Bioadsorbente magnético obtenido a partir de residuos de la producción de aceite de oliva para la remoción de metales pesados

Abstract

La presencia de metales pesados (MP) en suelos, aguas superficiales y subterráneas como consecuencia de distintas actividades antropogénicas, tales como la minería, las operaciones metalúrgicas y la industria petroquímica, representa una importante problemática ambiental debido a su alta toxicidad, movilidad, persistencia y capacidad de bioacumulación. La incorporación de estos compuestos en sistemas acuosos puede ocasionar efectos contraproducentes en los ecosistemas, la vida acuática y los seres humanos. Entre las distintas alternativas propuestas, el uso de bioadsorbentes (BA) derivados de residuos agroindustriales ha adquirido gran interés en los últimos años debido al bajo costo, disponibilidad y elevada presencia de grupos funcionales capaces de interactuar con especies metálicas. Asimismo, la incorporación de partículas magnéticas permite su recuperación mediante separación magnética. En el presente trabajo se sintetizó un BA, funcionalizando partículas de magnetita con compuestos polifenólicos (Fe3O4-PF) extraídos de orujo de oliva proveniente de la industria olivícola regional de la provincia de Neuquén. Este extracto se obtuvo mediante extracción sólido-líquido con etanol y ácido cítrico. Los materiales obtenidos fueron caracterizados mediante diversas técnicas fisicoquímicas, incluyendo difracción de rayos X (XRD, X-ray diffraction), microscopía electrónica de transmisión (TEM, transmission electron microscopy), espectroscopía infrarroja por transformada de Fourier (FTIR, Fourier transform infrared spectroscopy), análisis termogravimétrico (TGA, thermogravimetric analysis), y mediciones de potencial zeta (ζ), con el objetivo de evaluar su composición superficial, estructura cristalina, tamaño y estabilidad térmica. Los resultados obtenidos confirmaron la formación de magnetita/maghemita con estructura cristalina característica de tamaño nanométrico y evidenciaron la presencia de compuestos orgánicos asociados al recubrimiento con polifenoles. Se evaluó la capacidad de adsorción de Fe3O4-PF y Fe3O4 ante diversos contaminantes. Para esto se realizaron ensayos de adsorción en modo batch utilizando soluciones acuosas de diferentes MP (Zn²⁺, Cd²⁺, Ni²⁺, Pb²⁺ y Cu²⁺). Considerando su toxicidad y lixiviación en condiciones ácidas, se utilizó Pb²⁺ como MP modelo. Las isotermas de adsorción se ajustaron mediante los modelos de Freundlich, Sips, BET y Dubinin–Radushkevich. Asimismo, considerando la naturaleza del material sintetizado se estudió la capacidad de adsorción con el colorante orgánico azul de metileno (AM). Si bien el BA no presentó una mejora sustancial de la capacidad de remoción de Pb2+ como modelo de MP, sí se evidenció un gran incremento en la capacidad de adsorción de AM, lo que pone de manifestó la versatilidad que confiere el recubrimiento con sustancias polifenólicas.

The presence of heavy metals (MP) in soils, surface waters, and groundwater as a result of anthropogenic activities such as mining, metallurgical operations, and the petrochemical industry represents a major environmental concern due to their high toxicity, mobility, persistence, and bioaccumulation capacity. The introduction of these compounds into aqueous systems may lead to adverse effects on ecosystems, aquatic life, and human health. Among the different proposed alternatives, the use of bioadsorbents (BA) derived from agro-industrial residues has gained increasing attention in recent years due to their low cost, availability, and high density of functional groups capable of interacting with metal species. Furthermore, the incorporation of magnetic particles enables their recovery by magnetic separation. In this work, a BA was synthesized by functionalizing magnetite particles with polyphenolic compounds (Fe3O4-PF) extracted from olive pomace from the regional olive industry in Neuquén Province. The extract was obtained by solid–liquid extraction using ethanol and citric acid. The obtained materials were characterized using various physicochemical techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and zeta potential (ζ) measurements, in order to evaluate their surface composition, crystalline structure, size, and thermal stability. The results confirmed the formation of magnetite/maghemite with a characteristic crystalline structure at the nanoscale and evidenced the presence of organic compounds associated with the polyphenolic coating. The adsorption capacity of Fe3O4-PF and Fe3O4 was evaluated against different contaminants. Batch adsorption experiments were carried out using aqueous solutions containing different MP (Zn²⁺, Cd²⁺, Ni²⁺, Pb²⁺ and Cu²⁺). Considering its toxicity and lixiviation under acidic conditions, Pb²⁺ was selected as the model MP. Adsorption isotherms were fitted using Freundlich, Sips, BET and Dubinin–Radushkevich models. Additionally, considering the nature of the synthesized material, its adsorption capacity toward the organic dye methylene blue (AM) was also studied. Although the BA did not show a significant improvement in Pb²⁺ removal as a model MP, a substantial increase in AM adsorption capacity was observed, highlighting the versatility provided by the polyphenolic coating.

The presence of heavy metals (MP) in soils, surface waters, and groundwater as a result of anthropogenic activities such as mining, metallurgical operations, and the petrochemical industry represents a major environmental concern due to their high toxicity, mobility, persistence, and bioaccumulation capacity. The introduction of these compounds into aqueous systems may lead to adverse effects on ecosystems, aquatic life, and human health. Among the different proposed alternatives, the use of bioadsorbents (BA) derived from agro- industrial residues has gained increasing attention in recent years due to their low cost, availability, and high density of functional groups capable of interacting with metal species. Furthermore, the incorporation of magnetic particles enables their recovery by magnetic separation. In this work, a BA was synthesized by functionalizing magnetite particles with polyphenolic compounds (Fe3O4-PF) extracted from olive pomace from the regional olive industry in Neuquén Province. The extract was obtained by solid–liquid extraction using ethanol and citric acid. The obtained materials were characterized using various physicochemical techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and zeta potential (ζ) measurements, in order to evaluate their surface composition, crystalline structure, size, and thermal stability. The results confirmed the formation of magnetite/maghemite with a characteristic crystalline structure at the nanoscale and evidenced the presence of organic compounds associated with the polyphenolic coating. The adsorption capacity of Fe3O4-PF and Fe3O4 was evaluated against different contaminants. Batch adsorption experiments were carried out using aqueous solutions containing different MP (Zn² ⁺, Cd² ⁺, Ni² ⁺, Pb² ⁺ and Cu² ⁺). Considering its toxicity and lixiviation under acidic conditions, Pb² ⁺ was selected as the model MP. Adsorption isotherms were fitted using Freundlich, Sips, BET and Dubinin–Radushkevich models. Additionally, considering the nature of the synthesized material, its adsorption capacity toward the organic dye methylene blue (AM) was also studied. Although the BA did not show a significant improvement in Pb² ⁺ removal as a model MP, a substantial increase in AM adsorption capacity was observed, highlighting the versatility provided by the polyphenolic coating.