RESUMEN

Hydrothermal aging is a matter of considerable concern for natural fiber-reinforced polymers; it can alter dimensional stability and induce microcracks and macro strain on the composite structure. This study applied a sorption kinetic model and examined the effects of water on the damping factor of sisal mat-reinforced polyester composites. The experimental data were fitted well using a Boltzmann sigmoid function, suggesting a promising first step toward kinetic water sorption modeling. Additionally, a damping test was carried out using the impulse excitation technique, highlighting the composite material's dynamic response under varying water absorption conditions. The result showed that damping exhibited sensitivity to water absorption, increasing significantly during the first 24 h of immersion in water, then remained steady over time, inferring a critical time interval. An empirical model proved satisfactory with the correlation coefficient for sorption rates and damping of sisal mat polymeric composites.

RESUMEN

The development of technologies capable of producing efficient and economically viable anodes is essential for the electrochemical treatment of water contaminated with complex organic pollutants. In this context, the use of ionic liquids as solvents to prepare mixed metal oxide (MMO) anodes has proven to be an up-and-coming alternative. Here, we analyze the influence of the temperature of calcination (300, 350, and 400 ºC) on the production of Ti(RuO2)0.8-(Sb2O4)0.2 anodes made using the thermal decomposition method using three ionic liquids (IL) as solvents: dipropyl ammonium acetate (DPA-Ac), dipropyl ammonium propionate (DPA-Pr), and dipropyl ammonium butyrate (DPA-Bu). The decomposition temperature for all IL, accessed by thermogravimetry, is below 200 ºC. Physical and electrochemical analyses demonstrate that the calcination temperature of the anodes is decisive for their durability and electrochemical properties. Anodes prepared with DPA-Bu at 350 ºC show higher stability (around 35 h) than those made with other ILs at temperatures of 300 and 400 ºC and improved results in terms of 4-NP mineralization, where 97% of TOC removal was achieved in 120 min. It could be verified that the calcination temperature and IL employed had a decisive influence on the characteristics of the presented anodes. Therefore, the anode prepared with DPA-Bu at 350 ºC is promising for application in the degradation of organic compounds.

RESUMEN

Oil spill from petrochemical industries into marine areas has resulted in severe environmental pollution. The use of natural sorbents to clean marine areas affected by petroleum contaminants is a promising approach to alleviate this problem. Therefore, this study aims at developing an technique that uses waste coconut fibres (Cocos nucifera L.) pre-treated with a "green" solvent, viz. protic ionic liquid (PIL) [2-HEA][Ac], for the remediation of oil in saline water. Conventional chemical pre-treatments (mercerisation/acetylation) and the innovative treatment (using PIL), chemical characterisation, Scanning Electron Microscope, Fourier-transform infrared spectroscopy, and oil sorption tests in hydrodynamic simulation on a laboratory scale were conducted. The fibres treated with PIL[2-HEA][Ac] possessed more pores and hydrophobic content than the mercerised/acetylated coconut fibres, indicating the efficiency of sorption. The average sorption of the PIL[2-HEA][Ac] fibre was 1.40 ± 0.06 g/g and that of the mercerised/acetylated fibre was 1.32 ± 0.12 g/g. Although the difference in sorption results is not significant, according to the Tukey test, fibre pre-treatment with PIL[2-HEA][Ac] is more advantageous than conventional treatments because it exhibits better average sorption results; furthermore, the synthesis procedure for PIL[2-HEA][Ac] is simple, reusable and non-toxic. Therefore, the use of these petroleum biosorbents is a technology with environmental benefits, such as the availability of the biosorbent in the form of biodegradable waste and treated with a "green" solvent, both of which can be reused. Thus, it adds value for its use in industries with a circular economy product; that are environment-friendly and economical.

Asunto(s)

Restauración y Remediación Ambiental , Contaminación por Petróleo , Petróleo , Contaminantes Químicos del Agua , Adsorción , Cocos , Contaminación por Petróleo/análisis , Aguas Salinas , Contaminantes Químicos del Agua/análisis

RESUMEN

As a natural adsorbent, sisal (agave sisalana) fibers were used to extract Cu, Ni, Mn, and Zn from diesel oil samples for posterior determination (i.e., direct analytical measurements on the solid support) of the analytes by energy dispersive X-ray fluorescence spectrometry (EDXRF). In the proposed procedure, 0.2 g of sisal fiber was directly added to 5.0 mL of diesel oil contained in a glass tube. After 5 min of contact time, the mixture was filtered, and the collected fibers were oven-dried for 30 min at 70 °C. After drying, the analytes were quantified directly by EDXRF using the sisal fibers as a solid support. The calibration curves showed linear concentration ranges of 0.09-1.00, 0.12-1.00, 0.09-1.00, 0.06-1.0 µg g-1 for Cu, Ni, Mn, and Zn, respectively. The limits of detection (LOD) for Cu, Ni, Mn, and Zn were 0.03, 0.04, 0.03, and 0.02 µg g-1, respectively. The repeatability, evaluated by performing ten measurements at a concentration of 0.50 µg g-1 for each metal, with the results expressed in terms of the relative standard deviation (RSD), was 3.2, 6.5, 6.8, and 6.1% for Cu, Ni, Mn, and Zn, respectively. The results obtained by the proposed method were compared with the results obtained by a comparative method using inductively coupled plasma optical emission spectrometry, and both results showed good agreement. The proposed method was applied for Ni, Cu, Mn, and Zn determination in diesel oil samples collected from different gas stations.

RESUMEN

Here, we have assessed the use of one packed bed or two packed bed reactors in series in which Burkholderia cepacia lipase (BCL) was immobilized on protic ionic liquid (PIL)-modified silica and used as a biocatalyst for the transesterification of crude coconut oil. Reaction parameters including volumetric flow, temperature, and molar ratio were evaluated. The conversion of transesterification reaction products (ethyl esters) was determined using gas chromatography and the quantities of intermediate products (diglyceride and monoglyceride [MG]) were assessed using high-performance liquid chromatography. Packed bed reactors in series produced ethyl esters with the greatest efficiency, achieving 65.27% conversion after 96 H at a volumetric flow rate of 0.50 mL Min-1 at 40 °C and a 1:9 molar ratio of oil to ethanol. Further, within the first 24 H of the reaction, increased MG (54.5%) production was observed. Molecular docking analyses were performed to evaluate the catalytic step of coconut oil transesterification in the presence of BCL. Molecular docking analysis showed that triglycerides have a higher affinity energy (-5.7 kcal mol-1 ) than the smallest MG (-6.0 kcal mol-1 ), therefore, BCL catalyzes the conversion of triglycerides rather than MG, which is consistent with experimental results.

Asunto(s)

Reactores Biológicos , Aceite de Coco/metabolismo , Ésteres/metabolismo , Lipasa/metabolismo , Biocatálisis , Burkholderia cepacia/enzimología , Aceite de Coco/química , Enzimas Inmovilizadas/química , Enzimas Inmovilizadas/metabolismo , Ésteres/química , Lipasa/química

RESUMEN

Pineapple fibre was treated with protic ionic liquids (PILs) and the effects on the structure, composition, and properties of the fibres were evaluated. Treatment with PILs efficiently exposed the fibre surface, as confirmed by scanning electron microscopy. The chemical composition analysis revealed reductions in the lignin and hemicellulose contents in the treated fibres, promoting exposure of cellulose. The results correlated with the crystallinity index, which was greater in the treated fibres compared with that in the untreated fibres. The generated residue from the treatment of fibres with PIL (1%, v/v) showed lower levels of toxic compounds, demonstrating the advantages of this treatment over conventional biomass treatments.

RESUMEN

Treated silica xerogel with protic ionic liquid (PIL) and bifunctional agents (glutaraldehyde and epichlorohydrin) is a novel support strategy used in the effective immobilization of lipase from Burkholderia cepacia (LBC) by covalent binding. As biocatalysts with the highest activity recovery yields, LBC immobilized by covalent binding with epichlorohydrin without (203%) and with PIL (250%), was assessed by the following the hydrolysis reaction of olive oil and characterized biochemically (Michaelis⁻Menten constant, optimum pH and temperature, and operational stability). Further, the potential transesterification activity for three substrates: sunflower, soybean, and colza oils, was also determined, achieving a conversion of ethyl esters between 70 and 98%. The supports and the immobilized lipase systems were characterized using Fourier transform infrared spectra (FTIR), scanning electron microscopy (SEM), elemental analysis, and thermogravimetric (TG) analysis.

Asunto(s)

Proteínas Bacterianas/química , Enzimas Inmovilizadas/química , Líquidos Iónicos/química , Lipasa/química , Aceite de Oliva/química , Aceite de Soja/química , Aceite de Girasol/química , Proteínas Bacterianas/aislamiento & purificación , Biocombustibles/provisión & distribución , Burkholderia cepacia/química , Burkholderia cepacia/enzimología , Reactivos de Enlaces Cruzados/química , Enzimas Inmovilizadas/aislamiento & purificación , Epiclorhidrina/química , Esterificación , Geles , Glutaral/química , Humanos , Concentración de Iones de Hidrógeno , Lipasa/aislamiento & purificación , Dióxido de Silicio/química , Temperatura

RESUMEN

Ionic liquids (ILs) are often claimed to be "environmentally friendly" compounds however, the knowledge of their potential toxicity towards different organisms and trophic levels is still limited, in particular when protic ionic liquids (PILs) are addressed. This study aims to evaluate the toxicity against various microorganisms and the biodegradability of four PILs namely, N-methyl-2-hydroxyethylammonium acetate, m-2-HEAA; N-methyl-2-hydroxyethylammonium propionate, m-2-HEAPr; N-methyl-2-hydroxyethylammonium butyrate, m-2-HEAB; and N-methyl-2-hydroxyethylammonium pentanoate, m-2-HEAP. The antimicrobial activity was determined against the two bacteria, Sthaplylococcus aureus ATCC-6533 and Escherichia coli CCT-0355; the yeast Candida albicans ATCC-76645; and the fungi Fusarium sp. LM03. The toxicity of all PILs was tested against the aquatic luminescent marine bacterium Vibrio fischeri using the Microtox(®) test. The impact of the PILs was also studied regarding their effect on lettuce seeds (Lactuta sativa). The biodegradability of these PILs was evaluated using the ratio between the biochemical oxygen demand (BOD) and the chemical oxygen demand (COD). The results show that, in general, the elongation of the alkyl chain tends to increase the negative impact of the PILs towards the organisms and biological systems under study. According to these results, m-2-HEAA and m-2-HEAP are the less and most toxic PILs studied in this work, respectively. Additionally, all the PILs have demonstrated low biodegradability.

Asunto(s)

Líquidos Iónicos/toxicidad , Compuestos de Amonio Cuaternario/toxicidad , Aliivibrio fischeri/efectos de los fármacos , Aliivibrio fischeri/metabolismo , Antibacterianos/química , Antibacterianos/metabolismo , Antibacterianos/toxicidad , Antifúngicos/química , Antifúngicos/metabolismo , Antifúngicos/toxicidad , Biodegradación Ambiental , Análisis de la Demanda Biológica de Oxígeno , Candida albicans/efectos de los fármacos , Escherichia coli/efectos de los fármacos , Fusarium/efectos de los fármacos , Líquidos Iónicos/química , Líquidos Iónicos/metabolismo , Lactuca/efectos de los fármacos , Lactuca/crecimiento & desarrollo , Luminiscencia , Compuestos de Amonio Cuaternario/química , Compuestos de Amonio Cuaternario/metabolismo , Staphylococcus aureus/efectos de los fármacos

RESUMEN

Ionic liquids (ILs) have evolved as a new type of non-aqueous solvents for biocatalysis, mainly due to their unique and tunable physical properties. A number of recent review papers have described a variety of enzymatic reactions conducted in IL solutions, on the other hand, to improve the enzyme's activity and stability in ILs; major methods being explored include the enzyme immobilization (on solid support, sol-gel, etc.), protic ionic liquids used as an additive process. The immobilization of the lipase from Burkholderia cepacia by the sol-gel technique using protic ionic liquids (PIL) as additives to protect against inactivation of the lipase due to release of alcohol and shrinkage of the gel during the sol-gel process was investigated in this study. The influence of various factors such as the length of the alkyl chain of protic ionic liquids (monoethanolamine-based) and a concentration range between 0.5 and 3.0% (w/v) were evaluated. The resulting hydrophobic matrices and immobilized lipases were characterised with regard to specific surface area, adsorption-desorption isotherms, pore volume (V(p)) and size (d(p)) according to nitrogen adsorption and scanning electron microscopy (SEM), physico-chemical properties (thermogravimetric - TG, differential scanning calorimetry - DSC and Fourier transform infrared spectroscopy - FTIR) and the potential for ethyl ester and emulsifier production. The total activity yields (Y(a)) for matrices of immobilized lipase employing protic ionic liquids as additives always resulted in higher values compared with the sample absent the protic ionic liquids, which represents 35-fold increase in recovery of enzymatic activity using the more hydrophobic protic ionic liquids. Compared with arrays of the immobilized biocatalyst without additive, in general, the immobilized biocatalyst in the presence of protic ionic liquids showed increased values of surface area (143-245 m(2) g(-1)) and pore size (19-38 Å). Immobilization with protic ionic liquids also favoured reduced mass loss according to TG curves (always less than 42.9%) when compared to the immobilized matrix without protic ionic liquids (45.1%), except for the sample containing 3.0% protic ionic liquids (46.5%), verified by thermogravimetric analysis. Ionic liquids containing a more hydrophobic alkyl group in the cationic moiety were beneficial for recovery of the activity of the immobilized lipase. The physico-chemical characterization confirmed the presence of the enzyme and its immobilized derivatives obtained in this study by identifying the presence of amino groups, and profiling enthalpy changes of mass loss.

Asunto(s)

Proteínas Bacterianas/metabolismo , Enzimas Inmovilizadas/metabolismo , Líquidos Iónicos/química , Lipasa/metabolismo , 2-Propanol/metabolismo , Proteínas Bacterianas/química , Burkholderia cepacia/enzimología , Rastreo Diferencial de Calorimetría , Emulsionantes/metabolismo , Enzimas Inmovilizadas/química , Esterificación , Geles , Hidrólisis , Interacciones Hidrofóbicas e Hidrofílicas , Ácidos Láuricos/metabolismo , Lipasa/química , Microscopía Electrónica de Rastreo , Aceite de Oliva , Aceites de Plantas/metabolismo , Porosidad , Gel de Sílice , Aceite de Soja/metabolismo , Espectroscopía Infrarroja por Transformada de Fourier , Propiedades de Superficie , Termogravimetría