Produção de nanofibras compostas de CuO para remoção de chumbo (II) de soluções aquosas

Abstract

Water contamination by heavy metals such as lead is a major concern due to the potential health hazards associated with exposure to this metal. In this context, the main objective of this study was the development of nanofibers composed of copper oxide (II) (CuO) and the evaluation of their performance as adsorbents for lead (II) in aqueous solutions. The nanofibers were produced using the centrifugal spinning technique with the Forcespinning® equipment, followed by calcination to obtain the nanofibers composed of CuO. The nanofibers were characterized before and after the calcination step using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and Brunauer-Emmet-Teller (BET) analysis. The SEM results showed a transition in the morphology of the smooth cylindrical fibers to a network of macroporous fibers after the calcination step. The FTIR spectrum of the nanofibers composed of CuO exhibited a peak at 528 cm-1, attributed to Cu-O vibrations, indicating the formation of CuO after calcination. In thermogravimetric analysis, the nanofibers composed of CuO exhibited a mass loss of 15.78% as the temperature was increased from 25 to 999.6 ºC, indicating good thermal stability of the material. X-ray diffraction analysis showed diffraction peaks corresponding to the monoclinic crystalline structure of CuO in the nanofiber composed of CuO. The results of BET surface analysis indicated a reduction in surface area from 36.18 m² g-1 for PAN/CuSO4 nanofibers to 2.37 m² g-1 for nanofibers composed of CuO. Adsorption studies were conducted using the nanofibers composed of CuO as adsorbents and lead (II) as the adsorbate in aqueous solution. Experiments were performed to evaluate the effect of pH, adsorption kinetics, adsorption equilibrium, and thermodynamic parameters. The adsorption of lead (II) was favorable at pH 5.8 and 298 K, with a maximum adsorption capacity of 151.34 mg g-1 according to the Hill model. The model that best described the kinetic data was the pseudo-first-order model. The Hill model provided the best fit for the equilibrium data. The thermodynamic parameters indicate that the adsorption process was favorable, spontaneous, and exothermic. The nanofibers composed of CuO exhibited excellent stability after two regeneration cycles, maintaining 97.51% of their original adsorption capacity in the second cycle. Therefore, the results showed that nanofibers composed of CuO have a high potential as a lead (II) adsorbent.