Understanding superhydrophobization for enhanced fine particle flotation

为了满足日益增长的世界人口和提高的生活水平的需要，容易加工的矿物迅速枯竭，这就要求勘探低品位矿床。为了有效地从矸石中分离出有价值的物质作为分离的先决条件，细磨变得必要，从而导致不可避免的细颗粒加工。 基于表面润湿性的浮选技术仍然是最通用和最有效的细颗粒分离方法。即使经过几十年的广泛研究，目前的细粒浮选技术也被发现对处理小于5微米的颗粒无效。细颗粒浮选的困难主要归因于细粒度颗粒的大表面积和低惯性。前者由于在较高的浮选化学品剂量下较少的选择性吸附而导致精矿质量较差，而后者由于细颗粒与浮选气泡的碰撞效率低而导致回收率较低。微气泡的使用已被证明可以提高细粒的回收率，但细粒浮选的最终性能仍受矿物颗粒表面化学性质的控制。 在这个发现项目中，将研究一个新的概念，该概念基于细颗粒的超疏水化，以增强气泡-颗粒附着，从而增强细颗粒浮选。认识到水对超疏水表面（例如蝴蝶或蜻蜓的翅膀、水虻的腿和荷叶）的亲和力极低，假设使细颗粒的表面超疏水将导致在超疏水化的细颗粒上自发原位形成纳米气泡，导致对浮选尺寸气泡的附着增强，从而改善细颗粒浮选。为了验证和实现这一假设，必须设计能够在目标矿物表面选择性吸附和自组装成纳米尺寸域的分子，以促进超疏水性。将使用分子动力学模拟研究自组装收集器聚集体或收集器分子结构（疏水链结构和长度）背景下的纳米域的形态，并与现有的收集器分子和原子力显微镜成像确认。超疏水表面上纳米气泡的形成将使用原子力显微镜来确定，并与自组装捕收剂分子聚集体的形态相关联。利用我们专门设计的表面力装置，通过测量纳米气泡磨砂矿物表面与气泡之间的相互作用力，研究了在矿物表面形成的纳米气泡对气泡-颗粒附着的影响。该研究结果将为细粒浮选的革命性概念奠定科学基础。

Rapid depletion of easy processing minerals to meet the needs of ever-growing world population and improved life standards calls for exploration of low grade mineral deposits. To effectively liberate valuables from gangues as a prerequisite for separation, fine grinding becomes necessary, leading to inevitable fine particle processing. Surface wettability-based flotation technology remains the most versatile and effective method to separate fine particles. Even with many decades of extensive research, current fine particle flotation technology has been found ineffective to treat particles less than 5 µm in size. The difficulty in fine particle flotation is largely attributed to large surface area and low inertia of fine size particle. The former contributes to poorer quality of the concentrate due to less selective adsorption at a higher flotation chemical dosage while the latter results in lower recovery due to low collision efficiency of the fine particles with flotation bubbles. Use of microbubbles has been shown to improve the recovery of fine particles, but the ultimate performance of fine particle flotation remains to be controlled by the nature of mineral particle surface chemistry. In this discovery project, a new concept based on superhydrophobization of fine particles to enhance bubble-particle attachment and hence fine particle flotation will be studied. Recognizing the extremely low affinity of water to superhydrophobic surfaces such as wings of butterfly or cicada orni, legs of water strider and leafs of lotus, it is hypothesized that making the surface of fine particles superhydrophobic would lead to spontaneous in situ nano bubble formation on superhydrophobized fine particles, leading to enhanced attachment to flotation size bubbles and hence improved fine particle flotation. To test and realize this hypothesis, it is essential to design molecules that could selectively adsorb and self-assemble on target mineral surfaces into nano size domains that promote superhydrophobicity. The morphology of self-assembled collector aggregates or nano domains in the context of collector molecular structure (hydrophobic chain structure and length) will be studied using molecular dynamics simulation and confirmed with existing collector molecules and atomic force microscope imaging. The nano bubble formation on superhydrophobic surfaces will be determined using atomic force microscope and linked to the morphology of self-assembled collector molecule aggregates. The effect of nano bubbles formed on mineral surfaces, on bubble-particle attachment will be studied by measuring interaction forces between the nano bubble-frosted mineral surfaces and air bubbles using our specially designed surface force apparatus. The results from this study will lay a scientific foundation for a revolutionary concept of fine particle flotation.