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Hollow lignin microsphere preparation and simultaneous urea encapsulation for controlled release using kraft lignin via slow and exhaustive acetone-water evaporation
(English)In: Article in journal (Refereed) Submitted
Abstract [en]

Lignin nano/micro-particles have recently attracted growing interest for various value-additive applications of lignin, including encapsulation. In order to establish a highly efficient and highly productive preparation process to effectively utilize technical lignin, a brand-new slow and exhaustive solution evaporation process following simple self-assembly principle has been developed using industrial softwood kraft lignin from a starting acetone-water (80/20, v/v) solution to recover 100% of the lignin as homogeneous and well-shaped microspheres. The prepared microspheres have a typical average diameter of 0.81±0.15 μm and are hollow with very thin shells (of nanoscale thickness). For the first time, encapsulation of urea by these lignin microspheres has been achieved using the same process as hollow lignin microspheres with urea attached to the outside and entrapped inside of the wall. Two distinct urea release rates were observed for the urea-encapsulated microspheres: a fast release of the urea outside the shell wall and a slow (controlled) release of the urea inside the shell wall. The slow and exhaustive solution evaporation procedure reported here is a simple, straightforward and inexpensive method for the valorization of industrial kraft lignin, either as microspheres with controllable, homogeneous and desired morphologies or as a lignin-based encapsulating fertilizer for controlled release.

National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:kth:diva-214044OAI: oai:DiVA.org:kth-214044DiVA, id: diva2:1139937
Note

QC 20170911

Available from: 2017-09-10 Created: 2017-09-10 Last updated: 2017-09-11Bibliographically approved
In thesis
1. Physical, Chemical and Biochemical Modifications of Industrial Softwood Kraft Lignin for Different Applications
Open this publication in new window or tab >>Physical, Chemical and Biochemical Modifications of Industrial Softwood Kraft Lignin for Different Applications
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Various technical lignins, e.g. industrial Softwood Kraft lignin (SKL), are now largely available while they are generally underutilized due to their heterogeneous and complicated structures and/or the poor properties. SKL has here been modified by physical, chemical and biochemical methods for preparation of lignin microspheres, phenol substitution in phenol-formaldehyde (PF) resin preparation and preparation of highly efficient fertilizers.

Physically, a brand-new slow and exhaustive solution evaporation process was developed for the highly efficient and productive preparation of microsphere structures. Highly homogenous SKL hollow microspheres were obtained and for the first time, urea encapsulating SKL microspheres were similarly prepared which could be an excellent controlled release urea fertilizer.

Chemically, Mannich reaction (one type of amination) was deeply investigated by including for the first time an LC-MS study of vanillin reaction, resulting in the establishment of a fast and reliable lignin reactivity (for phenol substation in PF resin) quantification method. In addition, SKL was functionalized using the Mannich reaction or esterification, leading to an improved hydrophobicity and compatibility for blending with polylactic acid (PLA). Using dip-coating technique for the first time, PLA-functionalised SKL-coated urea pellets were prepared, leading expectedly to a highly efficient urea fertilizer with simultaneous controlled- and slow- release and biological stabilization effects.

Biochemically, SKL was demethylated via incubation with different laccase-mediator combinations, which in principle will increase its reactivity in PF resin preparation. However, polymerization occurred which would decrease the reactivity.  The overall effects need to be further investigated.

Conclusively, broader or larger scale SKL applications can expectedly be realized after the development of SKL modifications tailored towards the optimum desired structures and properties.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. p. 83
Series
TRITA-CHE Report 2017:34, ISSN 1654-1081
National Category
Polymer Chemistry
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-213985 (URN)978-91-7729-492-4 (ISBN)
Public defence
2017-09-18, Kollegiesalen F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 170912

Available from: 2017-09-12 Created: 2017-09-07 Last updated: 2017-10-05Bibliographically approved

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Wang, Miao

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