Technical and environmental improvement of the bleaching sequence of dissolving pulp for fibre production

Abstract

Reactivity of dissolving pulp is one of the main parameters to determine its availability to be transformed into viscose. It is related to the use of carbon disulphide (CS2). An industrial sequential totally chlorine free bleaching process is used as case study. It is carried out in two stages: 1) Alkaline extraction (EOP) and 2) peroxide bleaching (PO). In order to assess how to decrease the use of carbon disulphide, several experiments were performed at laboratory scale for the two stages mentioned before by modifying the operating conditions: NaOH and H2O2 dosages, time and temperature. Reactivity using a modified Fock's method and pentosan content was analysed along with quality pulp parameters: α-cellulose, viscosity and lignin content (kappa number). Results showed that reactivity increases through the bleaching process and varies with the chemical dosage in both stages. Pulp obtained at the best conditions had the following characteristics: reactivity, 95.3 %; α-cellulose 91.17 %; intrinsic viscosity, 448 mL/g; kappa number, 1.81 and pentosan content 2.86 %, and as a result, CS2 usage was reduced by 11.88 %. At the best conditions obtained in this work, NaOH dosage in PO stage was reduced to zero and temperature was slightly lower, when compared with industrial operating conditions.

Cellulose through the Lens of Microfluidics: A Review

“…Only a few effective solvent systems capable of dissolving cellulose have been discovered thus far. As a result, researchers discovered functionalization pro-cesses such as xanthation [184], esterification [185], and etherification [186] on the cellulose hydroxyl group as a method of disrupting hydrogen bonds and breaking cellulose's tenacity to dissolve. However, non-derivatizing solvents such as ionic liquid [187] can also dissolve cellulose without requiring chemical changes, which is advantageous in many instances [188].…”

Facile stearoyl chloride grafted cotton filter fabric and its application in oil-water separation

“…In fact, the -OH on glucose monomer is active to be reacted after special treatment, but they are always tied with each other due to hydrogen bond interaction in macromolecule . Relative researches has pointed out that CS 2 can dissolve cellulose and make it decrystalization [Arce et al 2020;. Thus, in order to gure out this problem, we launched CS 2 /NaOH pretreatment to activate -OH on the cotton lter fabric before ARGET-ATRP process and successfully improved the hydrophobic durability that the droplet can be held for 150 min [Luo et al 2020].…”

Use of green solvents as pre-treatment of dissolving pulp to decrease CS2 consumption from viscose production

“…CS2 consumption was calculated using Fock reactivity, α-cellulose content and the stoichiometric value required for the xanthation phase which is 23.5 % (expressed in g CS2 per 100 g of cellulose) (Arce et al, 2020;Gondhalekar et al, 2019a). Considering Fock's reactivity as a reaction yield of xanthation, and the α-cellulose content of the pulp, the theoretical quantity of fibres (TF) is obtained using equation 2.…”

“…Carbon disulphide is a critical compound in the manufacture of viscose fibre and environmental wise, one of the most concerning. CS2 consumption was calculated, as stated by Arce et al (2020). This calculation considers the α-cellulose content and Fock's reactivity, to measure the theoretical quantity of fibres, and the stoichiometric quantity of CS2, used in the xanthation phase to calculate the quantity used of this compound, described by Gondhalekar et al (2019b).…”

“…Cellulose reactivity is defined as the ability of chemicals to dissolve cellulose, and it has a direct relationship with CS2 consumption (the higher the reactivity, the lower the CS2 needed). Such parameter can be determined by several methods such as Iodine sorption, NMR spectroscopy, viscose filterability and Fock's test (Arce et al 2020).…”