RR2 with 98% purity (Merck Company, Germany) has been used for preparing stoke solution, 1,000 mg L−1 of RR2 was dissolved in 1 L of distilled water. The RR2 specification is shown in Table 1 (Hameed & Ismail 2018). The chemical activation of the adsorbent was carried out by using 85% phosphoric acid (H3PO4). In this experiment, sulfuric acid (98%) and sodium hydroxide (Merck, Germany) were used to adjust the pH. The RR2, sodium hydroxide (NaOH), sulfuric acid (H2SO4), and phosphoric acid were all analytical grades and used without further purification.
Table 1
The characterization of RR2 dye
| Characteristics | Values |
|---|---|
| Molecular formula | C19H10Cl2N6Na2O7S2 |
 max (nm) | 540 |
| Molecular weight (MW) | 615.33 g/mol |
| Chemical structure |  |
| Characteristics | Values |
|---|---|
| Molecular formula | C19H10Cl2N6Na2O7S2 |
| max (nm) | 540 |
| Molecular weight (MW) | 615.33 g/mol |
| Chemical structure | |