| Sample | FT-IR data | ||
| Peak (cm−1) | Bond | Attribution | |
| AC | 3391 | -OH | Phenol (graphitic structure) |
| 1709 | -C=O | Saturated carboxylic acid | |
| 1530 | -OH | Carboxylic acid | |
| 1221 | -COOH | Carboxylic acid | |
| 771 | -O-M | Metal-oxygen (impurities) | |
| AC/Fe3O4 | 1704 | -C=O | Saturated carboxylic acid |
| 1578 | -OH | Carboxylic acid | |
| 1220 | -COOH | Carboxylic acid | |
| 773 | -O-M | Metal-oxygen (magnetite) | |