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Abstract There is great concern about decreasing the amounts of polychlorinated dibenzo- p -dioxins and dibenzofurans (PCDD/Fs) that are formed and emitted during the chlorine bleaching of pulp. The formation of PCDD/Fs during non-woodpulp chlorine bleaching was investigated in the study described here. Wheat straw was separated into three components, cellulose, hemicellulose, and lignin. Chlorination experiments were performed, and lignin and hemicellulose contributed more than cellulose to PCDD/F formation when the pulp was bleached using chlorine. The chemical components of lignin were identified by gas chromatography mass spectrometry, and nine possible PCDD/F precursors were quantified by gas chromatography tandem mass spectrometry. Spiked chlorination experiments were performed to investigate the effects of these compounds on PCDD/F formation. 4-Ethyl-2-methoxyphenol had the strongest effect on PCDD/F formation, followed by p -chlorophenol, and guaiacol. All the test compounds promoted polychlorinated dibenzofuran formation but had limited effects on polychlorinated dibenzo- p -dioxin formation. The results allowed mechanisms for the formation of PCDD/Fs from phenol, chlorophenol, catechol, and guaiacol to be proposed. Highlights • The formation of PCDD/Fs during non-wood pulp chlorine bleaching was investigated. • Lignin and hemicellulose contributed more than cellulose to PCDD/F formation. • Spiked chlorination experiments were performed. • Formation mechanisms of PCDD/Fs were proposed of possible precursor compounds. [ABSTRACT FROM AUTHOR]

In this work, treatments with a xylanase (X) and carbohydrases mixture (Cx) were applied on a TCF bleached sisal pulp in order to obtain high-cellulose content fibers applicable on a wide range of uses. A limit of ≈12% w/w final content in hemicelluloses was found regardless of the enzymatic treatment assessed. An extraction with 4% and 9% w/v NaOH was performed for further hemicelluloses removal. We found that NaOH dose could be strongly reduced if combined with Cx or Cx + X treatments. Also, if necessary, a stronger reduction could be obtained with 9% w/v NaOH, which was found to be boosted in a 14% if performed after a treatment with Cx. An end-product with a low content in xylans (≈2.9% w/w) and in HexA (5.8 μmol/odp) was obtained. Pulp Fock solubility was also increased (≈30%) by enzymatic treatments. HPLC analysis of effluents provided useful information of enzymatic catalytic mechanisms. [ABSTRACT FROM AUTHOR]

Abstract: The main papermaking characteristics of rapeseed straw (Brassica napus L.) as an agricultural residue were investigated. The average fiber length, width, lumen, and cell wall thickness were found to be 1.03 mm, 28.00 μm, 19.1 μm, and 4.91 μm, respectively. Cellulose, lignin, holocellulose, acetone-soluble extractives and ash content were determined as 41.66, 16.00, 78.9, 1.63, and 3.46%, respectively. Soda and soda-anthraquinone (AQ) pulping were conducted using 16, 18, and 20% sodium hydroxide and 0.2% AQ in soda-AQ pulping, based on oven-dried straw, cooking temperatures of 175 and 185 °C, cooking times of 40 and 70 min, and liquor-to-straw ratio of 8:1. The results showed that lower Kappa number, higher screened pulp yield, and improved bonding strength properties were obtained in the soda-AQ pulping at even 2% less alkali consumption as compared to the soda process. In general, the pulp strength characteristics of rapeseed straw were comparable to those of hardwoods and short-fiber non-wood plants. [Copyright &y& Elsevier]

This paper deals with the determination of chemical composition and the study of the pulping potentialities of banana pseudo-stems growing in Madeira Island (Portugal). First, the raw material was both studied as a whole (type I) and as the outer bark part (type II), which is richer in cellulose fibres. Before starting the cooking of banana wastes, the main components of the two types of material were quantified, and showed that the polysaccharide content was high enough (about 60–70%) to justify the pulping investigations. Moreover, the lignin content was very low (approximately 12%). The only discouraging finding was the relative high amounts of ashes and extractives. The pulping of these residues was carried out using soda, kraft and soda-anthraquinone (AQ) cooking processes and the optimal pulping conditions were established. Thus, pulps with a yield of about 37–38% with a Kappa number (Kappa no.) about 30–32 were obtained when cooking in the presence of 0.25–0.35% of anthraquinone at 120 °C for a short cooking time, i.e. 30 min. The longer times and higher temperatures of cooking as well as the use of kraft pulping conditions did not give rise to better performances, comparing to those mentioned above. These severe conditions were detrimental to the hemicellulose preservation. [Copyright &y& Elsevier]

• The alkaline – HC miscanthus fibers lignin content was decreased by 41.54% • Pulp fiber shape characteristics were negatively influenced due to cavitation force. • Results could verify the efficacy of alkaline - HC pretreatment as a delignification method. • The alkaline – HC process displayed similar results with other conventional methods. • Miscanthus grass fibers could potentially substitute hardwood fibers in pulp blends. One way of satisfying increased market demand and simultaneously achieving a reduced environmental load in the industrial paper production is the use of fibrous agricultural residues. The aims of this study were i) to investigate the effect of alkaline – hydrodynamic cavitation (HC) pre-treatments on the delignification of Miscanthus × giganteus stalks (MGS) and ii) establishing the suitability of MGS as feedstock and their exploitation in pulp and paper manufacturing. It was demonstrated that the proposed treatment is an efficient delignification method for the non-wood fiber sources, such as miscanthus. A significant outcome of this work was the observation that HC treatment preserved the fibres lengths and surface quality of raw MGS, but at the same time increased the amount of kinked and curled fibers present in cavitated miscanthus fibers. The average miscanthus fiber length was found to be relatively short at 0.45 (±0.28) mm, while the slenderness ratio, the flexibility coefficient and Runkel ratio values were calculated to be 28.13, 38.16 and 1.62, respectively. The estimated physical properties of MGS pulp hand-sheets were 24.88 (±3.09) N m g−1 as the tensile index, 0.92 (±0.06) kPa m2 g−1 as the burst index and 4.0 (±0.37) mN m2 g−1 as the tear index. Overall the current work demonstrated effective use of hydrodynamic cavitation for improving the processing in pulp and paper manufacturing. [ABSTRACT FROM AUTHOR]