| Wave number (cm−1) | ||
| Untreated sorbent | Treated sorbent | Description |
| 3427.62 | 3421.83 | Hydrogen bonded O-H stretching |
| 2852.81 | 2850.88 | C-H stretching |
| 2507.54 | 2509.47 | -------- |
| 2293.44 | 2297.30 | --------- |
| 2058.11 | 2065.83 | --------- |
| 1730.21 | 1735.99 | C=O stretching in carboxyl |
| 1627.97 | 1624.12 | C=O stretching |
| 1570.11 | ----- | C-N stretching in -CO-NH- |
| 1419.66 | 1417.73 | O-H in plane bending (carboxyl) |
| 1049.31 | 1053.17 | C-OH stretching |
| 893.07 | 895.00 | C-H stretching |
| 779.27 | 781.20 | Characteristic of substituted benzene |
| 586.38 | 590.24 | C-Br stretching |
| 468.72 | 462.93 | C-I stretching |