Meghdad Kamali Moghaddam

The best chance for an efficient bleaching of highly pigmented wool with minimum fiber damage is provided by the use of metal catalysts in mordanting step preceding peroxide bleaching. This study evaluates the catalytic effect of copper sulfate (CuSO4) in the bleaching process of pigmented wool fibers under the used condition. The effects of CuSO4 and Na4P2O7 (as a stabilizer) concentration, bleaching time and rinsing time after mordanting on yellowness index, optical and mechanical properties were investigated and the optimum conditions for each step was reported. The results showed that an excellent depigmentation with minimum fiber damage is provided by using 1 %w/v CuSO4 and subsequent rinsing for 60 min, as well as bleaching with 60 ml/l H2O2 and 7 %w/v Na4P2O7 for 15 min. The optical properties of fibers were improved after bleaching under optimum conditions compared with raw samples. The color indices revealed that the black wool fibers have turned into a pale light brown shade. The morphology and structure of wool fibers, before and after bleaching, were characterized by using optical microscopy, scanning electron microscopy (SEM), and EDAX test method.