Preparação de membranas de poliestireno expandido sulfonado para remoção de metais pesados

Abstract

Expanded polystyrene (EPS), commonly known as Styrofoam, is widely used in disposable packaging and thermal insulation applications. However, its low biodegradability, combined with inadequate waste management, confers a high potential for environmental impact in Brazil, thereby necessitating the adoption of recycling and valorization strategies. This study aimed to reuse post-consumer EPS waste for the preparation of electrospun sulfonated polystyrene membranes targeting the removal of metal ions. The methodology involved the collection and pre-treatment of disposable trays, followed by chemical modification through sulfonation and processing via electrospinning under different operational conditions. The membranes were characterized before and after sulfonation using Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA), and contact angle measurements. The adsorption capacity for Fe³⁺ and Co²⁺ ions was evaluated in a percolation-based filtration system, with monitoring by UV-Vis spectroscopy and quantification of residual ions by X-ray Fluorescence (XRF). The results revealed fibers with a microporous morphology favorable for adsorption and an increase in surface area resulting from the electrospinning process. The incorporation of sulfonic groups was confirmed by characteristic FTIR bands at 3347, 1185 and 1051 cm-¹, as well as by TGA, which indicated a sulfonation degree of 13.9%. XRD analysis confirmed that the polymer structure remained predominantly amorphous after sulfonation. An increase in water affinity was observed due to a reduction in the contact angle, although the hydrophobic character persisted. The adsorption efficiency for the Fe³⁺ ion reached 84.5% after two successive cycles, whereas for the Co²⁺ ion it was 55.33% in the first cycle, with no additional removal observed in the second cycle. It is concluded that EPS recycling via sulfonation and electrospinning is a sustainable and technically viable strategy, resulting in functional membranes that are effective for the removal of heavy metals in filtration processes.