Environmental Engineering Reference
In-Depth Information
In 1856, Sir William Perkin discovered a dye for the color mauve, which
was the first synthetic dye. The method related to the dyeing of this color
using coal and tar led to many scientific advances and the development of
synthetic dyes [24,25].
Initially the dye industry was based on the discovery of the principal that
dye chromogens associated with a basic arrangement of atoms were responsi-
ble for the color of a dye. Essentially, apart from one or two notable exceptions,
all the dye types used today were discovered in the 1800s. The discovery of
reactive dyes in 1954 and their commercial launch in 1956 heralded a major
breakthrough in the dyeing of cotton; intensive research into reactive dyes
followed over the next two decades and, indeed, is still continuing today. The
oil crisis in the early 1970s, which resulted in a steep increase in the prices of
dyestuff, created a driving force for more low-cost dyes, both by improving
the efficiency of the manufacturing processes and by replacing tinctorially
weak chromogens, such as anthraquinone, with tinctorially stronger chro-
mogens, such as (heterocyclic) azo and benzodifuranone [26,27].
1.1.3 Natural Dyes
Natural dyes which are obtained from plants, insects/animals and min-
erals are renewable and sustainable bioresource products with minimum
environmental impact. They have been known since antiquity for their use
in coloring of textiles, food substrate, natural protein fibers like wool, silk
and cotton, and leather as well as food ingredients and cosmetics [28-32].
Also, natural dyes are known for their use in dye-sensitized solar
cells [33], histological staining [34], as a pH indicator [35] and for several
other disciplines [36,37].
Over the last few decades, there has been increasing attention on vari-
ous aspects of natural dye applications, and extensive research and devel-
opment activities in this area are underway worldwide [29].
1.2
Classiication of Dyes
Dyes may be classified according to their chemical structures and their
usage or application methods. Dyes have different chemical structures
derived from aromatic and hetero-aromatic compounds, and their chro-
mophor and auxochrom groups mainly differ [18].
The most appropriate system for the classification of dyes is by chemi-
cal structure, which has many advantages. First, it readily identifies dyes
as belonging to a group that has characteristic properties, for example,
Search WWH ::
Custom Search