Estudo do bagaço de cevada e da palha de milho como materiais adsorventes alternativos para remoção do agrotóxico carbaril de meio aquoso contaminado
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Data
2018-08-17
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Universidade Federal de Goiás
Resumo
In this dissertation, the materials corn straw and barley bagasse were investigated as
alternative adsorbents for removal of the carbaryl pesticide from aqueous medium. For
this, both materials were ground to obtain uniform particles (granulometry between 20 and
48 mesh) and treated with hydrated ethyl alcohol. The quantification of the carbaryl
pesticide was made by High Efficiency Liquid Chromatography with UV-vis detector. The
values of LD and LQ for the determination of the carbaryl pesticide by liquid
chromatography using the method used were 0.01 mg L-1 and 0.10 mg L-1, respectively.
The characterization of the adsorbent materials by FTIR showed the presence of the
functional groups: hydroxyl, carbonyl and methyl, very common in lignocellulosic
materials. The pH at the zero loading point (pHPCZ) was 7.08 for barley bagasse and 6.44
for corn straw. The adsorption capacity of the investigated materials was evaluated under
different parameters such as material dose (g L-1), contact time between the pesticide
solution and the adsorbent material (min) and the concentration of the pesticide in the
solution (mg L-1). An alternative adsorption procedure was also proposed with the
adsorbents packaged in a column where different doses of the adsorbents were
evaluated and finally the adsorption process was evaluated using natural water samples.
From the study of the dose of the materials the dose of 20 g L-1, equivalent to 200 mg of
the adsorbent material in 10 mL of solution was selected, where 45.1% of the carbaryl
was obtained when the barley bagasse was used and 49.2% when corn straw was used.
For both adsorbents the kinetic study showed that the adsorption of the carbaryl
agrochemical is best represented by the Avrami kinetic model, indicating that the
adsorption of the carbaryl is not constant, but follows multiple orders. The maximum
adsorption capacity (Qmax) was obtained by the construction of adsorption isotherms,
where it was verified that the experimental data of the process of adsorption of the
carbaryl by the barley bagasse is better represented by the Langmuir model providing a
value of Qmax of 6, 5244 mg g-1. For corn straw, the Sips model was the most adequate
with a Qmax value of 1.2625 mg g -1. In the column adsorption procedure the barley
bagasse was efficient in all the doses evaluated, obtaining practically the same rate of
removal as the procedure performed in batch mode, however in a much shorter time. As
for the adsorbent corn straw, the removal through the column procedure was much less
effective, suggesting that for this material the batch procedure is more adequate. In the
adsorption study using natural water samples as an aqueous matrix, it was verified that
the adsorption process of the carbaryl by both adsorbents can be affected by the pH of
the medium and also by the presence of other compounds present in the aqueous matrix.
In general, the results indicate that the barleybagasse and corn straw materials can be
used as adsorbent materials in the treatment of aqueous medium contaminated with the
carbaryl pesticide.
Descrição
Palavras-chave
Adsorção, Agrotóxico, Carbaril, Cromatografia líquida, Adsorvente alternativo, Palha de milho, Bagaço de cevada, Adsorption, Pesticide, Carbaryl, Liquid chromatography, Alternate adsorbent, Corn straw, Barley bagasse
Citação
MILHOMEM, K. P. Estudo do bagaço de cevada e da palha de milho como materiais adsorventes alternativos para remoção do agrotóxico carbaril de meio aquoso contaminado. 2018. 103 f. Dissertação (Mestrado em Química) - Universidade Federal de Goiás, Catalão, 2018.