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1.
The process of peroxide bleaching of Populus tomentosa kraft pulp with H2O2 pretreatment under acid condition was studied. The variations of pulp characteristics such as brightness, Kappa number and viscosity during the peroxide bleaching process were discussed and the concept of the A/B value was presented for the first time. The results show that acid pretreatment with H2O2 is essential to improve pulp brightness and avoid viscosity loss. The conclusion is reached that the A/B value has great influence on pulp properties when the total amount of peroxide used in the bleaching process is 2%–5%. Pulp with a high viscosity and brightness can be obtained when A/B is about 0.15. 相似文献
2.
A marine white rot isolate, Phlebia sp. MG-60, secreted lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase under different sea salt incubation conditions.
Its MnP production was strongly enhanced by adding 3% sea salts, and the MnP showed high tolerance to sea salts and NaCl.
The crude enzyme secreted at 3% sea salt concentration by Phlebia sp. MG-60, in which the main component was MnP (cMnP), was then used to bleach unbleached hardwood kraft pulp (UKP) in vitro.
The pulp was brightened 11 points by 4 U of cMnP, and the kappa number was decreased 6 points when only 0.5 mM H2O2 was added continuously. When 0.5 mM H2O2 (1.22 mg H2O2 /g pulp) was added at the initial bleaching, the pulp brightness increased 6 points with a dosage of 4 U of cMnP. When crude
MnPs were employed to bleach UKP with organic-free model white-water instead of the Milli Q water usually used, the pulp was
brightened 10 and 13 points by 4 and 20 U of cMnP, respectively, and 5 and 6 points by 4 and 20 U of MnP, respectively, of
Phanerochaete chrysosporium.
Received: September 28, 2001 / Accepted: March 15, 2002
Correspondence to:R. Kondo 相似文献
3.
In this study, the response of Eucalyptus camaldulensis and Acacia mangium kraft pulp to different options of ECF bleaching was investigated. Oxygen-delignified pulps of both species having similar
kappa number (c.a. 12) were used. Both the pulps were prebleached using conventional ClO2 stage (D0), combined use of ClO2 and O3 (DZ), hot acid treatment before D0 (AhotD0) and hot acid treatment before (DZ) i.e., Ahot(DZ), hot ClO2 treatment (DHT) and Ahot followed by DHT (AhotDHT). All prebleached pulps were finally bleached to 90%+ ISO brightness using D1 option. The overall benefits of other options were not considerable compared to D0 and (DZ). From the ClO2 consumption point of view, for a certain species, the option Ahot(DZ) was the best. Instead of D1 in final bleaching, pressurized hydrogen peroxide (PO) was also investigated in the case of D0 and (DZ) prebleached pulps. (PO)-bleached pulp produced higher brightness stability but lower viscosity compared to D1. 相似文献
4.
5.
Daniel Van Opdenbosch Mariya H. Kostova Sabine Gruber Sebastian Krolikowski Peter Greil Cordt Zollfrank 《Wood Science and Technology》2010,44(4):547-560
Biomorphous Eu3+-doped Y2O3 was fabricated by replication of wood templates using vacuum-assisted infiltration of a water-based sol–gel mixture and subsequent
calcination at 750°C. The precursor sols were prepared from (Y0.95Eu0.05)2O3 dissolved in 10 vol% nitric acid and adding citric acid as the chelating agent. X-ray powder diffraction analyses and Rietveld
refinements confirmed that the calcined samples were solely composed of bixbyite Y2O3:Eu3+ phase with a mean crystallite size of 16 nm. Scanning electron micrographs and cathodoluminescence imaging showed that the
cellular preform anatomy was retained and that the original wood cell walls were completely transformed into phosphor struts
with pore sizes ranging from 5 to 20 μm. The optical properties of the biomorphous phosphor materials were analyzed by photoluminescence
spectroscopy and assigned to the characteristic Eu3+ (4f6 → 4f6) electric dipole or magnetic dipole transitions. From fluorescence lifetime measurements, the mean lifetime was calculated
as 1.62 ms. 相似文献
6.
Hermann Rodenkirchen Axel Göttlein Alessandra R. Kozovits Rainer Matyssek Thorsten E. E. Grams 《European Journal of Forest Research》2009,128(2):117-128
Saplings of Fagus sylvatica and Picea abies were grown under conditions of intra and interspecific competition in a 2-year phytotron study under combinations of ambient
and elevated ozone (+O3 which is 2 × O3, but <150 nl l−1) as well as carbon dioxide concentrations (+CO2 which is amb. CO2 + 300 μl CO2 l−1) in a full factorial design. Saplings were analysed for various mineral nutrients in different plant organs as well as biomass
production and crown development. The study was based on the assumption that nutritional parameters important for growth and
competitiveness are affected by stress defence under limiting nutrient supply. The hypotheses tested were (1) that nutrient
uptake-related parameters (a) as well as efficiencies in nutrient use for above-ground competition (b) of beech rather than
spruce are impaired by the exposure to elevated O3 concentrations, (2) that the efficiency in nutrient uptake of spruce is enhanced by elevated CO2 concentrations in mixed culture, and (3) that the ability to occupy above-ground space at low nutrient cost is co-determinant
for the competitive success in mixed culture. Clear nitrogen deficiencies were indicated for both species during the 2-year
phytotron study, although foliar nitrogen-biomass relationships were not so close for spruce than for beech. O3 stress did not impair nutrient uptake-related parameters of beech; thus hypothesis (1a). was not supported. A negative effect
of elevated O3 (under amb. CO2) on the N and P based efficiencies in above-ground space occupation (i.e. lower crown volume per unit of N or P invested
in stems, limbs and foliage) of beech supported hypothesis (1b). It appeared that ozone stress triggered a nutrient demand
for stress defence and tolerance at the expense of above-ground competition (trade-off). Crown volume of beech under O3 stress was stabilized in monoculture by increased nutrient uptake. In general, the +CO2-treatment was able to counteract the impacts of 2 × O3. Elevated CO2 caused lower N and S concentrations in current-year foliage of both tree species, slightly higher macronutrient amounts in
the root biomass of spruce, but did not increase the efficiencies in nutrient uptake of spruce in mixed culture. Therefore
hypothesis (2) was not supported. At the end of the experiment spruce turned out to be the stronger competitor in mixed culture
as displayed by its higher total shoot biomass and crown volume. The amounts of macronutrients in the above-ground biomass
of spruce individuals in mixed culture distinctly exceeded those of beech, which had been strongly reduced by interspecific
competition. The superior competitiveness of spruce was related to higher N and P-based efficiencies in above-ground space
occupation as suggested in hypothesis (3).
This article belongs to the special issue “Growth and defence of Norway spruce and European beech in pure and mixed stands”. 相似文献
7.
Abouzar Hatam Kambiz Pourtahmasi Hossein Resalati A. Hossein Lohrasebi 《Wood Science and Technology》2008,42(5):353-367
Due to the variations in opacity and brightness of peroxide bleached pulp at Mazandaran Wood and Paper Industries Company
(MWPI), empirical models were developed to predict chemimechanical pulp (CMP) brightness and opacity from peroxide bleaching
conditions and to drive the optimum operating conditions. To overcome the inconsistency problem, a multi-variate regression
analysis method was used for model building. The models were then validated using a new data set from the bleach plant at
MWPI, assessing the models’ predictive ability and performance. The results show that there is a relationship between bleaching
variables and such dependent variables as pulp brightness and opacity. In addition to the hydrogen peroxide charge and pulp
initial brightness, the initial opacity had a significant reverse effect on the final CMP brightness. It was also found that
the concentration of total Na+ in the CMP tower was the most important variable affecting the final pulp opacity. The validation results demonstrated that
these models can be employed as useful tools for process optimization purposes. 相似文献
8.
Our previous paper showed tobacco stalks to posses the characteristics of a raw material for pulp and paper application. It contains the major biomass constituents and cell components common to wood species. In this study, preparation and characterization of tobacco stalk pulp by steam explosion (SE) pulping at two chemical pretreatments were attempted. Chemical pretreatment prior to SE pulping improved the brightness, yield, and strength properties of the resulting tobacco SE pulps in the order: 6% Na2SO3 + 1% NaOH > 6% Na2SO3 > control (untreated). The 6% Na2SO3 + 1% NaOH-impregnated tobacco stalks produced SE pulps of good fiber length distribution and considerable properties that compare well with pulps from other raw materials obtained from previous studies, and the nonimpregnated ones showed strength properties superior to those of their poplar counterpart. Prior to bleaching, pretreating the tobacco stalk SE pulps with two stages, 2% NaOH at 90°C, improved the initial pulp brightness by about 5 points. Two-stage 6% H2O2 bleaching gave a comparable effect with hypochlorite bleaching for both tobacco and poplar, giving a 29–34 brightness point increase for tobacco SE pulp and 61 for the poplar samples. The differences in the bleaching responses for untreated tobacco and poplar SE pulps were attributed to the differences in their lignin structure, as shown in the total yield of their respective nitrobenzene oxidation products and FT-IR spectra. Tobacco SE pulps contain more of the guaiacyl-type lignin and poplar the syringyl-type lignin.This paper was presented in part during the 1998 CORESTA (Cooperation Centre for Scientific Research Relative to Tobacco) Congress, Brighton, UK, October 1998 相似文献
9.
Hot water extract (HWE) from Pinus radiata bark was fractionated into monomeric polyphenol (MPP), oligomeric proanthocyanidin (OPA), and polymeric proanthocyanidin
(PPA) fractions by monitoring the UV-visible spectrum of the eluted fractions. Nine polyphenols were identified in MPP: three
phenolic acids and six flavonoids. The major compounds of MPP were taxifolin (456 μg/mg), catechins (240 μg/mg), and protocatechuic
acid (46.2 μg/mg). The OPA components ranged from dimers to hexamers. PPA comprised procyanidin (PC, 94%), a small amount
of prodelphinidin (PD, 6%), and also the higher trans configuration, rather than the cis configuration, of C2-C3. The average molecular weight (Mw, Mn), polydispersity (Mw/Mn), and DP of PPA were 3,800 (Mw), 1,200
(Mn), 3.2 and 13, respectively. The potential antioxidant activities of HWE and the three fractions were estimated using proton-
or electron-donating assays containing 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical, 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate)
(ABTS) radical cation, superoxide anion (O2•−), hydrogen peroxide (H2O2), reducing power and lipid peroxidation. All the bark fractions exhibited potent quenching abilities against both commercially
available radicals (DPPH•, ABTS•+) and chemically induced radicals (H2O2, O2•−), as well as strong reducing power and inhibitory activity of lipid peroxidation. Particularly, OPA showed a hydrogen peroxide
scavenging activity significantly higher (p < 0.05) than that of the other fractions. From 2-thiobarbituric acid reactive substances and ferric thiocyanate assays, PPA
was suspected to act by essentially delaying the formation of hydroperoxide by quenching free oxygen radicals that operates
in oil-in-water emulsion. 相似文献
10.
11.
The changes of hydrogen peroxide (H2O2) metabolism and antioxidant enzyme activities in a hybrid poplar (Populus simonii × P. pyramidalis ‘Opera 8277’) in response to mechanical damage (MD) and herbivore wounding (HW) were investigated to determine whether H2O2 could function as the secondary messenger in the signaling of systemic resistance. Results show that H2O2 was generated in wounded leaves through MD and HW treatments and systemically in unwounded leaves around the wounded leaves.
The activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) were
also enhanced. However, the H2O2 accumulation and antioxidant enzyme activities were inhibited in MD leaves through the pretreatment with DPI (which is a
specific inhibitor of NADPH oxidase). The results of this study suggest that H2O2 could be systemically induced by MD and HW treatments, and H2O2 metabolism was closely related to the change in SOD, APX and CAT activities. A high level of antioxidant enzymes could decrease
membrane lipid peroxidation levels and effectively induce plant defense responses.
Foundation project: This research is supported by the Key Science Program of the Sate Forestry Administration of China (2006–59),
and the National Key Project of Scientific and Technical Supporting Programs Funded by Ministry of Science & Technology of
China (2006BAD01A15; 2006BAD24B04).
Biography: AN Yu (1982–), female, Postgraduate in College of Biological Sciences and Biotechnology, Beijing Forestry University,
Beijing 100083, P. R. China. 相似文献
12.
Land management practices that simultaneously improve soil properties are crucial to high crop production and minimize detrimental
impact on the environment. We examined the effects of crop residues on crop performance, the fluxes of soil N2O and CO2 under wheat-maize (WM) and/or faba bean-maize (FM) rotations in Amorpha fruticosa (A) and Vetiveria zizanioides (V) intercropping systems on a loamy clay soil, in subtropical China. Crop performance, soil N2O and CO2 as well as some potential factors such as soil water content, soil carbon, soil nitrogen, microbial biomass and N mineralization
were recorded during 2006 maize crop cultivation. Soil N2O and CO2 fluxes are determined using a closed-based chamber. Maize yield was greater after faba bean than after wheat may be due to
differences in supply of N from residues. The presence of hedgerow significantly improved maize grain yields. N2O emissions from soils with maize were considerably greater after faba bean (345 g N2O–N ha−1) than after wheat (289 g N2O–N ha−1). However, the cumulated N2O emissions did not differ significantly between WM and FM. The difference in N2O emissions between WM and FM was mostly due to the amounts of crop residues. Hedgerow alley cropping tended to emit more
N2O than WM and FM, in particular A. fruticosa intercropping systems. Over the entire 118 days of measurement, the N2O fluxes represented 534 g N2O–N ha−1 (AWM) and 512 g N2O–N ha−1 (AFM) under A. fruticosa species, 403 g N2O–N ha−1 (VWM) and 423 g N2O–N ha−1 (VFM) under Vetiver grass. We observed significantly higher CO2 emission in AFM (5,335 kg CO2–C ha−1) from June to October, whereas no significant difference was observed among WM (3,480 kg CO2–C ha−1), FM (3,302 kg CO2–C ha−1), AWM (3,877 kg CO2–C ha−1), VWM (3,124 kg CO2–C ha−1) and VFM (3,309 kg CO2–C ha−1), indicating the importance of A. fruticosa along with faba bean residue on CO2 fluxes. As a result, crop residues and land conversion from agricultural to agroforestry can, in turn, influence microbial
biomass, N mineralization, soil C and N content, which can further alter the magnitude of crop growth, soil N2O and CO2 emissions in the present environmental conditions. 相似文献
13.
M. Sarwar Jahan 《Wood Science and Technology》2009,43(3-4):213-224
Dissolving pulps are the raw materials for the production of many different end-products. Jute is a very good source of cellulose. In this investigation, jute fiber was subjected to pulping in soda process in order to produce dissolving pulp under different prehydrolysis conditions and compared with prehydrolysed kraft pulp from jute. An increase of the prehydrolysis temperature or H2SO4 in prehydrolysis liquor increased the α-cellulose content and decreased the viscosity of pulp. The effect of ethylenediamine in soda liquor was also investigated when producing dissolving pulp. Jute fiber produced pulp having 90–97% α-cellulose. Ethylenediamine in soda liquor produced pulp of higher yield, viscosity and higher α-cellulose content than that of prehydrolysis soda or kraft pulp. The α-cellulose content and viscosity were increased with the increase of amine in soda liquor. The kappa number of dissolving pulp from jute was very low (9–5), which indicated that less bleaching chemicals are required for bleaching. The bleachability of soda-ethylenediamine pulp was lower than prehydrolysed soda and kraft pulp in ECF bleaching sequences. The bleachability of soda-ethylenediamine pulp was improved at the sacrifice of pulp yield when prehydrolysis was done prior to pulping. The alkali solubility S 10 and S 18 were 4–9 and 2–4%, respectively. 相似文献
14.
15.
The amounts of CO2 that are absorbed and emitted by forest in a model stand area were determined using two calculation methods, namely the flow
approach and the stock approach for emission trading, to understand the relationships between the cutting age for the highest
profit rate (CAHPR; optimum tree ages to be cut so as to maximize the profit) and (1) the prices of CO2 and (2) the balance between CO2 emission and absorption. The resultant CAHPR differed between these two CO2 accounting methods, which give different tree ages for maximum log volume yield. A rise in CO2 price caused the CAHPR to approach the tree age of maximum log volume in the flow approach method, and to deviate from the
tree age of maximum log volume in the stock approach method. Even at the same CO2 price, the CAHPR differed between the CO2 accounting methods. At low CO2 prices, the CAHPR did not affect situations where the difference of average profit is large by cutting age. On the other
hand, the CAHPR was greatly affected at low CO2 prices when the mean log volume growth changed with tree age. These trends were found to be universal.
Received: September 18, 2001 / Accepted: October 25, 2002
Acknowledgments This study is one of the fifth science study subsidy projects of the Japan Forest Technology Association.
Correspondence to:K. Sakata 相似文献
16.
A study was conducted to determine the effects of elevated CO2 on soil N process at Changbai Mountain in Jilin Province, northeastern China (42°24′N, 128°06′E, and 738 m elevation). A
randomized complete block design of ambient and elevated CO2 was established in an open-top chamber facility in the spring of 1999. Changpai Scotch pine (Pinus sylvestris var. sylvestriformis seeds were sowed in May, 1999 and CO2 fumigation treatments began after seeds germination. In each year, the exposure started at the end of April and stopped at
the end of October. Soil samples were collected in June and August 2006 and in June 2007, and soil nitrifying, denitrifying
and N2-fixing enzyme activities were measured. Results show that soil nitrifying enzyme activities (NEA) in the 5–10 cm soil layer
were significantly increased at elevated CO2 by 30.3% in June 2006, by 30.9% in August 2006 and by 11.3% in June 2007. Soil denitrifying enzyme activities (DEA) were
significantly decreased by elevated CO2 treatment in June 2006 (P < 0.012) and August 2006 (P < 0.005) samplings in our study; no significant difference was detected in June 2007, and no significant changes in N2-fixing enzyme activity were found. This study suggests that elevated CO2 can alter soil nitrifying enzyme and denitrifying enzyme activities.
Foundation project: This research was supported by the National Natural Science Foundation of China (No. 90411020) and Major
State Basic Research Development Program of China (973 Program) (2002CB412502). 相似文献
17.
Manuel Acosta Marian Pavelka Ivana Tomášková Dalibor Janouš 《European Journal of Forest Research》2011,130(4):649-656
Branch CO2 efflux of Norway spruce tree [Picea abies (L.) Karst.] was measured in ten branches at five different whorls during the growing season 2004 (from June till October)
in campaigns of 3–4 times per month at the Beskydy Mts., the Czech Republic. Branch CO2 efflux was measured using a portable infrared gas analyzer (LI-6250, LI-COR, Inc., USA), operating as a closed system. Branch
woody-tissue temperature was measured continuously in 10-min intervals for each sample position during the whole experiment
period. On the basis of relation between CO2 efflux rate and woody-tissue temperature, a value of Q10 and of normalized CO2 efflux rate (E10–CO2 efflux rate at 10°C) was calculated for each sampled position. Estimated Q10 values ranged from 2.12 to 2.89, and E10 ranged from 0.41 to 1.19 μmolCO2m−2s−1. Differences in branch CO2 efflux were found between orientations, east-side branches presented higher efflux rate than west-side branches. The highest
branch CO2 efflux rate values were measured in August and the lowest in October, which corresponds with woody-tissue temperature and
growth processes during these periods. Branch CO2 efflux was significantly and positively correlated with branch position within canopy and woody-tissue temperature. Branches
from the upper whorls showed higher CO2 efflux activity and seasonal dynamics than branches from the lower whorls. 相似文献
18.
The steam explosion (SE) pretreatment associated with the organosolv process was investigated to produce dissolving pulp from eucalyptus. Prehydrolysis Kraft (PHK) pulping was also done to produce viscose and acetate grade pulps as reference. The organosolv pulps were delignified in two steps with sodium chlorite. Viscose and acetate grade PHK pulps were bleached by OD0(EH)D1P and OD0(EP)D1PCCE sequences, respectively. Dilute acid-catalyzed (with acid addition) SE pretreatment dissolved more xylan than auto-catalyzed (no acid addition) SE pretreatment. Steam-exploded unbleached organosolv pulps showed lower residual lignin content and screened yield than unbleached organosolv pulps without SE pretreatment. Steam explosion pretreatment helped to decrease lignin content and damaged fiber length of unbleached organosolv pulps. The 1.0% H2SO4 organosolv pulp (organosolv dissolving pulp at bioconversion conditions) showed the highest reactivity. Even showing low viscosity for some applications, in general, the organosolv dissolving pulps produced in this study can be used for making lyocell fibers. 相似文献
19.
Norway spruce dust was impregnated with aqueous solutions of chromated copper wood preservatives. Immediately after treatment,
observation of CO2 evolution and O2 consumption were performed. Significant quantities of CO2 were released during reaction of chromium (K2Cr2O7) containing solutions with wood or brown rotted wood. Nevertheless, during reaction of cellulose with these preservatives
we did not observe evolution of CO2. The presence of copper did not influence on concentration of CO2. Opposite to CO2 evolution, treatment of wood and brown rotted wood resulted in O2 consumption. The oxygen concentration decrease in the measuring chamber was approximately 5 times greater than increase of
concentration of carbon dioxide. Electron paramagnetic resonance (EPR) observations of chromium fixation showed that chromium
is reduced from Cr(VI) to Cr(III) with Cr(V) as an intermediate on wood, brown rotted wood and cellulose. However, the reduction
on wood and brown rotted wood was faster than the reduction on cellulose, as determined from changes of Cr signals in EPR
spectra. So, evolution of CO2 and consumption of O2 as well as EPR signals of Cr species thus indicate that brown rotted wood, consisting of lignin and hemicelluloses in contact
with Cr(VI) reacts more intensively than cellulose, and possibly, oxidation mechanisms of lignin and cellulose with Cr(VI)
are different.
Received: 20 July 2000 相似文献
20.
甲脒亚磺酸用于麦草Soda-AQ浆漂白的研究 总被引:2,自引:0,他引:2
对甲脒亚磷酸(FAS)用于麦草Soda-AQ浆漂白的可能性进行了研究,重点考察了麦草Soda-AQ浆过氧化氢(P)和甲脒亚磺酸(A)两段漂白中的几个过程变量(H2O2和FAS用量、温度、时间)对漂白的影响,找出了较佳的PF漂白工艺条件。结果表明,P段H2Q用量2%~3%(对绝干浆)、F段FAS用量0.5%(对绝干浆)、温度70℃、时间3()nd为较佳的漂白工艺条件。研究中发现,L*与白度呈线性正相关。a*与L*呈线性负相关,而b*与L*之间无明确的相关性。 相似文献