RESUMO
Engineered artificial minerals (EnAMs) are the core of a new concept of designing scavenger compounds for the recovery of critical elements from slags. It requires a fundamental understanding of solidification from complex oxide melts. Ion diffusivity and viscosity play vital roles in this process. In the melt, phase separations and ion transport give rise to gradients/increments in composition and, with it, to ion diffusivity, temperature, and viscosity. Due to this complexity, solidification phenomena are yet not well understood. If the melt is understood as increments of simple composition on a microscopic level, then the properties of these are more easily accessible from models and experiments. Here, we obtain these data for three stoichiometric lithium aluminum oxides. LiAlO2 is a promising EnAM for the recovery of lithium from lithium-ion battery pyrometallurgical processing. It is obtained through the addition of aluminum to the recycling slag melt. The high temperature properties spanning from below to above the liquidus temperature of three stoichiometric Li-Al-Oxides: Li5AlO4, LiAlO2, and LiAl5O8 are determined using molecular dynamic simulations. The compounds are also synthesized via the sol-gel route. The Li+ ion exhibits the largest diffusivity. They are quite mobile already below the liquidus temperature, i.e., for LiAlO2 at T = 1700 K, the diffusion coefficient of the lithium ion equals D = 3.0 × 10-9 m2 s-1. The other ions Al3+ and O2- do not move considerably at that temperature. The diffusivity of Li+ is largest in the lithium-rich compound Li5AlO4 with D = 32 × 10-9 m2 s-1 at 2500 K. The lower the viscosity, the higher the lithium content. The Li5AlO4 exhibits a viscosity of η = 2.2 mPa s at 1328 K which matches well with the experimentally determined 2.5 mPa s at this temperature. The viscosity of LiAlO2 at 1800 K is more than two times higher. These data sets can help to describe the melts on a microscopic level and understand how the melt properties will change due to gradients in the Li/Al concentration.
RESUMO
BACKGROUND: Previous studies have documented a negative impact of the COVID-19 pandemic on emergent percutaneous treatment of patients with ST-segment elevation myocardial infarction (STEMI), but few have examined recovery of healthcare systems in restoring prepandemic STEMI care. METHODS: Retrospective analysis was performed of data from 789 patients with STEMI from a large tertiary medical center treated with percutaneous coronary intervention between January 1, 2019, and December 31, 2021. RESULTS: For patients with STEMI presenting to the emergency department, median time from door to balloon was 37 minutes in 2019, 53 minutes in 2020, and 48 minutes in 2021 (P < .001), whereas median time from first medical contact to device changed from 70 to 82 to 75 minutes, respectively (P = .002). Treatment time changes in 2020 and 2021 correlated with median emergency department evaluation time (30 to 41 to 22 minutes, respectively; P = .001) but not median catheterization laboratory revascularization time. For transfer patients, median time from first medical contact to device changed from 110 to 133 to 118 minutes, respectively (P = .005). In 2020 and 2021, patients with STEMI had greater late presentation (P = .028) and late mechanical complications (P = .021), with nonsignificant increases in yearly in-hospital mortality (3.6% to 5.2% to 6.4%; P = .352). CONCLUSION: COVID-19 was associated with worsening STEMI treatment times and outcomes in 2020. Despite improving treatment times in 2021, in-hospital mortality had not decreased in the setting of a persistent increase in late patient presentation and associated STEMI complications.
