Reduction of Colorants in Nylon Flock Dyeing Effluent

摘要

The batch dyeing of fiber materials such as staple fibers and flock is usually carried out by exhaustion methods. However, the dyeing of flock fibers, either nylon, PET or acetate, with acid or disperse dyes is not 100 percent efficient in terms of dye utilization. Optimally only about 80 to 85percent of the dyes used for dark shade in a dye bath can be exhausted onto the target fibers. Therefore, the remaining dyes in the spent dye bath are generally not reused and are usually discharged with minimum treatment, together with the dyeing chemicals into the sewage wastewater system causing environmental pollution. We are presenting technical solutions to reduce the colorants and chemical auxiliaries in the fiber dyeing effluents by: (1) optimizing the acid dyeing conditions such as salt addition and pH control; (2) reuse of the spent dye bath that remain after the original dyeing process. In the lab scale trials, we have successfully raised the acid dye exhaustion to over 90percent by optimizing the dyeing conditions. The reuse of the spent acid dye bath also showed promising results with dye exhaustion ranging from 91 to 93percent after 4 times reuse.