Desenvolvimento de plataforma analítica de baixo custo para avaliação da adsorção do corante fluoresceína

Abstract

The use of dyes is present in industries ranging from textile, pharmaceuticals to food manufacturing. However, improper disposal into rivers and lakes represents a growing environmental concern, as it not only harms the environment but also human health. Globally, researchers have been dedicated to developing methods to remediate and quantify environmental contaminants, and among the various approaches explored, the use of adsorbents, in conjunction with low-cost detection techniques, stands out. This combination holds significant potential within emerging technologies, offering a viable and accessible solution for environmental contamination monitoring and mitigation. Thus, this study aims to develop a low-cost platform to assess the capacity of Typha angustifolia L. leaves in adsorbing Fluorescein Sodium (FS) dye in aqueous samples. The determination of adsorption percentage was conducted through readings before and after adsorption, where the sample is excited by a blue LED (460 nm), and the signal reading is performed by a TSL2561 sensor. Typha angustifolia L. leaves demonstrated an adsorption potential exceeding 40% against FS dye. Characterizations of Typha angustifolia L. leaves were carried out through infrared spectroscopy (IR) analysis, scanning electron microscopy (SEM), and zero point of charge (pHPCZ). The characterization results indicated a pHPCZ of 6.76. IR analysis revealed a characteristic composition of plant materials, with functional groups characteristic of cellulose, hemicellulose, and lignin structures. SEM unveiled a heterogeneous and porous surface. Kinetic data of adsorption were evaluated according to pseudo-first-order, pseudo- second-order, Avrami, Weber Morris, and Elovich models, with the Elovich model showing the best fit, reaching equilibrium after 30 minutes of contact. The influence of concentration on the adsorption mechanism was assessed using Langmuir, Freundlich, and Sips isotherm models, all showing excellent fit, with R2 values exceeding 0.95. A molecular dynamics study was conducted in conjunction with experimental assays, both indicating that the species at pH=2 interacts most with the adsorbent, resulting in greater dye removal. Adsorption results were measured through the developed platform and compared with those obtained from the spectrophotometer, showing no statistical differences (t and f, 95% confidence). The optimized conditions of the platform resulted in a linear range of 0.1 to 25 mg L−1, with an analysis time and sample volume of 1 minute and 3.0 μL, respectively. Recoveries between 82% and 103% were achieved. The obtained limits of detection (LOD) and quantification (LOQ) were 0.1 and 0.025 mg L−1, respectively. Thus, it is concluded that the developed platform can be employed in determining FS adsorption through Typha angustifolia L. leaves.