Role of in situ gas nucleation/hydrodynamic cavitation in fine particle flotation

用于矿物回收的细颗粒的浮选是采矿和矿物工业中公认的挑战，由于细颗粒与气泡的低碰撞和附着效率，通常导致低回收率，并且主要由于无意的活化、矿泥涂覆和不可避免的机械夹带导致泡沫质量差。在文献中，在受控的纸浆化学条件下的高强度搅拌（HIA）已经发现了改善细粒浮选的一些成功。然而，在以往的研究中，缺乏合适的仪器限制了对细粒浮选系统的基本理解的进展。在最近的一项研究中，我们证明了溶解空气在增强疏水化细颗粒的聚集和因此其浮选中起着关键作用。由于在环境条件下空气的溶解度有限，选择性细颗粒聚集的改善相当有限。为了通过充分利用溶解的气体来改善细粒浮选，高度期望用高溶解度的气体（例如CO2）使浆料饱和，或者设计一种系统，其中空气或CO2可以在HIA期间连续引入浆料中。概念与实践之间的关键差距是通过HIA选择性地在目标颗粒上原位产生足够数量的空腔气泡。为了填补这一空白，它是必不可少的，以了解气体成核在一个给定的HIA系统。

Flotation of fine particles for mineral recovery is a recognized challenge in mining and minerals industry, often leading to low recovery due to low collision and attachment efficiency of fine particles with air bubbles, and poor froth quality mainly by unintentional activation, slime coating and inevitable mechanical entrainment. In literature, high intensity agitation (HIA) under controlled pulp chemistry conditions has found some success for improving fine particle flotation. However, lack of suitable instrumentation in previous studies has limited the progress in fundamental understanding of fine particle flotation systems. In a recent study, we demonstrated that dissolved air played a key role in enhancing the aggregation of hydrophobized fine particles and hence their flotation. Due to limited solubility of air under ambient conditions, the improvement of selective fine particle aggregation was rather limited. To improve fine particle flotation by taking full advantage of dissolved gases, saturating the slurry with a gas of high solubility, such as CO2 or designing a system in which air or CO2 can be continuously introduced into the slurry during HIA is highly desirable. The key gap between the concept and practice is to generate a sufficient number of cavity bubbles in situ selectively on target particles by HIA. To fill this gap, it is essential to understand gas nucleation in a given HIA system.