Role of an Inorganic Phosphate in the Photogeneration of Hydrogen Peroxide in Aqueous Solutions of Adenine Derivatives at 77 K

2021 ◽  
Vol 95 (8) ◽  
pp. 1591-1600
Author(s):  
T. A. Lozinova ◽  
A. V. Lobanov ◽  
E. N. Degtyarev ◽  
O. N. Brzhevskaya ◽  
A. V. Lander
Holzforschung ◽  
1999 ◽  
Vol 53 (2) ◽  
pp. 181-187 ◽  
Author(s):  
C. C. Walker ◽  
R. J. Dinus ◽  
T. J. McDonough ◽  
K.-E. L. Eriksson

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.


1991 ◽  
Vol 56 (3) ◽  
pp. 657-662 ◽  
Author(s):  
Pavel Stopka ◽  
Oldřich Štrouf

The superoxide anion-radicals O2·- are generated by the ultraviolet irradiation of air- or oxygen-saturated aqueous solutions of tetramethylammonium mercaptoundecahydro-closo-dodecaborate(2-) at 77 K. The superoxide anion-radicals are formed from the oxygen molecule coordinated on the mercaptoundecahydro-closo-dodecaborate dianion. In the absence of this dianion no O2·- are generated. By the irradiation in the presence of hydrogen peroxide the formation of the superoxide anion-radicals is more intensive than in the presence of oxygen only. Simultaneously with O2·- generation the corresponding thiol radicals are formed. These radicals give the disulfide compound [B12H11S]24-. A possible role of sulfur-centered radicals in the autoxidation transformations of the mercaptoundecahydro-closo-dodecaborate dianion is discussed.


TAPPI Journal ◽  
2012 ◽  
Vol 11 (7) ◽  
pp. 37-46 ◽  
Author(s):  
PEDRO E.G. LOUREIRO ◽  
SANDRINE DUARTE ◽  
DMITRY V. EVTUGUIN ◽  
M. GRAÇA V.S. CARVALHO

This study puts particular emphasis on the role of copper ions in the performance of hydrogen peroxide bleaching (P-stage). Owing to their variable levels across the bleaching line due to washing filtrates, bleaching reagents, and equipment corrosion, these ions can play a major role in hydrogen peroxide decomposition and be detrimental to polysaccharide integrity. In this study, a Cu-contaminated D0(EOP)D1 prebleached pulp was subjected to an acidic washing (A-stage) or chelation (Q-stage) before the alkaline P-stage. The objective was to understand the isolated and combined role of copper ions in peroxide bleaching performance. By applying an experimental design, it was possible to identify the main effects of the pretreatment variables on the extent of metals removal and performance of the P-stage. The acid treatment was unsuccessful in terms of complete copper removal, magnesium preservation, and control of hydrogen peroxide consumption in the following P-stage. Increasing reaction temperature and time of the acidic A-stage improved the brightness stability of the D0(EOP)D1AP bleached pulp. The optimum conditions for chelation pretreatment to maximize the brightness gains obtained in the subsequent P-stage with the lowest peroxide consumption were 0.4% diethylenetriaminepentaacetic acid (DTPA), 80ºC, and 4.5 pH.


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