Textile Recycling Technologies, Colouring and Finishing Methods

Table 14: Dye Classes, Use on Textile Fibres and Fixation, and Associated Hazardous Substances 

Reproduced and modified from [145-148]. 
Dye Class -
Colourant/Dyestuff Type 
Fibre Type 
Hazardous Substances 
Fixation Degree 
(%) 
Interaction between dye 
and fibre 
Acid 
Wool, Silk 
Banned arylamines due to 
carcinogenic effects (from 
azo dyes) 
85-98 
Hydrogen bonding, ionic 
bonding, van der Waals 
forces 
Acid Subclass: Metal 
complex (Replaced 
banned azo dyes) 
Wool, Silk 
Toxic metals from heavy 
metal content in dyestuff 
82-98 
Hydrogen bonding, ionic 
bonding, van der Waals 
forces, hydrophobic bonding 
Basic 
Silk, Polyacrylic 
Carcinogenic dyestuff, 
complexing agents 
(quaternary ammonium 
compounds) 
95-100 
Hydrogen bonding, ionic 
bonding 
Direct 
(Azo-based direct dyes 
banned) 
Cellulose 
Salts, aftertreatment with 
water, toxic cationic agents 
64-96 
Hydrogen bonding, van der 
Waals forces 
Mordant 
Wool, Silk
Chromium VI, some banned 
95-98 
Dye fixative 
Reactive 
Cellulose, Wool, Nylon 
Salt emissions, unfixed 
dyestuff in effluent require 
treatment, metal complexes 
50-97 
Covalent bonding, hydrogen 
bonding 
Sulphur 
Cellulose 
Sodium hydrosulphite 
60-95 
Hydrogen bonding, van der 
Waals forces 
Vat 
Cellulose 
75-95 
Hydrogen bonding, van der 
Waals forces 
Disperse 
Polyester, Nylon 
Allergenic and carcinogenic 
dyestuff, chlorinated solvents 
88-100 
Van der Waals forces, 
hydrophobic bonding 
Solvent or Pigment 
Polyester, Cellulose, 
Nylon, Wool, Silk, 
Polyacrylic 
Chlorinated or aromatic, 
aliphatic solvents, residues 
(binders, VOC etc.) 
100 
Require additional substrate 
compound for attachment 

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Textile Recycling Technologies, Colouring and Finishing Methods | Le 
42 
Better Thinking Ltd. (2006 report) categorized fibre types based on dye class applied and 
associated pollution discharge, upon with a derived Pollution Category ranking (1 being the lowest 
and 5 being the highest polluting).
149
Cotton textile dyeing processes are primarily conducted by 
reactive dyeing, and are found to discharge larger amounts of effluent compared to other fibres, 
which are associated with high cleaning costs (Table 15). In addition, reactive dyes on cotton 
require large volumes of wash-off (dye transfer inhibiting polymers) to remove unfixed dyes, 
accounting for high energy consumption, and up to 50% of the total cost for the dyeing 
procedure.
150
Of conventional dyeing methods, vat and sulphur dyes are considered to pose the 
least environmental impact. Metal complex dyes are favoured for wool fibres and are also 
considered to have low environmental impacts.
145
The categorization was reproduced to also include nylon fibres and other effects from the fibre 
production process, in Table 15.