Selectivity and Efficiency of Biomimetic Catalysts in a Model System for Pulp Bleaching

Holzforschung ◽  
2001 ◽  
Vol 55 (4) ◽  
pp. 391-396 ◽  
Author(s):  
C. C. Walker ◽  
T. J. McDonough ◽  
R. J. Dinus ◽  
K.-E. L. Eriksson
Keyword(s):  
Kinetic Model ◽  
Hydroxyl Radicals ◽  
Chain Scission ◽  
Model System ◽  
Hydroxyethyl Cellulose ◽  
Pulp Bleaching ◽  
Sodium Lignosulfonate ◽  
Biomimetic Catalysts ◽  
Biomimetic Systems ◽  
Simple Kinetic Model

SummaryThree biomimetic systems were evaluated for their selectivity in a model system for pulp. FeSO4, Fe-EDTA and hemoglobin, in the presence of H2O2, constituted the biomimetic systems. Sodium lignosulfonate and hydroxyethyl cellulose (HEC) were used as a model system to represent lignin and carbohydrate fractions in pulp. A simple kinetic model was used to determine kinetic parameters for depolymerization of each substrate. Point selectivities at two different H2O2concentrations were evaluated on the basis of the resulting expressions. Hemoglobin demonstrated superior selectivity for lignosulfonate degradation at a high H2O2level. The production of hydroxyl radicals from each of the biomimetic systems was measured using a chemiluminescence assay. For the FeSO4and Fe-EDTA systems, depolymerization was related to the amount of radicals generated. The fate of reacted H2O2was evaluated using a specially designed reactor to measure H2O2consumed by reaction and that decomposed. To achieve a given number of chain scission in lignosulfonate, the hemoglobin system consumed the least amount of H2O2.

Use of an Improved Chemiluminescence Assay for Non-Intrusive Measurement of Hydroxyl Radicals in a Biomimetic Pulp Bleaching Model System

Holzforschung ◽  
1999 ◽  
Vol 53 (2) ◽  
pp. 181-187 ◽  
Author(s):  
C. C. Walker ◽  
R. J. Dinus ◽  
T. J. McDonough ◽  
K.-E. L. Eriksson
Keyword(s):  
Hydrogen Peroxide ◽  
Aqueous Solutions ◽  
Hydroxyl Radicals ◽  
Model System ◽  
Pulp Bleaching ◽  
Assay Sensitivity ◽  
Chemiluminescence Assay ◽  
Naturally Occurring ◽  
Excellent Tool

Summary A chemiluminescence assay was used to measure the production of hydroxyl radicals (·OH) in aqueous solutions of hydrogen peroxide and iron-containing catalysts. Preliminary experiments evaluating assay sensitivity revealed that one of the required reagents, phthalhydrazide (PtH), interfered with the studied reactions. In addition, undesirable degradation of the chemiluminescent form of PtH was observed. By removing PtH from reaction solutions and modifying the published procedures, a successful non-intrusive method for measurement of ·OH was obtained. The modified assay was used to compare the rate of ·OH generation in solutions of H2O2, either FeSO4 or Fe-EDTA and a substrate, lignosulfonate. This “biomimetic” pulp bleaching system is meant to simulate naturally occurring biological reactions utilized for degradation of lignins by wood-degrading fungi. Results from these experiments show that FeSO4 produced more ·OH than Fe-EDTA. The improved non-intrusive chemiluminescence assay has proven to be an excellent tool for investigating the role of the ·OH in biomimetic pulp bleaching and potentially other systems.

A Simple Kinetic Model of Polymer Adsorption and Desorption

Science ◽  
1993 ◽  
Vol 262 (5142) ◽  
pp. 2010-2012 ◽  
Author(s):  
J. F. Douglas ◽  
H. E. Johnson ◽  
S. Granick
Keyword(s):  
Kinetic Model ◽  
Polymer Adsorption ◽  
Adsorption And Desorption ◽  
Simple Kinetic Model

scholarly journals Analysis of stochastic excitability in a simple kinetic model of glycolysis

2017 ◽  
Vol 13 (1) ◽  
pp. 13-23
Author(s):  
И.А. Башкирцева ◽  
Keyword(s):  
Kinetic Model ◽  
Simple Kinetic Model

Dynamics of photoconversion processes: the energetic cost of lifetime gain in photosynthetic and photovoltaic systems

2021 ◽  
Author(s):  
Robert Godin ◽  
James R. Durrant
Keyword(s):  
Kinetic Model ◽  
Solar Energy ◽  
Energy Conversion ◽  
Energy Cost ◽  
Energetic Cost ◽  
Photovoltaic Systems ◽  
Simple Kinetic Model ◽  
Energy Conversion Systems ◽  
Order Of Magnitude ◽  
The Cost

The energy cost of lifetime gain in solar energy conversion systems is determined from a breadth of technologies. The cost of 87 meV per order of magnitude lifetime improvement is strikingly close to the 59 meV determined from a simple kinetic model.

scholarly journals A simple kinetic model for electron-beam-pumped KrF lasers

1991 ◽  
Vol 9 (3) ◽  
pp. 659-673 ◽  
Author(s):  
E. C. Harvey ◽  
M. J. Shaw
Keyword(s):  
Electron Beam ◽  
Kinetic Model ◽  
Gas Composition ◽  
Gain Saturation ◽  
Laser Amplifiers ◽  
Saturation Intensity ◽  
Fundamental Relationship ◽  
Pump Rate ◽  
Simple Kinetic Model ◽  
Analytical Expressions

A kinetic model for KrF is presented that, by neglecting all but the most important kinetic processes, adequately describes the performance of electron-beam-pumped KrF lasers by a few, simple analytical expressions. The expression for the saturation intensity as a function of pump rate and gas composition is checked by measurements of gain saturation in both argon-rich and krypton-rich laser mixtures. The effects of fluorine burn-up are considered and are shown to impose a fundamental relationship between output fluence and efficiency of KrF laser amplifiers.

SU-FF-T-496: A Simple Kinetic Model with a Mechanistic Basis for Tumor Survival Curves

2009 ◽  
Vol 36 (6Part16) ◽  
pp. 2637-2637
Author(s):  
R Martín-Landrove ◽  
M Martín-Landrove ◽  
N Guillén
Keyword(s):  
Kinetic Model ◽  
Survival Curves ◽  
Tumor Survival ◽  
Simple Kinetic Model ◽  
Mechanistic Basis
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