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Abstract:
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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.
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