# Chemical Characterization of Alkali Lignins Isolated from Rapeseed Stalks

## TL;DR

This study compares two methods for extracting lignin from rapeseed stalks to determine which is more effective and environmentally friendly.

## Contribution

The study provides a detailed chemical comparison of lignin from two pulping methods, highlighting the Soda-AQ process as a cleaner alternative.

## Key findings

- Lignin samples from Soda-AQ pulping showed structural similarities suitable for high-value applications.
- The Soda-AQ process avoids sulfur emissions, making it an environmentally cleaner alternative to the Kraft method.
- Advanced analytical techniques confirmed structural differences and performance indicators of the isolated lignins.

## Abstract

Rapeseed stalks (Brassica napus), an abundant agricultural residue, represent a promising non-woody raw material for the pulp and paper industry. This study focuses on the chemical and structural characterization of alkali lignins isolated from black liquors generated by two common delignification methods: Kraft and Soda-Anthraquinone Pulping of rapeseed stalks. The objective is to understand how the chemical environment of each process influences the final structure, fragmentation degree, and reactivity of the isolated lignin. In practice, lignin samples are recovered from black liquors produced under varying conditions (alkali charge, time, and temperature) to achieve defined levels of delignification. Detailed characterization was performed using advanced analytical techniques, including Gel Permeation Chromatography, Solid-State Cross-Polarization/Magic-Angle-Spinning Nuclear Magnetic Resonance, and FT-IR and UV-Vis Spectroscopy. The findings provide essential data on the structural differences, confirming the suitability of the resulting materials for potential high-value applications. Furthermore, the structural similarities and performance indicators suggest that the Soda-AQ process enables successful delignification of rapeseed stalks without the sulfur emission issues associated with the Kraft method, thus validating the former as an environmentally cleaner alternative for non-wood biomass utilization supporting the complete valorization of rapeseed agricultural waste.