| Magnesite reserves in China are in the forefront of the world.Rational and efficient exploitation and utilization of this dominant resource is great significance to the construction of the national economy.However,the high-quality magnesium resources in China are decreasing with the industrial development and utilization,thus the exploration for low grade magnesium resource is a must.In general,there are still some deficiencies of low grade magnesite need to be improved,such as the low resource utilization and weak theoretical research for a long time.In view of difficult separation of magnesite and calcareous gangue minerals,by adopting many modern testing technologis,combining the theoretical analysis and experimental study,the solubility of minerals,the occurrence state and migration law of dissolved components,the effect of combined reagents on minerals flotation behaviors in the flotation system of magnesite and dolomite were systematically studied.A method for controlling the directional migration of ions at the solid-liquid interface in magnesite flotation system has been found,and combined reagents for selective action between magnesite and dolomite have been found.Main conclusions and innovations are obtained as follows:Mineral properties and basic floatability of magnesite and dolomite were studied by ion concentration detection,solution chemical calculation and single minerals flotation tests.The dissolution rate of dolomite is larger than that of magnesite.Mg2+and Ca2+can be considered to be dissolved at the ratio of 1:1 in the dissolution process of dolomite.In the dissolution process,the ions dissolved from minerals exist in the form of various ions and compounds,and with the change of pH value,the distribution of mineral dissolution components will change.Sodium oleate,dodecyl amine and benzohydroxamic acid have certain collecting properties for magnesite and dolomite,but the selectivities of the three reagents are poor.Both sodium silicate and carboxymethyl cellulose have obvious inhibition on magnesite and dolomite.Sodium hexametaphosphate(SHMP)has little effect on magnesite flotation,but it can obviously inhibit dolomite floating.Through the study of solution chemistry calculation,X-ray photoelectron spectroscopy(XPS),adsorption tests,zeta potential tests and flotation tests,the occurrence state and migration law of dissolved components in solution and the influence of directional migration on minerals flotation behavior were investigated,and the method to eliminate the influence of directional migration on minerals flotation was found.The presence of Mg2+ can reduce the recovery of magnesite,but sodium hexametaphosphate could eliminate the adverse effect of Mg2+ on magnesite.In the presence of Ca2+and Mg2+,the recovery of dolomite decreases,and CO32-has little effect on the flotation behaviors of magnesite and dolomite.Mg2+ has little adsorption on the surface of two minerals,only when the pH value is high.Most calcium ions dissolved from dolomite migrate to magnesite surface in pulp.On the one hand,the magnesite surface may be transformed into dolomite by Ca2+;on the other hand,Ca2+ can adsorb on the magnesite surface in the form of CaCO3,resulting in the deterioration of magnesite floatation rate.Majking use of the complexing property of sodium hexametaphosphate,complexing Ca2+ into solution prevents the directional migration of Ca2+ to the magnesite surface and it also eliminates the adverse effect of Ca2+ on magnesite flotation.The floatability difference between magnesite and dolomite is kept,providing the conditions for flotation separation.The effects of various combination collectors on flotation behaviors of magnesite and dolomite were investigated by flotation tests,zeta potential tests and ion concentration detection.The combination use of SDBS and sodium oleate can promote the flotation separation of magnesite and dolomite in a certain extent.The mechanism is that SDBS and sodium oleate can occur coadsorption on the surface of minerals,and SDBS can promote the dispersion of sodium oleate in solution to improve the effect of sodium oleate on minerals surface.At the same time,sodium oleate+SDBS can alleviate the adverse effect of Ca2+dissolved from dolomite.Thus sodium oleate+SDBS can strengthen the separation of magnesite and dolomite.The inhibition of various modified sodium silicate on magnesite and dolomite flotation were studied by single mineral flotation tests,solution chemistry calculation,zeta potential tests and infrared spectrum analysis.The results show that:sodium silicate modified by zinc sulfate(ZS)mainly exists in the form of Zn·(SiO(OH)3)2.Zn-(SiO(OH)3)2 can adsorb on the surface of dolomite and prevent the adsorption of sodium oleate on dolomite surface,leading to the decrease of dolomite floating rate.Because Zn·(SiO(OH)3)2 can not adsorb on magnesite surface,it-will not affect the effect of sodium oleate on magnesite,thus magnesite floating is ensured.Therefore,the flotation separation of two minerals may be realized by using sodium silicate modified by zinc sulfate as depressant.The flotation tests for artificial mixed ores of magnesite and dolomite were carried out.When adding SHMP before Na2CO3,the flotation separation of magnesite and dolomite can be realized using suitable reagent system.In addition,using sodium silicate modified by zinc sulfate as inhibitor and sodium oleate as collector,to some extent,the flotation separation of magnesite and dolomite can also be realized.When using sodium oleate+SDBS as collector,SHMP as depressant,the grade of magnesite and dolomite in foam products are 59.13%and 40.87%,respectively,the recovery rates are 65.95%and 45.66%,respectively.The results show that sodium oleate+SDBS can promote the flotation separation of magnesite and dolomite to some extent.With ZS as the depressant,using sodium oleate,sodium oleate+isooctyl alcohol,sodium oleate+SDBS as collector can achieve flotation separation of two minerals in different degrees.It indicates that different collectors do not affect the selective adsorption of ZS on dolomite surface. |
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