Abstract
Valorization of lignocellulosic biomass into a biorefinery scheme requires the use of all biomass components; in this, the lignin fraction is often underutilized. Conversion of lignin to nanoparticles is an attractive solution. Here, we investigated the effect of different lignin isolation processes and a post-treatment homogenization step on particle formation. Lignin was isolated from birch chips by using two organosolv processes, traditional organosolv (OS) and hybrid organosolv-steam explosion (HOS-SE) at various ethanol contents. For post-treatment, lignin was homogenized at 500 bar using different ethanol:water ratios. Isolation of lignin with OS resulted in unshaped lignin particles, whereas after HOS-SE, lignin micro-particles were formed directly. Addition of an acidic catalyst during HOS-SE had a negative impact on the particle formation, and the optimal ethanol content was 50–60% v/v. Homogenization had a positive effect as it transformed initially unshaped lignin into spherical nanoparticles and reduced the size of the micro-particles isolated by HOS-SE. Ethanol content during homogenization affected the size of the particles, with the optimal results obtained at 75% v/v. We demonstrate that organosolv lignin can be used as an excellent starting material for nanoparticle preparation, with a simple method without the need for extensive chemical modification. It was also demonstrated that tuning of the operational parameters results in nanoparticles of smaller size and with better size homogeneity.
Highlights
Transition to a more sustainable society requires the use of renewable and sustainable resources for the production of fuels, chemicals, and materials
The present study demonstrates that organosolv lignin can serve as a promising raw material for the preparation of lignin nanoparticles using a simple mechanical method
Use of a newly established hybrid organosolv-steam explosion method allowed for the recovery of micro-particles directly after pretreatment
Summary
Transition to a more sustainable society requires the use of renewable and sustainable resources for the production of fuels, chemicals, and materials. Lignocellulosic biomass offers an important alternative as it consists of a renewable and plentiful resource [1]. Lignocellulosic biomass can be derived from a variety of sources, such as residues and by-products from forestry and agricultural sectors. The use of residues and by-products has many advantages, as they do not compete directly with the production of food and feed. Their conversion to fuels, chemicals, and materials could become an extra source of revenue for the forestry and agricultural sectors, contributing to the support of rural economies.
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