| Although China has the largest tin reserves in the world and co-associated tin ore is over 60%,tin ore,especially high-grade ore,is constantly consumed with the increasing demand for tin resources.Thus,the recoverable tin ore is becoming more and more“poor,fine and miscellaneous”.Cassiterite is brittle and fragile,and it is prone to produce large amounts of tin fines during grinding.There are some pollution concerns although the flotation method can recover fine cassiterite.Compared with traditional flotation chemical agents,biological agents are low-cost and environmentally friendly.Therefore,biological agents have been widely applied to the flotation system to replace the toxic and harmful chemical agents.Based on this,the flotation characteristics of pure cassiterite,quartz and calcite as well as binary artificial mixed minerals are systematically studied by using yeast as collector in this paper.In addition,the flotation characteristics of cassiterite with yeast,Paenibacillus polymyxa and Rhodococcus erythropolis as the collector are studied by taking the size of cassiterite as the main investigation condition.Based on the fourier transform infrared spectroscopy（FTIR）test,Zeta potential and scanning electron microscopy（SEM）analysis,the interaction mechanism between microorganisms and minerals is explored with extended DLVO theory,providing theoretical guidance for green and effective recovery of fine cassiterite.The main research contents and results are as follows:The results of the unitary pure mineral flotation test show that a proper amount of yeasts can promote the flotation recovery of minerals,while excessive yeasts can inhibit the flotation of minerals.The maximum recovery of cassiterite and calcite is 78.83%and 63.67%when the p H is 6 and the concentration of yeasts is 1.25 g·L-1.Yeast as the collector has a little effect on quartz flotation,whose recovery is stable at 15%.When the size of cassiterite is-13μm,the maximum recovery of cassiterite is 78.31%by yeast as the collector.The highest recovery rate of cassiterite is 84.7%when Paenibacillus polymyxa is used as the collector.The maximum recovery of cassiterite by Rhodococcus erythropolis as the collector is 56.32%.Yeast and Paenibacillus polymyxa have a better flotation effect on fine cassiterite of-13μm.It is feasible to separate cassiterite and gangue minerals quartz and calcite by flotation with yeast as the collector.When the p H is 6 and the yeast concentration is 0.125 g·L-1,the highest recovery rate of tin gold is 85.66%at the cassiterite-calcite binary mixture system and 90.71%at the cassiterite-quartz binary mixture system.The SEM show that cassiterite and calcite particles smaller than yeast cells are adsorbed on yeast cells.Yeast cells are adsorbed on cassiterite and calcite particles larger than yeast cells.When yeasts interact with quartz,a large number of yeasts gather together,and only a small part of yeasts adsorb on the quartz surfaces.The results of the FTIR test show that the chemical adsorption occurs between yeast and the cassiterite surface.There is no obvious chemisorption between yeast,calcite and quartz.Zeta potential test results show that the potential curve shift to yeast after cassiterite and quartz interacted with yeast.The potential curve shift to the opposite direction of the potential of yeast after the interaction of calcite and yeast,and the adsorption of calcite and yeast is unstable.The results of the extended DLVO theoretical calculation show that when the total reaction energy of E-DLVO is negative,lewis acid-base interaction is the key factor affecting the adsorption behavior between microorganisms and cassiterite and calcite particles.Quartz and microorganisms tend to be in a stable dispersion state in solution.Under the same p H and a certain action distance,the interaction between microorganisms and mineral particles is in the order of yeast>Rhodococcus erythropolis>Paenibacillus polymyxa. |
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