Interaction Between Fine Cassiterite Particles And Bubbles And Its Effects On Flotation

In this thesis, the studies relating to surface properties and floatation behaviors of fine cassiterite as well as the mechanism of their interactions with bubbles were carried out. It was based on fine particle flotation, colloid chemistry, surface chemistry and particle-bubble interaction theory, with the help of flotation tests, the Zeta potential measurement, contact angle measurement, scanning electron microscope, laser scattering particle analyzer, high-speed camera. It was discovered the best match between cassiterite particle and bubble occurred when the best flotation recovery of cassiterite was achieved. Combined with the parameters determined by experiments, the fitting calculation was carried out, proving the matching between particle and bubble further. The influences of bubble quantity and bubble size on flotation response were analyzed. In Microcosmic View, forces between particle and bubble were studied and their influences on flotation were discovered.The factors influencing recovery of fine cassiterite were proved up as flollows:particle size, bubble size, bubble quantity, pH value, stirring intensity. It was based on the basic research of surface properties and floatation behaviors of fine cassiterite. There is an optimal matching range between cassiterite particle and bubble size, which differs according to different reagent system.①in salicylhydroxamic acid and tributyl phosphate system,-10μm,-20+10μm,-38+20μm of cassiterie size fractions match with59μm,69μm,45pm of bubble sizes respectively.②In sodium oleate system,-10μm,-20+10μm,-38+20μm,-74+38μm of cassiterie size fractions match with59pm,69μm,45μm,45μm respectively.③In MOS system,-10μm,-20+10μm,-38+20μm,-74+38μm of cassiterie size fractions match with69μm,69μm,45～59μm,69μm respectively.Both the increase of electrolyte and collector concentration can make the occurrence of the agglomerate groups between particles and bubbles, resulting in the increase of the apparent size of particle-bubbles. The average sizes of bubbles cut by38μm、50μm、74μm、150μm、250μm、420μm、1000μm of cathode aperture size were20.2μ、29.5μm、 44.6μm、59.2μm、68.7μm、78.5μm、88.8μm separately. When bubble sizes were21μm,32μm,41μm,52μm, the initial velocities of which were3.653cm/s,4.925cm/s,7.3059cm/s,9.336cm/s separately. Bubble quantity, size, speed and bridge role between bubbles are greatly influenced by current, electrolytic time, concentration of electrolyte.Collision probability, attachment probability, detachment probability between cassiterite particle and bubble were influenced by cassiterite particle size and bubble size greatly. Theory model calculation proved there is an optimal matching range between cassiterite particle and bubble size, and the best collection probability and flotation recovery can be obtained in this range. Greater bubbles were needed for bigger particles to acquire the best collection probability.The results of interaction and interface calculation of cassiterite-water-bubble system showed that the adhesion probability between cassiterite and bubble depends on cassiterite-bubble collision efficiency, once the collision between particle and bubble occurred, the probability of attachment between particle and bubble was increased. The greater the negative of ΔG (the freedom energy change of cassiterite particles-bubbles before and after contact and adhesion) is, the easier the adhesion will happen.The collision-attachment-detachment process between cassiterite and bubble was treated by high speed camera, and the model and probability of which were various with different conditions. Agglomerate formed by bubbles with different sizes have different probability of attachment after collision, because bubbles with different sizes have different velocity and carry different amount of cassiterite particles. Bigger bubbles carry more cassiterite particles, resulting in larger load and lower rising velocity, which have fewer adhesion probability with cassiterite particles carried by small bubbles. Agglomerate between bubble and cassiterite with same size and rising velocity is more easily be adhered to form larger agglomerate, resulting in being flotated. According to collision-adhesion phenomenon between cassiterites and bubbles and experimental data in the flotation systems, the parameters of the existing model were fixed. The results of studying on the interaction between cassiterite particles and bubbles provide a new way feasible for fine cassiterite flotation, and provide certain theoretical basis for the appilication of micro-bubble flatation on the recovery of fine cassiterite particles.