Various crystallite size estimation methods were used to analyze X-ray diffractograms of spherical cerium dioxide and titanium dioxide anatase nanoparticles aiming to evaluate their reliability and limitations. The microstructural parameters were estimated from several integral breadth methods such as Scherrer, Monshi, Williamson–Hall, and their variants: (i) uniform deformation model, (ii) uniform strain deformation model, and (iii) uniform deformation energy density model. We also employed the size–strain plot and Halder–Wagner method. For this purpose, an instrumental resolution function of an Al2O3 standard was used to subtract the instrumental broadening to estimate the crystallite sizes and strain, and the linear regression analysis was used to compare all the models based on the coefficient of determination. The Rietveld whole powder pattern decomposition method was introduced for comparison purposes, being the best candidate to fit the X-ray diffraction data of metal-oxide nanoparticles. Refined microstructural parameters were obtained using the anisotropic spherical harmonic size approach and correlated with the above estimation methods and transmission electron microscopy images. In addition, μ-Raman spectra were recorded for each material, estimating the mean crystallite size for comparison by means of a phonon confinement model.

The purpose of this study was to determine PM2.5 mass concentration and the contents of trace elements and water-soluble ions in samples collected inside the Metropolitan area of Huancayo. Four monitoring stations were installed at three urban areas (UNCP, HYO, and CHI) and one rural (IGP). The sampling campaign was carried out from March 2017 to November 2017. The PM2.5 content was determined by gravimetric method, and fifteen trace elements (TE) and seven water-soluble ions were detected by inductively coupled plasma mass spectrometry (ICP–MS), and ion chromatography (IC), respectively. Datasets were assessed by one ANOVA test to detect significant differences among monitoring station. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) were applied for source identification. The mean annual concentration of PM2.5 mass concentrations has ranged (average) from 3.4 to 36.8 µg/m3 (16.6 ± 6.8 µg/m3) for the monitoring stations under study. The annual World Health Organization thresholds and national air quality standards were exceeded. Significant differences (p < 0.05) were observed between most trace elements at urban and rural areas. PCA and HCA illustrated that the most important sources of traces element originated of natural origin (soil re-suspension) and vehicular sources (fuel combustion, abrasion of vehicles tires, wear car components).

Various crystallite size estimation methods were used to analyze X-ray diffractograms of spherical cerium dioxide and donut-like titanium dioxide anatase nanoparticles aiming to evaluate their reliability and limitations. The microstructural parameters were estimated from Scherrer, Monshi, Williamson-Hall, and their variants: i) uniform deformation model, ii) uniform strain deformation model, and iii) uniform deformation energy density model, and also size-strain plot, and Halder-Wagner method. For that, and improved systematic Matlab code was developed to estimate the crystallite sizes and strain, and the linear regression analysis was used to compare all the models based on the coefficient of determination, where the Halder Wagner method gave the highest value (close to 1). Therefore, being the best candidate to fit the X-ray Diffraction data of metal-oxide nanoparticles. Advanced Rietveld was introduced for comparison purposes. Refined microstructural parameters were obtained from a nanostructured 40.5 nm Lanthanum hexaboride nanoparticles and correlated with the above estimation methods and transmission electron microscopy images. In addition, electron density modelling was also studied for final refined nanostructures, and &mu;-Raman spectra were recorded for each material estimating the mean crystallite size and comparing by means of a phonon confinement model.

Esta investigación fue realizada con los efluentes de la Planta Piloto Metalúrgica de Yauris, con la intención de disminuir los niveles de contaminación con metales pesados, especialmente el plomo, por los daños que ocasiona al ecosistema. En este trabajo se determinó las condiciones óptimas de tiempo, temperatura y pH para la adsorción del plomo. La bentonita natural fue pilareada con una solución de aluminio polihidroxipolimérico proveniente de Mitupampa, distrito de Chongos Alto, provincia de Chupaca, el cual mediante el análisis de Difracción de Rayos X (DRX) presenta un elevado contenido de montmorillonita. Presentaron superficies especificas de 80,52 m2/g y 137,023 m2/g, determinada por adsorción de azul de metileno y una capacidad de intercambio catiónico (CIC) de 87,29 y 71,15 meq/100g de bentonita, respectivamente. Las condiciones óptimas de adsorción se realizaron en un tiempo de remoción de 5 horas, temperatura 30 OC y pH 5, encontrándose 99,085 % de plomo presente en estado iónico, lográndose un rendimiento de 5,39g de Pb/g de bentonita pilareada. Al evaluar la remoción del metal en la muestra de efluente metalúrgico se registró un 62,55 %, cantidad menor al obtenido con la solución en blanco de Pb, debido a la presencia de otros metales, que actúan como interferentes. Razón por la cual se realizó varias etapas de remoción alcanzando una concentración final de plomo de 0,205ppm, valor que resulta ser menor a los límites máximos permisibles.

La presencia del cadmio Cd(II) en las aguas residuales domésticas e industriales, es propia del desarrollo industrial y crecimiento poblacional, su toxicidad, su efecto cancerígeno y su naturaleza bioacumulable son peligrosas para la salud. Se ha elegido el estiércol de ganado vacuno como adsorbente para evaluar su capacidad de adsorción de Cd(II). De soluciones preparadas a diferentes concentraciones donde el pH y el tiempo de contacto son las variables críticas del proceso. Al caracterizar el estiércol de ganado vacuno, la mayoría a los grupos funcionales corresponden a la pectina, celulosa, hemicelulosa y lignina, con gran capacidad para fijar iones de Cd(II), el análisis MEB, muestra indicios de formación de poros, el microanálisis elemental EDX muestra que está compuesta por 48 % de carbono facilitando que los iones de Cd(II) se unan a las superficies del carbono, el análisis CIC indica que las superficies están cargados negativamente, atrayendo por fuerzas electrostáticas a los iones del Cd(II). La dosificación del estiércol de ganado vacuno fue de 0.0023 g/mL alcanzando una remoción alrededor del 90 %, haciendo innecesario un incremento de adsorbente. El pH óptimo para la adsorción de Cd(II) fue de 3.5, indicando que en un medio ácido se logra una desprotonación de los grupos carboxílicos, fenólicos y la mayoría de los grupos funcionales del estiércol, con uno y dos átomos de oxígeno cargados negativamente que actúan como agentes acomplejantes, que atraen a los iones de Cd(II). Finalmente, con 1 g de adsorbente se puede adsorber 2.3726 mg de Cd(II) de soluciones acuosas.