Flotación de minerales oxidados de plomo

The main oxidized lead minerals are: cerussite and anglesite, which due to their crystallography and wettability should not be buoyant, for this reason it is necessary to study the flotation properties for these minerals, the main ones are: solubility, surface physico-chemical , thermodynamics, fines content and others, it is concluded that anglesite is less buoyant than cerussite, both can be floated directly with amyl xanthate: long-chain hydrocarbon collector and cationic collectors such as alamine 26-D. The flotation of oxides improves when they are previously sulfurized before adding xanthate type collector, obtaining economically acceptable results. The above is applied to a polymetallic mineral of galena, sphalerite and cerussite; up to four flow charts are discussed, two are experimented, and with the bulk flotation scheme Pb-Zn, followed by flotation of oxides, after sulfurization with sodium sulfide excellent results are obtained, taking into account the complexity of the mineral.Los principales minerales oxidados de plomo son: cerusita y anglesita, los que debido a su cristalografía y mojabilidad no deberían ser flotables, por esta razón es necesario estudiar las propiedades de flotación para estos minerales, las principales son: solubilidad, físico-química de superficie, termodinámica, contenido de finos y otros, se concluye que la anglesita es menos flotable que la cerusita, ambas se pueden flotar directamente con xantato amílico: colector de cadena larga de hidrocarburo y colectores catiónicos como el alamine 26-D. La flotación de óxidos mejora cuando se sulfurizan previamente antes de adicionar colector tipo xantato, obteniéndose resultados económicamente aceptables. Lo anteriormente expuesto lo aplicamos a un mineral polimetálico de galena, esfalerita y cerusita; se discute hasta cuatro diagramas de flujo, se experimenta dos, y con el esquema de flotación bulk Pb-Zn, seguida de flotación de óxidos, previa sulfurización con sulfuro de sodio se obtienen excelentes resultados, teniendo en cuenta la complejidad del mineral

Evolution over Time of Ventilatory Management and Outcome of Patients with Neurologic Disease∗

OBJECTIVES: To describe the changes in ventilator management over time in patients with neurologic disease at ICU admission and to estimate factors associated with 28-day hospital mortality. DESIGN: Secondary analysis of three prospective, observational, multicenter studies. SETTING: Cohort studies conducted in 2004, 2010, and 2016. PATIENTS: Adult patients who received mechanical ventilation for more than 12 hours. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Among the 20,929 patients enrolled, we included 4,152 (20%) mechanically ventilated patients due to different neurologic diseases. Hemorrhagic stroke and brain trauma were the most common pathologies associated with the need for mechanical ventilation. Although volume-cycled ventilation remained the preferred ventilation mode, there was a significant (p < 0.001) increment in the use of pressure support ventilation. The proportion of patients receiving a protective lung ventilation strategy was increased over time: 47% in 2004, 63% in 2010, and 65% in 2016 (p < 0.001), as well as the duration of protective ventilation strategies: 406 days per 1,000 mechanical ventilation days in 2004, 523 days per 1,000 mechanical ventilation days in 2010, and 585 days per 1,000 mechanical ventilation days in 2016 (p < 0.001). There were no differences in the length of stay in the ICU, mortality in the ICU, and mortality in hospital from 2004 to 2016. Independent risk factors for 28-day mortality were age greater than 75 years, Simplified Acute Physiology Score II greater than 50, the occurrence of organ dysfunction within first 48 hours after brain injury, and specific neurologic diseases such as hemorrhagic stroke, ischemic stroke, and brain trauma. CONCLUSIONS: More lung-protective ventilatory strategies have been implemented over years in neurologic patients with no effect on pulmonary complications or on survival. We found several prognostic factors on mortality such as advanced age, the severity of the disease, organ dysfunctions, and the etiology of neurologic disease