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Chalcopyrite, the world's primary copper ore mineral, is abundant in Latin America. Copper extraction offers significant economic and social benefits due to its strategic importance across various industries. However, the hydrometallurgical route, considered more environmentally friendly for processing low-grade chalcopyrite ores, remains challenging, as does its concentration by froth flotation. This limited understanding stems from the poorly understood structure and reactivity of chalcopyrite surfaces. This study reviews recent contributions using density functional theory (DFT) calculations with periodic boundary conditions and slab models to elucidate chalcopyrite surface properties. Our analysis reveals that reconstructed surfaces preferentially expose S atoms at the topmost layer. Furthermore, some studies report the formation of disulfide groups (S22-) on pristine sulfur-terminated surfaces, accompanied by the reduction of Fe3+ to Fe2+, likely due to surface oxidation. Additionally, Fe sites are consistently identified as favourable adsorption locations for both oxygen (O2) and water (H2O) molecules. Finally, the potential of computer modelling for investigating collector-chalcopyrite surface interactions in the context of selective froth flotation is discussed, highlighting the need for further research in this area.

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AIM: To assess the effectiveness of Bacillus subtilis strain LN8B as a biocollector for recovering pyrite (Py) and chalcopyrite (CPy) in both seawater (Sw) and deionized water (Dw), and to explore the underlying adhesion mechanism in these bioflotation experiments. MATERIALS AND METHODS: The bioflotation test utilized B. subtilis strain LN8B as the biocollector through microflotation experiments. Additionally, frother methyl isobutyl carbinol (MIBC) and conventional collector potassium amyl xanthate (PAX) were introduced in some experiments. The zeta potential (ZP) and Fourier-transform infrared spectroscopy (FTIR) was employed to explore the adhesion mechanism of Py and CPy interacting with the biocollector in Sw and Dw. The adaptability of the B. subtilis strain to different water types and salinities was assessed through growth curves measuring optical density. Finally, antibiotic susceptibility tests were conducted to evaluate potential risks of the biocollector. RESULTS: Superior outcomes were observed in Sw where Py and CPy recovery was ∼39.3% ± 7.7% and 41.1% ± 5.8%, respectively, without microorganisms' presence. However, B. subtilis LN8B potentiate Py and CPy recovery, reaching 72.8% ± 4.9% and 84.6% ± 1.5%, respectively. When MIBC was added, only the Py recovery was improved (89.4% ± 3.6%), depicting an adverse effect for CPy (81.8% ± 1.1%). ZP measurements indicated increased mineral surface hydrophobicity when Py and CPy interacted with the biocollector in both Sw and Dw. FTIR revealed the presence of protein-related amide peaks, highlighting the hydrophobic nature of the bacterium. The adaptability of this strain to diverse water types and salinities was assessed, demonstrating remarkable growth versatility. Antibiotic susceptibility tests indicated that B. subtilis LN8B was susceptible to 23 of the 25 antibiotics examined, suggesting it poses minimal environmental risks. CONCLUSIONS: The study substantiates the biotechnological promise of B. subtilis strain LN8B as an efficient sulfide collector for promoting cleaner mineral production. This effectiveness is attributed to its ability to induce mineral surface hydrophobicity, a result of the distinct characteristics of proteins within its cell wall.

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Resumo A catação de materiais recicláveis é uma ocupação com crescente número de trabalhadores, que encontram nela sustento diante das desigualdades socioeconômicas e do desemprego. Este artigo descreve as estratégias de resistência de mulheres catadoras que fazem parte de uma associação no Nordeste brasileiro, além da forma como elas lidaram com problemas de saúde durante a pandemia de covid-19, especialmente no que se refere aos medicamentos. Utilizamos uma abordagem quantitativa e uma etnográfica, coletando dados sociodemográficos de 13 participantes e dos medicamentos presentes em suas casas, e também realizando observação participante e entrevistas aprofundadas. Em meio à crise sanitária, foram mencionados problemas como o desemprego, as relações de gênero, a violência e os estigmas do trabalho. Se por um lado a pandemia vulnerabilizou ainda mais alguns segmentos populacionais, por outro potencializou estratégias coletivas de enfrentamento. As catadoras e a associação se organizaram para obter insumos e melhorias tanto na sede quanto no bairro. Identificamos 58 unidades de medicamentos, prescritos e obtidos principalmente na Unidade Básica de Saúde. Desses, 27,6% tinham ação sobre o sistema nervoso (analgésicos, psicolépticos e psicoanalépticos) e 17,2% sobre o sistema cardiovascular e sobre o trato alimentar e metabolismo. As catadoras desenvolveram práticas de autoatenção com os medicamentos, destacando o papel central deles no enfrentamento dos problemas de saúde.

Abstract The collection of recyclable materials is an occupation with an increasing number of workers, who find in it a livelihood in a context of socioeconomic inequalities and unemployment. This article describes resistance strategies of women collectors who are part of an association in Northeast Brazil, in addition to describing how they managed health problems during the COVID-19 pandemic, especially regarding medicines. A quantitative and an ethnographic approach were used by collecting data on sociodemographic and medicines present in the homes of 13 participants and conducting participant observation and in-depth interviews. Amid the health crisis, the participants mentioned problems such as unemployment, gender relations, violence, and work stigmas. If, on the one hand, the pandemic has further increased vulnerability for certain population segments, on the other hand, it has enhanced collective resistance strategies. The collectors of the association organized to obtain various materials and benefits both for their headquarters and their neighborhood. We identified 58 units of medicines, prescribed and obtained mainly at the Basic Health Unit. Of these, 27.6% had action on the nervous system (analgesics, psycholeptics, and psychoanaleptics) and 17.2% on the cardiovascular system and on the alimentary tract and metabolism. The collectors developed self-attention practices with the medicines highlighting their central role in facing health problems.

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Los captadores de niebla son usados para interceptar agua contenida en la niebla y abastecer de agua a comunidades que habitan en lugares donde este recurso escasea. Se evaluó el uso de captadores de niebla para la captación de agua en un área ubicada en el páramo Pan de Azúcar, Duitama-Boyacá. Se instalaron 60 captadores de niebla, 24 de ellos, con dispositivos para medir los volúmenes de agua interceptados. Los volúmenes de agua captados, se midieron en periodos de 24 horas, por 26 días, durante un año y se usó el modelo geométrico para diferenciar el agua proveniente de la niebla. La precipitación registrada fue mayor a la reportada en la literatura. La precipitación mensual osciló entre 51 y 1198 mm y la temperatura media mensual entre los 6 y 8 °C. Los volúmenes de agua promedio colectados por los 24 captadores de niebla estuvieron entre los 0,02 Lm-2dia-1 hasta los 4,4Lm-2dia-1. Los aportes de agua provenientes de la niebla oscilaron entre los 0,02 y 1,77 mmdía-1. La dirección del viento no afectó la captación de agua y aún se presenta incertidumbre al separar el aporte real de agua proveniente de la niebla a partir de la lluvia orográfica, lo cual, sigue siendo un desafío en los ecosistemas de páramo, por lo que se debe ampliar la investigación, para mejorar los diseños y las eficiencias de los captadores de niebla.

Fog collectors are used to intercept water contained in fog and supply water to communities that live in places where this resource is scarce. We evaluated the use of mist collectors to collect water in an area located in the Pan de Azúcar paramo, Duitama-Boyacá. We installed 60 mist collectors, 24 of them with devices to measure the volumes of water intercepted. The volumes of water captured were measured in periods of 24 hours for 26 days during one year and we used the geometric model to differentiate the water from the fog. The recorded precipitation was higher than that reported in the literature. Monthly rainfall ranged between 51 and 1198mm and mean monthly temperature ranged between 6 and 8°C. The average volumes of water collected by the fog collectors were below 0.5Lm-2day-1 with a maximum of 4.4Lm-2day-1. The contributions of water from the mist ranged between 0.02 and 1.77 mmday-1. The direction of the wind did not affect the capture of water and there is still uncertainty when separating the real contribution of water from the fog from the orographic rain, which continues to be a challenge in the paramo ecosystems, for which it is necessary to expand research, to improve the designs and efficiencies of fog collectors.

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L'article présente une expérience d'analyse des activités du travailleur de la collecte des déchets dans une ville, basée sur le dispositif de l'Atelier photo et ayant comme référence théorique la Clinique de l'Activité. L'objectif de l'étude est d'analyser l'activité des travailleurs exerçant le métier d'éboueurs dans une ville de l'État de Rio de Janeiro. L'Atelier photo a été choisi comme dispositif de recherche et d'intervention afin d'utiliser les images comme déclencheurs de la coanalyse du travail, faisant émerger une réalité collective, présente dans toutes les activités de travail. L'objectif de ce dispositif est de déclencher, à partir de la production d'images, des questions et des réflexions sur l'activité de travail. En ce sens, à travers les résultats recueillis lors de cette recherche et intervention, il est devenu évident que l'Atelier photo peut être un dispositif possible dans le développement du pouvoir d'agir des travailleurs, permettant ainsi des échanges collectifs, le genre professionnel étant un instrument décisif du pouvoir d'agir des personnes impliquées.(AU)

The article presents an experience of analysis of the activities of the garbage collection worker in a city, based on the device of the Photo Workshop and having as a theoretical reference the Clinic of the Activity. The focus of the study is on the analysis of the activity of workers who work as garbage collectors in a city in the state of Rio de Janeiro. The Photo Workshop was chosen as a research and intervention device in order to use the images as triggers for the co-analysis of the work, giving rise to a collective reality, present in all work activities. The purpose of this device is to trigger, from the production of images, questions and reflections about the work activity. In this sense, through the results collected from this research and intervention, it became evident that the Photo Workshop can be a possible device in the development of the workers' power to act, thus enabling collective exchanges, with the professional genre being a decisive instrument of the workers' power to act. involved.(AU)

O artigo apresenta uma experiência de análise das atividades do trabalhador de coleta de lixo em uma cidade, com base no dispositivo de Oficina de fotos e tendo como referência teórica a Clínica da Atividade. O foco do estudo está na análise da atividade dos trabalhadores que exercem o ofício de coletores de lixo, em uma cidade do Estado do Rio de Janeiro. A Oficina de fotos foi escolhida como dispositivo de pesquisa e intervenção a fim de utilizar as imagens como disparadores da co-análise do trabalho, fazendo emergir uma realidade coletiva, presente em todas as atividades de trabalho. O objetivo desse dispositivo é disparar, a partir da produção de imagens, questionamentos e reflexões acerca da atividade de trabalho. Nesse sentido, através dos resultados coletados desta pesquisa e intervenção, ficou evidenciado que a Oficina de Fotos pode ser um dispositivo possível no desenvolvimento do poder de agir dos trabalhadores, possibilitando assim intercâmbios coletivos, sendo o gênero profissional um instrumento decisivo do poder de agir dos envolvidos.(AU)

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In the present work an intense bibliographic search is developed, with updated information on the microscopic fundamentals that govern the behavior of flotation operations of chalcopyrite, the main copper mineral in nature. In particular, the effect caused by the presence of pyrite, a non-valuable mineral, but challenging for the operation due to its ability to capture a portion of collector and float, decreasing the quality of the concentrate, is addressed. This manuscript discusses the main chemical and physical mechanisms involved in the phenomena of reagent adsorption on the mineral surface, the impact of pH and type of alkalizing agent, and the effect of pyrite depressants, some already used in the industry and others under investigation. Modern collector reagents are also described, for which, although not yet implemented on an industrial scale, promising results have been obtained in the laboratory, including better copper recovery and selectivity, and even some green reagents present biodegradable properties that generate a better environmental perspective for mineral processing.

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RESUMEN Objetivo: Determinar los valores de la bacteria e indicador fecal Escherichia coli (EC) para aguas de mar de uso seguro y recreacional de la playa Pucusana, Lima. Materiales y Métodos: Las campañas de muestreos se realizaron una vez por semana en el estío del 2019 y fueron procesados en el Laboratorio de Microbiología de la FCB de la Universidad Ricardo Palma mediante colimetría y el método del número más probable (NMP). Resultados: Se comprobó la presencia de EC en todas las muestras analizadas, con valores promedio superiores a 1000 NMP/100 ml. en todas las muestras recogidas. Diez cepas fueron enviadas al INS que determinó que no existe ningún serotipo patogénico, y de acuerdo con regulación peruana la calificación es inaceptable. Conclusiones: Se demuestra la carencia de salubridad ambiental y su relevancia en salud pública. Los factores de riesgo son producidos principalmente por la producción y vertido de las aguas residuales llevados por los colectores al mar y aunque una importante proporción de estas aguas son procesadas en la Planta de Tratamiento de Aguas Residuales PTAR Pucusana se identificaron vertimientos domésticos y municipales que descargan al Pacífico, problemática que debe tener un buen manejo y fiscalización ambiental porque deteriora el medio ambiente sobre todo los mares.

ABSTRACT Objective: To determine the values o f the bacteria and fecal indicator Escherichia coli (EC) for seawater of safe and recreational use of the Pucusana beach, Lima. Materials and Methods: The campaigns of samplings were carried out once a week in the summer of 2019 and were processed in the microbiology laboratory of the Faculty of Biological Sciences (FCB) of the Ricardo Palma University using colimetry and the method of the most probable number (NMP). Results: The presence of EC was verified in all the analyzed samples, with average values higher than 1000 MPN/100 ml. in all collected samples. Conclusions: The lack of environmental health and its relevance in public health is demonstrated. The risk factors are produced mainly by the production and discharge of wastewater. residuals carried by the collectors to the sea and although an important proportion of these waters are processed at the PTAR Pucusana Wastewater Treatment Plant. Domestic and municipal discharges that discharge into the Pacific were identified, a problem that must have good management and environmental control because it deteriorates the environment and the seas.

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ABSTRACT We tested a new type of wind-transported particle collector (multidirectional traps, MDt) in southeast Spain to forecast particle movement in three different soil types. The MDt collectors are easy to manufacture from thermoplastic filaments with an industrial 3D printer. The collectors tested were very efficient. Our research was carried out on unplowed Calcisols and on orange and olive-cropped Fluvisols and Luvisols, respectively. The results from the logs of nine vaned masts, each with four MDt collectors at different heights, on Calcisols, Fluvisols and Luvisols were compared with the wind erodible fraction of these soils (EF) empirically estimated and with their erosion rates calculated in a wind tunnel of our own design with a built-in laser scanner. These new collectors can differentiate the collected sediments by their direction of origin and arranged in a network of masts, enabling to distinguish overall particle loss or deposition, which is not detectable with the wind tunnel due to the work scale and no windward deposits, as it is a closed device. Comparison of the calculated EF and the total mass of transported particles recorded by the MDt collectors showed very good correlation (R2 = 0.9144) with an even better relationship between the results of the wind tunnel and collectors (R2 = 0.9741). Required precision, financing, and execution time are important in determining the use of the device. We conclude that this device shows good potential.

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The use of renewable energy is growing every year as an alternative to fossil fuel technology. Solar energy presents itself as a good alternative due to its great availability and energy potential. Solar thermal energy uses heat to warm fluids, and can also generate electricity, as well as being used in industrial processes and water desalination. The research and use of Parabolic Trough Collectors (PTCs) has been growing in recent years due to their ability to heat fluids at high temperatures in a relatively small area. In this work, two small PTCs were manufactured and tests were performed to improve the arrangements in order to increase the absorbed energy to reach temperature values for water disinfestation, aiming at the control of phytopathogens to control soil pathogens in small and medium farms. To control the automatic tracker, a low-cost system with Arduino, Light Dependent Resistors (LDRs) and step motors was used. The tracking times intervals analyzed were 1, 5 and 15 minutes. For the 1-minute tracking interval, the PTCs presented a thermal efficiency of 25.87%, with temperatures between 45 and 70 C and an average of 63.73 C. For the 5-minute tracking interval, the thermal efficiency was 18.48%, reaching temperatures between 41 and 68 ºC and an average of 57.9 ºC. For the 15-minute tracking interval, the PTCs presented a thermal efficiency of 14.80%, with temperatures between 39 and 62 °C and an average of 51.88 °C. The results showed that the tracking intervals of 1 and 5 minutes present more values between the lethal temperature range of 45 and 60 °C for phytopathogens. For agricultural application, the usage of a tracking interval of 5 minutes could be a good option for reducing the waste of system energy compared to the interval of 1 minute.(AU)

O uso de energia renovável está crescendo a cada ano como alternativa à tecnologia de combustíveis fósseis. A energia solar apresenta-se como uma boa alternativa devido à sua grande disponibilidade e potencial energético. A energia solar térmica utiliza o calor para aquecer os fluidos e também pode gerar eletricidade, bem como ser usada em processos industriais e dessalinização da água. A pesquisa e o uso de Coletores Solares Parabólicos (PTCs) têm crescido nos últimos anos devido à capacidade de aquecer fluidos em altas temperaturas em uma área relativamente pequena. Neste trabalho, dois pequenos PTCs foram fabricados, e testes foram realizados para melhorar os arranjos, a fim de aumentar a energia absorvida para atingir valores de temperatura para desinfestação de água, visando o controle de fitopatógenos no controle de patógenos de solo em pequenas e médias fazendas. Para controlar o rastreador automático foi utilizado um sistema de baixo custo com Arduino, Resistores de Potência Luminosa (LDRs) e motores de passo. Os intervalos de tempo de rastreamento analisados foram de 1, 5 e 15 minutos. Para o intervalo de rastreamento de 1 minuto, os PTCs apresentaram uma eficiência térmica de 25,87%, com temperaturas entre 45 e 70 ºC e 63,73 ºC de temperatura média. Para o intervalo de rastreamento de 5 minutos, a eficiência térmica foi de 18,48%, atingindo temperaturas entre 41 e 68 ° C e 57,9 ° C de temperatura média. Para o intervalo de rastreamento de 15 minutos, os PTCs apresentaram uma eficiência térmica de 14,80%, com temperaturas entre 39 e 62 ° C e 51,88 ° C de temperatura média. Os resultados mostraram que os intervalos de rastreamento de 1 e 5 minutos apresentam mais valores entre a faixa de temperatura letal de 45 e 60 ° C para fitopatógenos. Para aplicações agrícolas, o uso de um intervalo de rastreamento de 5 minutos poderia ser uma boa alternativa para uma redução no desperdício da energia do sistema em comparação com o intervalo de 1 minuto.(AU)

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The use of renewable energy is growing every year as an alternative to fossil fuel technology. Solar energy presents itself as a good alternative due to its great availability and energy potential. Solar thermal energy uses heat to warm fluids, and can also generate electricity, as well as being used in industrial processes and water desalination. The research and use of Parabolic Trough Collectors (PTCs) has been growing in recent years due to their ability to heat fluids at high temperatures in a relatively small area. In this work, two small PTCs were manufactured and tests were performed to improve the arrangements in order to increase the absorbed energy to reach temperature values for water disinfestation, aiming at the control of phytopathogens to control soil pathogens in small and medium farms. To control the automatic tracker, a low-cost system with Arduino, Light Dependent Resistors (LDRs) and step motors was used. The tracking times intervals analyzed were 1, 5 and 15 minutes. For the 1-minute tracking interval, the PTCs presented a thermal efficiency of 25.87%, with temperatures between 45 and 70 C and an average of 63.73 C. For the 5-minute tracking interval, the thermal efficiency was 18.48%, reaching temperatures between 41 and 68 ºC and an average of 57.9 ºC. For the 15-minute tracking interval, the PTCs presented a thermal efficiency of 14.80%, with temperatures between 39 and 62 °C and an average of 51.88 °C. The results showed that the tracking intervals of 1 and 5 minutes present more values between the lethal temperature range of 45 and 60 °C for phytopathogens. For agricultural application, the usage of a tracking interval of 5 minutes could be a good option for reducing the waste of system energy compared to the interval of 1 minute.

O uso de energia renovável está crescendo a cada ano como alternativa à tecnologia de combustíveis fósseis. A energia solar apresenta-se como uma boa alternativa devido à sua grande disponibilidade e potencial energético. A energia solar térmica utiliza o calor para aquecer os fluidos e também pode gerar eletricidade, bem como ser usada em processos industriais e dessalinização da água. A pesquisa e o uso de Coletores Solares Parabólicos (PTCs) têm crescido nos últimos anos devido à capacidade de aquecer fluidos em altas temperaturas em uma área relativamente pequena. Neste trabalho, dois pequenos PTCs foram fabricados, e testes foram realizados para melhorar os arranjos, a fim de aumentar a energia absorvida para atingir valores de temperatura para desinfestação de água, visando o controle de fitopatógenos no controle de patógenos de solo em pequenas e médias fazendas. Para controlar o rastreador automático foi utilizado um sistema de baixo custo com Arduino, Resistores de Potência Luminosa (LDRs) e motores de passo. Os intervalos de tempo de rastreamento analisados foram de 1, 5 e 15 minutos. Para o intervalo de rastreamento de 1 minuto, os PTCs apresentaram uma eficiência térmica de 25,87%, com temperaturas entre 45 e 70 ºC e 63,73 ºC de temperatura média. Para o intervalo de rastreamento de 5 minutos, a eficiência térmica foi de 18,48%, atingindo temperaturas entre 41 e 68 ° C e 57,9 ° C de temperatura média. Para o intervalo de rastreamento de 15 minutos, os PTCs apresentaram uma eficiência térmica de 14,80%, com temperaturas entre 39 e 62 ° C e 51,88 ° C de temperatura média. Os resultados mostraram que os intervalos de rastreamento de 1 e 5 minutos apresentam mais valores entre a faixa de temperatura letal de 45 e 60 ° C para fitopatógenos. Para aplicações agrícolas, o uso de um intervalo de rastreamento de 5 minutos poderia ser uma boa alternativa para uma redução no desperdício da energia do sistema em comparação com o intervalo de 1 minuto.

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