine how the calcination temperature affected the nanopowders produced and calcined at various temperatures, their microstructural, morphological, compositional, optical, and electrical properties were analyzed using corresponding characterization tools. The XRD results showed the coexistence of the rhombohedral polymorphs R-3c and Pm-3m for the perovskite phase under a calcination temperature of 1400 degrees C, which were eliminated with increased calcination temperature. The average grain size was found to increase with increasing calcination temperature. The EDS analysis showed better agreement of the stoichiometry with the theoretical composition. The apparent porosity decreased with increasing temperature due to the coalescence of sintering pores. The sample obtained after calcination at 1500 degrees C showed 10.3% porosity. The hardness also improved with increasing calcination temperature and reached a maximum value of 0.4 GPa, which matched the bulk density. A similar trend was observed in the resistivity studies as a function of temperature, and all the samples exhibited a low resistivity of similar to 1.4 Omega.cm in the temperature range of 500-600 degrees C. The optical characterization showed broad absorption at 560-660 nm and bandwidth values between 3.70 and 3.95 eV, according to the applied heat treatment.
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Rendon, R. C., Udayabhaskar, R., Salvo, C., Sepulveda, E., Rodriguez, J. J., Camurri-Porro, C., et al. (2022). Evaluation of La0.8Sr0.2MnO3 perovskite prepared by fast solution combustion. Ceram. Int., 48(23), 35100–35107.
Abstract: La0.8Sr0.2MnO3 (LSM) perovskite as oxygen electrode material for the reversible solid oxide fuel cells (ReSOFC) was synthesized by the fast solution combustion method and assessed for subsequent calcination influence. The microstructural, morphological, compositional and optical properties of the obtained material were analyzed with X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM) coupled with an energy-dispersive X-ray spectroscopy detector (EDS) and UV-visible spectroscopy techniques. The XRD results showed the coexistence of rhombohedral R-3c and Pm-3m polymorphs for the perovskite phase, with a decreased fraction of the cubic phase as the temperature and/or time used for the calcination were increased. The HR-TEM images confirmed the existence of the R-3c and Pm-3m polymorphs for the sample subjected to calcination at 1300 degrees C, showing that the rapid combustion method did not allow the pure formation of the La0.8Sr0.2MnO3 phase for the calcination temperatures below 1400 degrees C, due to the swiftness of the combustion synthesis 500 degrees C for 5 min. The average grain size was found to be increased with the calcination time. The EDS analysis depicted a better agreement in stoichiometry with the theoretical composition. The apparent porosity was decreased with the increase in the temperature and calcination time due to the coalescence of the sintering pores. The sample obtained after the calcination at 1400 degrees C for 8 h exhibited 1.6% of porosity. The hardness was improved with the higher calcination time and temperature and reached a maximum value of 5.7 GPa that merely matched the bulk density. A similar trend was observed in the temperature dependence resistivity studies and all the samples presented a low resistivity of similar to 1.2 Omega cm in the temperature range of 600-700 degrees C. The optical characterization exhibited a broad absorption in 560-660 nm.
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