Ultrasound Activated Biocomposite of Saccharomyces cerevisiae and Magnetic Nanoparticles with Cellulose Acetate Microfibers for Cadmium (II) Removal

Abstract

Heavy metal contamination in aquatic environments has become a serious global concern due to its toxicity, persistence, and bioaccumulation in living organisms. Therefore, the development of efficient, low-cost, and environmentally friendly adsorbents for heavy metal removal is of great importance. Conventional adsorbents such as Saccharomyces cerevisiae, Fe₃O₄ nanoparticles, and electrospun cellulose acetate (CA) microfibers have inherent limitations that restrict their practical applications in this field. Yeast cells, despite possessing abundant functional groups, suffer from low mechanical stability, difficult recovery, and limited adsorption capacity. Fe₃O₄ nanoparticles tend to aggregate, leading to a decrease in active surface area and potential secondary contamination. Furthermore, pure CA microfiber mats often exhibit low adsorption efficiency and surface fouling. To overcome these limitations, a biocompatible composite adsorbent was synthesized by combining ultrasound-treated Saccharomyces cerevisiae yeast, Fe₃O₄ magnetic nanoparticles, and electrospun cellulose acetate (CA) pads. The synergistic combination of these components resulted in increased surface area, improved mechanical stability, reduced nanoparticle aggregation, and facile magnetic separation of the adsorbent after use. SEM images and FTIR spectra confirmed the successful loading of Fe₃O₄ nanoparticles onto the yeast cells and the formation of the composite adsorbent. The maximum adsorption capacity of 11.84 mg g⁻¹ was achieved under optimal conditions, including a pH of 5.19, a contact time of 3 h, and an Fe₃O₄-loaded yeast dosage of 0.2 g. Isotherm modeling demonstrated a better fit with the Freundlich model (R² = 0.97), indicating a heterogeneous surface and multilayer adsorption behavior. Kinetic analysis showed that the adsorption process followed the pseudo-first-order model (R² = 0.97, qₑ = 3.6 mg g⁻¹), suggesting that physical adsorption was the dominant mechanism. The combined effects of the porous CA structure, bioactive yeast, and Fe₃O₄ nanoparticles contributed to the enhanced adsorption performance.