Síntese de um compósito empregando resíduo do processamento de quartzito e quitosana e sua utilização na adsorção do corante reativo preto 5
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Data
2020-02-20
Autores
Coura, Jean Cota
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Universidade Federal do Espírito Santo
Resumo
The ornamental rocks extraction and the culture of shrimps are activities that perform
an important role in the Brazil economy. However, the ornamental rocks
manufacturing, as well as the cleaning of shrimps yield a great quantity of solid wastes
that damage the environment when inappropriately discarded. Another environmental
problem is the release of effluent containing dye, such as Reactive Black 5 (RB 5),
causing the contamination and eutrophication of water. Among the methods of
wastewater treatment, the adsorption is highlighted due to its efficiency and operational
simplicity. Nevertheless, this method becomes feasible economically only when low-
cost alternative adsorbent materials are used. Thus, the aim of this study was
synthesizing a composite formed by chitosan extracted from shrimp husks dispersed
on the quartzite powder, which is a residue from the ornamental stone processing. This
adsorbent material was applied in adsorption of Reactive Black 5 dye. The composite
was characterized by Fourier transformed infrared (FTIR), scanning electron
microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and
thermogravimetric analysis (TGA). The adsorption kinetics, adsorption equilibrium and
adsorption thermodynamics of RB 5 onto quartzite/chitosan composite were
investigated. The main functional groups of chitin and chitosan were found in FTIR
analysis attesting the success of the synthesis. The SEM micrographs showed that the
composite has a rough surface with high porosity and heterogeneity. The active sites
in the surface was filled after adsorption of dye. The elemental analysis by EDS
indicated the predominance of Si, O, and C in the composite. The XRD analysis
assigned that the quartz is the main crystalline phase of the composite, and a small
diffraction peak could be attributed to the presence of chitosan. This specie was also
confirmed by TGA. The adsorption kinetics data were better fitted to the pseudo-
second-order model, indicating that chemical interactions occur between adsorbent
and adsorbate. The Sips and Liu isotherm models described the adsorption
equilibrium. The maximum capacity of removal was found as 171.50 mg/g, at 55 °C.
The thermodynamic studies showed that the adsorption of RB 5 onto quartzite/chitosan
composite is an endothermic process with higher spontaneity as the temperature
increases. Thus, the composite synthesized in this study is a sustainable and effective
adsorbent for RP 5 removal of aqueous solutions, presenting potential to be used, also,
in the decontamination of effluents containing such pollutant.
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Palavras-chave
quartzito , quitosana , compósito , adsorção , reativo preto 5