Development of o-phthalic anhydride as a low-temperature activator in H2O2 bleaching system for cotton fabric

Abstract

O-phthalic anhydride (PA) was developed as a low-temperature activator in the H2O2 bleaching system for cotton fabric. The performance of the H2O2/PA bleaching system was investigated by measuring the CIE whiteness index (WI) of the bleached cotton fabric, H2O2 decomposition rate and bursting strength, respectively. The effects of experimental conditions, including PA dosage, bleaching time, bleaching temperature and NaOH concentration, were discussed in the H2O2/PA bleaching system. Upon addition of PA, the WI and H2O2 decomposition rate increased significantly at 70 °C. The results showed that the bleaching system had a promising application prospect. Compared with the H2O2 system, the H2O2/PA system significantly promoted 1O2 generation under the same alkali condition by using 9,10-dimethylanthracene as a fluorescent probe for 1O2. And the generation of large amount of 1O2 did not obviously affect the bleaching performance in the H2O2/PA system. By using benzenepentacarboxylic acid as a fluorescent probe for HO· detection, it was found that the fluorescence intensity was enhanced 14 folds in the presence of PA, indicating that PA could strongly promote HO· generation. By using dimethyl sulfoxide as a scavenger to control HO· concentration, it was found that the WI of the fabric was closely related to the HO· concentration, revealing that the HO· could play an important role in the bleaching process. Phthalic acid was also added to the H2O2 bleaching system to investigate potential bleaching route of the H2O2/PA system. Based on these experimental results, a possible bleaching mechanism of the H2O2/PA system was proposed.