54
A. Geethakarthi
The pore size distribution was calculated by Barrett–Joyner–Halenda (BJH)
method and Horvath–Kawazoe (HK) method. N 2 isotherms at 77 K are used for practical reasons (e.g. simultaneous determination of the BET surface area). The method
proposed by Barrett–Joyner–Halenda (1951), known as BJH method, continued to be
used even today. In the BJH method, desorption branch of isotherm is used, which is
the desorption branch of the usual hysteresis loop of the isotherm for the mesoporous
sorbents and hence employed to deduce the mesopore size distribution. A simple and
popular method for evaluating pore size distribution of microporous materials was
proposed by Horvath and Kawazoe.
This technique has been successfully used for the determination of pore size
distribution in microporous sorbents such as activated carbons and zeolites. The
adsorption–desorption plot of the isotherm distribution showed the dominance of
the microporous carbon and the presence of mesoporous carbon (Figs. 11, 12 and
13). The optimum activation temperature was 650 °C after 180 min at a burn-off
level of 29% and 26% for SC300 and SC600, respectively.
5 Adsorption of Reactive Dyes onto Tannery
Sludge-Activated Carbons: Equilibrium Kinetic Studies
5.1 Reactive Dyes
The removal of colour from dye house liquid effluents is one of the main problems in textile industries. Reactive dyes are one of the largest problematic groups of
dyes used in the textile industries. As the reactive dyes are highly water soluble and
practically non-biodegradable, they are not degraded in municipal activated sludge
treatment plants; nor are they substantially removed via adsorption onto the biomass.
Removal of reactive dyes is necessary for preventing the recalcitrant compounds from
getting released into the environment and for efficient and complete dye removal.
Various types of reactive dyes are commercially available. Their common feature
is a chemical reaction with the textile fibre to achieve a covalent dye–fibre bond.
Reactive dyes are typically azo-based chromophores combined with different types
of reactive groups. Reactive dyes interact with the active groups on the cell surface
by surface adsorption, ion exchange, complexation, chelation and microprecipitation
[50]. They are characterized by nitrogen to nitrogen double bonds, azo bonds used
mainly for dyeing cellulose fibres. They differ from all other classes of dyes in that
they get bound to the textile fibres such as cotton to form covalent bonds. They have
the favourable characteristics of bright colour, simple application techniques and
low energy consumption and are used extensively in textile industries. The reactive
systems of these dyes react with ionized hydroxyl groups on the cellulose substrate
[68]. However under alkaline conditions, the hydroxyl ions compete with the cellulose substrate resulting in a percentage of hydrolysed dyes which can no longer react
with the fibre [3, 68]. Hence, their removal is of great importance. Dyes with two
A. Geethakarthi
The pore size distribution was calculated by Barrett–Joyner–Halenda (BJH)
method and Horvath–Kawazoe (HK) method. N 2 isotherms at 77 K are used for practical reasons (e.g. simultaneous determination of the BET surface area). The method
proposed by Barrett–Joyner–Halenda (1951), known as BJH method, continued to be
used even today. In the BJH method, desorption branch of isotherm is used, which is
the desorption branch of the usual hysteresis loop of the isotherm for the mesoporous
sorbents and hence employed to deduce the mesopore size distribution. A simple and
popular method for evaluating pore size distribution of microporous materials was
proposed by Horvath and Kawazoe.
This technique has been successfully used for the determination of pore size
distribution in microporous sorbents such as activated carbons and zeolites. The
adsorption–desorption plot of the isotherm distribution showed the dominance of
the microporous carbon and the presence of mesoporous carbon (Figs. 11, 12 and
13). The optimum activation temperature was 650 °C after 180 min at a burn-off
level of 29% and 26% for SC300 and SC600, respectively.
5 Adsorption of Reactive Dyes onto Tannery
Sludge-Activated Carbons: Equilibrium Kinetic Studies
5.1 Reactive Dyes
The removal of colour from dye house liquid effluents is one of the main problems in textile industries. Reactive dyes are one of the largest problematic groups of
dyes used in the textile industries. As the reactive dyes are highly water soluble and
practically non-biodegradable, they are not degraded in municipal activated sludge
treatment plants; nor are they substantially removed via adsorption onto the biomass.
Removal of reactive dyes is necessary for preventing the recalcitrant compounds from
getting released into the environment and for efficient and complete dye removal.
Various types of reactive dyes are commercially available. Their common feature
is a chemical reaction with the textile fibre to achieve a covalent dye–fibre bond.
Reactive dyes are typically azo-based chromophores combined with different types
of reactive groups. Reactive dyes interact with the active groups on the cell surface
by surface adsorption, ion exchange, complexation, chelation and microprecipitation
[50]. They are characterized by nitrogen to nitrogen double bonds, azo bonds used
mainly for dyeing cellulose fibres. They differ from all other classes of dyes in that
they get bound to the textile fibres such as cotton to form covalent bonds. They have
the favourable characteristics of bright colour, simple application techniques and
low energy consumption and are used extensively in textile industries. The reactive
systems of these dyes react with ionized hydroxyl groups on the cellulose substrate
[68]. However under alkaline conditions, the hydroxyl ions compete with the cellulose substrate resulting in a percentage of hydrolysed dyes which can no longer react
with the fibre [3, 68]. Hence, their removal is of great importance. Dyes with two