An environmentally friendly solvent-free approach was tested using spent coffee as a biomass sacrificial template for the preparation of TiO2 modified with CeOx. The use of coffee as a template ...pursues the preparation of a nanostructured heterojunction without the need for a solvent. Two variables were optimized in the synthesis process, i.e. calcination temperature and proportion of CeOx. Firstly, bare coffee-template titania was prepared to explore the effect of the calcination temperature, within 500–650 °C. The anatase phase was obtained up to 600 °C. Higher temperatures, i.e. 650 °C, led to the appearance of rutile (10%) and efficient removal of the sacrificial agent (0.6% residue). The maximum photocatalytic activity in terms of conversion, in the oxidation of benzyl alcohol, was achieved employing the bare coffee-template TiO2 at 650 °C, and it was found comparable to the benchmarked P25. The incorporation of ceria in the solvent-free approach considerably improved photocatalytic benzaldehyde production. No changes in the XRD pattern of TiO2 were appreciated in the presence of ceria due to the low amount added, within 1.5–6.0%, confirmed by XPS as superficial Ce3+/Ce4+. The UV–visible absorption spectra were considerably redshifted in the presence of Ce, reducing the bandgap values of bare titania. An optimum amount of ceria in the structure within 3-0% was found. In this case, the selectivity towards benzaldehyde was ca. 75%, 3 times higher than the selectivity value registered for the benchmarked P25 or the bare prepared TiO2.
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•Use of coffee as a sacrificial template for the preparation of nanostructured CeOx-TiO2.•The optimum temperature for template removal and crystalline anatase was 600 °C.•CeOx presence increases the selectivity reaction of benzyl alcohol to benzaldehyde.•CeOx reduces the recombination effect and redshifts the radiation absorption spectrum.•Bands alignment proposal with electron caption by Ce vacant and action by holes.
Green strategies for microplastics reduction Calero, Mónica; Godoy, Verónica; Quesada, Lucía ...
Current opinion in green and sustainable chemistry,
April 2021, 2021-04-00, Volume:
28
Journal Article
Peer reviewed
Currently, one of the biggest challenges is to reduce plastics contamination worldwide. In this scenario, some political, economic and social factors play a very important role in implementing ...efficient processes to control the plastic waste problem. In this work, some of the most recent advances in this field are presented. The eco-design of plastic products, the improvement of legislation for the manufacture, recycling and use of alternative materials, as well as for the intentional addition of microplastics to products, the development and research in biodegradable plastic and bioplastics, and the improvement of wastewater treatment facilities are important tools to reduce microplastic contamination and promote the circular economy.
The gasification of olive cake is a promising method for converting this material into valuable energy. This work offers interesting results about the effect of equivalence ratio and temperature on ...the composition and quality of the produced gas obtained during olive cake gasification in a fluidized bed plant with air as a gasification agent. Additionally, the efficiency of the gasification process was evaluated. The results show that, for a specific temperature, an equivalence ratio of 0.3 showed a higher cold gas efficiency. For example, at 850 °C and an equivalence ratio of 0.1, the cold gas efficiency was 22.7%; however, at the same temperature but at an equivalence ratio of 0.3, the cold gas efficiency was increased to 61.2%. In addition, for a constant equivalence ratio, by increasing the operating temperature, there was no significant increase in the lower heating value of the exit gas, and the gas flow was practically constant with temperature, but it varied substantially with the equivalence ratio, reaching values in the range of 3.44–14.89 NL/min (825.6–3573.6 NL/kg feed). Finally, the production of CO, Hsub.2, and CHsub.4 is estimated to be higher for tests conducted with an equivalence ratio of 0.3.
In recent years, the application of Lean models in manufacturing processes has received significant attention due to the successful implementation of relatively simple measures to eliminate or reduce ...waste. Similarly, Six Sigma has attracted the interest of the industry for reducing production costs through statistical methods and data analysis tools. The combination of both techniques constitutes a powerful management model known as Lean Six Sigma (LSS), whose application has been unevenly spread across the different services and industrial sectors. Despite the multiple studies conducted on the use of LSS methodologies in manufacturing processes, few studies have focused on its direct application in chemical manufacturing are less numerous. Consequently, many chemical companies still face major challenges in implementing the LSS model. This study explores the state of the art, current trends, and perspectives of Lean and Six Sigma integration in the chemical manufacturing sector. For this purpose, a bibliometric analysis was conducted covering topics from the implementation of the LSS on a global scale, i.e., non-manufacturing and manufacturing environments, to its application in the manufacturing of chemical products. The literature search was carried out in the Scopus and Web of Science databases using a different sequence of terms. The findings of this study revealed the most important contributions in terms of publications, authors, countries, and institutions over the past two decades. Additionally, avenues for future research are discussed.
The use of nonculture-based biomarkers such as the determination of galactomannan is sought for the diagnosis of invasive aspergillosis. To investigate the comparative yield of two tests for the ...detection of galactomannan in patients with or without proven or probable invasive aspergillosis. Overall, 327 samples (327 patients) were analyzed in a retrospective/prospective study performed in 3 hospitals in Madrid, comparing the determination results in serum or bronchoalveolar lavage of two techniques for galactomannan detection, namely, Platelia Aspergillus Ag (Bio-Rad) and Aspergillus galactomannan Ag Virclia Monotest (Vircell S.L.), following the manufacturer's instructions. Both techniques can automate the process, but the second technique has the advantage of individual processing and assembly of each sample without the need for the additional expense of single-dose strips in controls. In total, 288 of the 327 tests performed showed concordant results between both techniques. The agreement between both methods was к = 0.722, and the correlation between indices was ρ = 0.718. Only 39 samples showed discordant results. In those 39 cases, there were 15 patients with proven or probable invasive aspergillosis criteria. For the samples with clinical criteria as a reference, the areas under the curve of the receiver operating characteristic (ROC) curve were 0.962 for Platelia and 0.968 for VirClia. The VirClia test has been proven to be an alternative for diagnosis due to its friendlier automated format than that of the usual Platelia routine test. The VirClia test also allows individual action and, therefore, a more immediate clinical response.
Invasive mycoses are increasingly present in immunosuppressed or hospitalized patients with serious illnesses, leading to high rates of morbidity and mortality. Invasive aspergillosis is an infection caused, in a percentage greater than 50%, by the genus Aspergillus. It is vitally important to make an early diagnosis that leads to the application of antifungals in the initial stage of the infection. Therefore, tools are required to help with the early diagnosis of the infection. This comparative study of two enzyme immunoassays is based on the detection of galactomannan antigen in serum and bronchoalveolar lavage samples. A new design based on chemiluminescence and presented in an automated single-dose format is compared to a conventional ELISA technique marketed for years. The results obtained from the prospective and retrospective study indicate a high correlation and degree of agreement between both techniques, as well as in their diagnostic performance.
Plastic waste management is a current environmental issue that demands potential solutions since complete mechanical recycling is limited to the complexity and feasibility regarding the quality and ...purity of plastic waste. Pyrolysis has emerged as a reasonable solution for the recycling of those fractions that are not further suitable for recycling. Although the implementation of this technology is mature, the generated solid fraction or char has not been completely inserted in the closed loop of plastic recycling. This work explores the possibility of using the carbonaceous char as a precursor for the preparation of porous activated carbons for environmental application as CO2 adsorbent and biogas upgrading. The effect of the pyrolysis temperature (450 or 500 ºC) on the obtained chars has been assessed for the benefits in the second stage of chemical activation, exploring the possibility of the use of diverse chemical agents. The composition, textural, and surface properties of the porous materials were characterized. N2 isotherms showed that the char prepared at 500 ºC provided the best textural properties with a performance of K2CO3 ∼ KOH > Na2CO3 > NaOH > ZnCl2 > FeCl3. Isotherms of CO2 adsorption showed that the activation with K2CO3 displayed the best uptake (130.2 mg g−1 at 273 K), closely followed by KOH (125.0 mg g−1 at 273 K), also confirmed by dynamic tests in a fixed bed column configuration. The uptake was well correlated with the ultramicropore volume and the oxygenated functional groups. The CO2 and CH4 adsorption were studied either in static or dynamic assays. The behavior of the sample activated with K2CO3 was studied in detail in column tests, suggesting that the activated material exhibits promising behavior for biogas upgrading.
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Emulsions can be used as delivery systems for bioactive ingredients for their incorporation in food products. Essential oils are natural compounds found in plants that present antioxidant and ...antimicrobial activity. Therefore, the main goal of this work was to develop emulsions, containing mandarin essential oil stabilized by two food-grade surfactants and guar gum, and to evaluate their physical stability. The initial droplet size of emulsions developed by microfluidization was optimized, obtaining diameters below one micron regardless of the processing conditions. However, the emulsion processed at 25,000 psi and one pass exhibited the lowest mean droplet sizes and polidispersity, and therefore, a higher stability. Different ratios of Tween 80 and Span 80 were assessed as stabilizers. Results obtained indicated that the ratio of surfactants had a significant effect on the mean droplet sizes, physical stability, and rheological properties. Thus, we found that the optimum ratio of surfactants was 75/25 (Tween80/Span80) on account of the lowest droplet mean diameters, lack of coalescence, and a low creaming rate. The rheological characterization of the stable emulsions showed a shear thinning flow behavior, and G″ (loss modulus) values higher than G′ (storage modulus) values, in all the frequency range. The rheological behavior may be governed by the guar gum, which was confirmed by field emission scanning electron microscopy (FESEM). This research can be considered as the starting point for future applications of mandarin essential oil in emulsions, which can be incorporated in products as food preservatives.
This research aims to develop a new strategy to valorize wasted COVID-19 masks based on chemical recycling by pyrolysis to convert them into useful products. First, surgical and filtering face piece ...masks, as defined in Europe by the EN 149 standard (FFP2), were thermally pyrolyzed at temperatures of 450, 500, and 550 °C, and the yields of valuable solid (biochar), liquid (biooil), and syngas products and their characteristics were determined. At low temperatures, biochar formation was favored over biooil and syngas production, while at high temperatures the syngas product yield was enhanced. The highest yield of biooil was found at a pyrolysis temperature of 500 °C, with both surgical and FFP2 masks achieving biooil yields of 59.08% and 58.86%, respectively. Then, the pyrolysis experiments were performed at 500 °C in a two-stage pyrolysis catalytic reactor using sepiolite as a catalyst. Sepiolite was characterized using nitrogen adsorption–desorption isotherms and Fourier-transform infrared spectroscopy. Results showed that the two-stage process increased the final yield of syngas product (43.89% against 39.52% for surgical masks and 50.53% against 39.41% for FFP2 masks). Furthermore, the composition of the biooils significantly changed, increasing the amount of 2,4-Dimethyl-1-heptene and other olefins, such as 3-Eicosene, (E)-, and 5-Eicosene, (E)-. Additionally, the methane and carbon dioxide content of the syngas product also increased in the two-stage experiments. Ultimately, the effect of sepiolite regeneration for its use in consecutive pyrolysis tests was examined. Characterization data showed that, the higher the use-regeneration of sepiolite, the higher the modification of textural properties, with mainly higher changes in its pore volume. The results indicated that the pyrolysis of face masks can be a good source of valuable products (especially from biooil and syngas products).
This work is focused on the removal of cobalt from aqueous solutions using the greenhouse crop residue and biochars resulting from its pyrolysis at different temperatures, which have not been ...previously used for this purpose. This study aims to provide insights into the effect of pyrolysis temperature as a key parameter on the cobalt adsorption capacity of these materials. Firstly, the main physicochemical properties of greenhouse crop residue and its biochars prepared under different pyrolysis temperatures were characterized by elemental analysis and FT-IR, among others. Then, the cobalt adsorption capacity of materials was evaluated in batch systems. The best results were obtained for the biochar prepared by pyrolysis at 450 °C (adsorption capacity of 28 mg/g). Generally, the adsorption capacity of the materials increased with pyrolysis temperature. However, when the treatment temperature was increased up to 550 °C, a biochar with worse properties and behavior than cobalt adsorbent was produced. Rather than surface area and other physical properties, functional groups were found to influence cobalt adsorption onto the prepared materials. The adsorption kinetics showed that the adsorption followed pseudo-second-order kinetics model. The obtained equilibrium data were fitted better by the Langmuir model rather than the Freundlich model. Finally, decomposition of loaded-materials was analyzed to assess their possible recycling as fuel materials. The study suggested that greenhouse crop residue can be used as a low-cost alternative adsorbent for cobalt removal from aqueous solutions.
This work focuses on the use of a char produced during the pyrolysis of a mixture of non-recyclable plastics as a precursor for the preparation of porous activated carbon with high developed ...adsorption uptake of lead in water. Physical and chemical activation was used to enhance the porosity, surface area, and surface chemistry of char. The final activated carbon materials were deeply characterized through N2 adsorption isotherms, scanning electron microscopy, Fourier transformed infrared spectroscopy, analysis of the metal content by inductively coupled plasma mass spectroscopy, and pH of point zero charge. The native char displayed a Pb adsorption uptake of 348 mg Pb·g−1 and considerably high leaching of carbon, mainly organic, ca. 12%. After stabilization with HCl washing and activation with basic character activators, i.e., CO2, NaOH, and KOH, more stable adsorbents were obtained, with no organic leaching and a porous developed structure, the order of activation effectiveness being KOH (487 m2·g−1) > NaOH (247 m2·g−1) > CO2 (68 m2·g−1). The activation with KOH resulted in the most effective removal of Pb in water with a saturation adsorption uptake of 747 mg Pb·g−1.
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