| The tin tailings from tin flotation separation contain a lot of micro-fine cassiterite.,When the traditional chemical flotation reagents are used for the froth flotation of micro-fine cassiterite,the recovery of tin is low.In addition,the process will leading to environment pollution.Bioflotation is suitable for treating low grade and fine particles ore recovery,which is considered as a novel technology.In this work,effective microbial agents were obtained,and their adsorption to micro-fine mineral mud and stone mainly associated minerals quartz and calcite were investigated.The adsorption mechanism for three types of minerals were discussed.The optimal conditions of micro-fine cassiterite flotation separation were obtained through the flotation experiments with two types of biological agents and chemical agents.The main results are as follows:(1)Among four microorganism reagents tested,Rhodotorula rubra(R.rubra)and Rhodococcus opacus(R.opacus)were found to be selectively adsorbed onto the surface of cassiterite calcite,and quartz..The maximum adsorption rate of R.rubra and R.opacus on cassiterite is83.97% and 90.57%,on calcite 70.18% and 88.3% respectively,but on quartz both less than 10%.With red reagent,TGS and Fx-?in pure mineral flotation,experimental results showed that p H is the key factor of influence on cassiterite flotability.The optimum p H of cassiterite flotation with red agent,TGS and Fx-?is7,4 and 2 respectively.Compared with TGS and Fx-?,red agent gave maximum recovery,61.10% with concentration of 0.05g/L.The surface potential of cassiterite indicated maximum change when interacted with red reagent at p H = 6-7,which matched with the condition of the optimal recoveriy rate.This provides a reference for the evaluation of bioflotation.(2)With R.rubra and R.opacus as flotation agents,time and temperature are not the main factors affecting the adsorption rate and recovery but p H.The maximum adsorption rate of R.rubra and R.opacus on cassiterite reached at p H 4.5 and 4 respectively.The addition of R.rubra or R.opacus in the flotation of cassiterite,calcite,or quartz pure mineral showed that the recovery of cassiterite and calcite could be significantly improvedbut quartz was not affected basically.With concentration of R.rubra 2.0g/L and p H = 4.5,the recovery rates of cassiterite,calcite and quartz are 70%,50% and 15% respectively.With concentration of R.opacus 1.24g/L and p H = 4,the recovery rates of cassiterite,calcite and quartz are about 62%,35% and 15% respectively.Sodium silicate can reducecalcite floatability but with no effluence on the activity of R.rubra and R.opacus.R.rubra and R.opacus suspension possesses the properties of surfactant,resulting in lower dosage of foaming agent used in flotation.(3)R.opacus has a higher bacterial concentration,less amount needed for flotation,shorter culture period and other advantages in cassiterite flotation over R.rubra.Through the actual tin open ore flotation experiments,it was found that muddy bacterial can improve tin ore grade,and conducive to the recovery of cassiterite.The cassiterite surface potential underwent significant changes after the action of microorganisms,Similar to the chemical reagent flotation the adsorption rate increased with the surface potential change Infrared spectroscopy results showed that R.rubra and R.opacus have a lot of surface chemical groups that interacted with each other on the surface of cassiterite and effectively improved the adsorption rate and recovery rate.(4)Adsorption phenomena can be explained by the change of surface free energy of particle cassiterite and microbial cells If the surface free energy is negative after adsorption the adsorption will be spontaneous EDLVO theorybasded on electrostatic force between particles can give better explanation to different adsorption rate at different p H.The results obtained above will be beneficial for specific strain screening for subsequent flotation of cassiterite. |
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