Table 1.
Treatment conditions [5], solubility, chemical compositions [19], advantages and disadvantages of technical lignin (ND—No data). Copyright © (2018) Elsevier; Copyright © (2019) John Wiley and Sons.
| Parameter | Lignosulfonate | Kraft Lignin | Organosolv Lignin | Soda Lignin | Enzymatic Hydrolysis Lignin |
|---|---|---|---|---|---|
| Treatment conditions | Metal sulfite + sulfur dioxide (Ca2+, Mg2+ or Na+) (pH = 2–12, T = 120–180 °C, for 1–5 h) | First: Sodium hydroxide and sodium sulfide (pH = 13–14, T ≈ 170 °C); Second: Sulfuric acid (pH = 5–7.5) |
Organic solvents (such as acetone, ethanol, and methanol), usually mixed with water (T = 170–190 °C) | 13–16 wt % of sodium hydroxide solutions (T = 140–170 °C) + anthraquinone (catalyzer) | Cellulases and hemicellulases [10] |
| Solubility | Water | Alkali, organic solvents | Organic solvents | Alkali | Partially in organic solvents |
| Ash content (mass%) | 4.0–9.3 | 0.5–3.0 | 1.7 | 0.7–2.3 | 1.0–3.0 |
| Sulfur (%) | 3.5–8.0 | 1.0–3.0 | 0 | 0 | 0–1.0 |
| Carbohydrates (mass%) | ND | 1.0–2.3 | 1–3 | 1.5–3.0 | 10.0–22.4 |
| Molecular weight (Da) | 1000–50,000 | 1500–5000 | 500–5000 | 1000–3000 | 5000–10,000 |
| PDI | 4.2–8.0 | 2.5–3.5 | 1.5–2.5 | 2.5–3.5 | 4.0–11.0 |
| Advantages | A good aqueous solubility [5] | A higher purity [41] | A higher purity [9]; sulfur-free; basically preserves the native structure of lignin [5] | Sulfur-free [41] | Basically non-sulfur; possesses a closer structure to native lignin [19] |
| Disadvantages | A structural change of lignin and the low purity after isolation [5] | A worse solubility [19] | Difficult to produce on a large scale [1] | Difficult to recover through centrifugation or filtration [56] | Very low solubility in either water or some organic solvents [19] |