Application Of Oxidized Starch In Flotation Separation Of Fluorite And Calcite And Study On Its Inhibition Mechanis

Fluorite is the main source of fluorine in the fluorine chemical industry and is a strategic mineral resource.Although China has large reserves of fluorite resources,the amount of rich ore resources is small and the amount of poor ore resources is large.With the continuous exploitation of high-grade fluorite deposits,the reserves of high-grade fluorite resources are gradually decreasing,and low-grade fluorite ore has become the focus of current development and utilization.Calcite is one of the main vein minerals in carbonate fluorite ore,often in close symbiosis with fluorite in the form of fine-grained dip.Flotation is the main method to separate fluorite and calcite,but due to the similar calcium active sites on the surface of fluorite and calcite,the trapping agent sodium oleate is poorly selective for both minerals,making it difficult to achieve effective separation.It is usually necessary to add inhibitors to increase the floatability difference between the two minerals,and the development of highly selective inhibitors is one of the current research priorities.This paper takes fluorite and calcite as research objects,introduces oxidized starch as flotation inhibitor,studies the influence of oxidized starch on the flotation behavior of fluorite and calcite through micro flotation test,and focuses on the selective inhibition mechanism of oxidized starch by combining modern analytical detection technology and theoretical calculation model.Experiments on the oxidation conditions of corn starch showed that the reaction at a temperature of 40°C and a system p H of 9 for 3h resulted in the preparation of oxidized starch with high carboxyl group content.The results of scanning electron microscope analysis showed that after the oxidation of corn starch,the starch granules could be uniformly dispersed in the slurry,which was favorable to the adsorption of starch granules and mineral particles.The results of Fourier infrared spectroscopy test and zeta potential test showed that some hydroxyl groups in corn starch molecules would be oxidized to carbonyl or carboxyl groups,which would lead to more negative zeta potential values of starch.The analysis of the molecular structure of starch and oxidized starch showed that the H atom and C and O atoms in the glucose unit interacted strongly with each other and had obvious shared electron behavior,and the oxidation would lead to more electron transfer from the C atom to the O atom,and the oxidation would reduce the chemical valence of the O atom to be reduced,and the generated C=O bond would cause new peaks in the 2p orbitals of the C and O atoms.The results of single mineral flotation tests showed that sodium oleate was difficult to achieve effective separation of fluorite from calcite without the addition of inhibitors.Flotation results with the addition of unoxidized corn starch,oxidized corn starch with 3%active chlorine concentration and oxidized corn starch with 5%active chlorine concentration as inhibitors,respectively,showed that oxidized starch was more inhibitory and selective than corn starch,but too high an oxidation level would lead to a decrease in oxidized starch selectivity.The artificial mixed ore flotation results are consistent with the single mineral flotation results,corn starch selectivity is poor,inhibition of calcite at the same time a large number of fluorite is also inhibited,the fluorite recovery in the concentrate is only 45.40%.The 3%active chlorine concentration oxidized corn starch has good selectivity for both minerals,and the fluorite recovery in the primary separation concentrate is 84.87%,and the grade is kept at 86.74%,which not only improves the fluorite grade in the concentrate,but also ensures the fluorite recovery in the concentrate,and achieves a better flotation separation effect.The results of total organic carbon adsorption analysis and SEM-EDS analysis showed that oxidation would reduce the adsorption of starch on the surface of fluorite and improve the agglomerative adsorption behavior of starch particles on the surface of fluorite;however,the adsorption pattern on the surface of calcite was opposite,oxidation would greatly increase the adsorption of starch on the surface of calcite and make the surface of calcite wrapped with a starch film.The results of Fourier transform infrared spectroscopy and XPS analysis indicate that starch and oxidized starch interact with mineral surfaces through hydroxyl and carboxyl groups in the molecules,but this interaction does not alter the chemical environment of calcium atoms on the mineral surface.Zeta potential test analysis showed that the zero electric point of fluorite was 6.8 and that of calcite was 8.7.In the range of p H=7～9 of the ore slurry,the addition of oxidized starch would significantly reduce the kinetic In the range of pulp p H=9,the addition of oxidized starch significantly reduces the dynamic potential of calcite,but has less effect on the dynamic potential of fluorite,and oxidized starch is more likely to have electrostatic adsorption with calcite surface,while it shows electrostatic repulsion on fluorite surface.The electronic structure study of fluorite and calcite shows that the Ca atoms on the surfaces of fluorite and calcite have similar physicochemical properties,and since the valence band near the Fermi energy level of fluorite is mainly contributed by the 2p orbital electrons of F atoms and calcite by the 2p orbital electrons of O atoms,this may be the basis for achieving the selective separation of the two.the DFT calculations show that the starch C₆ and C₂ and C₃positions connected to the The hydroxyl hydrogen atoms are adsorbed on the surfaces of fluorite and calcite through hydrogen bonding.The hydrogen bonding of oxidized starch on the surface of fluorite is weakened and the adsorption energy decreases,while the hydrogen bonding on the surface of calcite is enhanced and the adsorption energy increases.The difference in hydrogen-bonding adsorption and electrostatic adsorption of oxidized starch on fluorite and calcite surfaces is the main mechanism leading to its selective inhibition.The results of this thesis help to understand the mechanism of deep oxidation of starch and to determine the suitable oxidation conditions.Addition,the study on the inhibition effect and mechanism of action of oxidized starch provides a direction and theoretical reference for the development of organic inhibitors for fluorite and calcite flotation separation.