| Fine magnetic particles produced by chemical synthesis can adsorb on mineral surface without remarked selectivity due to small radius and large surface energy, resulting in unsatisfactory recovery of weakly magnetic minerals through magnetic separation method. Therefore, increasing the selective adsorption of fine magnetic particles on mineral surface through surface-modification is very important in terms of improving the grade and recovery of weakly magnetic minerals.First, the fine magnetic particles, also known as magnetic seeds, with average diameter of2.5microns which synthetized via air oxidation method, were modified by different surface modifiers via a two-step surface modification method to carry some special functional groups. And then the particles modified by glucose, citric acid and glutamic acid were characterized by infrared spectroscopy to find out the mechanism of the interaction between the reagents and the particles. The results show that glucose was adsorbed on magnetite surface via hydrogen bonding while citric acid and glutamic via chemical reactions.Meanwhile, the influence of magnetic field intensity and the dosage of Fe3O4particles on the recovery of hematite and quartz in magnetic separation were studied. The optimum magnetic intensity and magnetite particles dosage were0.21T and0.79mg/mL respectively. Also the influence of the type and dosage of surface-modification reagents and pH values on the recovery of hematite and quartz with surface-modified magnetite was tested.Pure mineral tests showed that compared with unmodified magnetic particles, the recovery difference between hematite and quartz increased from34.52%to49.56%when the particles treated by glucose, and the differences increased by more than40%when the particles was treated by oxalic acid, citric acid and oleic acid respectively. Using the magnetic particles treated by glutamic acid containing amino-group would make the recovery of quartz reduce from61.57%to39.05%, and the difference of the recovery of hematite and quartz merely increased20%. However, dodecylamine had no effect on selective surface-magnetization. The manually mixed ore test showed that compared with the magnetic separation with untreated magnetic particles, magnetic separation with magnetic particles treated with citric acid and glucose could improve the concentrate grade by nearly2%and recovery by nearly3%, the grade of the concentrate obtained by magnetic separation with magnetic particles treated with oxalic acid kept unchanged and the recovery increased by3%, magnetic seeds treated by surface modifiers magnetization separation compared with magnetization separation displayed obvious effects in terms of improving the concentrate grade and recovery.Zeta-potential tests showed that the PZC of hematite and magnetic particles were4.50and7.93respectively. Quartz carried negative charge within the testing pH range. The PZC of magnetic particles both showed left move trend when the magnetic particles were treated by different surface-modification reagents, and the sequence of the offset was as follows:Oleic acid> Citric acid> Oxalic acid> Glutamic acid> GlucoseThe theoretical model of EDLVO among magnetic particles treated by citric acid, hematite particles and quartz was established, as well as the interaction force among magnetite treated by citric acid, hematite particles and quartz particles was tested by the AFM. The result showed that the interaction force between the modified magnetite and hematite changed a little, while the interaction force between the modified magnetite and quartz decreased in the process of withdrawing the probe. This paper had37figures,6tables and83references. |
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