Estudio experimental de la separación de enargita desde un concentrado de Cu-As mediante flotación

159 p.El procesamiento de concentrados de cobre altamente contaminados en arsénico está representando un considerable impacto ambiental, pues en las etapas principales de fusión y conversión, el arsénico forma productos volátiles, gases fugitivos altamente tóxicos que en algún momento del proceso son emitidos al ambiente. Con el enfoque de reducir las fuentes emisoras de arsénico, el objetivo de la presente memoria consistió en evaluar experimentalmente, las condiciones del proceso de flotación para la separación de un sulfosal de Cu-As, como la enargita, desde un concentrado de cobre industrial proveniente de la División Ministro Hales de la Corporación Nacional del Cobre (Codelco). La separación de minerales arsenicales previos a su procesamiento en los hornos a alta temperatura permitiría controlar el contenido global del elemento en los concentrados y posibilitar tener un mejor manejo de los gases residuales de acuerdo a lo establecido en la norma de emisiones que rige en las fundiciones del cobre (D.S 28). Para ello, la metodología adoptada mediante ensayos experimentales por microflotación, permitió evaluar el efecto del pH, dosificación, tipos de reactivos y distribución de tamaños de partícula, a fin de identificar las condiciones bajo las cuales se promoviera la separación de la enargita y el resto de las menas de Cu. Los resultados mostraron que el pH fue la variable que influenció en mayor medida la recuperación de la enargita, obteniéndose los mejores resultados en las pruebas colectivas realizadas a pH 7,5 en la cual se lograron recuperaciones del 55,3% de enargita y 43,4% de calcopirita. En pruebas con preacondicionamiento del material, el tratamiento de oxidación con gas ozono, promovió una mejoría en la recuperación de ambas menas de cobre, aumentando en un 4% la recuperación de enargita respecto a las pruebas donde no se utilizó este pretratamiento. Se identificó también que, entre los colectores utilizados, el tionocarbamato modificado AERO 5100p, fue el más selectivo para la enargita, mejorando la recuperación de este mineral en la etapa selectiva, sobre el 70%. Es recomendable estudiar en más detalle las variables de flotación que se evaluaron en este estudio con el objetivo de mejorar la eficiencia selectiva en la separación de menas complejas, para ello, resultaría pertinente realizar pruebas de flotación batch para la obtención de parámetros cinéticos, utilizar técnicas de análisis que permita comprender de forma más exacta los fenómenos químicos que intervienen en el sistema o una metodología complementaria, que permita aprovechar los gases arsenicales,caso del As2O3(g),como una fuente de materia prima para fabricar productos comerciales. // ABSTRACT: In this dissertation, an experimental evaluation of the separation of enargite (Cu3AsS4) from a copper concentrate provided by the Ministro Hales Division of Codelco by means of froth flotation tests, is presented. Currently, the copper mining industry operates under harder environmental standards. This includes reducing the solid, liquid and gaseous metallurgical wastes generated in the different stages of the copper production process due to the high environmental impact associated with their releasing into the environment. The separation of mineralogical species before they are processed in the high temperature furnaces to control the arsenic content in the copper concentrates would help that the fugitive gasses emanated during the operation of the Chilean smelters comply with the environmental regulations in terms of their As concentration (D.S 28). The experimental work focused on evaluating the effect of pH, dosage of reagents and particle size distribution on the separation of enargite from a copper concentrate (mainly composed of enargite and chalcopyrite) through microflotation tests in order to identify the operational conditions that promote the separation of enargite from the rest of copper ores. The results allowed identifying that the pH of the flotation medium was the variable with the greatest influence on enargite recovery. The highest enargite and chalcopyrite recovery values were obtained in the tests conducted at pH 7,5, being 55,3% and 43,4%, respectively. The preconditioning tests that consisted of exposing the material to oxidizing media to remove the possible oxidized layers on the surface of the particles, led to lower recovery values of enargite. However, the tests that include ozone insufflation led to higher recoveries of enargite. Also, among the collectors used in this study, it was identified that the modified thionocarbamate (AERO 5100p) was the most selective for enargite, improving the recovery of such mineral. The results obtained in this dissertation represent an excellent source of information that can be used for further experimental studies or even for froth flotation processes in which the isolation of enargite from the rest of copper ores is one of the main purposes

Global attitudes in the management of acute appendicitis during COVID-19 pandemic: ACIE Appy Study

Background: Surgical strategies are being adapted to face the COVID-19 pandemic. Recommendations on the management of acute appendicitis have been based on expert opinion, but very little evidence is available. This study addressed that dearth with a snapshot of worldwide approaches to appendicitis. Methods: The Association of Italian Surgeons in Europe designed an online survey to assess the current attitude of surgeons globally regarding the management of patients with acute appendicitis during the pandemic. Questions were divided into baseline information, hospital organization and screening, personal protective equipment, management and surgical approach, and patient presentation before versus during the pandemic. Results: Of 744 answers, 709 (from 66 countries) were complete and were included in the analysis. Most hospitals were treating both patients with and those without COVID. There was variation in screening indications and modality used, with chest X-ray plus molecular testing (PCR) being the commonest (19\ub78 per cent). Conservative management of complicated and uncomplicated appendicitis was used by 6\ub76 and 2\ub74 per cent respectively before, but 23\ub77 and 5\ub73 per cent, during the pandemic (both P < 0\ub7001). One-third changed their approach from laparoscopic to open surgery owing to the popular (but evidence-lacking) advice from expert groups during the initial phase of the pandemic. No agreement on how to filter surgical smoke plume during laparoscopy was identified. There was an overall reduction in the number of patients admitted with appendicitis and one-third felt that patients who did present had more severe appendicitis than they usually observe. Conclusion: Conservative management of mild appendicitis has been possible during the pandemic. The fact that some surgeons switched to open appendicectomy may reflect the poor guidelines that emanated in the early phase of SARS-CoV-2