Abstract
In this paper, the effect of D0 temperature, Kappa factor and the final pH value on bleaching sulfate bleached pine wood pulp was studied. The results showed that the bleaching efficiency was better when the pH value was 4, and the amount of absorbable organic halogen (AOX) in the bleaching wastewater was decreased. The Kappa factor is linear with the whiteness in the range of 0–0.15. With the increase of the Kappa factor, the amount of AOX in bleaching wastewater of D0 and Ep gradually increases. High temperature bleaching can reduce AOX production, but some fibers are hydrolyzed, leading to a decrease in pulp viscosity. The effects of chlorine dioxide solution adding sodium dihydrogen phosphate (NaH2PO4) and dimethylsulfoxide (DMSO) on pulp bleaching were investigated. The results showed that both solutions could reduce the amount of AOX in bleaching wastewater. Among them, the addition of NaH2PO4 in chlorine dioxide increased pulp whiteness, while the addition of DMSO was the opposite. Scanning electron microscope showed that a small amount of hollow cracks and more voids appeared on the surface of pulp fibers after the addition of NaH2PO4. Pulp fibers bleached by the chlorine dioxide adding DMSO have more folds and less voids on the surface. The surface wrinkles of pulp fibers increased with the addition of DMSO and the voids were less. FT-IR showed that the number of chromophore groups in the pulp bleached by chlorine dioxide adding NaH2PO4 were decreased. However, the lignin characteristic absorption peak in the pulp bleached by chlorine dioxide adding DMSO increased at the intensity of 1062 and 1160 cm−1, which indicated that there were more residual chromophore groups.
Highlights
Chlorine dioxide (ClO2) was found to be a very effective oxidant for textile1 and wood pulp bleaching2 so far
The results showed that the bleaching efficiency was better when the pH value was 4, and the amount of absorbable organic halogen (AOX) in the bleaching wastewater was decreased
Scanning electron microscope showed that a small amount of hollow cracks and more voids appeared on the surface of pulp fibers after the addition of NaH2PO4
Summary
Chlorine dioxide (ClO2) was found to be a very effective oxidant for textile and wood pulp bleaching so far. Bleached pulp has high whiteness, high strength and less damage to the fiber. No other process or technique has been achieved such high-quality effects of chlorine dioxide. Elemental chlorine free (ECF) bleaching technology which main bleaching is chlorine dioxide as the is internationally recognized as cleaner production bleaching methods.. Compared with other bleaching agents, chlorine dioxide is an efficient bleaching agent that does not produce carcinogenic substances such as Trihalomethanes (THM) and haloacetic acid HAAs.. One of the key of bleaching process is reduce the generation of chlorate and chlorite, for which a large number of optimization experiments have been carried out. In order to control the pH value of bleaching to
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