Z. Yuan, Y. Wen, N. S. Kapu, R. Beatson and D. Mark Martinez, A biorefinery scheme to fractionate bamboo into high-grade dissolving pulp and ethanol, Biotechnol. Biofuels, 2017, 10(1), 1–16, DOI: 10.1186/s13068-017-0723-2. Dissolving pulp is a starting material for producing viscose and lyocell fibers or cellulose derivatives such as cellulose esters and ethers. It is high-purity cellulose pulp (90–99%), with low contents of hemicellulose (<4%) and lignin (<0.05%) and a small amount of inorganic compounds. Besides, it has unique properties, such as high brightness, uniform molecular weight distribution, and high cellulose reactivity. 5–7 The quality of dissolving pulp mainly depends on the raw material used and the processing technique. 8 Dissolving-grade pulp is commercially produced from 85% hardwood or softwood and 10% cotton linters. 9 Due to increased demand, much research has been devoted to producing dissolving-grade pulp from non-wood materials such as bamboo, straw and bagasse. 9–12 Fig. 4 ISO brightness of pulps before and after oxygen (O) bleaching (A) after OQP 1 and OQP 2 (B), after OQP 2P 2 and OQP 2P 3 (C) and after OQP 2D (D) (temperature of O-stage in the sequences are indicated by for 90 °C and for 100 °C).

For PH soda pulps after O-bleaching followed by the mild P 2 stage, a second peroxide bleaching stage P 2 (2% H 2O 2, 1% NaOH) and P 3 (3% H 2O 2, 1.5% NaOH) was performed ( Fig. 3C and 4C). The second P-stage gives an additional brightness increment, reaching 83% ISO for pulp with high PH severity and high peroxide charge in P 3. This holds for both samples from O-stage at 90 °C and 100 °C. However, the viscosity of these samples has been reduced to 400 ml g −1 (O: 90 °C) and 364 ml g −1 (O: 100 °C). Accordingly, samples are at the lower limit of the targeted viscosity range. Learn the procedures for closing a business including what forms to file and how to handle additional revenue received or expenses you may incur. D. Lorenz, N. Erasmy, Y. Akil and B. Saake, A new method for the quantification of monosaccharides, uronic acids and oligosaccharides in partially hydrolyzed xylans by HPAEC-UV/VIS, Carbohydr. Polym., 2016, 140, 181–187, DOI: 10.1016/j.carbpol.2015.12.027.

Furan composition was analyzed directly from the extracted fraction by reverse-phase high-performance liquid chromatography (Jasco, Tokyo, Japan) according to Krafft et al. 34 The carbohydrate composition and acid-soluble lignin in the extract fractions were analyzed after freeze drying and acid hydrolysis of lyophilisate. All hydrolysis was done in triplicate. X. Luo, J. Liu, H. Wang, L. Huang and L. Chen, Comparison of hot-water extraction and steam treatment for production of high purity-grade dissolving pulp from green bamboo, Cellulose, 2014, 21(3), 1445–1457, DOI: 10.1007/s10570-014-0234-2. The yield was calculated based on the oven dry weight of the resulting pulp and reported as the percentage of the initial weight of raw material. The carbohydrate and lignin content of soda pulp was determined by acid hydrolysis and AEC, as described in the section below. 2.4. Characterization of the PH fiber and PH soda pulp The extractive content of the raw fiber bundle was analyzed using Accelerated Solvent Extraction ASE 350 (Thermo scientific T. M. Dionex TM, Waltham, Ma, USA) using petrol ether, acetone water (9 : 1), and water consecutively.

Massive tonnes of fibrous residues are produced during the harvesting of the Enset plant for food preparation. The fibers are characterized by high cellulose and hemicellulose content and low lignin and extractive content. These make the fiber a good candidate for its concurrent valorization aimed at dissolving grade pulp and biogas. Prehydrolysis soda pulping was performed using steam pretreatment as a prehydrolysis step at a severity ranging from 2.95 to 4.13. The steamed fiber (PH fiber) was subjected to subsequent soda pulping under mild (160 °C and 16% alkali concentration) and severe (180 °C and 24% alkali concentration) pulping conditions. At higher steaming severity, a pulp with a xylose content of <4% and glucose content of 96% was obtained. A simple bleaching stage was envisaged to develop oxygen-peroxide (OQP 1), oxygen-double peroxide (OQP 2P 2, and OQP 2P 3) and oxygen-peroxide-chlorine dioxide (OQP 2D) sequences. Brightnesses up to ∼85% ISO could be reached for all sequences with CUEN viscosities of ∼350–500 ml g −1. Higher viscosities with higher brightness were achieved mainly by OQP 2D sequence. However, even with OQP 1 and OQP 2P 3 sequences the pulps met the requirements for lyocell production. An intense steam treatment reduces the biochemical methane potential (BMP) of prehydrolysis liquid (PHL) from 462 ml g −1 vs to 315 ml g −1 vs. The reduction might be due to the inhibition effect of furan concentration increase in the corresponding PHL from 2 ppm to 24 ppm. However, due to the higher yield and carbohydrate concentration of the prehydrolysis liquid, the biogas production volumes per initial raw material were still higher at higher steaming severity. The viscosity of dissolving pulp is one essential parameter that reflects the average degree of polymerization. It indicates the degradation of cellulose molecular weight during steaming and soda pulping. 14 The viscosity of PH soda and soda pulps was determined to evaluate the effect of process severity on cellulose degradation. M. Chem, K. Tanifuji, S. P. Utami, A. S. Putra, H. Ohi and A. Nakagawa-izumi, Development of dissolving pulp from Phyllostachys pubescens stem by prehydrolysis soda cooking with 2-methylanthraquinone, Ind. Crops Prod., 2022, 178, 114570, DOI: 10.1016/j.indcrop.2022.114570. Peroxide bleaching stage. The peroxide bleaching was done after removing transition metal by the complexing treatment (Q-stage). The Q-stage was performed using 0.3% diethylenetriamine penta acetic acid (DTPA) and 1 mol l −1 H 2SO 4 at 65 °C for 60 min to remove transition metals. 35 The metal content in the pulp before and after Q-stage was analyzed by ICP-OES (Optima 3000, PerkinElmer) after hydrolysis with nitric acid in a microwave oven, according to Janzon et al. 36 The pulp brightness decreased with steaming intensity and increased with pulping intensity. It decreased from 48% to 40% brightness and from 58% to 50% brightness for mild and severe pulping, respectively ( Fig. 2B). The condensation reaction of lignin at high temperatures might explain the brightness drops due to streaming severity. Lourenço et al. also report this phenomenon in the steam explosion pretreatment of cardoon. 5,8,15 An increment in alkali dosage results in a decrease in kappa number, viscosity and hemicellulose content but an increase in brightness and cellulose content, as reported by Salaghi et al. 39 An appropriate bleaching sequence is still necessary to improve the brightness and lower the kappa number in the resulting pulp.

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Moreover, extensive research on innovative techniques for dissolving grade pulp production directly from lignocellulose biomass or paper-grade pulp has also been investigated in response to environmental and cost considerations. But, the typical processes for commercial uses of wood are still the prehydrolysis kraft (PHK) and acid sulfite (AS) processes. 13,14 Soda pulping is solely used for processing monocotyledons and especially cotton linter. The AS process is better suited than the regular kraft process due to the spontaneous cleavage of glycosidic bonds in the hemicellulose chain under the acidic condition. 13 An acidic prehydrolysis is added to the kraft process to achieve a comparable result by removing the hemicelluloses before the alkaline cooking process. 9 When one substance dissolves into another, a solution is formed. A solution is a homogenous mixture consisting of a solute dissolved into a solvent. The solute is the substance that is being dissolved, while the solvent is the dissolving medium. Solutions can be formed with many different types and forms of solutes and solvents. In this chapter, we will focus on solution where the solvent is water. An aqueous solution is water that contains one or more dissolved substance. The dissolved substances in an aqueous solution may be solids, gases, or other liquids.

begin{align} &\ce{NaCl} \left( s \right) \rightarrow \ce{Na R. Janzon, B. Saake and J. Puls, Upgrading of paper-grade pulps to dissolving pulps by nitren extraction: Properties of nitren extracted xylans in comparison to NaOH and KOH extracted xylans, Cellulose, 2008, 15(1), 161–175, DOI: 10.1007/s10570-007-9154-8. N. Seid, P. Griesheimer and A. Neumann, Investigating the Processing Potential of Ethiopian Agricultural Residue Enset/Ensete ventricosum for Biobutanol Production, Bioengineering, 2022, 9(4), 1–14, DOI: 10.3390/bioengineering9040133. C. Heitner; D. Dimmel and J. Schmidt, Lignin and Lignans: Advances in Chemistry, Taylor and Francis, 2016 Search PubMed. On the other hand, Harsono et al. reported that pre-hydrolyzed biomass could be delignified with fewer chemicals and shorter time than the non-prehydrolyzed material because the treatment disrupts the lignocellulose matrix and increases the accessibility of lignin during the subsequent pulping and bleaching. 8,19 The mechanism of steam PH is similar to weak acid hydrolysis, which degrades polysaccharides to monosaccharides. 20 Acetic acids are cleaved off from hemicellulose, assisting the further breakdown of the cellulose–hemicellulose–lignin matrics by creating an acidic medium. 20,21 This theory is anticipated by Garrote et al. during the autohydrolysis of wood. The prehydrolysis step does not cause delignification and complete dissolution of hemicellulose. 22,23 The alkaline pulping step is necessary for delignification and further hemicellulose removal. Sulfur-free soda pulping in the subsequent delignification stage is preferable and suitable for non-wood material by considering the environmental concerns. 19 Both prehydrolysis (PH) and pulping are essential to achieve dissolving pulp with the required purity. 6,14It was not possible to obtain a high purity cellulose pulp during soda pulping solely or from low-severity PH fiber, as it is also reported by Jahan et al. 7 The xylose content of soda pulp without prehydrolysis was 13.2% and 9.5% for mild and severe soda pulping, respectively. Xylose content dropped only slightly after low severity steaming (2.95) and subsequent soda pulping, which were 12.7% and 9.1%. However, the values decreased continuously with steaming severity for both pulping conditions. At higher steaming severity, the difference in xylose content between mild and intense soda pulping conditions becomes smaller and smaller ( Fig. 2C). At the severity of 4.13, the xylose content of PH soda pulps are 3.5% and 3%. The corresponding cellulose content of pulp reached 96% and 96.5% for both mild and severe pulping conditions, as shown in Fig. 2C. The pulp yield was 44% and 40% at this severity level based on the starting material, and the kappa number was 16 and 4, respectively. The same phenomenon is also reported by Jahan et al. that increasing prehydrolysis temperature improved the cellulose content in the resulting pulp. 7

Slowly but surely, it's going in. So remember, acetone's the stuff that you've actually got in nail varnish remover. A multi-stage bleaching step is usually added to achieve the desired goal. 9 The most environmentally friendly method of bleaching pulp is the TCF method, where no chlorine is used. This method has been proven to reduce emissions while offering excellent bleaching properties. TCF bleaching is often performed by using oxygen delignification before the further bleaching steps, where hydrogen peroxide or ozone bleaching is used. An additional extraction of hemicelluloses might be required after the cooking process in the form of cold caustic extraction. 30 Water in the liquid or vapor phase is a low-cost and effective medium to pre-hydrolyze lignocellulosic materials. 15,16 The process provides several potential advantages, including no requirement for catalysts due to its simplicity and a significant decrease in chemical and material construction costs compared to other pretreatment techniques. 17 In steam treatment, the biomass is treated with high-pressure saturated steam at high temperatures for a certain period. During the treatment, hemicellulose is partially degraded by autohydrolysis, whereas the lignin structure is altered. 5 The more severe treatment causes lignin condensation and a viscosity drop after the subsequent alkaline pulping process. 18 R. Janzon, F. Schütt, S. Oldenburg, E. Fischer, I. Körner and B. Saake, Steam pretreatment of spruce forest residues: Optimal conditions for biogas production and enzymatic hydrolysis, Carbohydr. Polym., 2014, 100, 202–210, DOI: 10.1016/j.carbpol.2013.04.093.

Fig. 2 PH soda pulp yield based on initial raw material (A), kappa no and ISO brightness of PH soda pulp. (B) Carbohydrate composition of PH soda pulp. (C) Viscosity of PH soda pulp. (D) mild soda pulping (160 °C and 16% NaOH concentration). Severe soda pulping (180 °C and 24% NaOH concentration). Chlorine dioxide was also used as the last bleaching stage for (OQP 2D) bleaching sequence. The pulp consistency of 7% and chlorine dioxide concentration of 0.4% was used for the chlorine dioxide stage. By heating the water to boiling point, we have decreased the solubility of the dissolved gases. They come out of the solution as bubbles and the remaining water has less gases dissolved, so is less cloudy.