Sulfite Pulp Research Articles

Retene and resin acid concentrations in sediment profiles of a lake recovering from exposure to pulp mill effluents

The stratigraphy of resin acids (pimaric, isopimaric, sandaracopimaric, dehydroabietic and abietic acids) and base neutral compounds (retene, tetrahydroretene, dehydroabietin and fichtelite) in sediments of a lake recovering after the mill closure from exposure to effluents from sulphite pulp mill was studied. The highest concentrations of these compounds were detected 1.5 km downstream from the effluent pipe in sediment depth of 7–11 cm. This sediment layer is approximately 30 yrs old. The highest concentration of resin acids was 1100 and of retene 3300 μg/g d.w. The retene concentration observed is the highest reported in the literature so far. The results imply that high concentrations of retene may be common in sediments of Finnish lakes polluted by pulp mill effluents.

Fibre morphology and soda–sulphite pulping of switchgrass

This paper describes the fibre morphology of switchgrass ( Panicum virgatum L.) and its pulping characteristics using sodium hydroxide and a combination of sodium hydroxide and sodium sulphite as the cooking agents. It was found that the fibre length of switchgrass is similar to that of poplar despite its high population of short fibre elements (<0.2 mm). The switchgrass used in this study had a lignin content comparable to that of poplar, but a particularly high content of extractable materials. The soda pulp from switchgrass showed excellent mechanical properties and showed a great potential as a reinforcement component in newsprint making.

Dielectric spectroscopic results and chemical accessibility of sulfite pulps

The relation between the chemical reactivity of a dissolving pulp and the molecular mobility of cellulose was investigated by an unconventional method for these problems: dielectric relaxation spectroscopy (DRS). Carrefully dried pulps show better reactivity in comparison to a mill dried sample. A specific deformation of the local polymeric backbone dynamics (β-relaxation) was observed in the former samples. The intensity of the dielectric β-relaxation correlates with the acetylation velocity in an excellent manner. A similar correlation was found between the relaxation strength and the water retention capacity of pulps. All experimental results support th explanation (here named δ-relaxation) outside of th real β-peak in the dielectic spectrum are preferably substituted. The relusts of the investigation indicate that dielectric spectroscopy can provid a new, additional alternative tool to charcterize the accessibility and chemical reactivity of cellulose. Comparison of the dielectric loss spectra of machine sulfite pulp (sample C) at the temperature 0° before and after annealing at 170°C.

Dielectric spectroscopic results and chemical accessibility of sulfite pulps

Dielectric spectroscopic results and chemical accessibility of sulfite pulps

Structural Characterisation of the Coloured Organic Matter from an Eucalyptus Bleached Kraft Pulp Mill Effluent

XAD-8 and XAD-4 resins in tandem were used to isolate and fractionate the coloured organic matter from an eucalyptus bleached Kraft pulp mill effluent which is discharged into river Vouga (Portugal) near the lagoon that exists in its terminal part. The composition of the isolated organic matter was investigated by FTIR and CPMAS-13C-NMR and compared to that of humic matter isolated before from the same river at a non-polluted site and a site very contaminated with the effluent of a sulphite pulp mill. The results put into evidence that the organic matter from both kinds of effluent is more aromatic and contains more lignin derived structural units than the humic matter from the unpolluted site. However, the organic matter from the sulphite pulp mill effluent is more soluble due to its content of sulphonic functional groups.

Bleachability of Alkaline Pulps. Part 1. The Importance of β-Aryl Ether Linkages in Lignin

Summary Analytical and structural studies were done on different types of alkaline pulps and their isolated residual lignins. Although having the same degree of delignification after cooking, some pulps were easier to bleach than others. All isolated residual lignins were found to contain β-aryl ether (β-O-4) structures in reasonable amounts when analysed by thioacidolysis (≥10 % of the native lignin value). At decreasing kappa numbers, there was also a corresponding decrease in the amount of β-aryl ether structures in the residual lignin. Moreover, a high β-aryl ether content in the unbleached residual lignin after cooking was found to contribute to a better bleachability of the pulp, especially when hydrogen peroxide stages were involved. At the same degree of delignification, the superior bleachability of alkaline sulfite pulps over kraft pulps was shown to be attributable to a higher content of β-aryl ether linkages in the former type of pulps.

Influence of process variables on the properties of pulp and paper sheets obtained by sulphite pulping of olive tree wood

A central composition design was developed to study the influence of process variables (temperature, pulping time, sulphite concentration, anthraquinone concentration and liquid/solid relation) on the properties of pulps (yield, holocellulose, α-cellulose and lignin contents, and brightness) and the paper sheets (stretch, burst index and tear index) obtained from them, in the sulphite pulping of olive tree wood. Equations that reproduce the properties of pulps prepared by sulphite pulping and of paper sheets obtained from it are reported. The proposed equations fit the experimental yield and the holocellulose and α-cellulose contents of the pulps with errors less than 5%, as well as brightness with errors less than 10%. Also, they reproduce the lignin content of the pulps, and the stretch, burst index and tear index of the paper sheets with errors less than 15%. Obtaining pulps with acceptably high yield, holocellulose and α-cellulose contents, and also a high brightness, in addition to low lignin contents, entails operating at a temperature of 193 °C for 143 min, using a sulphite concentration of 19.85%, an anthraquinone concentration of 0.1% and a liquid/solid relation of 6.24. These are also the most suitable conditions for obtaining paper sheets with a high stretch, burst index and tear index.

Chemiluminescence from the thermal and photo-oxidation of several wood pulps

Thermo- and photo-oxidative degradation of several wood pulps; thermo-mechanical pulp (TMP), bleached sulfite pulp (NBSP), bleached kraft pulp (NBKP), unbleached kraft pulp (NUKP) and filter paper, were examined mainly by chemiluminescence (CL). The CL behavior of the pulps was extremely different from each other and the decreasing order of its intensity was: TMP>NBKP>NBSP>NUKP>Filter paper. In the case of the bleached pulps; NBKP, NBSP and filter paper, the CL intensity increased with photo-irradiation time, but only a small change in its intensity was observed in the unbleached pulps; TMP and NUKP. From the measurement of ultraviolet-visible (UV-V) spectra of the degraded samples, a small change in the CL intensity observed in the unbleached pulps was ascribed to the shielding and/or absorption of the emitted light by the colored materials in the pulps.

Modified Kraft Pulping of Bagasse: Infrared Spectroscopy of Lignin

The infrared spectroscopy of precipitated lignin from waste black liquors of bagasse pulping with kraft sulfite pulping process was investigated. Also the effect of anthraquinon and methanol addition in the soda, kraft and kraft-sulfite pulping liquor on the infrared specra of the precipitated lignin was studied. The presence of methanol in the pulping liquor causes an increase in the degradation as well as increase in the carboxylic group in the precipitated lignin. Also, the phenolic hydroxyl group in case of kraft lignin is higher than soda lignin. Presence of sulfite in the kraft-sulfite pulping liquor produces lignin hydroxyl groups.

Chemical retardation of phosphate diffusion in simulated acid soil amended with lignosulfonate

The availability and movement of inorganic phosphate fertilizer is usually low due to precipitation and adsorption reactions in soil. Lignosulfonate (LS), which is produced from acid sulfite pulping processes, has similar characteristics to soil organic materials. An experiment was designed to study the effects of LS on P movement in a simulated acid soil containing aluminum-saturated cation exchange resin and acid-washed fine sand. The resulting simulated soil had a cation exchange capacity of 22 cmolc kg−1 and either no or 10 g kg−1 gibbsite. Movement of surface-applied monopotassium phosphate was studied in soil columns, either with 20 g kg−1 LS or without LS. Lignosulfonate reduced phosphate fixation and sustained a higher water extractable phosphate concentration near the surface of the columns, but had no effect on downward phosphate movement in the columns with gibbsite. Lignosulfonate reduced the solution concentration of P near the surface and reduced downward phosphate movement in the columns without gibbsite. The resin-sand column with gibbsite closely reflected an acid soil, and this research showed that adding LS would increase fertilizer P availability in a gibbsite-rich acid soil. Adding Ca-LS to Al-rich soil is beneficial for another reason, improving Ca nutrition, which is poor for these soils. Key words: Chemical retardation, phosphate diffusion, lignosulfonate amendment

Oxygen-Weak Base Pulping of Rice Straw with Minimum Silica Removal

As we attempt to preserve forests and to decrease impact on environment, the development of novel technologies for the utilization of rice straw, especially to achieve complete delignification with minimum silica removal during its pulping, seems to be important and significant. It was examined whether or not oxygen-weak base pulping is useful for rice straw to control silica removal in this study. Delignification, silica removal and carbohydrate retention of rice straw during oxygen-sodium sulfite pulping and oxygen-ammonia pulping were compared with those during conventional alkaline pulping and oxygen-sodium hydroxide pulping. By an oxygen-sodium sulfite pulping of rice straw, sufficient delignification could be achieved without significant removal of silica into cooking liquor. The carbohydrate yield of oxygen-sodium sulfite pulping method was quite high (more than 80%) even when 95% of delignification was achieved, which is supported by the high retention of both cellulose and hemicellulose. In contrast to this, carbohydrate yield of oxygen-ammonia pulping was found to be rather low, even though high retention of silica was achieved. Low carbohydrate yield by this pulping was attributed to the significant degradation of both cellulose and hemicellulose.

Comparative study of paper sheets from olive tree wood pulp obtained by soda, sulphite or kraft pulping

Paper sheets from olive tree wood pulp obtained by soda, sulphite or kraft pulping were studied to examine the influence of pulp beating on properties of the paper sheets. Paper sheets from kraft and sulphite pulps exhibited the highest resistance, and sulphite pulp the highest brightness. Soda pulp required more intensive beating than did kraft or sulphite pulps; in fact, the PFI beater had be operated at a 40–50% higher number of beating revolutions to obtain soda pulp with 70–80° SR. The breaking length, stretch, burst index and tear index of paper sheets obtained from kraft pulp, beaten to a Shopper–Riegler index of 70–80° SR were 20–30%, 30–50%, 50–60% and 15–35% higher, respectively, than those of sheets obtained from soda pulp.

Production, partial characterization and use of fungal cellulase-free xylanases in pulp bleaching

Seven fungal strains were screened for their ability to produce cellulase-free xylanases that could be used in pretreatment of sulphite pulp prior to bleaching. The potential xylanase producers were subjected to shake flask fermentations using four different carbon sources: wheat bran, corn cobs, oat spelts xylan and bleach plant effluent. When grown on corn cobs, Aspergillus foetidus (ATCC 14916) produced significant levels of xylanase (547.4 U/ml), accompanied however by 6.6 U/ml of cellulase activity. Two other strains, Aspergillus oryzae (NRRL 1808) and Gliocladium viride (CBS 658.70), produced high yields of cellulase-free xylanase on oat spelts xylan. The crude enzymes of these two isolates were characterized with respect to pH and temperature optima and stability in order to standardize the optimum conditions for their use on pulp. Although the two xylanases differed in their abilities to remove reducing sugars from pulp, their biobleaching abilities, when assessed in hydrogen peroxide delignification of pulp, were very similar: both of them increased brightness by 1.4 points and removed 7% of hemicellulose from pulp.

Degradation of lignosulfonated compounds by Streptomyces viridosporus: effect of the culture medium and the nature of the lignosulfonate molecule

Lignosulfonated compounds are by-products of the sulfite pulping of wood and have a higher level of biological resistance than lignin. Degradation of lignosulfonated compounds by Streptomyces viridosporus strain T7A growing on nutritive or chemically defined culture media was quantified. Two lignosulfonated compounds, differing in their molecular mass distribution and chemical structure, were used: lignosulfonate (1–80 kDa) and vanisperse, a sulfonated oxylignin (1–20 kDa). The use of nutritive culture medium (containing Biosoyase) allowed both the growth of S. viridosporus and the production of lignin peroxidase (LiP) leading to in vitro lignocellulose solubilization, but no lignosulfonate degradation was observed. Twenty per cent of the lignosulfonate underwent a molecular transformation, producing non-biodegradable acid precipitable polymeric lignin (lignosulfonate-APPL). When a defined culture medium (containing glycerol as additional organic carbon source) was used, LiP production was growth-associated. Under these conditions with periodic addition of glycerol, 21% of the lignosulfonate was degraded after 21 d of incubation. An inhibitory effect of lignosulfonate on biomass growth was suspected. When using vanisperse with the defined culture medium, a degradation yield of 35% was obtained after 20 d of incubation. S. viridosporus was unable to degrade a large amount of either lignosulfonated compound though significant modifications of the molecular mass distributions were observed by gel permeation chromatography.

Modification of the carbohydrate composition of sulfite pulp by purified and characterized beta-xylanase and beta-xylosidase of Aureobasidium pullulans.

Both beta-xylanase and beta-xylosidase were purified to homogeneity from a xylose-grown culture of Aureobasidium pullulans. Cellular distribution studies of enzyme activities revealed that beta-xylanase was an extracellular enzyme, during both the exponential and stationary phases, whereas beta-xylosidase was mostly periplasmic associated. The beta-xylanase exhibited very high specificity for xylan extracted from Eucalyptus grandis dissolving pulp, whereas the beta-xylosidase was only active on p-nitrophenyl xyloside and xylobiose. Comparison of kcat/Km ratios showed that the beta-xylanase hydrolyzed xylan from dissolving pulp 1.3, 2.1, and 2. 3 times more efficiently than Eucalyptus hemicellulose B, Eucalyptus hemicellulose A, and larchwood xylan, respectively. The beta-xylosidase exhibited a transxylosylation reaction during the hydrolysis of xylobiose. When applied on acid sulfite pulp, both enzymes released xylose and hydrolyzed xylan to a different extent. Although beta-xylosidase (0.4 U/g pulp) liberated more xylose from pulp than beta-xylanase (4.7 U/g pulp), it was responsible for only 3% of xylan solubilization. Treatment of pulp with beta-xylanase liberated 51.7 microgram of xylose/g and hydrolyzed 10% of xylan. The two enzymes acted additively on pulp and removed 12% of pulp xylan. A synergistic effect in terms of release of xylose from pulp was observed when the enzyme mixture of beta-xylanase and beta-xylosidase was supplemented with beta-mannanase. However, this did not result in further enzymatic degradation of pulp xylan. Both beta-xylanase and beta-xylosidase altered the carbohydrate composition of sulfite pulp by increasing the relative cellulose content at the expense of reduced hemicellulose content of pulp.

イネワラのアルカリ系蒸解における脱シリカ反応に影響する因子

Relationship between the progress of delignification and silica removal from rice straw was studied under various pulping conditions. Alkali pulping and oxygen-alkali pulping were found to remove lignin and silica significantly from pulp, while sulfite and ammonia pulping were found to retain a certain amount of silica in pulp with low lignin content. Delignification with higher carbohydrate yield can be achieved by the multi-stage process of 0.05 M sodium alkali treatment. It was confirmed that there is a strong relationship between silica removal and the pH of cooking liquor. Comparison between oxygen-alkali pulping and conventional alkali pulping at the same degree of delignification shows that oxygen-alkali pulping can keep higher silica content than conventional alkali pulping probably because of lower pH in the former case. Oxygen-alkali pulping can, however, remove more silica under the same pH condition than conventional alkali pulping, which suggests the silica removal is not only dependent upon pH condition. Silica removal up to 30% was observed at any pH with various cooking liquor. However, it depends on alkali concentration and cooking temperature whether further removal of silica proceeds or not.

Farmland treatment and utilization of straw pulp mill effluents

Straw pulp production accounts for 74% of the total raw pulp production in China. The pulping waste, containing high contents of silicate and high pH, is difficult to treat. Instead of the conventional alkaline process, ammonia sulfite pulping discharges neutral effluent with nitrogen, phosphorus, potassium, sulfur and organic matter which are potential fertilizers and water resources for agriculture. The effect of effluent from ammonia sulfite pulping on rice growth and yield, was studied in Baigezhuang farm, Hebei province. Diluted rice straw digester waste or composite waste were irrigated on a paddy field. In plot tests, rice output increased by 16.2–25.3% with 0.7–6% pulp digester waste and by 22.9–37.9% with 2.7–5.4% composite waste. In field tests, rice output increased by 8.6–15.9% with 2.7–4.1% composite waste. Due to clean water dilution and paddy purification, the removal efficiency of biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended solid (SS), sulfide and phenol can reach over 97%. Rice quality also tested had higher protein content than the control. The study suggests that the effluents from ammonia sulfite pulping can be widely used in the farming industry. The ammonia sulfite process is a good approach to overcome pulp pollution in rural areas.

The potential of biosulfite pulping in dissolving pulp production

Biological alternatives which could aid the hemicellulose and lignin removal from dissolving-grade pulps imply the use of microorganisms to pretreat wood chips prior to pulping (biopulping) and/or use of enzymes to pretreat pulp prior to bleaching (biobleaching). Five strains of the white-rot fungus Ceriporiopsis subvermispora (SS-1; SS-3; SS-4; SS-5; SS-10) have been screened for their abilities to facilitate the acid sulfite pulping and bleaching processes of Eucalyptus grandis wood to dissolving pulp. Pulp properties such as brightness, kappa number, α-cellulose, alkali solubilities S 10 (degraded cellulose content) and S 18 (hemicellulose content), and yield have been measured and compared. After sulfite pulping, kappa numbers decreased by up to 10% and did not correlate with the brightness values. Yieldwise, only C. subvermispora SS-3 strain produced pulp comparable to the control of 47.4%. Biosulfite pulp was fully bleached in three bleaching combinations: OD 1E oD 2H, OD 1E oD 2P, and XOD 1E oD 2P. In most instances, a brightness gain over the controls (up to three brightness points) was observed. Interestingly, xylanase pretreatment of pulp when used in conjunction with biopulping did not always improve brightness and at the same time reduced viscosity of dissolving pulp. Although the yield of the SS-5 pretreated pulp was lower than the control after biosulfite pulping (by 0.5%), it was higher after bleaching in all three combinations (by up to 1%). Results suggested that pretreatment of wood with selected strains of white-rot fungi may be used as a means of improving the selectivity of both pulping and bleaching, thereby increasing either the final pulp yield or brightness.

Lung cancer mortality in a cohort of older pulp and paper workers.

The occurrence of deaths due to lung cancer was studied among 883 white male workers from a pulp and paper company in northern New Hampshire. All subjects had participated in a longitudinal study of respiratory morbidity, and data from interviews were used to construct lifetime cigarette smoking and occupational histories. Most of the subjects had entered follow-up in the 1960s and, at that time, their mean age was 51 years and they had worked for the pulp and paper company a mean of 25 years. By the end of follow-up in 1992, the 512 deceased subjects included 35 whose underlying cause of death had been lung cancer. With an internal comparison using the Cox proportional-hazards model, the hazard ratio for sulfite pulp mill work was 2.5 (95% CI 1.3-4.9), while controlling for the effects of age, cigarette smoking, and work in other parts of the pulping operation. In addition, the hazard ratio for the combination of >35 pack-years of smoking and >10 years sulfite mill work was greater than the product of the hazard ratios for each factor alone. While these findings are consistent with past asbestos exposure in the sulfite pulp mill environment, the absence of mesothelioma cases is inconsistent with this type of exposure.

A mathematical model for neutral sulfite pulping of various broadleaved wood species

A mathematical model for neutral sulfite pulping of various broadleaved wood species