| The mineral processing technology of hematite has been developed in a rapid speed in recent years. And the combined flowsheet at the core of anionic reverse flotation has become a mainstream of beneficiation for hematite. Excellent industrial performance can be obtained by employing corn starch as the depressant of iron minerals. However, it still has some disadvantages with coin starch as depressant such as complicated preparation, high energy consumption and high tailing grade. Therefore, further research on finding new depressant of iron minerals not only can meet the need of industrial production of mineral processing but also can improve the sustainable development of our steel industry.Starch1#as a new depressant of iron minerals has been investigated in this paper. This depressant can be prepared to form stable solution by cold water in room temperature. In this way can the energy consumption be reduced compared with preparation of corn starch in hot water at the temperature of85℃.Corn starch, starch1#, glutinous corn starch, dextrin and phosphate starch were investigated as depressants of iron minerals in this paper. The mechanism of these depressants on mineral surfaces and the effect of these depressants on the flotation behavior of hematite and quartz in sodium oleate system were studied. Simultaneously The flotability of hematite and quartz, the effect of depressants on flotation behavior of hematite, the effect of Ca2+on mineral flotability and the effect of Ca2+reacted with depressants on mineral flotability were employed. Furthermore, Zeta potential and FTIR were tested to analyze the mechanism of depressants. In addition, the relationship of flocculent characteristic with inhibitive characteristic was discussed for starch depressants.The results showed that when the recovery of hematite flotation is95%for manual combined minerals, the concentrate grade follows a descending order as dextrin, corn starch, glutinous corn starch, starch1#and phosphate starch. When the recovery of hematite flotation reaches91.5%for practical minerals, the concentrate grade follows the same order as that for manual combined minerals. During the benefication process of hematite and quartz, starch is a non-selective flocculant. The flocculation is mainly caused by hydrogen bonding. The better the flocculation is, the worse the selectivity is.Reverse flotation technology was adopted with primary rougher, primary cleaner and tertiary scavenger. With corn starch as depressant the optimal conditions are obtained as follow:Sodium oleate dosage is150g/t,.calcium oxide dosage is500g/t, corn starch dosage is800g/t, slurry temperature is35℃and pH value of slurry is11.75. Meanwhile the optimal technological conditions with starch1#as new depressant are sodium oleate dosage15Og/t,.calcium oxide dosage600g/t, starch1#dosage600g/t, slurry temperature35℃and pH value of slurry11.75.Under the optimal conditions with corn starch as depressant,64.26%concentrate grade,88.43%metal recovery and17.74%tailing grade are obtained. As compared,63.53%concentrate grade,80.15%metal recovery and16.78%tailing grade are obtained under the optimal conditions with starch1#as new depressant. Although the benefication performance of starch1#is the same as that of corn starch, starch1#can be prepared by cold water to form stable and uniform solution.The research results indicated that when the pH value is between10and12.5, all starches play strong inhibitive roles on hematite. The inhibitive mechanism is the chemical bonding reaction between hydroxyl oxygen of starch and iron element on the naked hematite surface. When the pH value is between11.5and12.5, all starches show weak inhibitive effects on quartz, the mechanism of which is electrostatic and hydrogen bonding interaction. When the pH value is between8and13, Ca2+show an extraordinary activating interaction, the mechanism of which is that chemical reaction happened between the Ca2+and CaOH+adsorbed on the mineral surfaces and the oleate ions. Therefore, when pH value is between11.5and12.5in oleate system, there exists big flotability difference between hematite and quartz, which can lead to the ideal separation of them. The factors that influence inhibition of starch include the chain length of starch, the content of straight and branched chain of starch, impurities of starch and group species and group substitution degree introduced in modified starch. The research results play a guidance role on improvement of the benefication efficiency of Anshan hematite resources and cost reduction. |
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