Dyeing in catalase-treated bleaching baths

The conventional rinsing after bleaching to remove the residual hydrogen peroxide, harmful to the dyes either in solution or on the fabric, was replaced by enzymatic cleaning using catalases. The catalase-treated bleaching liquor was reused for dyeing. Though no hydrogen peroxide was detected after the enzymatic process, the bleaching bath composition caused unacceptable colour changes on dyed fabrics. By varying the parameters of the dyeing process - dye, salt, alkali and enzyme concentrations the colour difference could be reduced significantly and a good dyeing result could be achieved

Effect of temperature and bath composition on the dyeing of cotton with catalase-treated bleaching effluent

Conventional rinsing to remove residual hydrogen peroxide after the bleaching of cotton fabric can be replaced by enzymatic cleaning using catalases. Our previous study showed that dyeing in such catalase-treated bleaching baths results in a shade change on the dyed fabrics. The aim of this present study was to investigate the reasons for the unacceptable colour differences of the dyed fabrics. Experiments were performed to study the possible temperature-dependent dye interactions in the standard dyebath, and in the dyebath prepared with bleaching effluent. Fluorescence emission spectra were used to detect changes in the structure of the catalase related to the thermal unfolding and denaturing of the protein. It was found that the colour difference on the dyed textiles could be attributed to the temperature-dependent dye-enzyme interaction and precipitation, as well as to the complexity of the bleaching bath composition