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A
significant amount of Achyranthes aspera is discarded
as agriculture waste weed from paddy field. In the present
investigation, the carbonaceous product obtained by the treatment
of A. aspera with sulphuric acid was used to study
its efficiency as an adsorbent for the removal of methylene
blue from aqueous solution. Batch adsorption of methylene
blue (MB) on A. aspera carbon (AAC) was studied as
a function of agitation time, initial dye concentration, adsorbent
concentration and pH in order to explore the potential use
of this material as low cost adsorbent for dye removal. Among
the isotherm models applied to the equilibrium data, Redlich-Peterson
model better predicted the experimental values. The adsorption
capacity was 204.23 mg/g at an initial pH of 7.0 ± 0.1
and at 32 °C. The kinetics analyses were made by using
pseudo-first order and pseudo-second order models. It was
found that the adsorption kinetics of MB on AAC obeyed pseudo-second
order sorption kinetics. The results indicated the potential
use of AAC as sorbent for the removal of basic dye from aqueous
solution.
The
color removal from dyeing industry effluents becomes day-by-day
more than an important objective of wastewater treatment processes.
A number of methods have been developed for the removal of
synthetic dyes from water and wastewater to minimize their
effect on the environment. The technologies that have been
used to reduce the pollution content of water include chemical
precipitation, membrane processes, adsorption, aerobic and
anaerobic microbial degradation, catalytic oxidation, photo
catalytic oxidation and electro chemical treatment. Among
the various treatment technologies adsorption is one of the
most efficient methods. The successful prediction of adsorption
isotherms of dyes on activated carbon has been reported (McKay
et al., 1998). However, commercially available activated
carbons are expensive, so they may not be economical for wastewater
treatment purpose. Recently various kinds of activated carbon
have been used as low cost adsorbents for the removal of heavy
metals, organics and dyes from water and wastewater (Chaudhary
et al., 2002; Banat et al., 2003; Ho et al.,
2005; Gregorio, 2006; Stephen and Sulochana, 2006; and Hameed
et al., 2007).
In
the present study, A. aspera, which is a locally available
and naturally abundant agricultural waste product was evaluated
for its ability to remove MB from aqueous solution. The MB
is a thiazine (cationic) dye, which is one of the most commonly
used dye for coloring among all other dyes of its category.
It is generally used for dyeing cotton, wool, etc. The dye
causes eye burns, which may result in permanent injury to
the eyes of human and animals. If swallowed, the dye causes
irritation to the gastrointestinal tract with symptoms of
nausea, vomiting, and diarrhea. It may also cause methemoglobinemia,
cyanosis, convulsions, tachycardia, and dyspnea, if inhaled.
It is likely to cause irritation to the skin (Senthil et
al., 2004).
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