Photodissolution of iron oxides. IV. A comparative study on the photodissolution of hematite, magnetite, and maghemite in EDTA media

1992 ◽  
Vol 70 (9) ◽  
pp. 2502-2510 ◽  
Author(s):  
Marta I. Litter ◽  
Miguel A. Blesa
Keyword(s):  
Reaction Rates ◽  
Thermal Reaction ◽  
Oxidation Products ◽  
Experimental Conditions ◽  
Spinel Type ◽  
Long Term Stability ◽  
Initiation Step ◽  
Edta Complexes ◽  
Photooxidation Reaction

The thermal and 254-nm photochemical dissolution reactions of magnetite (Fe3O4), maghemite (γ-Fe2O3), and hematite (α-Fe2O3) suspended in EDTA aqueous solutions were compared. γ-Fe2O3 and Fe3O4 are thermally and photochemically more reactive than α-Fe2O3. Both thermal and photochemical dissolution reactions are governed by an initiation step, which involves the production of FeIIaq, and a subsequent thermal reaction of these ions with the solid, to produce FeIIIaq. The initiation step under UV irradiation involves the photoreduction of surface >FeIII – EDTA complexes to yield FeIIaq and the photooxidation of adsorbed EDTA to yield CH2O and other oxidation products. After FeIII – EDTA complexes build up in solution through the following step, homogeneous photolysis is the main source of FeII and CH2O. Oxides with spinel type structure are characterized by faster rates in the two processes, and O2 may inhibit the dissolution processes by changing the stoichiometry of the initiation step to that of the autooxidation of EDTA. The relative importance of autooxidation and photodissolution depends on the nature of the oxide and the experimental conditions. Photooxidation reaction rates parallel those of the photodissolution initiation steps, and long-term stability towards photocorrosion (dissolution) implies low photocatalytic activity for the oxidation of EDTA. The set of differential equations describing all the reaction rates is discussed and applied to the different cases.

scholarly journals Polarization lidar: An extended three-signal calibration approach

2018 ◽  
Author(s):  
Cristofer Jimenez ◽  
Albert Ansmann ◽  
Moritz Haarig ◽  
Ronny Engelmann ◽  
Jörg Schmidt ◽  
...  
Keyword(s):  
Polarization Plane ◽  
Laser Pulses ◽  
Experimental Conditions ◽  
New Formalism ◽  
Long Term Stability ◽  
Receiver Unit ◽  
Water Cloud ◽  
Elliptically Polarized

Abstract. We present a new formalism to calibrate a three-signal polarization lidar and to measure highly accurate height profiles of the volume linear depolarization ratios under realistic experimental conditions. The methodology considers elliptically polarized laser light, angular misalignment of the receiver unit with respect to the main polarization plane of the laser pulses, and cross-talk between the receiver channels. A case study of a liquid-water cloud observation demonstrates the potential of the new technique. Long-term observations of the calibration parameters corroborate the robustness of the method and the long-term stability of the three-signal polarization lidar. A comparison with another polarization lidar shows excellent agreement regarding the derived volume linear polarization ratio of biomass burning smoke throughout the troposphere and the lower stratosphere up to 16 km height.

Advances in Research, Development, and Testing of Single Cells at Forschungszentrum Jülich

2009 ◽  
Vol 6 (2) ◽  
Author(s):  
V. A. C. Haanappel ◽  
N. Jordan ◽  
A. Mai ◽  
J. Mertens ◽  
J. M. Serra ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Research And Development ◽  
Solid Oxide Fuel Cells ◽  
Power Output ◽  
Single Cells ◽  
Experimental Conditions ◽  
Microstructural Parameters ◽  
Long Term Stability ◽  
Measurement Results

This paper presents an overview of the main advances in solid oxide fuel cells (SOFCs) research and development (R&D), measurement standardization, and quality assurance in SOFC testing at the Forschungszentrum Jülich. These activities have resulted in both a significant improvement of the electrochemical performance and a better understanding of the electrochemical behavior of SOFCs. Research and development of SOFCs was mainly focused on two types of anode-supported cells, namely, those employing either La0.65Sr0.3MnO3 (LSM) or La0.58Sr0.4Co0.2Fe0.8O3−δ (LSCF) cathode materials. In both cases the optimization of processing and microstructural parameters resulted in satisfactory power output and long-term stability at reduced operation temperatures. Standardization and quality assurance in SOFC testing was also addressed with the goal of producing consistent and reliable tests and measurement results. At present, under optimized experimental conditions, SOFCs with LSM or LSCF cathodes can deliver a power output of about 1.0 W/cm2 and 1.9 W/cm2 at 800°C (700 mV), respectively.

Electrochemical nanogravimetric studies of adsorption, deposition, and dissolution processes occurring at platinum electrodes in acid media

2010 ◽  
Vol 83 (2) ◽  
pp. 269-279 ◽  
Author(s):  
György Inzelt ◽  
Balázs B. Berkes ◽  
Ákos Kriston
Keyword(s):  
Proton Exchange ◽  
Platinum Electrodes ◽  
Experimental Conditions ◽  
Acid Media ◽  
Surface Mass ◽  
Long Term Stability ◽  
Platinized Platinum ◽  
Electrochemical Double Layer ◽  
Electrochemical Quartz Crystal Nanobalance

Polycrystalline smooth and platinized platinum electrodes have been extensively employed in electrochemistry. It is of utmost importance to gain a deeper insight into the processes occurring during their electrochemical transformations. Piezoelectric nanogravimetry by using electrochemical quartz crystal nanobalance (EQCN) is one of the most powerful tools for obtaining information on the events occurring at the electrode surface. This method has been exploited to monitor the surface mass changes as a function of the electrode potential varying the experimental conditions (time scale, solution composition, temperature), which allows one to draw conclusions in respect of the formation and removal of adsorbed and deposited species as well as changes in the electrochemical double layer. Furthermore, platinum dissolution processes, which are of importance (e.g., regarding the long-term stability of proton exchange fuel cells), are also discussed.

scholarly journals Use of Various Zero Valent Irons for Degradation of Chlorinated Ethenes and Ethanes

2015 ◽  
Vol 22 (4) ◽  
pp. 577-587 ◽  
Author(s):  
Stanisław Wacławek ◽  
Jaroslav Nosek ◽  
Lucie Cádrová ◽  
Vojtech Antoš ◽  
Miroslav Černík
Keyword(s):  
Environmental Remediation ◽  
Reaction Rates ◽  
Zero Valent Iron ◽  
Chlorinated Ethenes ◽  
Substantial Contribution ◽  
Long Term Stability ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Kinetic Test

Abstract Amongst all of the reducing agents that can be used in environmental remediation, zero valent iron (ZVI) is one of the most common due to its environmental acceptance, high reaction rate, good availability, and long-term stability. Moreover, ZVI mobility, stability and reactivity can be enhanced by the application of a DC electric current, ie electrokinetics (EK). In the study, six various slurries containing different ZVI were tested for their efficacy for chlorinated ethenes and ethanes degradation. Chlorinated compound concentrations, pH, oxidation-reduction potential (ORP) and conductivity were determined during the long-term kinetic test. Kinetic rate constants calculated for the degradation of three chlorinated ethenes (PCE, TCE and cis-DCE) concluded that EK brings substantial contribution to chlorinated compounds degradation. Nano-scale zero valent iron STAR had the highest reaction rates compare to the other ZVI tested. The performed study could serve as a preliminary assessment of various available ZVI before in-situ application.

scholarly journals Polarization lidar: an extended three-signal calibration approach

2019 ◽  
Vol 12 (2) ◽  
pp. 1077-1093 ◽  
Author(s):  
Cristofer Jimenez ◽  
Albert Ansmann ◽  
Ronny Engelmann ◽  
Moritz Haarig ◽  
Jörg Schmidt ◽  
...  
Keyword(s):  
Polarization Plane ◽  
Laser Pulses ◽  
Experimental Conditions ◽  
New Formalism ◽  
Long Term Stability ◽  
Receiver Unit ◽  
Water Cloud ◽  
Elliptically Polarized

Abstract. We present a new formalism to calibrate a three-signal polarization lidar and to measure highly accurate height profiles of the volume linear depolarization ratios under realistic experimental conditions. The methodology considers elliptically polarized laser light, angular misalignment of the receiver unit with respect to the main polarization plane of the laser pulses, and cross talk among the receiver channels. A case study of a liquid-water cloud observation demonstrates the potential of the new technique. Long-term observations of the calibration parameters corroborate the robustness of the method and the long-term stability of the three-signal polarization lidar. A comparison with a second polarization lidar shows excellent agreement regarding the derived volume linear polarization ratios in different scenarios: a biomass burning smoke event throughout the troposphere and the lower stratosphere up to 16 km in height, a dust case, and also a cirrus cloud case.

scholarly journals Bio-Analytical Stability Studies of Nadolol Material

2021 ◽  
pp. 130-140
Author(s):  
B. Veeraswami ◽  
V. M. K. Naveen
Keyword(s):  
Quantitative Measure ◽  
Drug Analysis ◽  
Stability Study ◽  
Stability Studies ◽  
Experimental Conditions ◽  
Long Term Stability ◽  
Analytical Stability ◽  
Ich Guidelines

The best practices of Bio-analytical stability studies on drug samples are very crucial and essential for the drugs development process as it specify the acceptancy, purity, efficacy, prediction of strength and quality of the drugs. The main objective of this stability studies on Nadolol the proposed approach of chromatographic separation was administered in isocratic way by using asymmetric C18 column of 40:60 percent of acetonitrile and 0.1% OPA at a flow rate of 1 ml/min is a quantitative measure for drug analysis in biological matrix for more reliable, selective, reproducible and sensitive.  This stability study constituents several methods like Bench-Top, Auto-sampler, Freeze-Thaw, Dry-extract, Wet-extract, Short-term, long-Term stability studies at various intervals gave the complete stability information about these drugs. The results of these stability studies are accepted based on ICH guidelines represents this drug has a good stability under the present experimental conditions. 

SEM analysis of the change in the reaction rates with deposit structures in the copper-iron cementation system

1978 ◽  
Vol 36 (1) ◽  
pp. 456-457
Author(s):  
V. Annamalai ◽  
L.E. Murr
Keyword(s):  
Structural Characteristics ◽  
Secondary Electron Emission ◽  
Copper Deposit ◽  
Reaction Rates ◽  
Sem Analysis ◽  
Experimental Conditions ◽  
Major Drawback ◽  
Emission Mode ◽  
Scrap Iron ◽  
Image Position

Economical recovery of copper metal from leach liquors has been carried out by the simple process of cementing copper onto a suitable substrate metal, such as scrap-iron, since the 16th century. The process has, however, a major drawback of consuming more iron than stoichiometrically needed by the reaction.Therefore, many research groups started looking into the process more closely. Though it is accepted that the structural characteristics of the resultant copper deposit cause changes in reaction rates for various experimental conditions, not many systems have been systematically investigated. This paper examines the deposit structures and the kinetic data, and explains the correlations between them.A simple cementation cell along with rotating discs of pure iron (99.9%) were employed in this study to obtain the kinetic results The resultant copper deposits were studied in a Hitachi Perkin-Elmer HHS-2R scanning electron microscope operated at 25kV in the secondary electron emission mode.

Stability and Change in Emotional Intelligence: Exploring the Transition to Young Adulthood

2005 ◽  
Vol 26 (2) ◽  
pp. 100-106 ◽  
Author(s):  
James D.A. Parker ◽  
Donald H. Saklofske ◽  
Laura M. Wood ◽  
Jennifer M. Eastabrook ◽  
Robyn N. Taylor
Keyword(s):  
High School ◽  
Emotional Intelligence ◽  
Postsecondary Education ◽  
Life Transition ◽  
Full Time ◽  
Major Life ◽  
Long Term Stability ◽  
Time Period ◽  
Transition From High School

Abstract. The concept of emotional intelligence (EI) has attracted growing interest from researchers working in various fields. The present study examined the long-term stability (32 months) of EI-related abilities over the course of a major life transition (the transition from high school to university). During the first week of full-time study, a large group of undergraduates completed the EQ-i:Short; 32 months later a random subset of these students (N = 238), who had started their postsecondary education within 24 months of graduating from high school, completed the measures for a second time. The study found EI scores to be relatively stable over the 32-month time period. EI scores were also found to be significantly higher at Time 2; the overall pattern of change in EI-levels was more than can be attributed to the increased age of the participants.

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