Effect Of Hydroxycarboxylic Acid On The Separation-of Fluorite And Calcite And Its Mechanism

The surface physicochemical properties of fluorite and calcite are similar,and there is the phenomenon of mutual transformation of mineral surfaces in the flotation process,which makes the flotation separation difficult and greatly limits the development and utilization of fluorite resources.In this paper,the inhibition behavior of five hydroxycarboxylic acids on fluorite and calcite was investigated through single mineral flotation test and artificial mixed ore flotation test.The inhibition mechanism of hydroxycarboxylic acids on fluorite and calcite and the interaction between minerals were explored by means of contact angle test,Zeta potential and X-ray photoelectron spectroscopy.The main results are as follows:（1）Through the single mineral flotation test,under the condition that the dosage of sodium oleate is 45mg/L and the p H of fixed pulp is 7,the inhibition ability of five hydroxyl carboxylic acids on fluorite is citric acid>tartaric acid>malic acid>gallic acid>salicylic acid,and the inhibition ability of five hydroxyl carboxylic acids on calcite is ascorbic acid>tartaric acid>malic acid>citric acid>salicylic acid.The difference of inhibitory ability of five hydroxycarboxylic acids on the two minerals was citric acid>gallic acid>tartaric acid>malic acid>salicylic acid.（2）Citric acid and gallic acid were used in the flotation test of fluorite and calcite.When citric acid is used as an inhibitor,the dosage of citric acid is 1.6×10^-3mol/L,at p H=7,when fluorite:calcite=1:1,the recovery and grade of tailings fluorite can reach 46.3%and 81.2%.When fluorite:calcite=3:1,the recovery and grade of tailings fluorite can reach 60.3%and 91.8%.Fluorite and calcite have a good separation effect.Using gallic acid as an inhibitor can not produce a good separation effect between fluorite and calcite.（3）The results of mechanism study show that citric acid acts on the surface of fluorite and calcite to produce chemical adsorption and produce calcium citrate.The hydrophilicity of fluorite and calcite is enhanced in varying degrees,and the floatability of the two minerals is changed.In sodium oleate system,after adding citric acid,the surface potential of both minerals increased,indicating that there is competitive adsorption between sodium oleate and citric acid on the mineral surface.The chemical component analysis of the solution confirmed that when the p H value of the solution is greater than 6.8,Cit^3-is mainly used in citric acid solution and Ol^-is mainly used in sodium oleate solution.The two anions will combine with Ca²⁺on the mineral surface at the same time,so competitive adsorption will occur.XPS analysis shows that after adding citric acid,more Ca ions are dissolved in fluorite,and the active sites of Ca ions on the surface are reduced,which reduces the adsorption capacity of sodium oleate.In addition,the double peaks of calcium citrate on the surface of fluorite account for 39.97%of the relative content of Ca 2p orbit and calcite account for 23.12%.The proportion of calcium citrate on the surface of fluorite is significantly more than calcite.The above reasons lead to the difference of inhibitory ability of citric acid on fluorite and calcite.Through the action of sodium carbonate solution with different p H values,the analysis of Ca 2p orbit on the surface of fluorite shows that with the increase of pulp p H value,the surface of fluorite transforms more to calcite,which leads to the poor separation effect of fluorite and calcite under alkaline conditions.