2.2. Reaction of chlorine dioxide with lignin model compounds

Chlorine dioxide solution was transferred into a conical bottle, and the pH of the solution was adjusted to 3 with 2 mol l⁻¹ H₂SO₄ at room temperature. Then, a corresponding quantity of VA or VE was added. The reaction was carried out under magnetic stirring (400 rpm) at 343 K. The selection of pH and temperature was based on actual chlorine dioxide bleaching of pulp. The reaction solution was sampled at 1, 2, 3, 4, 6, 8, 10, 15 and 30 min. The samples were stored in a refrigerator, and the AOX content was determined as soon as possible.