Basic Research On The Flotation Separation Of Cassiterite, Calcite And Clinochlorite

In modern industry,tin is an indispensable metal,which is widely used in many industry fields such as atomic energy industry,electronics industry and aerospace industry.Tin resources are abundant in China,which rank first in the world,accounting for 24%of the world's proven reserves.However,the ore of tin resources that can be exploited and utilized are poorly endowed with complex dissemination characteristics,fine particle size of cassiterite,high content of gangue minerals and serious muddy.As a result,the grade and recovery of tin concentrate are low.According to the six typical tin deposits in China,the gangue minerals such as carbonate mineral calcite,layered silicate mineral chlorite and oxidized mineral quartz,widely present in the tin deposits.Currently,the researches on the flotation separation of cassiterite are mainly focused on the development of flotation reagents and the optimization of process flow.There are few studies focus on the influence of gangue minerals on cassiterite flotation.The reason that the low-grade polymetallic tin ore is difficult to separate efficiently is still unclear and the internal mechanism between cassiterite and gangue minerals is ambiguous.Therefore,it is essential to study the high-efficiency separation of cassiterite and gangue minerals.In this study,cassiterite,calcite,clinochlore and quartz are investigated.The main approaches include flotation tests,Zeta potential tests,XPS analysis,ICP-MS analysis and contact angle measurements.The effects of three minerals on cassiterite flotation are investigated systematically.In order to improve the separation efficiency of cassiterite,different control methods are proposed.The floatabilities of cassiterite,calcite,clinochlore and quartz are investigated by using the single mineral flotation tests.The flotation separation of cassiterite and gangue minerals is studied by using the binary mixed minerals flotation tests.The results of flotation tests show that compared with salicylhydroxamic acid,sodium oleate has a good collector ability for the flotability of cassiterite.Moreover,among the three systems of the flotation separation of cassiterite and gangue mineral,salicylhydroxamic acid has a good ability to select cassiterite,and lead nitrate could effectively activate the flotability of cassiterite.It is difficult to ensure the efficient recovery of cassiterite,because sodium silicate,sodium hexametaphosphate and carboxymethyl cellulose all have different degrees of inhibition to cassiterite,calcite,clinochlore and quartz.In the flotation separation of cassiterite and quartz,quartz has little effect on the flotation of cassiterite.In the flotation separation of cassiterite and calcite,calcite has an adverse impact on the enrichment of cassiterite in the concentrate.In the flotation separation of cassiterite and clinochlore,clinochlore could interfere with the improvement of the grade of cassiterite in the concentrate.Since calcite has a negative effect on the recovery of cassiterite,the effect of Ca²⁺dissolved from calcite surface on cassiterite flotation is investigated based on the dissolution characteristic of calcite surface.In addition,lead nitrate is added to regulate the inhibition of calcium ions on cassiterite flotation.The results of dissolution tests demonstrate that with the increase of dissolution time,the dissolution of Ca²⁺in the surface of calcite increases continuously.As sodium oleate or salicylhydroxamic acid is a collector,Ca²⁺dissolved from the calcite surface could lead to a decrease in the recovery of cassiterite.Zeta potential measurements and XPS analysis reveal that calcium ions in the form of Ca?OH?₂ and Ca?OH?⁺absorb on the cassiterite surface,which affect the adsorption of collector on cassiterite surface.According to the results of flotation tests and solution chemistry,the consumption of sodium oleate and salicylhydroxamic acid is due to precipitin reactions and complexation reactions in the pH value of 8,respectively.Since the precipitation reaction and complexation reaction both lead to the decrease of the concentration of effective collector in the pulp,the effective concentration can be increased by increasing the amount of collector.Adsorption tests are employed to analyze the adsorption behavior of lead ions and calcium ions on the cassiterite surface.The adsorption capacity of lead ions and calcium ions on the surface of cassiterite is measured and calculated by using the kinetic adsorption equation,the adsorption isotherm equation and the adsorption free energy.It is found that the Gibbs free energy of the two ions adsorbed on the cassiterite surface is less than zero,indicating that the process of adsorption is spontaneous.Lead ions are preferentially adsorbed on the cassiterite surface when calcium ions and lead ions are present at the same time.The adsorption process of leads ions or calcium ions on cassiterite surface is a complex adsorption process,in which both chemical reaction and physical adsorption account for a certain proportion.And the adsorption on the surface of cassiterite is close to single-layer adsorption.Because the clinochlore could interfere with the improvement of the grade of the cassiterite,the reason for the deterioration of the cassiterite flotation by clinochlore is studied systematically,and the separation of cassiterite and clinochlore is proposed by the reverse flotation process.The results reveal that the main reasons for the entry of clinochlore into the cassiterite concentrate are divided into two aspects:coating and entrainment.The surface of cassiterite and clinochlore has obvious hydrophilicity difference.Therefore,the interaction forces of cassiterite and clinochlore are not only the Van der Waals force and electrostatic force,but also the interfacial polar force.The particles of cassiterite and clinochlore attract each other as the distance of particles is less 15nm.The result of SEM-EDS shows that the fine particles of clinochlore are attached on the cassiterite surface.Since there is a linear relationship between water recovery and the recovery of the clinochlore when sodium oleate or salicylhydroxamic acid act as collector,it indicates that clinochlore could be entrainment into the concentrate.The entrainment rate of clinochlore is increased with the decrease of particle size,the increase of frother concentration,as well as the increase of pulp concentration.The results of reverse flotation tests show that the flotation separation of cassiterite and clinochlore could achieve by using the reagent combination of sodium oleate as collector and aluminum ion as inhibitor of cassiterite.Based on the results of Zeta potential,XPS analysis and solution chemistry calculation,the main reason for the depression of cassiterite by aluminum ions is Al?OH?₄^-adsorbed on the surface of cassiterite,in which cause the adsorption amount of OL^-and?OL?₂^2-on the surface of cassiterite decrease.These effects all led to the decrease of the floatability of cassiterite.The results presented in the study enrich the understanding for the separation of cassiterite and gangue.It reveals the influencing factors for the separation process of cassiterite from calcite and clinochlore,and the flotation separation characteristics and rules of cassiterite and gangue minerals are explained.The results can provide a theoretical support for the separation of cassiterite and common gangue minerals.