Table 2.
Some important aspects of the applications of synthetic dyes in the service sectors and in industry.
| Sectors | Dyes Used | Applications | Characteristics | Referencias |
|---|---|---|---|---|
| Service providers (hospitals and universities) | Dyes used between the sector differ depending on the process of application. | Biological staining techniques, colouration of pharmaceuticals, staining of cells and for chemotherapy process as the detection of lymph nodes, and the location of the tumor lesions. | Volume of dye solutions is relatively small but with a concentration very high (~1 to 10 g L−1). | [78,95,106,107] |
| Textile | The textile industry uses a large variety of synthetic dyes. However, Azo dyes are the most employed. Further, textile industry dyes are classification according to their industrial application as acid, basic, reactive, vat, disperse and direct dyes. | Cellulosic fibers account for the highest world textile consumption. The different dyes applied depends on properties such as affinity for the fibre, diffusion, reactivity and stability of the bond between the dye and the fibre. | This industry is the greatest generators of colored effluents. The affinity of dyestuffs to cellulosic fibers relies on the nature of chromophore. Textiles industry consumes around 80% of the total production of dyestuff. | [4,9,87] |
| Printing | Dyes used vary according to the type of the fiber. For example, in polyester fabric printing, disperse dyes are the only dyes available. | Application of dyes to a restricted area on the fabric, paper, cardboard that is selected for applying the abstract of the design. Manufacture of decorative trims in paper. | Printing industry delivers a reduction of waste products this benefits for the printing facilities through reducing the number of raw materials and inadequate high costs for waste disposal. Printing machines have broad applications associated to fiber and dyes. | [9,97,108,109] |
| Cosmetics | The main components used in the cosmetic industry are pigments, although dyes are also used in small quantities. Over 80% of the colorants used are organic and more than 60% of them are azo-pigments. | Lipsticks, blushers, eye shadows, eyeliners and nail polish. Hair dyes, representing almost 80% of cosmetic products in Europe. | Methodologies for the determination of dyes in cosmetics are scarce with respect to those reported. The content of colorants in cosmetics vary widely depending on the type of product. | [78,110,111] |
| Food and Pharmaceutical | Currently, there are more than 60 known synthetic dyes for use in food. Some colorants (e.g., Tartrazine) must be used in accordance with the maximum allowable limit. | Carbonated drinks, fruit drinks, energy drinks, candies, cereals, desserts and snacks, among others. | Make products more attractive or to compensate for colour variations after food processing. Food and pharmaceutical industry dyes used are based on standards issued by the Codex Alimentarius Commission (CAC). | [99,100,104,105] |
| Leather and Tanning | Most leather dyed is using azo dyes or metal complex dyes. However, the structural of dye may be different from textile dyes. | Leather dyeing operations. | Approximately between 1% and 10% of pigments used in leather industries are lost as waste and its varying concentration is function of tanning and dyeing technology. | [112,113] |