Color Removal from textile effluents using flyash as a low cost adsorbent
Industrial development is directly related to quantum of power generation and utilization
in any country. Therefore, industrial development and environmental pollution go hand in
hand. In India, where a projected quantity of about 220 million tones of coal and lignite
are to be used in power generation by the turn of century, an estimated 70-80 million
tones of fly ash will be generated. The concentration and effective utilization of fly ash
generated from burning fuels in thermal power plants have attracted worldwide attention
in view of the large disposal problem without detriment to environment. The potentiality
of fly ash as catalyst in destructive decolorization of various aqueous dye solutions using
hydrogen peroxide was reported . Also, it is widely reported that fly ash generated
from coal / lignite fired thermal power stations is a very good adsorbent for the color
removal [3].
On the other hand, India is facing another type of environmental problem. Thousands of
small scale dyeing units, employing millions of people, generates enormous amount of
polluted water. Mostly the areas situated around industrial belts are under stress due to the
continuous disposal of the untreated water. The quality of water is continuously
deteriorating due to addition of toxic dyeing effluents. Dyeing effluents from textile
in any country. Therefore, industrial development and environmental pollution go hand in
hand. In India, where a projected quantity of about 220 million tones of coal and lignite
are to be used in power generation by the turn of century, an estimated 70-80 million
tones of fly ash will be generated. The concentration and effective utilization of fly ash
generated from burning fuels in thermal power plants have attracted worldwide attention
in view of the large disposal problem without detriment to environment. The potentiality
of fly ash as catalyst in destructive decolorization of various aqueous dye solutions using
hydrogen peroxide was reported . Also, it is widely reported that fly ash generated
from coal / lignite fired thermal power stations is a very good adsorbent for the color
removal [3].
On the other hand, India is facing another type of environmental problem. Thousands of
small scale dyeing units, employing millions of people, generates enormous amount of
polluted water. Mostly the areas situated around industrial belts are under stress due to the
continuous disposal of the untreated water. The quality of water is continuously
deteriorating due to addition of toxic dyeing effluents. Dyeing effluents from textile
industries are highly toxic as they contain a large number of metal complex dyes [4&5]
(e.g. Cr and Co complexes). The high concentration of such dyes causes many water
borne diseases and increases the BOD of receiving waters [6]. Hundreds of small-scale
dyeing industries are facing closure since they are not treating their effluents. It is not
economical for them to treat the effluent. Hence, it is imperative that a suitable treatment
method should be devised. In the present work, adsorption studies are carried out for
treatment of dyeing effluents by using fly ash and activated carbon as adsorbents. Fly ash
obtained from Vijayawada Thermal Power Plant (VTPS), Vijayawada & National
Thermal Power Corporation (NTPC), Ramagundam and activated carbon from M/S R.K.
Carbons, Hyderabad in Andhra Pradesh, India were taken for experiments.
(e.g. Cr and Co complexes). The high concentration of such dyes causes many water
borne diseases and increases the BOD of receiving waters [6]. Hundreds of small-scale
dyeing industries are facing closure since they are not treating their effluents. It is not
economical for them to treat the effluent. Hence, it is imperative that a suitable treatment
method should be devised. In the present work, adsorption studies are carried out for
treatment of dyeing effluents by using fly ash and activated carbon as adsorbents. Fly ash
obtained from Vijayawada Thermal Power Plant (VTPS), Vijayawada & National
Thermal Power Corporation (NTPC), Ramagundam and activated carbon from M/S R.K.
Carbons, Hyderabad in Andhra Pradesh, India were taken for experiments.
CHARACTERISTICS OF FLY ASH
Fly ash is a finely divided residue resulting in from the combustion of powdered coal or
lignite and collected from flue gas of pulverized fuel fired boilers with the help of
electrostatic precipitators. It is generally gray in color, abrasive, refractory, acidic in
nature. It has a specific surface area, which varies between 2500 to 7000 cm2/gram.
Particle size of fly ash ranges from as high as 120 to 960 microns to less than 5 microns.
The specific gravity is found to vary between 2.3 to 2.5 and bulk density is in the range of
600 to 900 kg/m3. Fly ash possesses an adsorbent capacity, which depends mainly on the
amount of unburnt substances within its surface, usually ranging from 12 to 30% by
weight [7]. This adsorbent capacity allows the removal from waste waters of either the
color or the soluble and suspended organic pollutants. Fly ash is found to have also good
settling capacity, which enables it to remove suspended solids by behaving as a “settling
aid”. The quick fly ash settling also provokes the formation of an impermeable layer on
the bed of the receiving body which prevents the pollutants from going up to the surface
water. It has been noticed that the increase of water hardness induced by fly ash addition
is not remarkable [7]. Further more, Calcium salts contained in fly ash (mainly CaSO4
and CaO) lead to the neutralization of acid waters and alkaline dephorisation up to such
low concentrations as to permit the reduction of the eutrophications phenomena [8]. By
such absorptive treatment of effluents from chemical industries and textile dying
industries with different amounts of fly ash, significant reductions induced in COD and
adsorbance were clearly observed.
Fly ash is a finely divided residue resulting in from the combustion of powdered coal or
lignite and collected from flue gas of pulverized fuel fired boilers with the help of
electrostatic precipitators. It is generally gray in color, abrasive, refractory, acidic in
nature. It has a specific surface area, which varies between 2500 to 7000 cm2/gram.
Particle size of fly ash ranges from as high as 120 to 960 microns to less than 5 microns.
The specific gravity is found to vary between 2.3 to 2.5 and bulk density is in the range of
600 to 900 kg/m3. Fly ash possesses an adsorbent capacity, which depends mainly on the
amount of unburnt substances within its surface, usually ranging from 12 to 30% by
weight [7]. This adsorbent capacity allows the removal from waste waters of either the
color or the soluble and suspended organic pollutants. Fly ash is found to have also good
settling capacity, which enables it to remove suspended solids by behaving as a “settling
aid”. The quick fly ash settling also provokes the formation of an impermeable layer on
the bed of the receiving body which prevents the pollutants from going up to the surface
water. It has been noticed that the increase of water hardness induced by fly ash addition
is not remarkable [7]. Further more, Calcium salts contained in fly ash (mainly CaSO4
and CaO) lead to the neutralization of acid waters and alkaline dephorisation up to such
low concentrations as to permit the reduction of the eutrophications phenomena [8]. By
such absorptive treatment of effluents from chemical industries and textile dying
industries with different amounts of fly ash, significant reductions induced in COD and
adsorbance were clearly observed.
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