Mechanism And Applications Of Potential-controlled Flotation In Lime Adjust High Alkali Pulp

Froth flotation is a commonly used separation technique for sulfide minerals. It is proved that several electrochemical processes occur in flotation which involve the valuable minerals, flotation reagents, and the species dissolved in aqueous phase and grinding media. All these kinds of actions including mineral oxidation, dissolution, adsorption, surface reaction, mechanical reaction and precipitation will lead to undesired flotation and difficulties in separation. This thesis is focused on these behaviors in order to find a better way to enhance the efficiency of flotation.To better understand the relation between mineral electrode potential and flotation behaviors, the Cyclic Voltammeter of freshly fractured sulfides electrodes and single mineral potential-controlled flotation tests were used. The results showed that the recovery of sulfide minerals depended on its surface potential. Different minerals have different potential region for flotation. It predicted that to control the potential of sulfide minerals could modify the results of flotation. The factors, which can affect the variation of mineral surface potential, were also studied. These factors can be divided into two classes, one of them can affect not only potential of sulfides but also range of flotation potential, including concentration of reagents, pH value, the other can only affect sulfides potential, such as grinding media, pH modifiers, agitation etc. From these conclusions, a new technique of sulfides flotation, Original Potential Flotation (OPF), which controlled potential of minerals by grinding environment in alkali pulp, was invented for Lead-Zinc complex sulfides. The flotation results implied that it is doable.In order to investigate the mechanism of oxidation and reduction occurring on mineral surface, the Rotating Disc Electrode technique was undertaken. The results illustrated that the activity of surface have an important effect on reaction mechanism.The Electrochemical Impedance Spectroscopy (EIS) was used to probe the interaction among minerals, reagents, grinding medias. The inhibition efficiency ( η) was used to weigh the action between reagents and minerals. The results suggest that alkali pulp have different effect on different sulfide minerals, the ranking of anti-alkali ability of sulfides is >ZnS>FeS2.To make out the function of lime in OPF, the Force Field Method was employed to simulating the adsorption of calcium species on sulfides minerals.The result indicated that both OH" and CaOH can adsorbed on pyrite surface, but only CaOT have adsorptive action on saphalerite surface. As far as PbS is concerned, neither of above ions can adsorb on it.A special cell was designed to study mechanical electrochemistry phenomena in grinding environment. The effect of grinding media type and mechanical pressure on potential and current of mineral surface was researched; the galvanic couple between mineral and medias were also researched. The results showed that these effects can change activity of surface, which have an important effect on reaction mechanism.The quantum methods were employed to investigate the micro mechanism of reaction between mineral surfaces and collectors. The conclusion expressed that every minerals has it own surface electro-structure, different structure has different properties, which determine what kind of reaction would be occur.At last, the OPF was applied in Fankou Lead-Zinc Mine, the index of industrial experiment showed that the new technique has glorious foreground.