Avaliação da fibra de coco (mesocarpo do fruto de Cocos nucifera L.) como adsorvente para remoção do agrotóxico parationa metílica de meio aquoso
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Data
2017-04-07
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Universidade Federal de Goiás
Resumo
In this work, experiments were performed to study the potential of coconut fiber (Cocos
nucifera L.) as adsorbent for removing the pesticide parathion methyl from water. The
analytical methodology used to quantify the pesticide in the adsorption studies was based on
solid phase extraction (SPE) and gas chromatography with electron capture detection
(GC/ECD). The method were validated and showed good analytical features in terms of
selectivity, linearity, accuracy (recovery: 100.4%), precision (coefficient of variation:
9.63%;), limit of detection (0.003 mg L-1
) and quantification (0.010 mg L-1
). The matrix effect
in pesticide quantification was evaluated and the results showed an enhanced
chromatographic response for the parathion methyl in all the concentrations evaluated due to
interference of endogenous coconut fiber compounds present in the solution after adsorption
tests, therefore, the quantification was made using matrix-standard calibration solutions to
compensate for matrix-induced effects and to obtain more accurate results. The adsorbent
characterization (FTIR, MEV, surface area and pHpcz) showed that coconut fiber surface is
composed of very irregular particles, with many cavities (pore diameter: 3.48 nm) and
external surface area of 3.64 m2
g
-1
. The presence of several functional groups: carboxylate,
hydroxyl, carboxyl, among others was observed. The pH at point of zero charge (pHpcz) for
the adsorbent was 5.85. The adsorption capacity of the coconut fiber was evaluated under
different parameters: adsorbent treatment, adsorbent dosage, contact time and concentration
of the pesticide. The adsorbent treatment with water, HCl or NaOH did not affect the
adsorption capacity (75.6% of removal was obtained, independently of the treatment). The
increasing in the adsorbent dosage of 5 to 20 g L-1 caused an increasing in the adsorption
capacity from 25.0% to 76.6%. The adsorption equilibrium process was reached after 90
minutes of contact, with 86.1% of removal. The kinetic study showed that the Avrami kinetic
model was the best fit for the experimental data. The adsorption capacity improved as
function of the pesticide concentration increasing. The experimental data were fitted to
Langmuir, Freundlich and Sips isotherm models and the best fit was obtained with Freundlich
and Sips models. The maximum adsorption capacity (Qmax) were 39.8547 mg g-1
. Additional
tests showed that the adsorption capacity was slightly affected when using real samples
(natural water) in the adsorption experiments (82.24% removal) and presented excellent
adsorption capacity when used in an alternative column adsorption procedure (85.73%
removal). The results indicate that the coconut fiber has a great potential to be used as
adsorbent material for the treatment of water contaminated with the pesticide methyl
parathion.
Descrição
Palavras-chave
Fibra de coco, Adsorvente, Parationa metílica, Extração em fase sólida, Efeito de matriz, Cromatografia gasosa, Coconut fiber, Adsorbent, Methyl parathion, Solid phase extraction, Matrix effect, Gas chromatography
Citação
CARDOSO, J. M. Avaliação da fibra de coco (mesocarpo do fruto de Cocos nucifera L.) como adsorvente para remoção do agrotóxico parationa metílica de meio aquoso. 2017. 83 f. Dissertação (Mestrado em Química) - Universidade Federal de Goiás, Catalão, 2017.