Exploratory study on the presence of bisphenol A and bis(2-ethylhexyl) phthalate in the Santa Catarina River in Monterrey, N.L., Mexico.

The current problem related to the supply of drinking water for the metropolitan area of Monterrey, which comprises of five million inhabitants, and the important role played by the El Cuchillo Dam, found downstream of the Santa Catarina River basin as a surface source of drinking water for the city, renders this river an interesting site for assessment. This work evaluates the degree to which the surface water and the subsoil of the river are affected by emerging organic pollutants due to their existence, even at low concentrations, representing a toxic risk enhanced by the absence of stricter standards for regulating these substances. Based on fieldwork, three discharge points that could affect the quality of the surface water were selected: two points on the river stream, and three groundwater wells. Gas chromatography results showed the presence of BisPhenol A (BPA) and bis(2-EthylHexyl) Phthalate (DEHP) in both the surface water and subsoil at different seasons of the year. The highest concentration levels in the samples taken from both types of water were 0.9 and 60 µg L-1 for BPA and DEHP, respectively. Results of this research did not reveal the level at which the aquifer is affected by these substances.

Mechanical Properties and Durability of Composite Cement Pastes Containing Phase-Change Materials and Nanosilica.

Escalating global surface temperatures are highlighting the urgent need for energy-saving solutions. Phase-change materials (PCMs) have emerged as a promising avenue for enhancing thermal comfort in the construction sector. This study assessed the impact of incorporating PCMs ranging from 1% to 10% by mass into composite Portland cement partially replaced by fly ash (FA) and nanosilica particles (NS). Mechanical and electrochemical techniques were utilized to evaluate composite cements. The results indicate that the presence of PCMs delayed cement hydration, acting as a filler without chemically interacting within the composite. The combination of FA and PCMs reduced compressive strength at early ages, while thermal conductivity decreased after 90 days due to the melting point and the latent heat of PCMs. Samples with FA and NS showed a significant reduction in the CO2 penetration, attributed to their pozzolanic and microfiller effects, as well as reduced water absorption due to the non-absorptive nature of PCMs. Nitrogen physisorption confirmed structural changes in the cement matrix. Additionally, electrical resistivity and thermal behavior assessments revealed that PCM-containing samples could reduce temperatures by an average of 4 °C. This suggested that PCMs could be a viable alternative for materials with thermal insulation capacity, thereby contributing to energy efficiency in the construction sector.

Evaluation of the catalytic oxidation of soot by CeOX-LaMnO3 at different O2 pressures synthesized by ultrasonic-assisted hydrothermal method.

In this work, the synthesis of catalyst with perovskite structure and chemical formula La1-XCeXMnO3 at x = 0 - 0.5 were successfully obtained by an ultrasonic-assisted hydrothermal method. Results show that the addition of Ce in La1-XCeXMnO3 have not substantial effect in textural and morphological properties; however, the formation of a new crystalline phase with final composition CeOX-La1-XCeXMnO3 was detected at values x > 0.3. All synthesized catalysts were tested in the soot oxidation under both, loose and tight contact in 20% O2/N2 or 5% O2/N2 atmospheres. CeOX-La1-XCeXMnO3 at x = 0.3 resulted in the best catalytic activity with activation energy values of 57.9 kJ.mol-1. The interaction between Ce3+ and Mn4+ species in this catalyst can transfer electrons generating Mn3+ and Ce4+. This reduction from Mn4+ to Mn3+ is accompanied by migration of vacancies to the surface promoting the adsorbed oxygen from the gas phase, need for balancing the chemical states. By increasing the temperature above 300 °C, the bulk oxygen migration to the surface is enhanced being the responsible for the oxygen availability. The formation of CeOX-La1-XCeXMnO3 promotes a stable redox cycle allowing the reusability of this catalyst even at low oxygen pressures after three different reaction cycles.

Methylene blue degradation by NaTaO3 sol-gel doped with Sm and La.

In this work, NaTaO(3) compounds doped with 1M% of La and Sm, were prepared by the sol-gel (SG) method and solid state (SS) reaction; and tested as photocatalysts on the degradation of methylene blue (MB) under UV light. The structural characterization by X-ray powder diffraction revealed that the crystallization of the NaTaO(3) phase prepared by the sol-gel method started at 600 degrees C, reaching maximum crystallization at 800 degrees C. It was determined that the presence of Sm and La retard the crystallization of the NaTaO(3) phase. On the other hand, the compounds synthesized in this work showed particle sizes in the nanometric scale, as it was observed by scanning electron microscopy (SEM). The specific surface area of the compounds synthesized by the sol-gel method, showed values 4 times higher than those obtained by the solid state reaction, favoring their functional and photocatalytic performance in the methylene blue degradation. In addition, the best photocatalytic performance was shown by the NaTaO(3) doped with Sm and heated at 600 degrees C, having a half-life time of 65 min.