Preparo e aplicação de eletrodo de pasta de carbono modificado com biocarvão de tucumã (Astrocaryum aculeatum) para determinação de piridina em efluente industrial utilizando técnicas voltamétricas

Abstract

The pyridine is a nitrogen molecule heterocyclic belonging to the alkaloid class, find in plants and petroleum. This substance has toxic properties, can cause kidney and liver disease and lead to death. However, this molecule is widely used in several industrial sectors, generating significant quantities of waste, which can cause contamination of rivers and soil. Therefore, pyridine is considered an environmental contaminant. The determination of pyridine these effluents can be carried out using voltammetric techniques, which are fast and show sensitivity and limits of detection (LOD) and quantification (LOQ) suitable for the quantification of this compound. To improve the selectivity and sensitivity of these techniques, modifications can be made to the working electrodes, using materials such as biochar, able of improving the interaction of the electrode with the molecule of interest. Thus, the aim of this work was the development of electrochemical sensor made of carbon paste modified with tucuma biochar (BT) for the determining pyridine in industrial effluents. To develop the methodology, different proportions of pastes were evaluated, with the 40:30:30 ratio of graphite: BT: binder being chosen. The BT was characterized by infrared spectroscopy, which demonstrated a large number of functional groups that could assist in the interaction of the electrode surface with the pyridine. The modified carbon paste was characterized by scanning electron microscopy, which showed differences in the morphology of the paste demonstrating the presence of the modifier. Cyclic voltammetry was used to characterize the charge and mass transfer process of the electrochemical system, showing that the reaction occurs with the transfer of two electrons and is an irreversible reaction controlled by diffusion. The evaluation of the supporting electrolyte determined KCl acidified with BR buffer solution at pH 2 as the best electrolyte for pyridine analysis. Under these conditions, the voltammogram obtained showed a reduction peak for pyridine, close to -1.50 V. Four analytical curves were constructed, using differential pulse voltammetry, to calculate the matrix effect (EM). The analytical curve in the absence of matrix showed good linearity with r2 of 0.994, LOD of 25.0 nmol L-1 and LOQ of 85.0 nmol L-1. The analytical curves in the presence of matrix showed good linearity for the three effluents with r2 of 0.991, 0.997 and 0995, respectively. The LOD for effluents 1, 2 and 3 were 34.9, 5.5 and 36.8 nmol L-1, respectively. The LOQ were 116.6 for effluent 1, 18.4 for effluent 2 and 122.6nmol L-1 for effluent 3. The ME was evaluated for the three effluents, presenting values above 50.0 %, indicating strong EM. Quantification of pyridine in effluents was carried out using matrix curves. The method showed recoveries close to 100% for the three effluents. The repeatability and reproducibility studies of the method showed RSD%, close to 100%, demonstrating that the method has potential application in the quantification of pyridine in textile effluents.