18-05-2012, 01:22 PM
The use of freshwater fish scale of the species Leporinus elongatus
as adsorbent for anionic dyes
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Abstract
Fish scale of the species Leporinus elongatus
was tested as an adsorbent for anionic Remazol dyes.
Characterization has suggested that hydroxyl, phosphate,
amides I, II, and III, and carbonate groups are the potential
sites of adsorption. From solution calorimetry, values of
thermal effects, Qint, and amount of dye that interacts, nint,
were determined. The adsorption order observed was
Yellow-dye/scale[Red-dye/scale[Blue-dye/scale.
Introduction
Dyes used in the textile industry represent a large and
important group of chemicals among the different aqueous
pollutants that get mixed in wastewater. The use of reactive
dyes has grown rapidly due to the increasing use of cellulosic
fibers and the technical and economic limitations of
other dyes used for these fibers [1]. Most of the textile dyes
are anionic due to the presence of sulfonic acid groups in
their molecules to induce water solubility. Since these
species are soluble in water and not easily biodegradable,
they may still remain in the effluent even after extensive
treatment, thus their discharge is currently one of the
world’s major environmentaIn order to obtain the fish scales, Piau fishes (Leporinuselongatus) with an average length of about 20 cm
(1.5–2.0 kg) were obtained from a free market in Itabaiana-
SE in the summer of 2008. The anionic dyes Remazol
Yellow (RY), Remazol Blue (RB) and Remazol Red (RR)
were provided by The Dystar Dyes Company and used
without purification. The chemical structures of the dyes
were shown earlier [19].
Results and discussion
FTIR analysis suggests the importance of functional groups
of fish scale such as hydroxyl, phosphate, carbonate, and
amides during dyes interactions. The main information of
the FTIR spectrum of Piau fish scale can be find in Table 1.
FTIR spectrum of pure scale shows strong absorption
bands at 600 and 1,036 cm-1, corresponding to phosphate
groups in the apatite lattice, and peaks at 876
Conclusions
In this work, scales of Brazilian Piau fish were characterized
and used for adsorption of anionic dyes from aqueous
solutions in an isothermal calorimetric cell. The FTIR
spectra of Piau scales, before and after dyes adsorption,
suggest that the hydroxyl, phosphate, amides I, II, and III,
Table 2 Results of interaction for a saturated monolayer per gram of material, Qmon, maximum adsorption capacity to form a monolayer, Nmon,
and thermodynamic parameters of the interaction processes dyes/scale at 298.15 K
Interaction processes -Qmon/J g-1 Nmon/lmol g-1 -DmonHm/kJ mol-1 -DmonG/kJ mol-1 -DmonS/J K-1 mol-1
RB/SCALE 2.84 0.341 83.28 17.92 219.22
RY/SCALE 6.29 0.315 199.68 20.97 599.40
RR/SCALE 3.88 0.321 120.87 22.48 330.00
The use of freshwater fish scale
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and carbonate groups are the potential sites of adsorption.
The adsorption order observed was Yellow dye/scale[Red
dye/scale[Blue dye/scale. The adsorption data were successful
modeled to the Langmuir adsorption model. The
exothermicity of the adsorption systems suggests ionic
interactions as a major contribution.
1,438 cm-1 assigned to carbonate anions substituted for
phosphate ions in the apatite lattice [16].