Reactions of aromatic structures in brightness reversion of fully-bleached eucalyptus kraft pulps

Holzforschung ◽  
2009 ◽  
Vol 63 (3) ◽  
Author(s):  
Anna-Stiina Jääskeläinen ◽  
Katri Toikka ◽  
Anni Lähdetie ◽  
Tiina Liitiä ◽  
Tapani Vuorinen
Keyword(s):  
Resonance Raman ◽  
Kraft Pulps ◽  
Brightness Reversion ◽  
Vis Spectroscopy ◽  
Uv Resonance Raman ◽  
Hexenuronic Acid

Abstract The role of aromatic structures in brightness reversion of fully bleached pulps was studied by UV resonance Raman (UVRR) and reflectance UV-Vis spectroscopy. The results clearly showed that ageing increased the aromatic band at approximately 1600 cm-1 in the UVRR spectra and the lignin band at approximately 280 nm in the UV-Vis spectra. This increase was probably due to increased conjugation of lignin and it was observed for all pulps regardless of the bleaching sequence. In addition to these lignin reactions, other unsaturated structures, such as hexenuronic acid groups, reacted during ageing.

Study of Residual Lignin in Pulp by UV Resonance Raman Spectroscopy

Holzforschung ◽  
2001 ◽  
Vol 55 (6) ◽  
pp. 631-638 ◽  
Author(s):  
M. Halttunen ◽  
J. Vyörykkä ◽  
B. Hortling ◽  
T. Tamminen ◽  
D. Batchelder ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Lignin Content ◽  
Resonance Raman Spectroscopy ◽  
Resonance Raman ◽  
Residual Lignin ◽  
Highly Sensitive ◽  
Uv Resonance Raman ◽  
Uv Resonance Raman Spectroscopy ◽  
Hexenuronic Acid

Summary A major problem in the development of new bleaching technologies for pulp is the difficulty of analysing the changes induced by bleaching chemicals in the structures of residual lignin. Separation and isolation of the residual lignin before the analysis may modify the constituents of interest, whereas if the pulp is analysed directly, the responses from cellulose and hemicelluloses will overlap the signal from the residual lignin. In this study, UV resonance Raman spectroscopy, a powerful technique for detecting trace components in complex mixtures, was applied to detect the changes in the residual lignin content after bleaching stages. The resonance Raman technique was found to be highly sensitive and selective for lignin structures allowing the detection of trace amounts of lignin after the final bleaching stages. Furthermore, it enabled rapid and easy determination of hexenuronic acid content. UV resonance Raman spectroscopy would appear to be a technique of great potential for pulping and bleaching research.

Hemoglobin Site-mutants Reveal Dynamical Role of Interhelical H-bonds in the Allosteric Pathway: Time-resolved UV Resonance Raman Evidence for Intra-dimer Coupling

2004 ◽  
Vol 340 (4) ◽  
pp. 857-868 ◽  
Author(s):  
Gurusamy Balakrishnan ◽  
Ching-Hsuan Tsai ◽  
Qiang Wu ◽  
Martin A Case ◽  
Alex Pevsner ◽  
...  
Keyword(s):  
Resonance Raman ◽  
Time Resolved ◽  
Uv Resonance Raman ◽  
Allosteric Pathway

scholarly journals Contribution of xylan to the brightness development and stability in the final ECF bleaching of eucalypt (Eucalyptus globulus Labill.) kraft pulp

Holzforschung ◽  
2013 ◽  
Vol 67 (5) ◽  
pp. 497-503 ◽  
Author(s):  
Pedro E.G. Loureiro ◽  
Joana I.T. Sousa ◽  
M. Graça. V.S. Carvalho ◽  
Dmitry V. Evtuguin
Keyword(s):  
Analytical Methods ◽  
Kraft Pulp ◽  
Resonance Raman Spectroscopy ◽  
Size Exclusion ◽  
Kraft Pulps ◽  
Vis Spectroscopy ◽  
Exclusion Chromatography ◽  
Uv Resonance Raman Spectroscopy ◽  
Modern Analytical

Abstract Xylans isolated from eucalypt kraft pulps have been characterized by modern analytical methods. The pulps were partially bleached (DEOPD) and fully bleached with either a final ClO2 (DEOPDD) or an alkaline H2O2 (DEOPDP) bleaching stage. Alternatively, xylan isolated from the DEOPD pulp was treated with ClO2 or with H2O2 under the same conditions as pulps in a final bleaching stage and were further characterized. 1H nuclear magnetic resonance, size exclusion chromatography, UV-vis spectroscopy in cadoxen solution, and UV-resonance Raman spectroscopy were applied as analytical methods. The final ClO2 stage generated new unsaturated moieties in xylan, whereas H2O2 was very effective in the removal of xylan-related chromophores. The role of xylan to the delay of brightness development in the final ClO2 stage was highlighted by means of a pretreatment with xylanase Pulpzyme HC before the final bleaching stage. By this approach, the final bleachability of the pulp was boosted and the brightness stability of the fully bleached pulp was improved.

scholarly journals Use of UV resonance Raman spectroscopy for assessing the brightness stability of ozone TCF bleached pulp

Holzforschung ◽  
2020 ◽  
Vol 74 (6) ◽  
pp. 605-613
Author(s):  
Etienne Montet ◽  
Estefania Isaza Ferro ◽  
Jordan Perrin ◽  
Dominique Lachenal ◽  
Christine Chirat
Keyword(s):  
Raman Spectroscopy ◽  
Degradation Products ◽  
Resonance Raman Spectroscopy ◽  
Resonance Raman ◽  
Kraft Pulps ◽  
Residual Lignin ◽  
Bleached Pulp ◽  
Uv Resonance Raman ◽  
Uv Resonance Raman Spectroscopy ◽  
The Difference

AbstractThis study intends to explain the difference in brightness stability between hardwood ECF and TCFz kraft pulps bleached by DEpDD and A(ZEo)(ZEo)(ZP) sequences respectively, using UV Resonance Raman (UVRR) spectroscopy. The brightness stability of the pulps was tested via dry aging experiments where the Post-Color Number (PCN) of the ECF pulp was twice that of the TCF pulp. The aged and non-aged bleached pulps were analyzed with UVRR spectroscopy to identify the cause of the large difference in PCN. The spectra of ECF and TCF bleached pulps presented clear differences in the intensities of the Raman shifts associated to lignin, lignin-like compounds, and degradation products such as muconic acids. To identify more specifically the compounds affecting the PCN, several post-bleaching treatments were applied on the ECF pulp including single stages (E, B, P, Z) or combinations (ZE, ZB, ZP), and their UVRR spectra analyzed. It was found that alkaline-soluble compounds were the main culprits for the difference in PCN values between ECF and TCFz pulps. ZP combination was the most efficient in eliminating residual lignin and other unsaturated components and for the development of brightness and brightness stability.

Prebleaching of eucalypt kraft pulp with OP stages: Effect of an acid pretreatment or chelation step

TAPPI Journal ◽  
2012 ◽  
Vol 11 (6) ◽  
pp. 31-38
Author(s):  
TATIANA M. PÓVOAS ◽  
DINA A.G. ANGÉLICO ◽  
ANA P.V. EGAS ◽  
PEDRO E.G. LOUREIRO ◽  
LICÍNIO M. GANDO-FERREIRA ◽  
...  
Keyword(s):  
Eucalyptus Globulus ◽  
Comparative Evaluation ◽  
Kraft Pulp ◽  
Kraft Pulps ◽  
Acid Pretreatment ◽  
High Brightness ◽  
Pulp Viscosity ◽  
Brightness Reversion

We conducted a comparative evaluation of different treatments for the bleaching of eucalypt kraft pulps beginning with OP stages. The treatments tested were (1) an acid chelation stage with DTPA (OQP sequence); (2) a hot acid stage (AOP sequence); and (3) a chelant addition into the alkaline oxygen stage ((OQ)P and A(OQ)P sequences). The latter strategy was also studied for environmental reasons, as it contributes to the closure of the filtrate cycle. The OQP sequence leads to the highest brightness gain and pulp viscosity and the lowest peroxide consumption caused by an efficient metals control. Considering that the low biodegradability of the chelant is a problem, the A(OQ)P sequence is an interesting option because it leads to reduced peroxide consumption (excluding OQP) while still reaching high brightness values and similar brightness reversion to OQP prebleaching, with only a viscosity loss of 160 dm3/kg. Therefore, a hot acid stage could be considered when a separate acid Q stage is absent in a prebleaching sequence of Eucalyptus globulus kraft pulps involving OP stages.

scholarly journals The Role of the Disulfide Bridge in the Copper (II) Binding by the Cyclic His4-Peptide

2021 ◽  
Vol 22 (12) ◽  
pp. 6458
Author(s):  
Aleksandra Pieniężna ◽  
Weronika Witak ◽  
Aneta Szymańska ◽  
Justyna Brasuń
Keyword(s):  
Metal Ions ◽  
Coordination Mode ◽  
Transition Metal Ions ◽  
Disulfide Bridge ◽  
Chain Flexibility ◽  
Vis Spectroscopy ◽  
Ph Range ◽  
Cd Studies ◽  
Metal Ratios

In this paper, we present studies on the influence of the disulfide bridge on the copper (II) ions’ binding abilities by the cyclic His4-peptide. The studied ligand HKHPHRHC-S-S-C consists of nine amino acids. The cyclic structure was obtained through a disulfide bridge between two cysteinyl groups. Moreover, this peptide is characterized by the presence of four His residues in the sequence, which makes it an interesting ligand for transition metal ions. The potentiometric and spectroscopic (UV-Vis spectroscopy and circular dichroism spectroscopy (CD)) studies were carried out in various molar ligand to metal ratios: 2:1, 1:1, and 1:2, in the pH range of 2.5–11 at 25 °C. The results showed that the cyclic His4-peptide promotes dinuclear complexes in each of these systems and forms the final dinuclear species with the {NIm, 3N-amide}{NIm, 3N-amide} coordination mode. The obtained data shows that cyclization by the formation of the disulfide bond has an impact on the peptide chain flexibility and appearance of additional potential donors for metal ions and influences the copper (II) ions’ coordination.

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