Abstract
Effective bleaching conditions with sodium bromite (NaBrO2) aqueous solution in the presenceof metal ions were investigated by using a cellulose film and cotton fabric dyed with directdye (C. I. Direct Blue 78).
Bleaching efficiency was determined using absorbance at dominant wavelength (608 nm) in thecase of film and reflectance in the case of fabric.
The main results obtained are summarized as follows :
1) In five sodium bromite aqueous solutions, each containing a different kind of metal ion, bleaching efficiency decreased in the order of Al3+>Fe3+>Cu2+>Mg2+=Ca2+.
2) At room temperature, the most effective bleaching was observed in the presence of 6/100Al3+ mol ratio to NaBrO2, and the addition of more Al3+ decreased bleaching efficiency, probably due to self-decomposition of NaBrO2.
3) In bleaching of dyed cotton fabric at various temperatures (10-50°C), bleaching effectand rate of diminution of tensile strength became more remarkable as the temperature increased.
4) For dyed cotton fabrics having the same bleaching efficiency, the rate of diminution oftensile strength by the addition of Al3+ at room temperature were determined to be ca. 1/4by heat bleaching.
