scholarly journals Effects of three iron material treatments on hydrogen sulfide release from anoxic sediments

2021 ◽  
Author(s):  
Tetsunori Inoue ◽  
Yuki Hagino
Keyword(s):  
Hydrogen Sulfide ◽  
Release Rate ◽  
Laboratory Experiments ◽  
Reaction Rate ◽  
Reduction Potential ◽  
Reaction Rates ◽  
Reaction Rate Constant ◽  
Treatment Level ◽  
Port Authorities ◽  
Iron Material

Abstract In eutrophic coastal regions, hydrogen sulfide (H2S) is a harmful material released from sediments under anoxic conditions. To suppress its release, we conducted laboratory experiments and assessed the impacts of treatment with three iron materials (Fe, Fe2O3, and FeOOH), focusing on the area-specific H2S release rate. These materials qualitatively exhibited a substantial suppression of H2S release; however, smaller treatment levels (<150 mmol m−2) were ineffective. FeOOH exhibited the best performance, followed by Fe2O3, and Fe. These differences were likely caused by variations in the oxidation or reduction potential of the materials and their reaction rates with H2S. A simplified model suggested that the required minimum Fe2+ concentration was determined using the H2S diffusivity, reaction rate constant, and treatment penetration depth. As the former two are physical constants, the latter must control the H2S release rate. Iron materials were experimentally confirmed to persist for over three weeks, and the effective treatment level was theoretically estimated as being capable of suppressing H2S release for more than a year. Our results will contribute to coastal environmental management and particularly benefit port authorities who manage enclosed and eutrophicated harbors and navigation channels where slag application should be avoided.

Bisulfite Degrades Aflatoxin: Effect of Temperature and Concentration of Bisulfite

1978 ◽  
Vol 41 (10) ◽  
pp. 774-780 ◽  
Author(s):  
M. P. DOYLE ◽  
E. H. MARTH
Keyword(s):  
Rate Constant ◽  
Aflatoxin B1 ◽  
Reaction Rate ◽  
Reaction Rates ◽  
Reaction Rate Constant ◽  
Effect Of Temperature ◽  
Kcal Mole ◽  
First Order ◽  
Potassium Acid Phthalate ◽  
Acid Phthalate

Bisulfite reacted with aflatoxin B1 and G1 resulting in their loss of fluorescence. The reaction was first order with rate depending on bisulfite (or the bisulfite and sulfite) concentration(s). Aflatoxin G1 reacted more rapidly with bisulfite than did aflatoxin B1. In the presence of 0.035 M potassium acid phthalate-NaOH buffer (pH 5.5) plus 1.3% (vol/vol) methanol at 25 C, the reaction rate constant for degradation of aflatoxin G1 was 2.23 × 10−2h− and that for aflatoxin B1 was 1.87 × 10−2h− when 50 ml of reaction mixture contained 1.60 g of K2SO3. Besides bisulfite concentrations, temperature influenced reaction rates. The Q10 for the bisulfite-aflatoxin reaction was approximately 2 while activation energies for degrading aflatoxin B1 and aflatoxin G1 were 13.1 and 12.6 kcal/mole, respectively. Data suggest that treating foods with 50 to 500 ppm SO2 probably would not effectively degrade appreciable amounts of aflatoxin. Treating foods with 2000 ppm SO2 or more and increasing the temperature might reduce aflatoxin to an acceptable level.

scholarly journals Impacts of electronically photo-excited NO<sub>2</sub> on air pollution in the South Coast Air Basin of California

2010 ◽  
Vol 10 (3) ◽  
pp. 1171-1181 ◽  
Author(s):  
J. J. Ensberg ◽  
M. Carreras-Sospedra ◽  
D. Dabdub
Keyword(s):  
Particulate Matter ◽  
Rate Constant ◽  
Reaction Rate ◽  
Control Strategies ◽  
Reaction Rates ◽  
Reaction Rate Constant ◽  
South Coast ◽  
Nox Emissions ◽  
The South ◽  
South Coast Air Basin

Abstract. A new path for hydroxyl radical formation via photo-excitation of nitrogen dioxide (NO2) and the reaction of photo-excited NO2 with water is evaluated using the UCI-CIT model for the South Coast Air Basin of California (SoCAB). Two separate studies predict different reaction rates, which differ by nearly an order of magnitude, for the reaction of photo-excited NO2 with water. Impacts of this new chemical mechanism on ozone and particulate matter formation, while utilizing both reaction rates, are quantified by simulating two summer episodes. First, sensitivity simulations are conducted to evaluate the uncertainty in the rate of reaction of photo-excited NO2 with water reported in the literature. Results indicate that the addition of photo-excited NO2 chemistry increases peak 8-h average ozone and particulate matter concentrations. The importance of this new chemistry is then evaluated in the context of pollution control strategies. A series of simulations are conducted to generate isopleths for ozone and particulate matter concentrations, varying baseline nitrogen oxides (NOx) and volatile organic compounds (VOC) emissions. Isopleths are obtained using 1987 emissions, to represent past conditions, and 2005, to represent current conditions in the SoCAB. Results show that the sensitivity of modeled pollutant control strategies due to photoexcitation decreases with the decrease in baseline emissions from 1987 to 2005. Results show that including NO2 photo-excitation, increases the sensitivity of ozone concentration with respect to changes in NOx emissions for both years. In particular, decreasing NOx emissions in 2005 when NO2 photo-excitation is included, while utilizing the higher reaction rate, leads to ozone relative reduction factors that are 15% lower than in a case without photo-excited NO2. This implies that photoexcitation increases the effectiveness in reducing ozone through NOx emissions reductions alone, which has implications for the assessment of future emission control strategies. However, there is still disagreement with respect to the reaction rate constant for the formation of OH. Therefore, further studies are required to reduce the uncertainty in the reaction rate constant before this new mechanism is fully implemented in regulatory applications.

scholarly journals Mathematical approach to investigation of synthesis processes at high temperatures

2012 ◽  
Vol 10 (2) ◽  
pp. 380-385 ◽  
Author(s):  
Mažvydas Mackevičius ◽  
Feliksas Ivanauskas ◽  
Aivaras Kareiva
Keyword(s):  
High Temperatures ◽  
Inverse Modeling ◽  
Laboratory Experiments ◽  
Reaction Rate ◽  
Sol Gel ◽  
Reaction Rates ◽  
Solid State Reactions ◽  
Limited Information ◽  
Synthesis Time ◽  
Occurrence Of Synthesis

AbstractIn our work, we present a method for estimation of the diffusion and reaction rates of synthesis at high temperatures using limited information from laboratory experiments, such as synthesis time and dimensions of reactants. Synthesis by sol-gel and solid-state reactions is considered. The inverse modeling problem is solved for one- and two-dimensional models. Explicit formulas for the diffusion coefficient and reaction rate as functions of temperature are obtained. The activation energies are calculated, and the lower bounds of diffusion and reaction rates are estimated, thus obtaining conditions for occurrence of synthesis.

scholarly journals Investigation of chemical equilibrium kinetics by the electromigration method

2003 ◽  
Vol 91 (5) ◽  
Author(s):  
G. A. Bozhikov ◽  
P. I. Ivanov ◽  
G. D. Bontchev ◽  
O. D. Maslov ◽  
M. V. Milanov ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Complex Formation ◽  
Stability Constant ◽  
Chemical Equilibrium ◽  
Reaction Rate ◽  
Reaction Rates ◽  
Reaction Rate Constant ◽  
Diethylenetriaminepentaacetic Acid ◽  
Zone Electrophoresis ◽  
Chemical Reaction Rates

SummaryThe measurement of the chemical reaction rates for complex formation as well as hydrolysis type reactions by the method of horizontal zone electrophoresis is outlined. The correlation between chemical equilibrium kinetics and electrodiffusion processes in a constant d.c. electric field is described. In model electromigration experiments the reaction rate constant of the formation a complex by Hf(IV) and diethylenetriaminepentaacetic acid (DTPA) is determined. The electrophoretic mobility, diffusion coefficient and stability constant of the [HfDTPA]

New Procedure for Linear Sweep Voltammetric Determination of Catalytic Reaction Rate Constant. Oxidation of Some Aliphatic Alcohols with Electrolytically Generated Os(VIII)

1995 ◽  
Vol 60 (5) ◽  
pp. 795-801
Author(s):  
Dušan Bustin ◽  
Štefan Mesároš ◽  
Peter Tomčík ◽  
Miroslav Rievaj
Keyword(s):  
Catalytic Reaction ◽  
Oxidation Rate ◽  
Reaction Rate ◽  
Reaction Rates ◽  
Reaction Rate Constant ◽  
Sufficient Accuracy ◽  
Aliphatic Alcohols ◽  
Catalytic Reactions ◽  
Linear Sweep

Oxidation rate of methanol, ethanol and 2-propanol by Os(VIII) in 1 M KOH was determined by evaluating anodic voltammograms of Os(VI) in the presence of the aliphatic alcohols. The proposed method is based on the evaluation of the change of voltammogram shape by catalytic process and on the assumption of its approximation by fractionally integrated voltammograms. This assumption has been confirmed empirically for k'f /a in the interval of <0.04,1>. The rate constants from this interval could be determined with sufficient accuracy. The method is suitable for evaluation of reaction rates slow and moderately fast catalytic reactions. It was compared with other evaluation methods from the literature.

THE EFFECT OF REACTANTS' INITIAL TEMPERATURES ON THE RATE CONSTANT AND CONVERSION OF SAPONIFICATION REACTION TAKING PLACE IN A NON-ISOTHERMAL AND NON-ADIABATIC BATCH REACTOR

2020 ◽  
Vol 3 (2) ◽  
pp. 25-33
Author(s):  
Nader Kamal Nasar ◽  
Adli Omar Alznati ◽  
Abdulozez Arzoga
Keyword(s):  
Rate Constant ◽  
Reaction Rate ◽  
Batch Reactor ◽  
Reaction Rates ◽  
Reaction Rate Constant ◽  
Time Intervals ◽  
Isolation System ◽  
Reaction Conversion ◽  
Temperature Rate ◽  
Electrical Conductivity Data

This experimental research studied the saponification reaction of ethyl acetate with sodium hydroxide, which was carried out in a well-agitated non-isothermal and non-adiabatic batch reactor. As no isolation system was provided in this experiment, this study investigated other routes for boosting the reactants conversion. Subsequently, the effect of initial feed temperatures on the reaction rate constant and reaction conversion was assessed. For this purposes, the reaction rates of equimolar reactants were measured when they were heated from 20°C (ambient temperature) to 30°C, 40°C and 50°C. The decrease in the reactants concentrations throughout the reaction durationwas determined at equal time intervals by recording the electrical conductivity data of the reaction mixture. The results were represented graphically for time-conversion, temperature-conversion and temperature-rate constants profiles. They had shown that the reaction rate constant increased with rising of the initial feed temperatures. Even though, the conversion was boosted when the reactants were initially heated above 20°C, no significant change in conversion was achieved between 30, 40, and 50°C. The resulted value of activation energy was about 50 % less than the most accurate published values.

scholarly journals The impact of the confinement of reactants on the metal distribution in bimetallic nanoparticles synthesized in reverse micelles

2014 ◽  
Vol 5 ◽  
pp. 1966-1979 ◽  
Author(s):  
Concha Tojo ◽  
Elena González ◽  
Nuria Vila-Romeu
Keyword(s):  
Exchange Rate ◽  
Reverse Micelles ◽  
Reaction Rate ◽  
Reduction Potential ◽  
Bimetallic Nanoparticles ◽  
Chemical Reduction ◽  
Reduction Rate ◽  
Reaction Rates ◽  
Confined Media ◽  
The Impact

A kinetic study on the formation of bimetallic nanoparticles in microemulsions was carried out by computer simulation. A comprehensive analysis of the resulting nanostructures was performed regarding the influence of intermicellar exchange on reactivity. The objects of this study were metals having a difference in standard reduction potential of about 0.2–0.3 V. Relatively flexible microemulsions were employed and the concentration of the reactants was kept constant, while the reaction rate of each metal was monitored as a function of time using different reactant proportions. It was demonstrated that the reaction rates depend not only on the chemical reduction rate, but also on the intermicellar exchange rate. Furthermore, intermicellar exchange causes the accumulation of slower precursors inside the micelles, which favors chemical reduction. As a consequence, slower reduction rates strongly correlate with the number of reactants in this confined media. On the contrary, faster reduction rates are limited by the intermicellar exchange rate and not the number of reactants inside the micelles. As a result, different precursor proportions lead to different sequences of metal reduction, and thus the arrangement of the two metals in the nanostructure can be manipulated.

Location-thinking, value-thinking, and graphical forms: combining analytical frameworks to analyze inferences made by students when interpreting the points and trends on a reaction coordinate diagram

2021 ◽  
Author(s):  
Alexander P. Parobek ◽  
Patrick M. Chaffin ◽  
Marcy H. Towns
Keyword(s):  
Reaction Rate ◽  
Research Study ◽  
Reaction Rates ◽  
Reaction Coordinate ◽  
Structured Interviews ◽  
Chemistry Students ◽  
Qualitative Research Study ◽  
The Impact ◽  
Analytical Frameworks ◽  
Chemical Representations

Reaction coordinate diagrams (RCDs) are chemical representations widely employed to visualize the thermodynamic and kinetic parameters associated with reactions. Previous research has demonstrated a host of misconceptions students adopt when interpreting the perceived information encoded in RCDs. This qualitative research study explores how general chemistry students interpret points and trends on a RCD and how these interpretations impact their inferences regarding the rate of a chemical reaction. Sixteen students participated in semi-structured interviews in which participants were asked to interpret the points and trends along provided RCDs and to compare relative reaction rates between RCDs. Findings derived from this study demonstrate the diversity of graphical reasoning adopted by students, the impact of students’ interpretations of the x-axis of a RCD on the graphical reasoning employed, and the influence of these ideas on inferences made about reaction rate. Informed by analytical frameworks grounded in the resources framework and the actor-oriented model of transfer, implications for instruction are provided with suggestions for how RCDs may be presented to assist students in recognizing the critical information encoded in these diagrams.

scholarly journals Determination of exothermic batch reactor specific model parameters

2019 ◽  
Vol 292 ◽  
pp. 01063
Author(s):  
Lubomír Macků
Keyword(s):  
Rate Constant ◽  
Reaction Rate ◽  
Batch Reactor ◽  
Specific Model ◽  
Reaction Rate Constant ◽  
Order Reaction ◽  
First Order Reaction ◽  
Model Parameters ◽  
Reactor Model ◽  
First Order

An alternative method of determining exothermic reactor model parameters which include first order reaction rate constant is described in this paper. The method is based on known in reactor temperature development and is suitable for processes with changing quality of input substances. This method allows us to evaluate the reaction substances composition change and is also capable of the reaction rate constant (parameters of the Arrhenius equation) determination. Method can be used in exothermic batch or semi- batch reactors running processes based on the first order reaction. An example of such process is given here and the problem is shown on its mathematical model with the help of simulations.

Sign in / Sign up

Export Citation Format

Share Document