Meios filtrantes para ar de alta eficiência obtidos por eletrofiação usando poliestireno expandido reciclado

Abstract

The increasing generation of polystyrene (PS) waste has driven the search for efficient reuse strategies. A promising alternative lies in its reutilization to produce filter media via electrospinning, combining air pollution mitigation with waste recovery and enhancing the sustainability of the process. Therefore, this study proposes a rapid electrospinning method (5 minutes) for producing PS-based filters aimed at the removal of nano- and microparticles from the air. A statistical evaluation was conducted to investigate the influence of polymer solution concentration (5–25%), percentage of DL-limonene (10–50%), applied voltage (15–25 kV), and injection flow rate (0.4–1.2 mL/h) on particle collection efficiency, air permeability, and fiber diameter. To improve mechanical strength, PS/PET hybrid filters were developed using three different methods: a trilayer arrangement and dual-needle setups with separate solutions injected either from the same side or from opposite sides of a rotating collector. In this stage, the PET content was varied to assess its effect on elastic modulus, maximum tensile strength, and elongation at break. To enhance applicability, PS fibers were mechanically processed into short nanofibers to formulate suspensions in isopropyl alcohol, ethanol, water, and their mixtures. Suspensions in isopropyl alcohol were deposited onto twelve different substrates—including common materials and low-efficiency filters—using vacuum filtration and spray deposition, and subsequently evaluated for their micro- and nanoparticle collection performance. The optimal condition for nanoparticle collection was achieved with 13.5% PS, 50% DL-limonene, 25 kV, and 1.2 mL/h, resulting in a collection efficiency of 99.97 ± 0.01%, air permeability of 2.6 ± 0.5 × 10⁻¹³ m², mean fiber diameter of 708 ± 176 nm, and a quality factor of 0.19 Pa⁻¹. DL-limonene, a natural solvent, proved advantageous by significantly enhancing collection efficiency and reducing fiber diameter. Incorporation of PET increased the mechanical strength of the filters, with the configuration using opposite arranged needles showing the best performance. Although the collection efficiency dropped to approximately 95%, both the tensile strength and elongation at break increased by up to 16-fold compared to PS-only filters. While ethanol-based suspensions produced more uniform membrane surfaces, isopropyl alcohol yielded higher filtration efficiencies. The deposition of short nanofibers substantially improved the filtration efficiency of various substrates, achieving performance levels comparable to HEPA H13 filters. Among the tested methods, spray deposition was the most effective, providing up to 2% higher collection efficiencies and normalized pressure drops (∆P/L) up to 3.2 times lower. The FS-15P Needle-Punched foam stood out, exhibiting a ∆P/L approximately 75.6 times lower and collection efficiencies for both nano- and microparticles within 1% of the HEPA H13 standard. Beyond its technical performance, the spray method offers practical advantages in terms of applicability and ease of handling, particularly when compared to continuous electrospun nanofibers. This approach facilitates broader use by non-specialized operators and supports the commercial viability of nanofiber suspensions. Overall, the findings highlight the potential of recycled polystyrene as a promising raw material for the development of efficient and sustainable filter media for atmospheric pollution control.