Thesis Details

Thesis Title: Wash water purity and its effect on colorfastness properties
Thesis Author: Raymond Silva, Jr.
Abstract: Because of new and proposed 'Federal Effluent Guidelines and Standards,' the textile industry has been attempting to adapt various advanced systems in order to treat its effluent waste and possibly recycle process water. Even with improved efficiencies, such systems are too costly for the average finishing plant capacities. Approximately 80 percent of all water consumed in wet processing is utilized for the washing operation. Since rinse water is one of the least contaminated sources of wastes, it should therefore be the least difficult to treat. A practical method to alleviate the current problem is to recycle rinse water from an intermediate process such as a dye wash range. A recent Institute of Textile Technology thesis has demonstrated a simplified filtration process for removing color from rinse water with significant results. Although dyestuff is the major source of contamination in rinse water, dye bath assistants which are also present are even more difficult to remove. The basic objective of this study was to assess the possibility of using dye chemical contaminated rinse water from dyeing operations. in subsequent rinsing of fabrics dyed with the same dye class. From an analysis of a sulfur dye wash range, levels of concentrations of the original pad chemicals were estimated when compared to similar pH readings of pad chemical concentrations. For this study, 2, 5, 10, and 20 percent concentrations of the original pad chemicals were selected as the levels for the simulated recycled contaminated rinse water. Cotton print cloth continuously dyed with Red MX-2B and Brilliant Blue R fiber reactive dyes was washed at the four levels of contamination and compared to a control sample. The reflectance values were obtained from a Color Eye and used to calculate K/S values from which the percent dye strength difference between the samples and the control was calculated. No significant loss in dye depth was experienced by the fiber reactive colors. Sulfur dyes, Black 4GCF and Green 4YCF were washed in rinse water from two different simulated recycling procedures. By segregating the reduction and oxidation chemical contaminants in the first washing procedure, the sulfur dyed fabric experienced a significant sha,de change with increasing chemical contamination. In the second washing procedure, the reduction and oxidation chemical contaminants were mixed (50/50), and this washing procedure did not affect the shade, regardless of concentration. Being similar in application to sulfur dyes, the vat Bordeaux HRR and Blue N dyes were subjected to similar recycling procedures. Washing in segregated reduction and weak oxidation chemical contaminated rinse water resulted in a significant change in depth of shade with increasing chemical contamination. Although the mixing (50/50) of the reduction and weak oxidation chemical liquors showed a more extreme change in shade, an acceptable combination of reduction and oxidation chemical was selected with a pH near neutral which resulted in a negligible shade change from the control. Acceptable washed fabric samples were subjected to the A.A.T.C.C. wash, crock, and lightfastness tests. These tests showed no deterioration of the general fastness properties of the fiber reactive, sulfur, vat dyed fabrics at the levels of contamination being tested. In specific recycling arrangements, up to 20 percent contamination of the respective dye rinse water has been shown to be within acceptable limits of quality for recycling water with no significant decrease of general fastness properties. With an efficient removal of color by a secondary filtration system and recycling rinse water, significant reductions in water consumption, energy consumption, and the volume of effluent requiring further treatment will greatly alleviate the textile mill effluent problems.