Study On The Flotation Mechanism Of Fine-grained Ilmenite Activated By External Ions

The ilmenite in China is rich in resources but low in grade,and is dominated by primary ilmenite with poor selectivity.The effective recovery of micro-fine ilmenite from this type of ore resources has always been a difficult problem in the field of mineral processing.Flotation is an important method to deal with this type of ore resources.Therefore,it is of great practical significance to study the basic theory of ilmenite flotation.In this paper,based on the surface modification of micro-fine ilmenite,the surface oxidation and the introduction of external ions were used to improve the reactivity of the mineral surface,so as to realize the efficient flotation of ilmenite.In this paper,the activation effect of lead ion and copper-ammonia ion on ilmenite(-38?m)with H₂SO₄and H₂O₂as oxidants and sodium oleate as collector was investigated.Through pure minerals flotation test,dissolution test,Visual MINTEQ model simulation,mineral surface Zeta potential measurement,X-ray photoelectron spectroscopy(XPS),the time-of-flight secondary ion mass spectrometry(ToF-SIMS)and reaction thermodynamics calculation,etc,explored the influence of surface oxidation and the introduction of external ions on the surface active sites of ilmenite,the composition distribution rule of reagents in solution system and its interaction mechanism with the mineral surface.This paper will provide certain theoretical basis and technical support for the efficient flotation of micro-fine ilmenite in China.The activation mechanism of ilmenite by Pb(NO₃)₂in H₂SO₄system shows that pure ilmenite has good floatability at p H 5.5,and the recovery of ilmenite can be increased from 70%to 82%by adding 1×10^-4mol/L lead ions.The dissolution tests of ilmenite show that lead ions can adsorb on the mineral surface and thus prevent the dissolution of Fe and Ti active sites on the mineral surface.The solution component analysis shows that Pb(NO₃)₂mainly exists as Pb(II)ion,and the dominant component of Na OL(2×10^-4mol/L)is RCOOH_(l)molecule.Electrokinetic potential measurements and FT-IR analysis showed that RCOOH_(l)and RCOO^-chemisorbed on the ilmenite surface,and Pb-OL complex was formed.XPS results confirmed that H₂SO₄pretreatment promoted the transformation of iron element from Fe(?)to Fe(?)on the surface of ilmenite,and the Fe(?)proportion increased from 32.51%to63.22%.ToF-SIMS analysis showed that the addition of Pb(NO₃)₂strengthened the adsorption of ilmenite on Na OL,and the peak strength of C₄H₇⁺fragments increased from 16447 to 21089.The activation of mocro-fine ilmenite by lead ions in H₂SO₄system is mainly attributed to the oxidation of SO₄^2-ions and the co-adsorption of molecular/colloidal oleic acid and Pb-OL complex.Study on the mechanism of activated flotation of ilmenite by copper-ammonia ion in H₂SO₄-H₂O₂system indicates that adding hydrogen peroxide(1×10^-4mol/L)and copper-ammonia ion(1×10^-4mol/L)with sodium oleate as collector under the condition of p H 5.5,the flotation recovery of pure mineral can be increased by about18%.XPS analysis confirmed that the treatment of H₂SO₄and H₂O₂promoted the conversion of the valence state of iron from Fe(?)to Fe(?).Finally,the proportion of Fe(?)on the ilmenite surface increased from 44%to 66%.After the introduction of copper-ammonia ion,the concentration of copper atom on the mineral surface was0.4%.Thermodynamic analysis of the reaction shows that Fe(OL)₃is more easily formed than Fe(OL)₂at p H 5.5(The?G^?value of Fe²⁺/Fe³⁺and Na OL is-80.79k J/mol and-147.00 k J/mol,respectively).ToF-SIMS analysis showed that the addition of copper-ammonia ion enhanced the adsorption of Na OL on the ilmenite surface,and the normalized peak strength of C₁₈H₃₃O₂^-increased from 1.42×10^-2to1.80×10^-2.The activation of micro-fine ilmenite by copper-ammonia ion is mainly attributed to the double oxidation of H₂SO₄and H₂O₂,as well as the chemisorption of oleic acid and oleate in molecular/colloidal form with Fe and Cu sites on the surface of ilmenite.The actual ore flotation test shows that under the condition of H₂SO₄dosage 2000 g/t,Na OL dosage 2000 g/t,300 g/t dosage of lead ion and copper-ammonia ion is used as activator,respectively.A roughing selection of the agent can increase the recovery rate of ilmenite by approximately 5%.