Thesis Details

Thesis Title: Reuse of Hydrolyzed Reactive Dyebaths to Dye Nylon 66, Nylon 6, and Wool Under Acidic Conditions
Thesis Author: Charles Haryslak
Abstract: Hydrolyzed reactive dyebaths present dyers with a major problem. Recently it has been estimated that effluent treatment costs incurred for the batchwise reactive dyeing of cotton are virtually identical to the cost of water used in dyeing. This is a result of increasing environmental legislation which has lead to an increase in dyeing costs. An exhausted reactive dyebath may contain as much as 50 percent of the original dye used as well as auxiliary chemicals such as inorganic salts which do not exhaust during the dyeing process. Current treatment systems to remove hydrolyzed reactive dyes from the effluent have been proven costly and ineffective for some dye classes. Recent research has shown that hydrolyzed reactive dyebaths cannot be reused to dye cotton because of the change in dyeing behavior and fastness characteristics. However, this does not eliminate the possibility of using hydrolyzed reactive dyebaths to dye other fibers such as nylon and wool. The objectives of this thesis were to determine if it is technically feasible to dye nylon 66, nylon 6, and wool with hydrolyzed reactive dye baths and to determine if this method of reuse could be used as an alternative to current wastewater decolorization methods. This was accomplished by investigating the adsorption characteristics of four hydrolyzed reactive dyes under various conditions, comparing the washfastness and lightfastness characteristics of selected hydrolyzed reactive dyes to acid dyes with similar parent dye structures, by illustrating the percent exhaustion of hydrolyzed reactive dyes into selected fibers, and by comparing initial and final ADMI values. The results of this thesis revealed that hydrolyzed reactive dyes can be used to dye nylon 66, nylon 6, and wool under acidic conditions. The highest percent exhaustion values were attained when fibers were dyed at a pH of 4.0. In general, dye adsorption increased as sodium sulfate concentration increased. Lightfastness and washfastness characteristics were comparable to acid dyes, however, the modified dye structure resulted in poorer fastness in some cases. ADMI values were reasonably low for some dyes, but were dependent on the initial dye concentration as well as the fiber that was dyed. In all cases, there was a definite reduction in dye concentration after using the hydrolyzed reactive dyebath to dye the selected fibers. This factor coupled with the relatively low capital and operating costs of the reuse process would result in a decrease in treatment costs. In addition, there is the potential to recover the value of the reactive dye.