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From bio-based residues to nanofibers using mechanical fibrillation for functional biomaterials
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.ORCID iD: 0000-0002-6247-5963
2019 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Från biobaserade restprodukter till nanofibrer genom mekanisk fibrillering för funktionella material (Swedish)
Abstract [en]

Bio-based resource utilization in different forms has been driven by societal, industrial and academic research interests towards the development of “green”, sustainable materials from renewable sources. Within this context, exploiting biomass from different industrial residues is further advantageous from an environmental and economic point of view, leading to minimization of residues by means of waste treatment and to the development of high-addedvalue- products. Breaking down the cell wall structure to its smallest structural components is one means of turning bio-based residues into high-value products, leaving us with nanofibers. The aim of this work has been to understand how these nanofibers can be liberated from various cellulosic sources using mechanical fibrillation and how they can be assembled into functional hydrogels.

The production of bio-based nanofibers as a sustainable bio-based material is in the early stages of commercialization and considerable research has been devoted to explore different methods of reaching nanoscale. However, the extraction process by chemical and/or mechanical means is still associated with a relatively high energy demand and/or cost. These are key obstacles for use of the material in a wide range of applications. Another challenge is that methods to characterize nanofiber dimensions are still being developed, with few options available as online measurements for assessing the degree of fibrillation. Allowing for assessment during the fibrillation process would enable not only optimization towards a more energy efficient fibrillation, but also matching of the nanofiber quality to its intended function, since different applications will require widely different nanofiber qualities. Energy-efficient fibrillation and scalability from industrial residues were explored using upscalable ultrafine grinding processes.

Nanofibers from various industrial bio-residues and wood were prepared and characterized, including the development of a method for evaluation of the fibrillation process online via viscosity measurements as an indication of the degree of fibrillation down to nanoscale. Furthermore, the correlation of viscosity to that of the strength of the nanopapers (dried fiber networks) was evaluated for the different raw materials.

Switchable ionic liquids (SIL) were tested as a green pretreatment for delignification, without bleaching of wood prior to fibrillation, with the aim to preserve the low environmental impact that the raw material source offers.

In order to employ the hydrophilic nature and strong network formation ability of the fibrillated nanofibers, they were utilized in the preparation of functional biomaterials in the form of hydrogels. Firstly, brewer’s spent grain nanofibers were used to promote and reinforce hydrogel formation of lignin-containing arabinoxylan, resulting in a hydrogel completely derived from barley residues. In addition, alginate-rich seaweed nanofibers from the stipe (stem-like part of the seaweed) were used directly after fibrillation as an ink and hydrogels were formed via 3D printing.

Place, publisher, year, edition, pages
Luleå University of Technology, 2019.
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords [en]
Nanofibers, Industrial residues, Ultrafine grinding, Energy-efficiency, Network formation, Hydrogel
National Category
Materials Engineering Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
URN: urn:nbn:se:ltu:diva-76015ISBN: 978-91-7790-444-1 (print)ISBN: 978-91-7790-445-8 (electronic)OAI: oai:DiVA.org:ltu-76015DiVA, id: diva2:1352564
Public defence
2019-11-15, E632, Luleå tekniska universitet, 97187 Luleå, Luleå, 10:00 (English)
Opponent
Supervisors
Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2019-10-22Bibliographically approved
List of papers
1. Production potential of cellulose nanofibers from industrial residues: Efficiency and nanofiber characteristics
Open this publication in new window or tab >>Production potential of cellulose nanofibers from industrial residues: Efficiency and nanofiber characteristics
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2016 (English)In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 92, p. 84-92Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to evaluate the production potential of cellulose nanofibers from two different industrial bio-residues: wastes from the juice industry (carrot) and the beer brewing process (BSG). The mechanical separation of the cellulose nanofibers was by ultrafine grinding. X-ray diffraction (XRD) and Raman spectroscopy revealed that the materials were mechanically isolated without significantly affecting their crystallinity. The carrot residue was more easily bleached and consumed less energy during grinding, using only 0.9 kWh/kg compared to 21 kWh/kg for the BSG. The carrot residue also had a 10% higher yield than the BSG. Moreover, the dried nanofiber networks showed high mechanical properties, with an average modulus and strength of 12.9 GPa and 210 MPa, respectively, thus indicating a homogeneous nanosize distribution. The study showed that carrot residue has great potential for the industrial production of cellulose nanofibers due to its high quality, processing efficiency, and low raw material cost

National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-15472 (URN)10.1016/j.indcrop.2016.08.003 (DOI)000383821200011 ()2-s2.0-84981234074 (Scopus ID)efda8f84-abf4-42da-9c15-95ea7b63b56e (Local ID)efda8f84-abf4-42da-9c15-95ea7b63b56e (Archive number)efda8f84-abf4-42da-9c15-95ea7b63b56e (OAI)
Note

Validerad; 2016; Nivå 2; 20160815 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2019-09-19Bibliographically approved
2. Switchable ionic liquids enable efficient nanofibrillation of wood pulp
Open this publication in new window or tab >>Switchable ionic liquids enable efficient nanofibrillation of wood pulp
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2017 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 24, no 8, p. 3265-3279Article in journal (Refereed) Published
Abstract [en]

Use of switchable ionic liquid (SIL) pulp offers an efficient and greener technology to produce nanofibers via ultrafine grinding. In this study, we demonstrate that SIL pulp opens up a mechanically efficient route to the nanofibrillation of wood pulp, thus providing both a low cost and chemically benign route to the production of cellulose nanofibers. The degree of fibrillation during the process was evaluated by viscosity and optical microscopy of SIL treated, bleached SIL treated and a reference pulp. Furthermore, films were prepared from the fibrillated material for characterization and tensile testing. It was observed that substantially improved mechanical properties were attained as a result of the grinding process, thus signifying nanofibrillation. Both SIL treated and bleached SIL treated pulps were fibrillated into nanofibers with fiber diameters below 15 nm thus forming networks of hydrophilic nature with an intact crystalline structure. Notably, it was found that the SIL pulp could be fibrillated more efficiently than traditional pulp since nanofibers could be produced with more than 30% less energy when compared to the reference pulp. Additionally, bleaching reduced the energy demand by further 16%. The study demonstrated that this switchable ionic liquid treatment has considerable potential in the commercial production of nanofibers due to the increased efficiency in fibrillation.

Place, publisher, year, edition, pages
Springer, 2017
National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-63803 (URN)10.1007/s10570-017-1354-2 (DOI)000405612000013 ()2-s2.0-85020247731 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-08-10 (rokbeg)

Available from: 2017-06-08 Created: 2017-06-08 Last updated: 2019-09-19Bibliographically approved
3. Direct preparation of alginate/cellulose nanofiber hybrid-ink from brown seaweed for 3D biomimetic hydrogels
Open this publication in new window or tab >>Direct preparation of alginate/cellulose nanofiber hybrid-ink from brown seaweed for 3D biomimetic hydrogels
(English)Manuscript (preprint) (Other academic)
National Category
Materials Engineering Applied Mechanics
Research subject
Wood and Bionanocomposites; Experimental Mechanics
Identifiers
urn:nbn:se:ltu:diva-76059 (URN)
Projects
Sea-Surf-Snow
Funder
Interreg Nord, 225500
Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2019-10-10
4. Promoted hydrogel formation of lignin-containing arabinoxylan aerogel using cellulose nanofibers as a functional biomaterial
Open this publication in new window or tab >>Promoted hydrogel formation of lignin-containing arabinoxylan aerogel using cellulose nanofibers as a functional biomaterial
2018 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 8, no 67, p. 38219-38228Article in journal (Refereed) Published
Abstract [en]

In this work, three-dimensional (3D) aerogels and hydrogels based on lignin-containing arabinoxylan (AX) and cellulose nanofibers (CNF) were prepared. The effects of the CNF and the crosslinking with citric acid (CA) of various contents (1, 3, 5 wt%) were evaluated. All the aerogels possessed highly porous (above 98%) and lightweight structures. The AX-CNF hydrogel with a CA content of 1 wt% revealed a favorable network structure with respect to the swelling ratio; nanofiber addition resulted in a five-fold increase in the degree of swelling (68 g of water per g). The compressive properties were improved when the higher CA content (5 wt%) was used; when combined with CNF, there was a seven-fold enhancement in the compressive strength. The AX-CNF hydrogels were prepared using a green and straightforward method that utilizes sustainable resources efficiently. Therefore, such natural hydrogels could find application potential, for example in the field of soft tissue engineering.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2018
National Category
Bio Materials Applied Mechanics
Research subject
Wood and Bionanocomposites; Experimental Mechanics
Identifiers
urn:nbn:se:ltu:diva-71733 (URN)10.1039/C8RA08166B (DOI)000451075500012 ()2-s2.0-85057291251 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-11-23 (johcin)

Available from: 2018-11-23 Created: 2018-11-23 Last updated: 2019-09-19Bibliographically approved

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