Environmental Engineering Reference
In-Depth Information
In recent years, adsorption phenomenon has emerged as a most power-
ful tool for purification and separation. The beauty of the phenomenon
is that it is controlled by various parameters, viz. initial adsorbate con-
centration, pH, adsorbent dose, contact time, particle size of adsorbent,
temperature, etc., and this process is operative in most natural, physical,
biological and chemical systems [16]. Adsorption operations employing
solids such as activated carbon and synthetic resins as adsorbents are used
widely in industrial applications and for purification of water and wastewa-
ter. In the past few years, several types of adsorbents have been lucratively
employed for the removal of a wide range of pollutants including metals,
dyes, phenols, insecticides, poly-hydrocarbons, etc., from aqueous solu-
tions. Voluminous literature has piled up in the last two decades on this
subject and efforts have been made to keep pace with the latest develop-
ments reported in this direction.
In order to reduce the operation cost there has been considerable interest
in using low-cost adsorbents for decolorization of wastewater. These mate-
rials include chitosan, zeolite, fly ash, coal and oxides, agricultural wastes,
lignocellusic wastes, etc. Very limited work has been so far reported, where
animal waste material such as hairs, bones, etc., have been used as adsor-
bent. This laboratory developed Hen Feathers as potential adsorbent and
received exceptionally good results, particularly for the removal of dyes
from wastewater [17-26]. This chapter is an attempt to exhibit the efficacy
of hen feathers to eradicate azo dyes from wastewater. In order to demon-
strate the adsorption capabilities of hen feathers, azo dyes are deliberately
chosen due to the wide applicability and hazardous nature of azo dyes.
This chapter will present the results on the adsorption of two azo dyes,
Tartrazine and Amaranth, by Hen Feathers.
11.2
Adsorbate Materials - Azo Dyes
Azo dyes are the largest (more than 50% of all dyes) and most important
class of synthetic organic dyes due to their bright colors, excellent color
fastness, easy application, chemical stability and versatility. Azo dyes are
the class of dyes which are characterized by the presence of one or more
azo (-N=N-) groups, which is attached to aromatic ring(s). These dyes
possess different chemical structures, which are primarily based on substi-
tuted aromatic and heterocyclic groups. The presence of aromatic groups
in the structure of the dye accounts for the stable nature of the organic azo
molecules. Presence of the steady azo-group and complex aromatic struc-
ture makes these dyes resistant to light, acids, bases, oxygen, biological or
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