Study On Flotation Foam Stability Mechanism Of The Effect Of Surface Hydrophobicity And Shape Of Particles

Flotation is a sorting method to achieve selective separation of target minerals and gangues based on differences in the physical and chemical properties of mineral surfaces.The formation of a stable foam layer is a necessary condition for flotation to occur,which directly affects flotation recovery and selectivity.The particle properties in the foam layer can have a certain impact on the foam stability,but the current research is mostly focused on the influence of the particle properties on the macroscopic foam stability,and the mechanism of the effect of the particle properties on the foam stability at the microscopic scale is not yet clear.In view of this,this paper explores the effects of particle surface hydrophobicity and particle shape on foam properties by taking spherical particles and irregularly shaped particles with different surface hydrophobicity as the research objects,and systematically reveals the mechanism of the effect of particle surface hydrophobicity and particle shape on foam stability by studying the microscopic interactions between bubbles and particle-bubble interactions,aiming to provide a theoretical basis for the regulation of foam stability in flotation process.Firstly,the mechanism of the effect of particle surface hydrophobicity on foam stability was studied.The effect of particle surface hydrophobicity on the decay and growth kinetics of macroscopic foam was investigated using a foam stability test device,and the results showed that: the maximum foam layer height increased and then decreased with increasing particle surface hydrophobicity,reaching a maximum at moderate hydrophobicity,while the life time increases monotonously with the increase of particle hydrophobicity,and the particle foam system with high hydrophobicity has the longest decay time.Hydrophilic particles have no effect on the growth and decay of foam.Immediately afterwards,the effects of particle surface hydrophobicity on the foam instability index(TSI),foam drainage rate and average foam particle size were investigated with the multiple light scattering instruments,and the results showed that:the addition of hydrophobic particles significantly reduces the drainage rate and average bubble size growth rate of the foam system.As the contact angle of the particles increases,the drainage rate of the foam system shows a pattern of decreasing and then increasing,with the minimum value occurring in the particle system with moderate hydrophobicity.In contrast,the average bubble size growth rate monotonically decreases,with the slowest growth rate occurring in the highly hydrophobic particle system.Furthermore,the effect of particle surface hydrophobicity on the microscopic interactions between bubbles was investigated using the bubble coalescence experimental system and the interaction force between bubbles measurement system,and the results showed that: the coverage of particles significantly reduced the oscillation amplitude of the bubble coalescence process,while the inhibition of bubble coalescence by particles with high hydrophobicity was less effective than that by particles with low and medium hydrophobicity.Finally,the effect of particle surface hydrophobicity on particle-bubble interactions was investigated using a surface tension meter,and the results showed that: both the particle-bubble attachment force and the maximum detachment force increase with the increase of hydrophobicity of the particle surface.The greater the attachment force between the bubbles,the easier it is for the particles to adhere to the bubble surface,and the depth of the particles embedded in the bubbles increases with increasing particle hydrophobicity.Highly hydrophobic particles were embedded deeper into the bubble,facilitating the formation of "bridge" between bubbles under mutual compression.In contrast,moderate hydrophobicity particles are embedded relatively shallowly into the bubble,effectively inhibiting foam drainage and promoting foam growth,and hence resulting in the highest maximum foam layer height in the particle system with moderate hydrophobicity.At the same time,highly hydrophobic particles have the maximum detachment force,limiting particles motion at the gas-liquid interface and drainage during foam decay.The stable solid-liquid phase led to a relatively stable foam system,and hence resulting in the longest foam decay time in the highly hydrophobic particle system.Secondly,the mechanism of the effect of particle shape on foam stability was studied.The results showed that irregularly shaped particles with low and moderate hydrophobicity exhibited a slightly higher maximum foam height compared to spherical particles,while irregularly shaped particles with high hydrophobicity had a lower maximum foam height than spherical particles.A similar trend was observed for foam decay time.Comparison of foam properties,microscopic inter-bubble interactions,and inter-particle and inter-bubble forces between spherical and irregularly shaped particle systems revealed that the observed macroscopic foam stability trends were mainly due to the larger surface area and sharp edges and corners of the irregularly shaped particles.On the one hand,the increase in surface area enhanced the adhesion probability between particles and bubbles,and low hydrophobicity spherical particles adhered to bubbles were more prone to detachment,leading to system instability.Irregularly shaped particles with intermediate hydrophobicity adhered to the bubble surface had a larger contact area with the bubble than spherical particles,leading to denser adsorption at the gas-liquid interface and stronger suppression of bubble coalescence.On the other hand,the presence of sharp edges and corners of irregularly shaped particles might enhance the "bridging" effect between hydrophobic particles and bubbles,which was detrimental to the growth and stability of the foam.There are 67 pictures,6 tables and 99 references in this paper.