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1.
对麦草浆二氧化氯与氧气脱木素效率及相应的漂白流程进行了对比研究。结果表明,ClO2脱木素(D0)对木素的修饰和改性效果好于氧脱木素(O),在脱木素率低于及接近氧脱木素率的条件下,D0浆的可漂性均大于O浆。在D0段和O段脱木素率相同的条件下,采用D0A/QP、D0EP漂白流程漂后纸浆白度分别比OA/QP漂白流程高11.2和10.3个百分点。D0段废液和相应D0A/QP漂白流程三段混合废水的CODCr负荷均比O段和OA/QP漂白流程混合废水的CODCr负荷轻。D0段和O段废液的紫外光谱都呈现出木素苯环的特征吸收。纸浆的FT-IR谱图分析表明,D0浆和O浆中的羟基和羰基数量增多,随着漂白的进行,羰基等主要发色基团逐渐消除,纸浆白度得到提高。纸浆纤维形态的SEM分析显示,D0段和相应的D0A/QP漂白流程对纤维表面的破坏和损伤较O段和相应的OA/QP漂白流程轻。  相似文献   

2.
The supercritical fluid extraction of manganese and iron from solid matrix (wood pulp) is demonstrated experimentally. Supercritical carbon diodixe is used together with lithium bis(trifluoroethyl) dithiocarbonate (FDDC) as the ion-pairing reagent. The metal content of the pulp samples was determined by inductively couple plasma atomic emission spectroscopy (ICP-AES). Optimum conditions were determined to be 30 min each of static and dynamic extraction with 200 atm pressure at 40 °C. Thermomechanical pulp (TMP) extracted under these parameters exhibits an 80% decrease in manganese content, and 91% after a second, sequential extraction. The simultaneous removal of iron was found to be only 6% and supports evidence that it is much more strongly bound to the TMP matrix than manganese.  相似文献   

3.
The dissolution of lux bases and acids and the acid-base reactions of solutions of polyacidic bases with a gaseous mixture of NO2 + O2 acting as a lux acid were studied by measuring the potential of an oxygen electrode at a temperature of 260°C. The strength of the conjugate pairs of acids and bases was compared qualitatively with respect to the nitrate system using the shapes of the potentiometric curves for the acid-base reactions. Some effects that were found for the first time on poteniometric curves were explained on the basis of theoretical treatment of acid-base reactions in systems where the poorly soluble acid is precipitated from the melt.  相似文献   

4.
The selectivity of the water-soluble and highly active catalyst bis(o-phenanthroline)Cu in the oxygen bleaching of pulp was explored in model compound studies. The experiments were carried out under reaction conditions typical for industrial oxygen bleaching (90 °C, pH 12, p(O2) 8 bar). The generation of hydrogen peroxide was an essential step in the oxidation of the lignin model compounds, veratryl alcohol and 2,2′-biphenol. Unfortunately, bis(o-phenanthroline)Cu also catalysed the depolymerisation of the carbohydrate model compound, dextran, both with oxygen and with hydrogen peroxide. The results explain well the inadequate selectivity of bis(o-phenanthroline)Cu in the oxygen bleaching of pulp.  相似文献   

5.
在碱性麦草浆过氧化氢漂白过程中,利用微波加热,对漂白效果与进程都具有一定意义。另外,酰胺助剂TAED的加入,对双氧水漂白具有明显的改善作用,影响其漂白效果的因素有:TAED与双氧水的摩尔比,温度,时间,pH值及双氧水的用量。在一定限度下,漂浆的白度随这些因素的增加而提高。与此同时可降低漂白温度,缩短漂白时间,这就意味着可以减少能耗。降低生产成本。  相似文献   

6.
Soda—oxygen bleaching of commercially available kraft bagasse pulp has been investigated. Alkali charge, temperature and oxygen pressure are important factors in controlling brightness and physical properties of the pulps produced. Pulp yields, lignin and degree of polymerisation of the bleached pulps decreased with increasing alkali charge from 2 to 6%. Strength properties as well as brightness increased by increasing alkali charge at 368 K, whereas optimum strength properties are obtained with 4% alkali at 383 K. In the range of oxygen pressure used, 5–8 kg cm?2, DP as well as strength properties of the bleached pulps increased with increasing oxygen pressure. Brightness up to 61% was reached by soda-oxygen alone. To obtain higher brightness an afterbleaching step is necessary. The soda—oxygen—hypochlorite and soda—oxygen—chlorite pulps prepared have strength properties comparable with those of conventionally bleached pulps.  相似文献   

7.
This article focuses on the effect of pulp bleaching and emerging commercial compatibilizers on physical performance of pulp fiber reinforced poly(lactic acid) (PLA) biocomposites. Industrially bleached and unbleached hardwood kraft pulp fibers are treated with several additive types, and compounded with PLA to fiber content of 30 wt %. After injection molding, the produced biocomposites are evaluated by their mechanical performance and fiber–matrix adhesion. For selected materials, fiber surface and fiber properties are reflected to composite performance by analyzing the compositions, dimensions, and lignin coverage of original fibers, as well as fiber dispersion and dimensions after melt processing. As a conclusion, unbleached kraft pulp fibers provide significant improvement in physical properties of PLA/pulp fiber composites. Of the screened compatibilizers, epoxidated linseed oil has a clear positive effect on performance when bleached kraft pulp fibers are used. The improvements correspond to enhanced fiber–matrix adhesion and differences in remaining fiber length distributions. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47955.  相似文献   

8.
  • 1.1. Petroleum sulphides (obtained as concentrates from appropriate distillates) were oxidized with a mixture of air and nitrogen dioxide to sulphoxides, with yields of 75 to 80% for sulphoxide sulphur, but the process was complicated by secondary processes: the formation of up to 30% of nitrosulphoxides of variable structure; sulphones and carbonyl compounds were present as traces. The target product was separated from most impurities by an alkaline wash, followed by chromatography.
  • 2.2. Oxidation of individual sulphides under the conditions adopted gave sulphoxides, which contained only traces of compounds with a nitro-group, easily removed by recrystallization or elution chromatography.
  相似文献   

9.
In this study, a kinetic model of the final bleaching stage with hydrogen peroxide in a totally chlorine free (TCF) bleaching sequence for ALCELL® processed pulp was developed. The model was based on the rate of chromophore destruction characterized by the decrease in the light absorption coefficient of bleached pulp at 457 nm, CK. Based on the fact that the chromophore destruction proceeds rapidly in an initial phase followed by a much slower reaction during which a “floor-level” chromophore concentration is approached asymptotically, we propose that the hydrogen peroxide stage of the ALCELL® derived pulp in the studied TCF sequence consists of two distinct phases. The initial phase is a very fast reaction. The rate equation of the second phase was determined as: which is valid in a pH range of 10.5 to 11.5 and a temperature range of 60 to 92.5°C.  相似文献   

10.
二氧化氯在精制棉漂白上的应用   总被引:1,自引:0,他引:1  
国产精制棉采用二氧化氯漂白工艺,粘度可超过1000mPa·s,白度可达特级水平,创出国内一流的优质精制棉。二氧化氯应用于精制棉的漂白,国内尚属首次。  相似文献   

11.
徐峻  李智  李军  莫立焕  陈克复 《化工学报》2012,63(12):4062-4067
引言近年来,随着棉花价格的总体上涨和消费者对纺织材料舒适度的要求,给黏胶纤维带来了需求增长空间。作为黏胶纤维的原材料,国内目前的溶解浆产能难以满足客户需求。据统计,国内溶解浆存  相似文献   

12.
Adsorbable organic halides (AOX) compounds produced during bleaching of pulp are recalcitrant and known to have eco-toxic effect. We have studied the removal of pentachlorophenol (PCP) as a model AOX compound in water as well as in pulp bleaching effluent of a bamboo based mill by electrochemical treatment in batch mode. It was found that 10 mg L−1 of PCP in water was removed almost completely in <10 min at a current density of 6 mA cm−2 in the presence of 1000 mg L−1 NaCl serving as an electrolyte and source of chloride ions. The initial rate of PCP removal was found to decrease at alkaline pH (9.3) as compared to that at acidic pH (5.5). PCP removal in neutralized raw pulp bleach effluent (containing 1830 mg L−1 of chloride) was very slow and incomplete even after 2 h of electrochemical treatment at a current density of 15 mA cm−2. Various pretreatments of raw bleach effluent such as, alkaline sulfide using sodium sulfide, alkaline reduction using ferrous sulfate and coagulation using potash alum were evaluated. Electrochemical treatment of potash alum pretreated effluent (spiked with PCP) could achieve >90% removal of initial colour, COD and PCP in <1 h. The treatment scheme presented here may be a promising technology for removal of AOX, COD and colour from pulp bleaching effluent. The estimated cost of combined treatment (potash alum coagulation + electrochemical) is US$ 0.7–0.9 per cubic meter of the raw pulp bleach effluent.  相似文献   

13.
The reaction of methyl linoleate with low levels of nitrogen dioxide in a carrier gas, such as helium or air, at nitrogen dioxide concentrations ranging from 2 to 228 ppm was studied and the products formed were monitored. In both aerobic and anaerobic conditions, low concentrations of nitrogen dioxide reacted with methyl linoleate predominately to form allylic products. When a 1∶1 mixture of methyl palmitate/methyl linoleate was layered over an aqueous buffer and a nitrogen dioxide stream was passed from underneath, so that the stream passed through the aqueous layer before contacting the organic layer, allylic products again predominated. In the absence of air, the allylic products consisted of allylic nitro and nitrite derivatives of linoleate, whereas in the presence of air, allylic hydroperoxides were the principal products. The findings suggest that fatty acids with doubly allylic hydrogen atoms react preferentially by a hydrogen atom abstraction reaction rather than by the addition of nitrogen dioxide to a double bond.  相似文献   

14.
15.
The effect of an NO2+O2 gaseous mixture on a melt of sodium and potassium nitrates and the acid-base reactions of this mixture with some Lux bases were studied, measuring the potential of an oxygen electrode at a temperature of 260°C. It has been found that the NO2+O2 mixture acts as a Lux acid conjugated with NO3 anion as the base, even under the atmospheric pressure. The strengths of the NO2 +O2 acid and the NO3 base related to other studied conjugated acids and bases were qualitatively estimated from the shape of potentiometric curves of the acid—base reactions.  相似文献   

16.
17.
In situ single‐stage electrochemical bleaching of kraft bagasse pulp was carried out in a cylindrical agitated vessel fitted with four graphite rod anodes and a cylindrical stainless steel screen cathode, using NaCl as an electrolyte. The effect of current density, pH, NaCl concentration, impeller rotational speed, temperature, and pulp consistency on the rate of bleaching was studied. It was found that the rate of bleaching increased with increasing current density, NaCl concentration, and temperature and decreased with increasing pH and pulp consistency. The effect of temperature was found to fit Arrhenius equation with an activation energy of 0.515 kcal/mol, which denotes a diffusion‐controlled mechanism. Energy consumption (EC) calculation showed that EC ranged from 0.225 to 3.11 kWh/kg dry pulp depending on the current density. The strength of bleached pulp was little affected by bleaching lying within an acceptable range.  相似文献   

18.
The diffusion and solubility of oxygen, nitrogen and carbon dioxide have been studied in amorphous and biaxially oriented films of polyethylene terephthalate (PET). To measure the sorption and desorption of each gas simultaneously in cases where mixtures of gases were studied, a mass spectrometer was used as a detector. It was found that the solubility and diffusion of nitrogen in PET were markedly affected by the presence of the other gases, oxygen and carbon dioxide with differences in detail between results for the amorphous and biaxially oriented films. It is of particular interest that the presence of oxygen reduces the solubility and increases the diffusivity of nitrogen.  相似文献   

19.
Abstract

The delignification of kraft pulp with sodium dithionite was studied to remove lignin content in the pulp. The sodium dithionite dissolves the chromophoric groups and residual lignin present in the pulp. The increase in dosage of sodium dithionite and reaction temperature of delignification has positive effect on kappa reduction of pulp. X ray diffraction was used to determine the crystallinity index of bleached pulp. The crystallinity increased from 83.3% for unbleached pulp to 86.7% after delignification. Fourier transform infrared spectroscopy shows the reduction in hydrogen bonding in bleached pulp and also the conversion of cellulose I to cellulose II. FT-Raman spectra shows that the fluorescence observed in the spectra of unbleached pulp reduced significantly in comparison to the spectra of bleached pulp resulting in removal of residual lignin and chromophoric groups present in the pulp. Scanning electron imaging shows the smoothening of fiber surface after bleaching. The delignification reaction followed first-order kinetics and activation energy is 33.57kJ/mol.  相似文献   

20.
苇浆CEH漂白废水的毒性及毒性排放负荷   总被引:6,自引:2,他引:6  
方战强  李友明  陈中豪 《化工学报》2005,56(6):1086-1090
采用发光细菌法对苇浆CEH三段漂白废水进行了毒性研究,其中C段废水的毒性最大,其EC50为17.39%,属于强毒级别;E段、H段废水的EC50分别为163.6%、252.4%,均属于无毒级别.苇浆CEH漂白工艺总毒性排放因子(TEF)为472.021 TU&#8226;m3&#8226;(吨浆)-1,其中C段废水的毒性最大,其TEF为393.88 TU&#8226;m3&#8226;(吨浆)-1,约占总量的83.45%,其次是E段废水,约占10.03%,H段最小,约占6.52%.  相似文献   

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