Journal of Sustainable Metallurgy最新文献

Characterization of the off-gases from a 500 A inert electrode aluminum electrolysis cell operating at a temperature of ca. 800 °C has been conducted using characterization units comprising gas chromatography, tuneable diode laser spectroscopy, and Fourier-transform infrared spectroscopy. The off-gases detected from the inert electrode aluminum electrolysis cell have been compared to the off-gases released from the traditional Hall-Héroult aluminum electrolysis cell. All the measurements from the inert electrode cell confirmed oxygen as the main process gas during the electrolysis process. Hydrogen fluoride, HF, which is assumed to result from reactions between moisture in the alumina raw material or the surrounding air and the fluoride melt, was also observed together with gases assumed to come from air introduced, such as nitrogen and CO₂. There were no indications that these gases came from the production process. A very small amount of SiF₄ was also detected.

Graphical abstract:

The working mechanism of surfactant to reduce acid mist in copper electrowinning system is not well understood. Most of the studies are based on the surface tension reduction phenomenon but this is not the only function that causes acid mist reduction. In this paper, we investigated the effect of different surfactants on a bubble's residence time, terminal velocity, flow regime, and bursting dynamics using a high-speed camera. We have evaluated five different surfactants and found that the presence of surfactants reduces the terminal velocity, bubble diameter, and increases the residence time of the bubble in electrolyte. Especially for FC-1100, the low terminal velocity and high residence time allowed the bubble to shift its flow regime to stokes flow and allow ample time for stabilization. This was dependent on the small Weber and Ohnesorge number when FC1100 was added, which means the bubbles had less deformation and better stabilization. Therefore, the addition of FC1100 generated bubbles with the lowest kinetic energy during rupture as compared to other surfactants. Most of the kinetic energy is used to elongate the bubble film and a little kinetic energy is used to burst the bubble. To validate our study, we have performed acid mist experiments in a chamber to measure different surfactants' suppression efficiencies. The results of the study relate terminal velocity, residence time, kinetic energy and bubble diameter to suppression efficiencies that help the understanding of surfactant's mechanism. Compared to previous studies our work has certain novelties in understanding of bubble growth, propagation and bursting mechanism in a copper electrowinning system in the absence and presence of surfactants with emphasis on surface tension, bubble terminal velocity, residence time and Kinetic energy. While previous research has primarily examined bubble size and its influence on mist generation, as well as the role of surfactants in altering bubble size and suppressing mist, this study expands the focus to include the dynamic behavior of bubbles throughout the life cycle of the bubble.

Graphical abstract:

The Lindy Effect can be formulated as: the older the technology, the longer it is expected to last. In this paper, we examine the historical aspects of hydrometallurgy through the lens of the Lindy Effect, aiming to understand why research efforts by academic and industrial groups seldom result in new commercial hydrometallurgical processes. We argue that many researchers, particularly in academia, fail to recognize that mining and extractive metallurgy are economic activities. Companies engaged in mining, extraction, and refining of metals must generate profits to sustain their operations. The technical feasibility of a hydrometallurgical process does not inherently guarantee its economic viability. The industrial installations in a hydrometallurgical plant are highly capital-intensive. We will demonstrate that for the development of a robust hydrometallurgical process that could become Lindy-proof in the future, it is crucial to avoid fatal flaws arising from intrinsic problems with the chemical reactions behind the process. The concept of circular hydrometallurgy and its twelve principles provides a valuable framework for assessing the robustness of new hydrometallurgical processes. A paradigm shift in hydrometallurgy is anticipated with the widespread availability of inexpensive, renewable energy. High energy costs will no longer be a prohibitive factor, allowing the development of energy-intensive processes that offer significant chemical advantages. This shift may even lead to a reconsideration of older hydrometallurgical processes that were previously deemed too energy-intensive.

Graphical abstract: