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Even today, there is no full understanding of the relationship between the physical, chemical, and mechanical properties and the behavior of the lubricating films formed in tribological systems. Most of the published scientific research measures and reports the overall values of friction and wear, but the information given via statistical signals in the tribological tests is, in general, dismissed, leaving a hole in the study of the dynamics of tribological systems. In this work, an experimental study of statistical friction data, coating characteristics, and tribological performance is carried out using a pin-on-disk tribometer to test some metallic samples coated with lubricant films under several experimental conditions. The results indicate that long deposition times at high deposition temperatures of coatings from engine oil develop low-friction intervals, which fall until 20% of the uncoated coefficient friction. However, an unexpected and unfavorable behavior of the coatings was observed for the short deposition times and high temperature. In these conditions, the developed friction profiles reached a maximum level of friction that was 20% more than the uncoated coefficient friction. Moreover, it was found that the proper analysis and interpretation of the statistical data, in combination with the characterization of the coatings, describes the dynamics of the interactions between the bodies in contact and reveals the transitions of the surfaces with non-homogeneous properties throughout their depth.

The use of metal nanoparticles (NPs) to enhance hydrogen production in dark fermentation (DF) has become a pioneering field of interest. In particular, iron-based nanoparticles (FeNPs) play a pivotal role in enhancing the activity of metalloenzymes and optimizing feedstock utilization, resulting in improved hydrogen production. This study investigated the effect of FeNPs (magnetite) supplementation at three different concentrations of 50, 100, and 200 ppm in a continuous dark fermenter for the production of hydrogen from rice straw acid hydrolysate. The highest hydrogen production rate of 2.6 ± 0.3 NL H2/L-d was achieved with the addition of 100 ppm of nanoparticles, representing a 53% increase compared to the condition without FeNPs addition. This improvement was driven by a microbial community in which Clostridium was the major dominant genus. In addition, increasing the nanoparticle concentration to 100 ppm resulted in an increase in butyrate concentration to 2.0 ± 0.1 g/L, which is 43% higher than the butyrate concentration without FeNPs. However, when the NP concentration was increased to 200 ppm, the hydrogen production rate decreased to 1.6 ± 0.2 NL H2/L-d. This study can serve as a guideline for future research aimed at evaluating the effects of FeNPs in continuous dark fermentation systems. This work highlights the potential benefits and challenges associated with the use of FeNPs, paving the way for future studies to optimize their application and improve the efficiency of dark fermentation processes.

The sulfur content in crude oil varies between 1000 and 30,000 ppm (parts per million), meaning that its removal from fuels requires significant technical and economic effort. Growing concern about pollution, accompanied by stricter environmental regulations, have led to the development of strategies to mitigate the negative effects of sulfur-containing compounds in petroleum, which can cause malfunctions in manufacturing plants and refineries, such as causing catalyst poisoning in catalytic reforming equipment and sulfur dioxide emissions that have been generated through the use of fuels in vehicles, vessels, furnaces, etc. Sulfur is one of the main pollutants found in diesel and gasoline. The hydrodesulfurization method removes sulfur and nitrogen-containing compounds from diesel and gasoline, ensuring compliance with current environmental regulations established for the import and export of fuels. In addition, hydrodesulfurization contributes to reducing sulfur dioxide and nitrogen dioxide emissions into the environment and prevents corrosion, which increases safety for both manufacturing plants and end consumers. This situation is analyzed in this paper, considering Mexican legislation about fuels and their usage. Sulfur is an important pollutant contained in diesel and gasoline fuels; it exhibits lubricant properties, helping to reduce the maintenance intervals of the machines and increase engine life. Therefore, its removal from fuel blends is a topic of great scientific interest as researchers look for different lubricant alternatives, which are relevant to motor vehicle engines.

The average annual water availability worldwide is approximately 1,386 trillion cubic hectometers (hm 3 ), of which 97.5% is saltwater and only 2.5% is freshwater. Nearly 70% is not available for human consumption as it is in glaciers, snow, and ice. It is estimated that only 0.77% is accessible freshwater for human use. Mexico has an availability of 451,584.7 million cubic meters (m 3 ) of freshwater, with accessibility and distribution being unequal. The growth in urbanization, population, and industrialization has caused a decrease in water quality, and other parameters. Organic and inorganic contaminants evolved from various sources cause the degradation of water quality. The pollution of aquatic bodies, such as rivers and lakes, is one of the main problems in the world. In Salvador Escalante in México, the domestic wastewaters treatment plant (WWTP) is being exposed to effluents contaminated with metals like copper, cadmium, lead, and mercury. In this work, active sludges from the WWTP were analyzed. First, particle size distribution of flocs was measured by a sedimentation process. Secondly, analysis of the tolerance that microorganisms exhibit to metals ( i.e. , factors) was performed, based on a 2 $\\hat {}$ (4-1) factorial design of experiments at laboratory-scale, measuring pH, chemical oxygen demand (COD) and electrical conductivity (responses). This aims to evaluate the capacity of the WWTP for improve the water quality. Microbiologic cultures were used for a qualitative study of the microorganisms contained in the active sludges; it was found that Enterobacterium does not grow in presence of heavy metals. Cadmium is the most harmful metal for microorganisms according to Pareto diagrams presented in this study.

Lignin is an abundant component in biomass that can be used a feedstock for producing several value-added products, including biofuels. However, lignin is a complex molecule (involving in its structure three types of phenylpropane units: coumaryl, coniferyl and sinapyl), which is difficult to implement in any process simulation task. The lignin from softwood is formed mainly by coniferyl units; therefore, in this work the use of the guaiacol molecule to model softwood lignin in the simulation of the syngas process (H2 + CO) is proposed. A Gibbs reactor in ASPEN PLUS® was feed with ratios of water and guaiacol from 0.5 to 20. The pressure was varied from 0.05 to 1.01 MPa and the temperature in the range of 200–3200 °C. H2, CO, CO2, CH4, O2 and C as graphite were considered in the output stream. The pressure, temperature and ratio water/guaiacol conditions for syngas production for different H2/CO ratio are discussed. The obtained results allow to determine the operating conditions to improve the syngas production and show that C as graphite and water decomposition can be avoided.

Although the lubrication systems for internal combustion engines have been designed to prevent engine wear and friction, their configuration does not contemplate the maximum use of each load of lubricant; because of this limitation, lubricant consumption is currently an environmental and economic problem. In this work, the performance of lubrication systems to form the tribological film that prevents wear is simulated and optimized, through the mass balance of the lubricant precursors contained in the oil and the implementation of optimal control techniques. Optimization results indicate that regulating the flow of lubricant passing through the engine prevents excessive degradation of lubricant precursors, maximizing the life of each lube oil charge, giving the possibility to increase the sustainability of internal combustion engines.

Avoiding global dependence on fossil oils and improving the environmental impact of energy production are factors that drive research into renewable energies. Considering lignocellulosic biomass residues as a raw material for gasification, a thermochemical process that converts lignocellulosic resources into synthesis gas (H2, CO, CH4, and CO2) is an alternative under study due to its low costs, high efficiency, and wide variety of applications. Fortunately, there are still areas for its improvement and technological development. For example, this can be achieved by gasification. Distinct types of lignocellulosic biomass, such as sugarcane bagasse, wheat straw, pine sawdust, or corn cob, differ in their physical, chemical, and morphological properties, which can affect the characteristics of the gasification process. This work uses the generalized stoichiometry and mass and atomic balances in the gasification reactor to predict the composition of syngas produced via the gasification of both individual substrates and mixtures. The results provide useful information for the design and operation of gasification reactors with an operating region between 2.0 bar and 4.5 bar and between 1023.15 K and 1223.15 K, particularly with regard to understanding the effects of distinct types of biomasses in terms of their humidity and molecular weight on the operation and performance of the process. One important conclusion reached after simulating the addition of more vapor is that the (H2/CO) ratio cannot be increased indefinitely: it is limited by the thermodynamic equilibrium reached by the system.

Currently, energy generation based on fossil fuels is producing negative environmental impacts; two of the main symptoms of these impacts are water pollution and climate change. Consequently, the search for new technologies to satisfy the energy demand must have the goal to minimise possible impacts to the environment. There are alternatives with biofuels and, among them, biodiesel. The cheapest reaction pathway for biodiesel production is the transesterification of triglycerides by methanol in the presence of sodium hydroxide; however, this option can contaminate large volumes of water used in the final leach of the biodiesel product. Therefore, a feasible way of producing this biofuel while simultaneously minimising leaching water will be environmentally friendly and will improve economical savings. The present study developed an experimental design in order to minimise the addition of NaOH during biodiesel production by the basic homogeneous pathway. The best operating conditions were 46 °C, methanol in situ 7.5% v/v and NaOH 0.035 M. These conditions allowed to reduce the leaching water amount by 25% compared to techniques reported in the literature; however, the yield to biodiesel decreased from 98 wt.% to 87 wt.% when a model waste oil was used instead of virgin oil.

Global population growth requires the use of various natural resources to satisfy the basic needs of humanity. Fossil fuels are mainly used to produce electricity, transportation and the artificial air conditioning of habitats. Nevertheless, countries around the world are looking for alternative energy sources due to the decrease in the availability of these fuels and their high environmental impact. The mixture of hydrogen and carbon monoxide (H2 + CO), commonly called syngas, is a high-value feedstock for various industrial applications. By varying the composition of syngas, especially the H2/CO molar ratio, it can be used to produce methanol, fuels or synthetic natural gas. However, when this ratio is very low, the separation of this gas usually represents a great problem when making the energy balance, which is why it is proposed to adapt a combustion process in chemical cycles, taking advantage of the energy of this gas, reducing the energy impact of the process. During the present project, mass and energy balances were developed for combustion in chemical cycles, using ilmenite as a carrier, integrating heat exchangers to take advantage of the residual energy at the output of the process, to preheat the inlet current in the regenerator. Here, a comparative was made at different temperatures of the air stream and evaluating the mechanism of the ilmenite when a syngas stream is used as fuel.

In this study, total phenolics, total flavonoids, hesperidin and ascorbic acid contents in bagasse, juice and seed of mexican sweet lime ( Citrus limetta ) and mandarine ( Citrus reticulata ) were determined at two commercial maturity stages (maturation index), as well as their bactericidal effect on Escherichia coli and Staphylococcus aureus . The results showed that bagasses had the highest total phenolics, total flavonoids, and hesperidin content for both, C. limetta , and C. reticulata ; highest ascorbic acid contents were found in C. limetta juice (3.36 ± 0.25 mg g −1 DW) and C. reticulata bagasse (3.83 ± 0.37 mg g −1 DW). All tested extracts showed bacterial growth inhibition at 50 and 800 µg mL −1 . Bagasse extracts of both fruits showed the highest inhibitions (>90%) on tested bacteria. Total phenolics, total flavonoids, and hesperidin contents, as well as bactericidal effect increased with maturity. Results indicated that both Mexican citric fruits ( C. limetta and C. reticulata ) were good sources of antioxidant and bactericidal agents.