ABSTRACT
The manufacture and use of dyes and pigments is a multibillion-dollar industry. The use of these substances is an integral part of almost all manufacturing processes. Interestingly, the widespread use of synthetic colorants and the modern dye industry dates only to 1856 with the synthesis of mauveine by W.H. Perkin (Kirk-Othmer Encyclopedia of Chemical Technology 1992). Of all the different types of dyes, azo dyes are the most useful and widely used colorants. In 1858, J.P. Griess synthesized a yellow azo dye that was commercialized briefly (Kirk-Othmer Encyclopedia of Chemical Technology 1992). Other azo dyes that saw early commercialization included Chrysodine (in 1875), Congo Red (in 1884), and Bismark Brown. Following these early syntheses, numerous azo dyes have been made and it is estimated that over 2,000 are in use (Colour Index, 3rd Ed.). Wastewaters are produced during the synthesis and use of dyes. Such wastewaters must be treated. The most important criterion for treatment of wastewater is that associated toxicity is reduced to acceptable levels. Similarly, odors must be reduced and the amount of dissolved material must be reduced. Decolorization of water is also a primary goal of water purification processes and one that is critical to dye-containing wastewaters.
