The straw ammonium sulfite pulp is completely free from chlorine-based bleaching agents
This paper investigates sodium disulfite bleaching under the following process conditions: Na₂S₂O₄ at 1.0% concentration (5%), pH 5.5, temperature 60°C, and DTPA at 0.1%. The experimental results showed a whiteness value of 68.7% ISO and a potassium permanganate value of 2.6.
This paper investigates the OpAP process under the following conditions: pulp concentration of 10%, alkali dosage of 3%, oxygen pressure of 0.6 MPa, temperature of 80°C, treatment time of 80 minutes, magnesium sulfate content of 0.5%, and 1% H₂O₂. The experimental results showed that the whiteness increased from 43.3% ISO to 62.1% ISO. Similar acid treatment was applied prior to the hydrogen peroxide supplementation bleaching stage. The hydrogen peroxide supplementation bleaching conditions were as follows: H₂O₂ 3%, NaOH 2%, temperature 80°C, treatment time 80 minutes, DTPA 0.2%, MgSO₄ 0.05%, and Na₂SiO₃ 3%. The resulting whiteness was 71.3% ISO, with a potassium permanganate value of 2.6.
Keywords: straw ammonium sulfamate pulp; TCF; oxidative alkali bleaching; acid treatment; hydrogen peroxide; sodium hydrosulfite bleaching; enhanced oxidative alkali bleaching
