Table 3.
Significant peaks identified in IR analysis of raw soy hulls and coffee chaff and their derived biocarbons (see table 1 for abbreviations).
| wavenumber | description | references |
|---|---|---|
| 3320 − 3280 cm−1 | hydroxyl group stretching | [32] |
| 2915 + 2860 cm−1 | asymmetric and symmetric C–H groups on aliphatic hydrocarbons | [32] |
| 1770 + 1620 cm−1 | carboxyl groups conjugated and unconjugated with aromatics | [33] |
| 1513 + 1442 cm−1 | aromatic alkene stretching | [33,34] |
| 1350 − 1260 cm−1 | in-plane bends of hydroxyl groups | [34] |
| 1240 + 1215 cm−1 | aromatic C–O stretching | [33] |
| 1000 + 1100 cm−1 | the ring and side group vibrations of backbone of any cyclic carbohydrates | [32] |
| 818 + 775 cm−1 | aromatic out-of-plane vibrations | [35] |