Dyes: environmental chemistry

The widespread use of biphenyl and methyl-substituted biphenyls as dye carriers (qv) in the textile industry has given rise to significant environmental concern because of the amount released to the environment in wastewater effluent. Although biphenyl and simple alkylbiphenyls are themselves biodegradable (48—50), the prospect of their conversion by chlorination to PCBs in the course of wastewater treatment has been a subject of environmental focus (51—53). Despite the fact that the lower chlorinated biphenyls are also fairly biodegradable (49,54,55) continued environmental concern has resulted in decreased use of biphenyl as a dye carrier (see Dyes, environmental chemistry). 

The use of natural dyes as food colorants evolved over a period spanning thousands of years. During that period, by trial and error, some dyes were found to be safe while others were not. By comparison, the development of synthetic dyes as food colorants has taken place over a comparatively short time. During that period, some synthetic dyes considered safe by existing health standards were used as food colors. Later, with iacreased knowledge, these were found to create health problems and were removed from the marketplace. The manufacture of synthetic dyes for use on foods creates more of a health and environmental problem than natural dyes, but offers greater variety and stabiUty of color (see Dyes, environmental chemistry). 

Bioaugmentahon -in dyewater treatment [DYES, ENVIRONMENTAL CHEMISTRY] (Vol 8)... 

Flocculation - [ACRYLAMIDE POLYMERS] (Vol 1) - [FLOCCULATING AGENTS] (Vol 11) - [SEDIMENTATION] (Vol 21) -dye water effluent treatment [DYES, ENVIRONMENTAL CHEMISTRY] (Vol 8) -of emulsions [EMULSIONS] (Vol 9) -minerals processing [MINERALS RECOVERY AND PROCESSING] (Vol 16) -PEO in [POLYETHERS - ETHYLENE OXIDE POLYMERS] (Vol 19) -useofethyleneimines [IMINES,CYCLIC] (Voll4) -useofSCFs [SUPERCRITICALFLUIDS] (Vol 23) -water treatment for steam prdn [STEAM] (Vol 22)... 

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