Dye Bath Reconstitution and Reuse

[6] [30] With low hydrolysis of dye molecules, dyebaths may be recharged with bath chemicals and reused repeatedly. Dyebath analysis tends to be difficult with reactive type dyes due to the difficulty of differentiating unhydrolyzed and intact colorant using spectrophotometry [2]. According to Smith [30], the easiest systems to manage for dyebath reuse are dye classes which give high affinity (exhaustion) and which undergo minimum changes during the dyeing processes.

The features mentioned in the consulted bibliography are:

• reduction in freshwater and chemical consumption [2] [30]
;
• it has been shown to reduce flow [2], BOD and COD loading up to 33% [30]
;
• The used dyebath will usually be hot (over 60 degC), considerable time and energy are saved by starting the next dyeing at the highest possible temperature consistent with desired quality factors [30]
;
• savings, as well as installation costs and operating expenses, are site-specific. The payback period is generally 13 to 20 months [30]
.

References from reviewed literature:

In [2] B. Smith, A Workbook for Pollution Prevention by Source Reduction in Textile Wet Processing, Pollution Prevention Pays Program, North Carolina Department of Environment, Health, and Natural Resources, Raleigh, N.C., 1988