On the Use of Styrene-Based Nanoparticles to Mitigate the Effect of Montmorillonite in Copper Sulfide Recovery by Flotation.

Clay minerals have different negative effects on the froth flotation process such as low adsorption of collectors on valuable minerals, increased pulp viscosity, and the reduction in recovery and grade concentrates of copper sulfides. This study aims to evaluate the use of polystyrene-based nanoparticles (NPs) for the froth flotation of chalcopyrite and their ability to mitigate the negative effect of montmorillonite on the recovery of this sulfide. The experimental stage consisted of preparing a type of polystyrene-based nanoparticle (St-CTAB-VI), which was analyzed by dynamic night scattering (DLS) to establish its hydrodynamic size. Then, the effect of NPs on chalcopyrite's angle's in the presence and absence of montmorillonite (15%) was evaluated and compared with the contact angle achieved using potassium amyl xanthate (PAX) and a mixture of PAX and NPs. In addition, zeta potential measurements were carried out to investigate the interactions between the chalcopyrite and the montmorillonite or the NPs under fixed concentrations and microflotation tests were performed employing different times to evaluate the chalcopyrite recovery in the presence of montmorillonite, using NPs and mixtures with PAX. Finally, turbidity analysis as a function of time was performed to evaluate the occurrence of sedimentation and flocculation phenomena in suspensions of 15% montmorillonite in the presence and absence of chalcopyrite, nanoparticles, and mixtures of NPs and PAX. The results indicated that the mixture of NPs and PAX contributed to increasing the contact angle of chalcopyrite in the presence of montmorillonite. This can be associated with the presence of molecular and nanometric collectors that generated a higher hydrophobicity on the chalcopyrite particles, contributing to reducing the presence of clay minerals on the mineral surface. In addition, the mixture of NPs and PAX promoted the generation of nanoparticles on the sulfide mineral surface, which helps to detach the slime and facilitate the bubble/mineral attachment step during flotation.

Foaming Properties of Lignosulfonates in the Flotation Process.

The widely used technology for the selective flotation of copper and molybdenite using sodium hydrosulfide (NaSH) to depress copper sulfides creates environmental issues related to the potential emissions of toxic hydrosulfide gas (H2S) and bad odors. Previous studies showed that molybdenite flotation can be depressed by the action of lignosulfonates, but no significant progress has been made in studying the effect that these reagents have on the foaming/frothing phenomena in flotation. The objective of this work was to investigate the foaming properties of three samples of lignosulfonates through measurements of surface tension, foamability, bubble size distributions, and water recovery. A sugared sodium lignosulfonate (NaLS), a calcium lignosulfonate (CaLS), and a sample prepared by sulphomethylation of kraft lignin (KLS) were tested. It was found that all lignosulfonates displayed surface activity that decreased with pH and was related to the degree of anionicity and molecular weight. The NaLS lignosulfonate showed the highest dynamic foamability index (DFI) value, compared to that of the CaLS and KLS samples. The lignosulfonates tested in this study strongly affected bubble size. Water recovery tests performed using flotation experiments in a two-phase system showed that the KLS and NaLS samples had the strongest effect, which correlated with the surface tension, foamability, and bubble size results.

Evaluating natural and anthropogenic inputs on the distribution of potentially toxic elements in urban soil of Valdivia, Chile.

The increasing population in urban areas in the last decades requires an effort to understand the geochemistry of contaminant elements in urban soil. Topsoil plays a crucial role in the exposure of Potentially Toxic Elements (PTEs) to humans through ingestion, dermal contact, and inhalation. In Chile, the last census revealed that 88.6% of people live in cities or towns and only 11.4% in rural areas. This study presents the first systematic geochemical survey of urban soil in the city of Valdivia, in the South of Chile. Topsoil samples (0-10 cm depth) were collected in less disturbed locations within the city at 130 sampling sites using a grid of 0.25 km2 squares covering a total area of approximately 30 km2. The concentrations of Al, Fe, Na, Ca, Mg, K, Ti, Be, V, Cr, Mn, Co, Ni, Cu, Zn, As, Mo, Sn, Cd, Se, Pb and Hg were measured. The results showed that high concentrations of Cu, V, Zn and Pb are located mainly in the city's northern area and exceed international soil quality legislation for agricultural use. Data processing comprised plotting of individual spatial distribution maps and the use of a combination of multivariate statistical methods. Hierarchical cluster analysis and principal component analysis identified three element associations. The two element groups V-Al-Ti-Fe-Cr-Co-Mn-Be-Ni and Ca-Na-K-As-Mg are interpreted as a dominant lithological origin related to the most pristine soil conditions in less populated areas. By contrast, the Sn-Pb-Zn-Mo-(Cu-Hg) association presents a significant correlation with urbanization indicators, including vehicular traffic and industrial activities developed since the end of the nineteenth century in Valdivia.

Use of Polystyrene Nanoparticles as Collectors in the Flotation of Chalcopyrite.

This study proposes the use of polymeric nanoparticles (NPs) as collectors for copper sulfide flotation. The experimental phase included the preparation of two types of polystyrene-based NPs: St-CTAB and St-CTAB-VI. These NPs were characterized by Fourier-Transform Infrared (FTIR) spectroscopy and dynamic light scattering (DLS). Then, microflotation tests with chalcopyrite under different pH conditions and nanoparticle dosages were carried out to verify their capabilities as chalcopyrite collectors. In addition, the zeta potential (ZP) measurements of chalcopyrite in the presence and absence of NPs were carried out to study their interaction. Lastly, some Atomic Force Micrographs (AFM) of NPs and Scanning Electronic Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis of NPs on the chalcopyrite surface were conducted to analyze the size, the morphology and their interaction. The results obtained at pH 6 and pH 8 show that the NPs under study can achieve a chalcopyrite recovery near or higher than that obtained with the conventional collector. In this study, it was possible to observe that the NPs functionalized by the imidazole group (St-CTAB-VI) achieved better performance due to the presence of this group in its composition, allowing to achieve a greater affinity with the surface of the mineral.

Frequency of Candida spp. in the Oral Cavity of Asymptomatic Preschool Mexican Children and Its Association with Nutritional Status.

Malnutrition is a public health problem in developing countries, affecting the child population, which favors the appearance of infections such as oral candidiasis. In Mexico, information on the presence of oral colonization by Candida spp. in asymptomatic children is scarce. The present study aimed to determine the presence of Candida spp. in the oral cavity of asymptomatic preschool Mexican children and its association with their nutritional status. A sample of oral mucosa was obtained using a sterile swab and then inoculated in Sabouraud dextrose agar with antibiotics, and the yeast growth was phenotypically identified. The anthropometric profile of children was performed based on the guidelines of the International Society for the Advancement of Kinanthropometry. In addition, eating habits were investigated. The possible associations between the variables were determined through the chi-square test (IC95%, p < 0.05) (GraphPad Prism 8.0). Among the 743 assessed children (403 boys and 340 girls), the average age was 4.6 years, and the average nutritional status was normal (53.7%), followed by undernutrition (28.4%), overweight (12.4%) and obesity (5.5%). In 52 children, Candida was isolated, and the identified species were C. albicans (87.8%), C. glabrata (11.5%), C. krusei (5.8%) and C. parapsilosis (1.9%). The frequency of colonization was greater in males of six years (69.23%). There was no significant association between the colonization by Candida spp. and the nutritional status; however, a relation was observed with a high intake of simple carbohydrates.

Molecular Dynamics Simulations of the Interactions between a Hydrolyzed Polyacrylamide with the Face and Edge Surfaces of Molybdenite.

Process water used in mineral processing operations corresponds to water recovered from the thickeners and tailings dams, containing residual reagents such as hydrolyzed polyacrylamides (HPAMs). These polymers depress the flotation of different minerals, and their effect on molybdenite has been experimentally demonstrated. The objective of this work was to study the interactions between a segment of a HPAM with the face and edge of molybdenite. The sigma profile, the radial distribution functions of the HPAM, and the orientation and atomic density profiles of water molecules on the face and edge surfaces of molybdenite were calculated. The results obtained from molecular dynamics simulations showed that the interactions between the HPAM and molybdenite are mainly explained by the interactions of the amide group with the faces and edges of the mineral. Molecular dynamics simulations also showed that the HPAM molecule rearranges in such a way that the amide group moves towards the molybdenite face or edge, and the carboxylate group moves away from the mineral surface. The results obtained in the simulations showed that the interactions of the HPAM with the molybdenite edge are slightly stronger than the interaction of this molecule with the mineral face. Simulations demonstrated that the presence of the sodium and hydroxide ions reduces the concentration of HPAM around the face and edge surfaces, which is expected to affect HPAM adsorption on molybdenite. The conclusions obtained through molecular dynamics simulations are in line with the results obtained in previous studies carried out at a macroscopic scale, which reported that HPAMs adsorb onto molybdenite particles and reduce their hydrophobicity.

Understanding the Interaction of Lignosulfonates for the Separation of Molybdenite and Chalcopyrite in Seawater Flotation Processes.

The selective separation of molybdenite from copper sulfide concentrate in flotation process is realized using sodium hydrosulfide (NaHS) to depress the chalcopyrite and permit only the flotation of the molybdenite. However, this reagent is a highly toxic and flammable gas. The objective of this research was to study the feasible application of commercial lignosulfonates (LSs) in the separation by froth flotation process of molybdenite and chalcopyrite in seawater to present a novel application for LSs, as well as an alternative reagent to sodium hydrosulfide (NaHS). To achieve this, microflotation, absorbance tests and zeta potential measures were performed at pH 8 in seawater and 0.01 M NaCl. The results obtained in this study showed that it is possible to achieve selective separation of copper and molybdenum in both aqueous media due to high depressant effect of molybdenite and low depression of chalcopyrite in microflotation tests at 10 ppm of LSs, when the collector, PAX, is added prior to the addition of LSs. Absorbance study and zeta potential measurements showed that LSs adhere more to the molybdenite surface in seawater than in freshwater. This is related to the high ionic charge of the media that influences a greater interaction of LSs with the mineral surface.

The Impact of Residual Dispersant on the Flocculation and Sedimentation of Synthetic Tailings in Seawater.

Dispersants under certain conditions favor the flotation of molybdenite in seawater; however, it is not clear if the entrainment of residues to the thickening stage can compromise the quality of the clarified water. In this work, the impact of small concentrations of sodium hexametaphosphate (SHMP) on the flocculation and sedimentation of synthetic tailings containing kaolinite, muscovite, and quartz in seawater is evaluated. The flocculant polymer is a high-molecular-weight polyacrylamide, and the pH is alkaline. The results are auspicious for mineral processing. On the one hand, the impact of SHMP is not entirely negative and can be lessened by limiting entrainment, which is good for copper and molybdenum ore processing. On the other hand, if the small increase in turbidity generated by the SHMP is tolerated, it is possible to expect improved settling speeds. Without SHMP, large but light agglomerates are formed. With SHMP, smaller but denser aggregates are formed, settling faster, and minute aggregates increase turbidity. The underlying mechanism derives from the competition between SHMP and polymer chains for the cations in solution; the result is a greater repulsion between the chains, which leads to greater repulsion and thus dispersion of smaller flocculant coils. The study shows that SHMP in concentrations of 1 to 3 kg/t is perfectly acceptable. The results represent an advance in the understanding of SHMP interactions with polymers and minerals in water clarification, which should be of interest to the industry whose sustainability in some regions depends on closing the water cycle.

Evaluación comparativa del pie plano en preescolares / Comparative assessment of flatfoot in preschool children

Resumen Introducción: El aumento o la reducción del arco longitudinal medial (ALM) puede afectar funciones esenciales en la biomecánica del pie, con repercusiones en la salud a largo plazo. El objetivo del presente estudio fue determinar la altura del ALM en niños de 3 a 6 años, a través de cinco métodos de análisis de huella para el diagnóstico de pie plano. Métodos: Se realizó un estudio observacional transversal con 367 niños de 3 a 6 años en un municipio del Estado de México. Se llevó a cabo una evaluación postural completa, plantoscopía por medio de la clasificación de Viladot y análisis de la huella en pedigrafía, calculando la altura del ALM mediante el ángulo de Clarke (AC), el índice de Staheli (IS), el índice de Chippaux-Smirak (ICS) y el ángulo gamma (Ag). Resultados: La prevalencia de pie plano utilizando el podoscopio fue del 57.7%. Mediante los ángulos y los índices, la prevalencia fue del 86.9% por IS, del 83.3% por ICS, del 95.9% por AC y del 22.3% por Ag. El Ag fue menos sensible para la detección de pie plano en comparación con el ICS, el IS y el AC. Conclusiones: De acuerdo con los resultados del presente estudio, se propone utilizar métodos de análisis de huella para el diagnóstico de pie plano, además de la valoración clásica con el podoscopio. Se recomienda incluir el diagnóstico y la vigilancia del pie plano en la consulta del niño sano, ya que desde edades tempranas puede detectarse la tendencia en la arquitectura podálica.

Abstract Background: The increase or reduction of the medial longitudinal arch (MLA) can affect essential functions in the foot biomechanics with long-term health consequences. The aim of the present study was to determine the height of the MLA in children from 3 to 6 years of age through five methods of footprint analysis for the diagnosis of flat foot. Methods: A cross-sectional observational study was conducted with 367 children aged 3 to 6 years in a municipality of the State of Mexico. We conducted a complete postural evaluation, plantoscopy by Viladot classification, and footprint analysis calculating the height of the ALM using the Clarke angle (CA), the Staheli index (SI), the Chippaux-Smirak index (CSM), and the gamma angle (gA). Results: The prevalence of flat feet using the podoscope was 57.7%. Through the angles and indexes, the prevalence was 86.9% for SI, 83.3% for CSI, 95.9% for CA, and 22.3% for gA. The gA was less sensitive for flat foot detection compared to CSI, SI and CA. Conclusions: Based on the present results, we propose that footprint analysis should be used for flat foot diagnosis besides the classic evaluation by podoscope. We recommend that flat foot diagnosis and surveillance should be included on in the consultation of the healthy child, as a trend for podalic architecture can be detected from early ages.

Comparative assessment of flatfoot in preschool children.

Background: The increase or reduction of the medial longitudinal arch (MLA) can affect essential functions in the foot biomechanics with long-term health consequences. The aim of the present study was to determine the height of the MLA in children from 3 to 6 years of age through five methods of footprint analysis for the diagnosis of flat foot. Methods: A cross-sectional observational study was conducted with 367 children aged 3 to 6 years in a municipality of the State of Mexico. We conducted a complete postural evaluation, plantoscopy by Viladot classification, and footprint analysis calculating the height of the ALM using the Clarke angle (CA), the Staheli index (SI), the Chippaux-Smirak index (CSM), and the gamma angle (gA). Results: The prevalence of flat feet using the podoscope was 57.7%. Through the angles and indexes, the prevalence was 86.9% for SI, 83.3% for CSI, 95.9% for CA, and 22.3% for gA. The gA was less sensitive for flat foot detection compared to CSI, SI and CA. Conclusions: Based on the present results, we propose that footprint analysis should be used for flat foot diagnosis besides the classic evaluation by podoscope. We recommend that flat foot diagnosis and surveillance should be included on in the consultation of the healthy child, as a trend for podalic architecture can be detected from early ages.

Background: Introducción">El aumento o la reducción del arco longitudinal medial (ALM) puede afectar funciones esenciales en la biomecánica del pie, con repercusiones en la salud a largo plazo. El objetivo del presente estudio fue determinar la altura del ALM en niños de 3 a 6 años, a través de cinco métodos de análisis de huella para el diagnóstico de pie plano. Métodos: Se realizó un estudio observacional transversal con 367 niños de 3 a 6 años en un municipio del Estado de México. Se llevó a cabo una evaluación postural completa, plantoscopía por medio de la clasificación de Viladot y análisis de la huella en pedigrafía, calculando la altura del ALM mediante el ángulo de Clarke (AC), el índice de Staheli (IS), el índice de Chippaux-Smirak (ICS) y el ángulo gamma (Ag). Resultados: La prevalencia de pie plano utilizando el podoscopio fue del 57.7%. Mediante los ángulos y los índices, la prevalencia fue del 86.9% por IS, del 83.3% por ICS, del 95.9% por AC y del 22.3% por Ag. El Ag fue menos sensible para la detección de pie plano en comparación con el ICS, el IS y el AC. Conclusiones: De acuerdo con los resultados del presente estudio, se propone utilizar métodos de análisis de huella para el diagnóstico de pie plano, además de la valoración clásica con el podoscopio. Se recomienda incluir el diagnóstico y la vigilancia del pie plano en la consulta del niño sano, ya que desde edades tempranas puede detectarse la tendencia en la arquitectura podálica.

Polipectomía colónica en niños: experiencia de 6 años / Polypectomía of the colon in children: a six-year experienceç

En una revisión retrospectiva de 6 años que abarcó un total de 4287 expedientes de los servicios de Endoscopia y Coloproctología del hospital general Dr. Fernando Quiróz Gutiérrez del ISSSTE en México D.F., encontramos 72 pacientes con pólipos del tubo digestivo con la siguiente distribución topográfica: Faringe 7, esófago 2, estómago 28, duodeno 7 y colon 28, de estos el 46 por ciento (trece) eran niños con edad entre 2 y 12 años con una media de 7 años, siete eran del sexo masculino y 6 del femenino. En todos se practicó polipectomía transendoscópica usando anestesia general en el 92 por ciento de ellos. Todos, excepto uno que presentó rectorragia al quinto día de la resección, evolucionaron satisfactoriamente. Histológicamente siete fueron polipos juveniles, 3 adenomatosos y uno hiperplásico. No hubo muertes.