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Cleaner Technology Transfer to the Polish Textile ... - Miljøstyrelsen

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Topic 28.<br />

Neutralization after dyeing<br />

Case illustration:<br />

Use only neutralization after<br />

reactive dyeing of cot<strong>to</strong>n<br />

when needed<br />

Concept After dyeing in <strong>the</strong> alkaline range, it is normal <strong>to</strong> neutralize. Typically, acetic<br />

acid is used giving a contribution <strong>to</strong> COD in <strong>the</strong> waste-water. Acid is added <strong>to</strong><br />

assure that dyes are not washed out from fibres, e.g. in <strong>the</strong> first rinse after dyeing<br />

with certain reactive dyes. However, often <strong>the</strong>re seems <strong>to</strong> be no need for<br />

this acid addition. Alternatively, formic acid – or an even better mineral acid<br />

like diluted hydrochloric acid – could be used giving a smaller or no contribution<br />

of COD. This is documented in detail in a paper in Part 3.<br />

Improvement potentials Chemical savings. Reduction of COD load.<br />

Relevance Most companies.<br />

46

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