Study Of Multi-interface Interactions Between Coal Particles And Micro-nanobubbles

Froth flotation is an effective method for separating fine target minerals from gangue minerals,depending on their surface hydrophobicity differences.However,the low probability of collision between coal particles and flotation bubbles severely limits the high-efficiency flotation of fine and ultra-fine coal particles.To address this issue,in this study,we proposed the idea of strengthening the flotation of fine and ultra-fine coal particles by introducing micro-nanobubbles(MNBs).Based on revealing the basic properties of MNBs under different conditions,the interaction between MNBs and coal particles was further studied,and the process of MNBs enhanced agglomeration-flotation technique of ultra-fine coal particles was preliminarily explored.Through dissolved oxygen test and dynamic light scattering(DLS)analysis,the preparation method and fundamental properties of MNBs generated were ascertained initially.The results showed that the average size of MNBs prepared by the bubble generator was from 200 nm to 700 nm.Meanwhile,MNBs are negatively charged,which is probably one of the main contributors to the long life-time of MNBs.It was also found that the concentration of 2-octanol,the setting time,the cycle time of the bubble generator,the additional aeration and p H were all critical factors affecting the basic properties of MNBs.Afterward,the interaction between MNBs and ultra-fine TX coal was revealed by FT-IR,contact angle test and DLS analysis.The results showed that the hydrophobicity of TX coal decreased as the increase in oxidation temperature.On the other hand,MNBs adhered to the hydrophobic coal particles easily so to increase their surface hydrophobicity while had little effect on the hydrophobicity of hydrophilic coals.Compared with hydrophilic coal particles,higher coal particle's surface hydrophobicity triggered more MNBs,inducing a more significant reduction of coal particle Zeta potential.Through laser particle size analyzer,microscope observation,and rheometer test,the effect of MNBs on the agglomeration-flotation of ultra-fine TX coal was further studied,with a preliminary study on the ultra-fine JD coal-MNBs flotation test was carried out to propose a new process.The results showed that MNBs increased the flotation rate and combustible recovery of hydrophobic coal but had little effect on hydrophilic coal.The main reason was probably that MNBs promoted the aggregation of hydrophobic coal while the fitting results of flotation kinetics showed that the classical first-order kinetics model had the best fitting effect on the TX coal flotation test.The new process of ultra-fine JD coal-MNBs flotation showed that the introduction of MNBs improved the flotation efficiency,and the combustible recovery is up to 35.2%,and the ash content was reduced from 52.35% to 15.6%.