Mass Transport in Wood Disintegration: Implications for the Pulp and Paper Industry
Doctoral thesis, 2023
Efficient delignification and fractionation processes are essential in the pulp and paper industry. Mass transport events in wood fractionation are of great importance, specifically in two main stages, namely, the mass transport of chemicals into wood and the mass transport of degraded lignin molecules out of cellulose confinements. It has been previously suggested that the mass transport of lignin molecules through fibers is the rate-determining step in kraft pulping. This thesis first investigates the effects of pore sizes, the alkalinity of the solution, the molecular weight of lignin, and specific ion effects on the mass transport of lignin through model cellulose membranes using diffusion cells. Furthermore, the adsorption of lignin on cellulose substrates in the presence of salts chosen from the Hofmeister series was studied using a quartz crystal microbalance with dissipation monitoring (QCM-D). It was observed that mass transport rates through the cellulose membrane were enhanced by an increase in pore size, alkalinity of the solution, and a decrease in lignin molecular weight. Higher alkalinity of the solution decreases the association between the lignin molecules, which increases the mass transport. QCM-D measurements showed that the adsorption of lignin on cellulose was increased in the presence of chaotropic anions. This behavior can be rationalized by the system's entropy gain, facilitated by the release of adsorbed ions and water molecules from the cellulose surface upon lignin adsorption. The thesis also explores the rate-determining step in the ionoSolv fractionation process. To achieve a more homogeneous fractionation, the effects of temperature, water content, and vacuum on the impregnation of wood by ionic liquids (ILs) were further studied. This thesis not only highlights the complexity of mass transport events in wood fractionation but, by comparing the concentration of lignin released from dry wood, IL-impregnated wood, and previously reacted wood samples over time, has also revealed that the mass transport of the IL into wood is the rate-determining step.
mass transport
specific ion effects
impregnation
Kraft pulping
ionoSolv
ionic liquids
delignification
10:an, Department of Chemistry and Chemical Engineering, Chalmers University of Technology
Opponent: Prof. Gerard Mortha, Grenoble Institute of Technology, Pagora (international school of paper, printed communication and biomaterials), France
Author
Roujin Ghaffari
Chalmers, Chemistry and Chemical Engineering, Applied Chemistry
Effect of alkalinity on the diffusion of solvent-fractionated lignin through cellulose membranes
Cellulose,;Vol. In Press(2023)
Journal article
Ghaffari, R., Arumughan, V., Larsson, A., Specific ion effects on lignin adsorption and transport through cellulose confinements
Ghaffari, R., Brandt-Talbot, A., Larsson, A. Mass transport of ionic liquids into wood
In the current era with growing environmental concerns, finding renewable and green alternatives for the fossil-based products is central. One of the promising renewable and abundant resources for production of low environmental impact products is lignocellulosic biomass. However, there are two main challenges we need to address in using lignocellulosic biomass effectively.
First, is designing efficient and cost-effective methods to break down the biomass into its components, like polysaccharides and lignin. Second challenge is to separate and recover all the valuable components from the biomass.
For over a century, the kraft pulping process has been a go-to method for breaking down lignocellulose. It involves cooking wood chips in an alkaline mixture to dissolve lignin and free up fibers. But despite its long history, there's still a lot unknown about how this process works at the molecular level.
Furthermore, new techniques like the ionoSolv pretreatment process, which uses special liquids to separate cellulose and lignin are being developed for wood pretreatment. This method shows great promise but has its own challenges, such as effectively getting the ionic liquids into the porous structure of wood.
This thesis is focused on studying the challenges associated with mass transport events in wood disintegration at two levels: one when chemicals are transported into wood and second when degradation products need to diffuse out of the wood structure.
First, is designing efficient and cost-effective methods to break down the biomass into its components, like polysaccharides and lignin. Second challenge is to separate and recover all the valuable components from the biomass.
For over a century, the kraft pulping process has been a go-to method for breaking down lignocellulose. It involves cooking wood chips in an alkaline mixture to dissolve lignin and free up fibers. But despite its long history, there's still a lot unknown about how this process works at the molecular level.
Furthermore, new techniques like the ionoSolv pretreatment process, which uses special liquids to separate cellulose and lignin are being developed for wood pretreatment. This method shows great promise but has its own challenges, such as effectively getting the ionic liquids into the porous structure of wood.
This thesis is focused on studying the challenges associated with mass transport events in wood disintegration at two levels: one when chemicals are transported into wood and second when degradation products need to diffuse out of the wood structure.
Driving Forces
Sustainable development
Subject Categories
Paper, Pulp and Fiber Technology
Roots
Basic sciences
Infrastructure
Chalmers Materials Analysis Laboratory
Learning and teaching
Pedagogical work
Areas of Advance
Materials Science
ISBN
978-91-7905-929-3
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5395
Publisher
Chalmers
10:an, Department of Chemistry and Chemical Engineering, Chalmers University of Technology
Opponent: Prof. Gerard Mortha, Grenoble Institute of Technology, Pagora (international school of paper, printed communication and biomaterials), France