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Although numerous studies have been implemented on identifying the impact of acoustic waves on mineral beneficiation, its fundamental aspects remain unclear in the literature. The present work, for the first time, systematically investigates the role of ultrasound pre-treatment (UPT) in the carbonaceous copper-bearing shale flotation. To this end, conditioning was carried out at different powers of applied ultrasound. Non-treated and UPT shale flotation tests were performed in the presence of frother (MIBC) and collector (KEX). To analyse particle surface charge variation and collector adsorption properties after application of UPT, zeta potential and ultraviolet–visible spectroscopy measurements were implemented, respectively. The generation of sub-micron bubbles due to the acoustic cavitation was characterised by laser-based particle size measurements. Shale hydrophobicity was determined using the sessile drop and captive bubble techniques.The micro-flotation results showed that the mass recovery increased by 40% at 20 W of applied ultrasonic power. The positive effect of UPT on the copper-bearing shale flotation was related to: i) generation of ultrafine bubbles due to the acoustic cavitation phenomenon and ii) the cleaning effect through transient bubble collapse. However, rigorous ultra-sonication diminished the recoverability of the sample owing to the less intensified number of ultrafine bubbles on the particle surfaces and formation of free H and OH radicals, which led to the oxidation of particle surfaces. These statements were correlated well with the observations of the zeta potential, particle size analysis and quantified ultrafine bubbles. Finally, we briefly highlighted fundamental knowledge gaps in flotation and ultrasound-related issues for future work. 相似文献
243.
采用零温条件下的赝势-平面波方法和有限温度下的Car-Parrinello分子动力学方法,模拟了不同压力环境下氦原子在金属铌中的行为特征,研究了宿主缺陷和氦泡的形成机制。结果表明,闭电子壳层的氦原子在金属铌中具有刚球模型特征,其占据区域为金属自由电子的禁区,从而破坏铌原子之间的金属性键合。在常温条件下,局域高浓度的氦原子优先凝聚于近邻宿主空位缺陷处,从而形成氦泡;完整晶格中高浓度的氦将促使铌原子易位,形成间隙-空位模式的宿主缺陷,氦原子聚集于空位区域。完整宿主在压力(40 GPa)的作用下,晶格参数减小,铌原子之间的相互作用增强,尽管氦原子的存在削弱了铌原子之间的相互作用,位于格点上的铌原子仍难以借助热振动偏离格点形成空位,因而未能形成间隙-空位对和氦泡。 相似文献
244.
Statistical analysis of financial data mostly focused on testing the validity of Brownian motion (Bm). Analyses performed on several time series have shown deviation from the Bm hypothesis, that is at the base of the evaluation of many financial derivatives. We analyze the behavior of performance measures based on maximum drawdown movements (MDD(T)), testing their stability when the underlying process deviates from the Bm hypothesis. In particular we consider the fractional Brownian motion (fBm), and fluctuations estimated empirically on raw market data. The case study of the rising part of speculative bubbles is reported. 相似文献
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