Removal of wood extractives as pulp (pre-)treatment: a technological review

Abstract

Wood extractives usually do not exceed five percent of dry wood mass but can be a serious issue for pulping as well as for the pulp itself. They cause contamination and damages to process equipment and negatively influence pulp quality. This paper addresses not only the extractives-related problems but also different solutions for these issues. It is an extensive review of different technologies for removing wood extractives, starting with methods prior to pulping. Several wood yard operations like debarking, knot separation, and wood seasoning are known to significantly decreasing the amount of wood extractives. Biological treatment has also been proven as a feasible method for reducing the extractives content before pulping, but quite hard to handle. During pulping, the extractives reduction efficiency depends on the pulping method. Mechanical pulping removes the accessory compounds of wood just slightly, but chemical pulping, on the other hand, removes them to a large extent. Organosolv pulping even allows almost complete removal of wood extractives. The residual extractives content can be significantly reduced by pulp bleaching. Nevertheless, different extraction-based methods have been developed for removing wood extractives before pulping or bleaching. They range from organic-solvent-based extractions to novel processes like supercritical fluid extractions, ionic liquids extractions, microwave technology, and ultrasonic-assisted extraction. Although these methods deliver promising results and allow utilization of wood extractives in most cases, they suffer from many drawbacks towards an economically viable industrial-scale design, concluding that further research has to be done on these topics. Graphical abstract

Moisture‐Thermal Stable, Superhydrophilic Alumina‐Based Ceramics Fabricated by a Selective Laser Sintering 3D Printing Strategy for Solar Steam Generation

“…[ 6b,8a ] During the process of being dried out, its surface temperature can be up to ≈83.2 °C (Figure S14b, Supporting Information) due to the low thermal conductivity of wood, [ 17 ] making the shape of wood small buckle (Figure 3d). This process just like the cooking pretreatment of wood pulp, [ 18 ] which can soften the wood and damage its pore structures (Figure S12d–f, Supporting Information).…”

Production and Downstream Integration of 5-(Chloromethyl)furfural from Lignocellulose

“…Wood extractives are the nonstructural components in wood, and depending on the wood type, they can constitute about 4–13% w/w of the wood . Extractives in wood are defined as a family of organic compounds that can easily be extracted from wood using neutral solvents . They are commonly found in the heartwood inside the trunk, and they protect the tree from environmental stress .…”

Microwave-Assisted Soda Pulping of the Banana Pseudo Stem (Musa Cavendish) for Pulp and Paper Production: Production, Characterization, and Optimization

“…This may result in high maintenance costs and decrease the quality of the final product (Vieira et al, 2021). A high number of extractives can be extracted using pre hydrolyzing before pulping (Lehr et al, 2021).…”