| The main minerals in Donganshan carbonate-containing iron ore are hematite, magnetite, quartz, limonite, siderite, iron dolomite, amphibole and small amounts of chlorite. The content of iron carbonate has increased with the increasing of mining depth. It has been shown that iron carbonate had great impact on the flotation process with its content increasing, the flotation indexes decrease, even concentrate and tailings can not be separated effectively.For this kind of iron ore, a new technology called "stepped-flotation" was proposed by some researchers in NEU. The closed-circuit test in laboratory has obtained iron concentrate grade of 66.34% and recovery of 71.60%.Single mineral flotation tests, artificial-mixed mine floatation tests were carried out, and further "stepped-flotation" mechanism was studied on the basis of a large number of related literatures at home and abroad. The mass and size fraction of siderite on the influence of general reverse flotation index has been systematically examined. And the mechanism of reagents with minerals and interation between minerals in "stepped-flotation" process had been fully justified with the help of Zeta potential test, SEM and EDS analysis, infrared spectrum analysis, molecular dynamics simulation and calculation using EDLVO theory.Under the conventional reverse flotation system, the regression model of adsorption percentage of siderite on hematite and quartz with variable particle size and mass fraction was obtained as y= 17.7449+0.1833x1-12.2172x2.The supercritical adsorption percentage of siderite sliming coating was 17.89%. When the relation of mass fractionx1,and particle sizex2 of siderite is x1≤ 66.6514x2 +0.7916, the reverse flotation index was better.Infrared spectrum analysis showed that starch had chemical adsorption on siderite, hematite, and quartz, which adsorbed on the mineral surface and formed hydrogen bonding associated groups. Ions in sodium oleate had molecular adsorption on the minerals, and CaCl2 can active quartz to make it easier to float.Dynamics simulation results indicated that the sequence of competitive adsorption coefficient of sodium oleate on the surfaces of siderite, hematite and quartz was siderite (101)> hematite(001)>quartz(110), which indicated that sodium oleate had perfect catching role for siderite. Under the reverse flotation system, starch had strongly inhibitory effect on hematite, and the system interaction energy lowed to-61.75987476kJ/mol. The order of competitive adsorption coefficient of sodium oleate on the surface of siderite, hematite, and quartz activated by Ca2+ was quartz(110)>hematite(001)> siderite (101), which showed that sodium oleate had perfect catching role for activated quartz.The calculation using EDLVO theory indicated that fine siderite particles adhered on the coarse hematite and coarse quartz, resulting in the serious deterioration of the flotation index, which can be reduced by increasing the absolute value of Zeta potential of siderite, so as to increase the electrostatic repulsion between particles.Those research results may be used to guide the industrial utilization of "stepped-flotation" of Donganshan carbonate-containing iron ore. |
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