2.2. Heavy Metal content in Dyestuff


Heavy metals of concern include:

  • cadmium
  • lead
  • copper
  • nickel
  • cobalt
  • chromium
  • chromium 6
  • arsenic
  • mercury
  • selenium
  • antimony


Some Reactive dyes contain metal complexes in their chromophores. In these the heavy metal is bonded within the chromophore. But it is possible that free metals can be produced as impurities through incomplete reaction.


Heavy metals used in this context would include:


  • Copper
  • Nickel
  • Cobalt
  • and chromium


Reactive dye examples would include:


  • copper phthalocyanines (turquoise dyes)
  • nickel phthalocyanines (bright green dyes)


It is also possible for dyestuffs with metal-free chromophores to contain metallic impurities, originating from the raw materials used in manufacture. Limits for the amount of metallic impurities permitted in dyestuffs are defined by ETAD and the EU Eco-label are shown in Table 1.


Table 1:


Examples of Regulations concerning Heavy Metals are available on the internet, and a typical example would be as follows:


Heavy Metal

Oeko Tex Standard 100


Leaching from Dyed Textile

Oeko Tex Standard 100


In Effluent

ETAD



In Dyestuff

Arsenic (As)

0.2 1.0 ppm

-

50 ppm

Lead (Pb)

0.2 1.0 ppm

-

100 ppm

Cadmium (Cd)

< 0.1 ppm

-

20 ppm

Total Chromium (Cr)

0.2 1.0 ppm

0.1 2.0 ppm

100 ppm

Chromium 6

nd

0.02 0.70 ppm

-

Cobalt (Co)

1.0 4.0 ppm

0.1 2.0 ppm

-

Copper (Cu)

25.0 50.0 ppm

0.1 2.0 ppm

250 ppm

Nickel (Ni)

1.0 4.0 ppm

0.1 2.0 ppm

200 ppm

Mercury ( Hg)

< 0.02 ppm

-

4 ppm

Antimony (Sb)

5.0 10.0 ppm

-

50 ppm

Tin (Sn)

-

-

250 ppm

Zinc (Zn)

-

-

1500 ppm