From: Latest development in the fabrication and use of lignin-derived humic acid
Type of lignin | Solubility | Carboxylic acid group, mmol/g | Phenolic OH, mmol/g | Aliphatic OH, mmol/g | Molecular weight (Mw, g/mol) | C/N | Refs. |
---|---|---|---|---|---|---|---|
Humin | Not soluble | 3–4 | 2 | NA | > 300,000 | NA | |
HA | pH > 2 | 2–5 | 2–6 | 1–4 | 2000–1,000,000 | 8–61 | |
FA | soluble | 8–9 | 3–6 | 3–5 | 600–900 | 6.7–9.2 | |
Kraft lignin (KL) | pH > 7 | 0.3 | 2.6 | 2.45 | 1000–15,000 | 135 | |
Lignosulfonate (LS) | soluble | 0.1–0.53 | 1.5–2 | 1.9–4 | 1000–50,000 | 240 | |
Organosolv lignin | pH > 7 | 0.05–0.25 | 2.6–5.1 | 1.3 | 500–5000 | 203 | |
Soda lignin | pH > 7 | 0.9–1 | 2.5–3.7 | 2.4 | 800–3000 | 68 |