McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L7.
Langmuir. 2011 Sep 6;27(17):10438-46. doi: 10.1021/la2016534. Epub 2011 Aug 3.
This is the first report describing a new technology where hydrophobic nanoparticles adsorb onto much larger, hydrophilic mineral particle surfaces to facilitate attachment to air bubbles in flotation. The adsorption of 46 nm cationic polystyrene nanoparticles onto 43 μm diameter glass beads, a mineral model, facilitates virtually complete removal of the beads by flotation. As little as 5% coverage of the bead surfaces with nanoparticles promotes high flotation efficiencies. The maximum force required to pull a glass bead from an air bubble interface into the aqueous phase was measured by micromechanics. The pull-off force was 1.9 μN for glass beads coated with nanoparticles, compared to 0.0086 μN for clean beads. The pull-off forces were modeled using Scheludko's classical expression. We propose that the bubble/bead contact area may not be dry (completely dewetted). Instead, for hydrophobic nanoparticles sitting on a hydrophilic surface, it is possible that only the nanoparticles penetrate the air/water interface to form a three-phase contact line. We present a new model for pull-off forces for such a wet contact patch between the bead and the air bubble. Contact angle measurements of both nanoparticle coated glass and smooth films from dissolved nanoparticles were performed to support the modeling.
这是首次报道一种新技术，其中疏水性纳米颗粒吸附在更大的亲水性矿物颗粒表面上，以促进在浮选过程中附着在气泡上。46nm 阳离子聚苯乙烯纳米颗粒吸附在 43μm 直径的玻璃珠（矿物模型）上，几乎可以完全通过浮选去除这些珠子。只需将纳米颗粒覆盖在珠子表面的 5%，就可以促进高浮选效率。通过微力学测量了从气泡界面将玻璃珠拉入水相所需的最大拉力。涂有纳米颗粒的玻璃珠的拔出力为 1.9μN，而清洁的玻璃珠的拔出力为 0.0086μN。使用 Scheludko 的经典表达式对拔出力进行了建模。我们提出气泡/珠的接触区域可能不是干燥的（完全不润湿）。相反，对于坐在亲水表面上的疏水性纳米颗粒，只有纳米颗粒可能穿透空气/水界面形成三相接触线。我们提出了一种用于珠与气泡之间这种湿接触斑点的新拔出力模型。进行了涂有纳米颗粒的玻璃和溶解的纳米颗粒的光滑膜的接触角测量，以支持模型。
