Table 3.
Analyses of pKa and the amounts of organic groups present in the biochar samples, measured at 25 °C in 0.10 mol L−1 KCl. The values in parentheses are the variations of the measurements (last decimal place).
| Sample* | pKa | Organic groups mmol g−1) | |
|---|---|---|---|
| Partial | Total | ||
| CR | 10.90 (4) | 0.700 (3) | 1.65 |
| 8.70 (1) | 0.320 (1) | ||
| 6.20 (1) | 0.270 (2) | ||
| 4.16 (14) | 0.362 (6) | ||
| CS | 10.61 (20) | 0.204 (4) | 0.20 |
| OP | 11.40 (4) | 0.460 (7) | 0.62 |
| 9.45 (20) | 0.160 (30) | ||
| PO | 10.93 (5) | 0.978 | 0.98 |
| SB | 11.06 (6) | 0.051 (7) | 0.09 |
| 9.23 (3) | 0.024 (1) | ||
| 6.70 (2) | 0.007 (5) | ||
| 3.74 (3) | 0.011 (1) | ||
| WH | 10.90 (10) | 0.780 (2) | 1.19 |
| 6.32 (1) | 0.406 (22) | ||
*CR = charcoal fines; CS = coconut shell; OP = orange peel; PO = palm oil bunch; SB = sugarcane bagasse; WH = water hyacinth.