“Pure lignin” usually means lignin with a high lignin content and low ash, sugars and sulfur. It is produced by separating lignin from a pulping or biorefinery stream and then purifying it. This page explains the steps and how purity is measured.
Production Steps (Kraft Example)
- Take black liquor from the kraft evaporation plant.
- Acidify it (commonly with carbon dioxide) so the lignin precipitates.
- Filter the precipitated lignin.
- Wash with acid and water to remove sodium and other inorganic salts, which lowers ash.
- Dry to a powder.
Further Purification
| Method | What it removes or improves |
|---|---|
| Extra acid washing | Ash and inorganic salts |
| Solvent fractionation | Separates fractions by molecular weight and purity |
| Membrane filtration | Removes low-molecular-weight impurities |
| Organosolv processing | Gives low-sulfur lignin from the start |
How Purity Is Measured
| Test | Purpose |
|---|---|
| Lignin content (e.g. Klason lignin) | Share of acid-insoluble lignin |
| Ash | Inorganic matter |
| Carbohydrates / reducing sugar | Residual sugars |
| Sulfur | Important for resins and fuels |
| Moisture | Water content |
Our Lignin
Our lignin is a black powder that does not dissolve in water, with 50% min lignin content, pH 4 – 6 and 0% reducing sugar (TDS Rev. 1.0). See LigninCorp lignin and lignin extraction methods.
Frequently Asked Questions
How is pure lignin produced?
By precipitating lignin from black liquor with acid, filtering it, washing it with acid and water to remove salts, and drying it; further fractionation raises purity.
How is lignin purity measured?
By lignin content (for example Klason lignin), ash, residual sugars, sulfur and moisture.
Is pure lignin soluble in water?
No. Lignin does not dissolve in water.
