Avaliação da capacidade de remoção do herbicida metribuzin por adsorção utilizando pó de basalto

Abstract

The use of pesticides, although their application increases agricultural productivity, generates a set of negative externalities, with both environmental and human impacts. Thus, the present study aimed to evaluate the ability to remove the herbicide metribuzin in aqueous medium using the adsorption technique using basalt powder as adsorbent. For the characterization of the adsorbent, a morphological analysis was carried out using the SEM method (scanning electron microscopy) and the determination of the functional groups using FTIR (infrared spectroscopy with Fourier transform). The SEM indicated an irregular basalt powder surface, presenting several filaments and unevenness in its structure, demonstrating favorable sites for adsorbate binding during adsorption. In FTIR, the observed spectra were comparable to mineral features in the silica polymerization range, such as plagioclase, pyroxene and olivine, characteristic of basaltic rocks, in addition to the presence of peaks of H-OH, OH, SiO2 (main component of basalt) and FeO. To quantify the metribuzin herbicide, a calibration curve was performed, based on the absorbance measured in a spectrophotometer, through which it was possible to determine the adsorbate concentration after adsorption. As for the adsorption process, the basalt powder showed a maximum adsorption capacity of 47.43 mg g-1, with the data best fitted to the linear isotherm model (R² = 0.9979). Based on the classification of the isotherms, the adsorbent indicated a favorable adsorption and physisorption process. The thermodynamic adjustments indicated that the adsorption process for the basalt powder occurs spontaneously (ΔG° < 0) and exothermally, with the release of heat (ΔH° < 0). Thus, the results obtained demonstrated that the basalt powder is efficient for the adsorption process of the metribuzin herbicide, being an economically viable and sustainable source of raw material.