Delignification of Low-Energy Mechanical Pulp (Asplund Fibers) in a Deep Eutectic Solvent System of Choline Chloride and Lactic Acid

Abstract

Deep eutectic solvents (DESs) are considered as a green and environmentally benign solvent class for various applications, including delignification of biomass. One of the major challenges in the delignification of biomass by DES is attributed to the limitations in mass transfer. By subjecting wood chips to a low-energy mechanical refining, i.e., the Asplund process, the accessible surface area increases greatly, which in turn improves the mass transfer and increases the reaction rate. In this research, the DES delignification of Asplund fibers made of Norway spruce was studied as a strategy to produce papermaking fibers under mild conditions. A DES consisting of lactic acid and choline chloride was used due to its proven performance in delignification. Various operational conditions, such as temperature, time, DES-to-wood ratio, and the type of stirring were studied. A novel parameter, Q, allowed to evaluate the impact of the operational conditions on the quality of the pulp in terms of delignification degree and fiber length. The results showed that cooking temperature had the most significant effect on the pulp quality. Additionally, it was observed that cooking times between 30 and 45 min result in a pulp yield of about 50%, while fibers have a lignin content of about 14% and a fiber length of 0.6 mm. These results demonstrate that it is possible to obtain fibers of relatively good quality from DES delignification using Asplund fibers as the starting material.

Ultra-Thin Wood-Based Acoustic Diaphragms Fabricated via an Environmentally Friendly Strategy

“…As for the ChCl–OA DES-delignified wood, ChCl–OA DES was made by mixing choline chloride and oxalic acid (1:1 molar ratio) at 80 °C for 1 h to create a transparent and homogeneous solution. After that, the wood sample was dipped into ChCl–OA DES for 6 h at 80 °C, and then, the sample was cleaned using ethanol to eliminate the extra chemicals . All delignified wood samples remained in ethanol before use.…”

“…After that, the wood sample was dipped into ChCl−OA DES for 6 h at 80 °C, and then, the sample was cleaned using ethanol to eliminate the extra chemicals. 13 All delignified wood samples remained in ethanol before use. The samples were lyophilized at −58 °C for 36 h by a freeze-dryer (BK-FD10S, Shandong) to obtain delignified wood in a dry state.…”

Cationized dialdehyde cellulose synthesized with deep eutectic-like solvents: Effects on sheet dewatering and mechanical properties when used as wet-end additive

“…In the case of cationic cellulose production, they can be used as reagents and media for adding functional cationic groups (Sirviö 2018;Jaekel et al 2021). DES can be used for delignification of wood fibers as an alternative to conventional pulping (Pérez et al 2021).…”

Ultrafiltration-based diafiltration for post-delignification fractionation of lignin from a deep eutectic solvent comprised of lactic acid and choline chloride

“…Nowadays, kraft pulping plants are the state-of-the-art in the pulp and paper industry, and commonly accepted as being integrated and energyefficient plants. In the kraft process, cellulose is isolated from lignocellulosic biomass for use in the pulp and paper industry, which is the primary use of this biomass [4]. The waste stream from this process is called black liquor, which contains highly sulfurized lignin [5,6].…”