Diseño de adsorbentes selectivos para la eliminación de compuestos orgánicos peligrosos

Tesis con mención internacional y por compendio de publicacione

Diseño de adsorbentes selectivos para la eliminación de compuestos orgánicos peligrosos

[ES] Se desarrollaron métodos de preparación de materiales para la recuperación y pre-concentración de contaminantes orgánicos, tanto en aire como en medio acuoso. En la primera parte de esta Tesis Doctoral, se sintetizaron carbones activados (ACs) con porosidad y morfología diversas. En el caso de materiales mesoporosos, se utilizaron sílice SBA-15 y MCM-48 como plantilla. Los ACs se obtuvieron mediante pirolisis con vapor y activación química. El poliestireno mejoró la resistencia mecánica de los ACs mesoporosos de morfología esférica. ACs de morfología esférica se utilizaron como adsorbentes en la extracción de componentes peligrosos en humo de cigarrillos. Se utilizaron subproductos de pipas de girasol, procedentes de una central eléctrica industrial, para la síntesis en tres etapas (pretratamiento ácido-base/disolventes, carbonización y activación química) de ACs, con capacidad de adsorción hacia azul de metileno superior a la de ACs comerciales. La segunda parte de este trabajo se focalizó hacia la síntesis de nanopartículas de magnetita tipo core-shell y la aplicación de estos materiales como adsorbentes o agentes de limpieza para la determinación de contaminantes orgánicos en matrices diversas. Se han obtuvieron nanopartículas de magnetita decoradas con capas de sílice y modificadas con el tensioactivo no iónico Triton X-100 (Fe3O4@Triton). Fe3O4@Triton pre-concentó eficazmente pesticidas organoclorados (OCPs) en medio acuoso. Los nanocompuestos magnéticos se separaron fácilmente de la disolución mediante un campo magnético externo, sin centrifugación ni filtración. Asimismo, se desarrolló el procedimiento QuEChERS con el Fe3O4@Triton como agente limpiador de componentes no polares. El procedimiento QuEChERS modificado se utilizó para monitorizar el seguimiento de 20 OCPs en muestras de frutas, hortalizas y suelos. Los adsorbentes desarrollados son susceptibles de aplicación práctica, tanto desde una perspectiva económica como ecológica.[EN] In the present PhD Thesis is to develop methods preparation of effective materials for the removal and pre-concentration of organic contaminants in air/water medium. In the first part, the synthesis activated carbon (AC) materials with various porosity and morphology were described. The synthesis of the mesoporous samples was based on the using of SBA-15 and MCM-48 silica as templates. The steam-pyrolysis and chemical activation has been used for obtained AC. Then, polystyrene was used to increase the mechanical resistance of the mesoporous AC with spherical morphology. The adsorption performance of spherical AC was studied by extraction of cigarette smoke. The possibility of using on sunflower husk by-products obtained at industrial power plant as precursor for the synthesis of AC also investigated. The AC has been synthesized in three steps: acid-alkali/solvents pretreatment, carbonization and chemical activation. The adsorption capacity toward methylene blue was higher than commercial AC. The second part of work focuses on the synthesis core-shell type magnetite nanoparticles and application of these materials as adsorbents or clean-up agent for determination organic pollutants in various matrixes. Magnetite nanoparticles decorated with silica layers and modified with non-ionic surfactant Triton X-100 (Fe3O4@Triton) have been obtained. The Fe3O4@Triton is effectively pre-concentrate the organochlorine pesticides (OCPs) in the water medium. The magnetic nanocomposites can be easily separated from the solution by an external magnetic field without centrifugation or filtration. Also, the QuEChERS procedure with the Fe3O4@Triton as clean-up agent of non-polar components was developed. The modified QuEChERS procedure has been applied for the monitoring of 20 OCPs in fruit, vegetable and soil samples. This study opens up possibilities for the developed adsorbents with focus on the economic and eco-friendly effects.Peer reviewe

Surface engineering: binary Mg,Fe-LDH·xFe3O4 nanocomposites for improved magnetic solid-phase extraction of pharmaceuticals from aqueous solution

In this work, binary Mg,Fe-LDH·xFe3O4 (x = 0 to 2.0) nanocomposites were prepared via the in situ growth of Mg,Fe-layered double hydroxides (LDHs) onto magnetite nanoparticles and applied for the removal of diclofenac motives. These materials were prepared by a simple prolonged sonication method and systematically characterized by several techniques (e.g. XRD, VRM, SEM, FTIR, TEM, etc.). The XRD patterns of the magnetic nanocomposites confirm the formation of both LDHs and magnetic phases. The intricate surface functional groups of the starting components played pivotal roles in the formation of magnetic composites, according to FTIR spectra. The hexagonal plate-like morphology of the Mg,Fe-LDHs and Mg,Fe-LDH·xFe3O4 samples is evident from TEM data. The Mg,Fe-LDH·1.0Fe3O4 nanocomposite exhibited high agglomeration of the magnetite nanoparticles, which broke their layered structure. Various influencing factors (e.g., concentration, pH medium, and contact time) that are known to influence the adsorption properties of materials were systematically studied to clarify the mechanism of the adsorption process. To assess the safety of the adsorbents, the effect of the adsorbed DCF on the release of metal ions from the LDHs structure was also monitored. Moreover, the Mg,Fe-LDH·xFe3O4 (x = 0.1 to 1.0) nanocomposites can be quickly separated from the 400 mL solution by an external NdFeB magnet before and after the magnetic solid-phase extraction process. The capacity of the magnetic nanocomposites to adsorb diclofenac increased with increasing solution pH. At 25 °C and pH = 7.5, the maximum adsorption capacities for Mg,Fe-LDH·0.1Fe3O4 and Mg,Fe-LDH·0.3Fe3O4 were 153.2 mg g−1 (0.48 mmol g−1) and 143.2 mg g−1 (0.45 mmol g−1), respectively, which do not exceed the capacities for the starting Mg,Fe-LDHs (158.1 mg g−1). Further results indicated that the adsorption isotherm for diclofenac anion retention could be fitted to the Langmuir equation. The FTIR and XRD data indicate that organic molecules are adsorbed on the obtained materials by electrostatic and complex-forming processes without significant anion-exchange reactions. Moreover, after 3 regeneration cycles, the magnetic nanocomposites still retained a highly ordered structure and morphology with a magnetic response.The authors gratefully acknowledge the support of MINECO (Spain) for MCI-21-PID2020-113558RB-C41 and PID2020-119130 GB-I00 grants, providing materials characterization facilities. Dr Natalia Kobylinska would like to thank the European Chemistry School for Ukrainians.Peer reviewe

Efficient adsorption of pharmaceutical drugs from aqueous solution using a mesoporous activated carbon

The removal of widely used pharmaceuticals by new granular mesoporous activated carbon materials prepared via a simple one-step pyrolysis process was studied. The series of mesoporous carbons (MC) were derived from sucrose/polystyrene using two mesoporous matrices: MCM-48 and SBA-15 sieves. Two different activation schemes were used to obtained samples: steam-pyrolysis at 900 °C, and chemical modification (with HNO3, H2O2 and their mixture) at 200 °C. The studied conditions of chemical oxidation led to significant structural alterations. Compared to the activated carbon treated by steam at 900 °C, the treatment via chemical oxidation increased the total volume of pores from 1.09 to 2.73 cm3 g−1. The total adsorption capacity towards tetracycline was found to be proportional to the mesoporous volume and the amount of surface O-containing groups. From the experimental adsorption isotherms, the maximum adsorption capacity was calculated 909.2 mg g−1 for tetracycline at pH 7. The kinetics of adsorption fits the pseudo-second order model perfectly. The adsorption data treated by both Langmuir and Freundlich models indicates that the adsorption was monomolecular. This research provides insight into the adsorption behavior of antibiotics on non-activated and activated mesoporous carbonous materials and facilitates their application to removal of pharmaceuticals from contaminated aqueous solutions. The potential adsorption mechanism of mesoporous carbons for the adsorption of antibiotics was proposed. The granular mesoporous carbon after oxidation by mixture of HNO3 and H2O2 with ration 1:1 exhibited much higher adsorptive activity and still showed relatively high adsorption stability even after five cycles, which were potentially suitable for easy separation and high efficiency.This study was supported by grants from EU FP-7-PEOPLE-2009-IRSES (№ 247603). The University of Oviedo is grateful for financial support from Spain’s Ministry for the Economy and Business - MINECO (MAT2016-78155-C2-1-R).Peer reviewe

Optimization of QuEChERS procedure by hydrophobic magnetic nanocomposites for residual OCPs determination coupled with GC-MS

Resumen del póster presentado a la XX Conference EuroAnalysis, celebrada en Estambul (Turquía) del 1 al 5 de septiembre de 2019.Food safety and environmental protection issues have attracted significant international attention in the recent years. The detection of organochlorine pesticides (OCPs) in food products is of key importance for the health of the consumers. Pesticides are found in food at very low concentrations, the separation and pre-concentration of the target analytes has become one of the most critical steps in the sample preparation technology. The QuEChERS is a type of sample preparation method for screening of pesticides in completely food matrixes. This procedure involves initial extraction with acetonitrile followed by a solid phase extraction with amine-loaded adsorbents in combination with hydrophobic C18 and graphitized carbon black for cleaning-up. In this work the application of magnetite nanoparticles modified with hydrophobic non-ionic surfactant Triton X-100 motives as an excellent clean-up agent is proposed. Hydrophobic groups grafted to the surface of magnetite nanoparticles can effectively remove non-polar components from the food matrix (fat, pigment, etc.) and then the particles can easily be separated from the extract by external magnetic field avoiding additional steps of centrifugation or filtration. The sample preparation method based on QuEChERS implying the use of new magnetic nanocomposite has been applied for the monitoring of various OCPs in food products. Under the found optimal conditions such parameters as sensitivity, precision, recoveries have been evaluated for the target analytes by GC-MS method. The results have shown a good linearity (R2≥ 0.9916), satisfactory average recoveries reaching the values between 89 and 110%, RSD of 2-15 %, except those for the hexane extraction of strawberry, radish and watermelon samples. The OCPs have been detected in strawberry (α- HCH; lindane) and radish (α, β-HCH isomers) samples. The magnetic nanocomposites have provided the lower level of co-extracted interferences (including pigments) in the samples and have displayed a better clean-up performance than C18 or carbon adsorbents. Thus, the developed method demonstrates the improved purification and simultaneous recovery of various OCPs

Sunflower biomass power plant by-products: Properties and its potential for water purification of organic pollutants

The present study explores possibility of using sunflower seed husk agricultural biowastes from industrial pyrolysis power plant as a feedstock for preparation of activated carbon (AC). Sunflower biomass by-products contain up to 70 % of carbon with residual seed husk components, have low specific surface area (less than 21 m2 g−1) and smaller number of oxygen-containing groups in comparison with wood-based biochars. The main process parameters of AC preparation, namely a type of an activation agent (organic solvent, HNO3, NaOH), temperature and duration of the carbonization step, were optimized in respect to adsorption efficiency. We found that simple pre-treatment of sunflower biomass with tetrahydrofuran easily converts it into biochar precursor having large number of carbonyl and hydroxyl groups. Further thermal and chemical activation of the biochar precursor results in formation of AC products with specific surface area in the range from 625 to 980 m2 g−1 and from 1000 to 1755 m2 g−1, respectively. Methylene blue (MB) was used as a test molecule for characterization of adsorption properties of the obtained AC. Kinetics studies showed that MB adsorption on AC is fast and follows pseudo-second-order model. MB adsorption on biochar and AC is well described by Langmuir isotherm, assuming monolayer formation of MB on the surface of adsorbents via chemical interactions. Adsorption capacity of AC towards MB achieved by nitric acid activation is higher (379.0 mg g−1) than capacity of benchmark commercial activated carbon from Norit. The study opens up possibilities for the development of by-product-based adsorbents via the straightforward, eco-friendly approach, with specific focus on the economic effect achieved with these materials.The University of Oviedo is grateful for financial support from Spain’s Ministry for the Economy and Business - MINECO (MAT2016-78155-C2-1-R).Peer reviewe

Different approaches to the solid-phase extraction of pollutants from water and food products

Resumen del trabajo presentado al congreso Nanomaterials applied to Life Sciences (NALS), celebrado en Gijón (España) del 13 al 15 de diicembre de 2017.Control of the presence of various organic pollutants in agricultural products is one of the major issues preoccupying the regulatory agencies and industrial laboratories worldwide. The pesticides, produced by the agricultural sector, are regarded as one of the most hazardous contaminants found in the environment. They are not only toxic but also mobile and capable of bioaccumulation. Nowadays, pesticides are found in surface waters and in a growing number of aquifers, thus even if present at low concentration levels constituting a potential risk for ecosystems, drinking water quality and human health. Due to the low concentration of analytes, the complexity of some sample matrices and incompatibility of sample medium with analytical instrument a preliminary sample pre-concentration and/or separation is required. Magnetic nanoparticles have attracted significant attention because of their strong magnetic response combined with easily regulated properties via the surface modification. In this communication we report a new approach for preparation of magnetic nanoadsorbent with covalently grafted non-ionic Triton X-100 surfactant. Mesoporous Triton X-100-immobilized (Fe3O4@Triton) magnetic nanoparticles were successfully synthesized by core-shell technology and characterized using transmission electron microscopy, X-ray diffractional analysis, nitrogen physisortpion, energy-dispersive X-ray elemental analysis, vibrating sample magnetometry. The produced Fe3O4@Triton solid was employed as an adsorbent for the pre-concentration of pesticides present in water and food products before analyzing them by gas chromatography coupled with mass spectrometry GC-MS technique. The variables affecting the performance of the adsorbent in the both extraction steps such as type and volume of eluent and extraction solvent, breakthrough volume, salt addition, extraction time were thoroughly investigated. The proposed method resulted in good linearities (R2 > 0.9915) in the range of 1–10000 ng kg−1, with the limit of detection of 0.5-1.0 ng kg−1 at S/N=3, and precision of % RSD of ≤11.8. Under optimal conditions, the pre-concentration factors obtained were in the range of 2362–10593 for 100 mL of sample solution. In addition, the Quick, Easy, Cheap, Effective, Rugged, and Safety (QuEChERS) method along with the application of the novel magnetic adsorbent (Fe3O4@Triton) was applied for the monitoring of 20 organochlorine pesticides (OCPs) present in fruits and vegetables available in supermarkets of Kyiv, Ukraine. The analyses were carried out by GC-MS. The parameters of the developed analytical method, such as sensitivity, precision, linear range, the lower limits of detection and quantification, were determined for each pesticide. The results showed good linearity and the average recoveries were considered satisfactory reaching values between 69 and 110%, RSD of 2-15 %, except for hexane in strawberry, radish and watermelon samples. The OCPs were detected in strawberry (α- HCH; lindane) and radish (α, β-HCH isomers) samples. The QuEChERS method and GC-MS technique were successfully used to analyze OCPs in commercially available fruit pulps and can be applied for routine laboratory analysis.Peer Reviewe