ZnAl hydrotalcites modified with nanocomposites nZVI–PAA for environmental remediation

Diffraction patterns of polyacrylic acid (PAA) encapsulated-(Fe)-modified ZnAl hydrotalcite (ZnAlH) showed the integration of Fe in the H lattice, resulting in a hybrid nanocomposite (Fe-PAA-ZnAlH), which was mainly verified with the characteristic shift in the 59–63° (2θ) region of the ZnAlH (110) reflection plane. The rise in the unit cell parameters (c and a) as the Fe % incremented, denoted incorporation of Fe in the ZnAlH red. Nonetheless, changes in the immobilizer molecular weight (PAA MW) from 1250 kDa to 5.1 kDa did not cause a difference in the distance between layers (c parameter) but in the cation-cation separation (a parameter), which meant that the nanoparticle was not located between layers, but in the lattice. The resulting band gap energies of the calcined hybrid nanocomposites were among 1.07–1.21 eV, which is an additional support of Fe+3 integration, suggesting insertion of Fe+3 3d orbitals between the valence and the conduction band of ZnO. Furthermore, nZVI were prepared through a pre-agglomeration reduction method, where COOH-groups were bound to metal cations. Initially, aqueous Fe+2 was bound to PAA [Fe+2-PAA], then reduced to obtain enclosed hybrid (nZVI-PAA). Less stability and more aggregation were observed with the lower molecular weight PAA. Additionally, PAA dissociation caused by pH changes affected the clustering of the nZVI particles. At higher MW, the hydrodynamic diameter and size distribution become smaller and tighter, respectively, allowing a more monodispersed population with sphere shape and organized in core–shell beads chains.Fil: Nieto Zambrano, Sorelis. Universidad de Guanajuato; MéxicoFil: Ramos Ramirez, Esthela. Universidad de Guanajuato; MéxicoFil: Tzompantzi Morales, Francisco. Universidad Autónoma Metropolitana; MéxicoFil: Boffito, Daria Camilla. No especifíca;Fil: Naccache, Rafik. Concordia University; CanadáFil: Gutiérrez Ortega, Norma L.. Universidad de Guanajuato; MéxicoFil: Litter, Marta Irene. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigación e Ingeniería Ambiental; ArgentinaFil: Cipagauta Diaz, Sandra. Universidad Autónoma Metropolitana; MéxicoFil: Barbosa López, Aida Liliana. Universidad de Cartagena.; Colombi

Ecoinhibidores para mitigar los efectos de corrosión en artefactos antiguos

Muestras de artefactos antiguos de la batería de San Rafael-Bocachica �Colombia, fueron analizados por microscopia estereoscópica, Ramán, FT-IR-MIR y DRX, con el fin de determinar su grado de corrosión. Paralelamente se desarrollo la optimización de la extracción de cera presente en el bagazo de caña, residuo agroindustrial de la zona, paso primario en la obtención de un ecoinhibidor de corrosión enriquecido con propoleo y una base de fosfato de molibdeno y zinc

Películas pasivantes protectora de óxido/carbonato de cinc en la zona splash de estructuras metálicas de acero al carbón

Películas pasivantes con zinctape® fueron inducidas, sobre estructuras de acero al carbón de un muelle expuesto en ambiente salino y aireación diferencial, el brazo de descarga, con elevado desgaste mecánico y los pilotes de soporte, fueron limpiados con ultra alta presión y realizadas soldaduras tipo cañuelas (casquetes) para reconstruir las zonas perdidas. Las columnas fueron protegidas con zinctape® desde la zona de splash hacia arriba, con un cinta de cinc de 100 mm de ancho, espesor de la capa de cinc 0,08mm, espesor de adhesivo electro conductivo de 0,025 mm. Paralelamente fue habilitado el sistema de protección catódica con corriente impresa. Las estructuras fueron rehabilitadas en un 100% por acción conjunta de los dos métodos de protección. Uno químico al inducir con la cinta, la formación de una capa delgada, resistente, compacta y estable (insoluble en agua) del carbonato de cinc y otro fisicoquímico como corriente impresa. Esta mitología es amigable con el medio ambiente y económicamente rentable, con una duración asegurada de mínimo 10 años

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved

Diminishing benefits of urban living for children and adolescents’ growth and development

Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified