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Highlights • 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.

In this work, treatments with a xylanase (X) and carbohydrases mixture (Cx) were 19 applied on a TCF bleached sisal pulp in order to obtain high-cellulose content fibers 20 applicable on a wide range of uses. A limit of ˜12% w/w final content in hemicelluloses 21 was found regardless of the enzymatic treatment assessed. An extraction with 4% and 22 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