Preparação e aplicação de eletrodos de pasta de carbono modificados com materiais adsortivos para detecção de compostos organonitrogenados por voltametria

Abstract

Organonitrogen compounds are inserted in various forms, such as model molecules in laboratories for various syntheses, in industrial waste, petroleum, textile effluents, active ingredient of drugs, among others. However, in spite of being applied enough, these molecules are considered environmental pollutants of difficult degradation, besides being potentially carcinogenic and mutagenic. For the control of the molecules, electrochemical techniques can be used, they are techniques that do not require previous analysis of samples, reducing the use of reagents and the time of the analyzes, besides the use of work electrodes that can be applied in diversified ones. In this context, this project has as main objective the development of work electrodes based on carbon mass modified with adsorbent material capable of detecting and quantifying molecules of quinoline and pyridine in textile effluent and (bio)fuels. For modification of the carbon mass with HZSM-5 steel fiber treated with sulfated lanthanum oxide, HZSM-5 zeolite treated with citric acid, sulfated lanthanum oxide and activated carbon (CA). Only the latter modifier presented satisfactory results in the quantification of the molecules due to the surface presentation of acid dethronation. The best proportion of the components in the composition of the carbon mass was 50:20:30 m/m graphite:CA:silicone and the optimum support electrolyte in the ammonium chloride solution acidified to pH 2 on average with Britton-Robson's solution. By cyclic voltammetry, a reduction of the embassies as molecules characterized by mass transfer by diffusion with the application of the adsorption and transfer of the irreversible type was observed, as well as the reduction mechanisms for this system. Using differential pulse voltammetry (DPV) for a pyridine and square wave (SWV) for a quinoline, LD was obtained in the order of 2.0x10-7 mol L-1 and LQ of the order of 7.0x10-7 mol L-1. The linear range of concentration varied from 1.0x10-4 to 9.0x10-7 mol L-1, with linear correlation coefficients of 0.990 and with recovery values above 92% for both as molecules. In addition, a matrix interference is observed for the analysis of the organic compounds, as well as a need for the application of surfactants for analysis, as if they were the proper analyzes.