Table 7. Fitting Results of Hydroxyl Functional Groups for PT and AT Coal.
| PT coal | AT coal | |||||
|---|---|---|---|---|---|---|
| number | peak position (cm–1) | area ratio (%) | functional group | peak position (cm–1) | area ratio (%) | functional group |
| 1 | 3173 | 5.89 | ring hydrogen bond | 3061 | 2.54 | free hydroxyl |
| 2 | 3266 | 12.76 | alcoholic hydroxyl | 3154 | 4.96 | ring hydrogen bond |
| 3 | 3361 | 20.91 | O–H or N–H | 3223 | 9.13 | alcoholic hydroxyl |
| 4 | 3439 | 27.42 | OH-OH | 3290 | 11.52 | alcoholic hydroxyl |
| 5 | 3514 | 20.97 | OH-OH | 3355 | 14.28 | alcoholic hydroxyl |
| 6 | 3580 | 7.54 | O-OH | 3413 | 16.29 | OH-OH |
| 7 | 3608 | 4.51 | free hydroxyl | 3473 | 16.40 | OH-OH |
| 8 | 3537 | 13.00 | hydroxyl-π bond | |||
| 9 | 3605 | 8.06 | free hydroxyl | |||
| 10 | 3665 | 3.82 | free hydroxyl | |||