Study On The Process And Mechanism Of Iron Extraction From Micro-fine Disseminated Magnetite By Selective Flocculation

The micro-fine disseminated magnetite is a kind of refractory iron ore.Its beneficiation indexes is not ideal because of micro-fine disseminated characteristic.With the continual depletion of free-milling iron ores,the experimental studies of micro-fine disseminated magnetite is especially important.In this paper,the test of selective flocculation-magnetic separation for extraction iron from refractory magnetite,which was took from Gansu province,was conducted on the base of technological mineralogy analysis and conventional magnetic separation test.The best optimal separation process and optimal parameters were confirmed,and the mechanism of flocculant selective flocculate magnetite was analyzed.Results showed that the total iron grade of the ore 28.36%and distribution rate of iron in magnetite is 88.75%.The main ferrous mineral is magnetite with subordinately siderite,hematite,etc.Main gangue minerals are quartz,and miner ores are ankerite,feldspar,etc.The ore dissemination character is complex and micro-fine.The magnetite is embedded characteristics and little independent distribution.It belongs to uneven tiny distribution that main mineral dissemination particle sizes is-38 ?m.The quartz is main gangue mineral.Coarse particle quartz is scattered or adjacent with each other,while fine-graded is crumb aggregate or nervation shape.It belongs to very uneven distribution that main mineral dissemination particle sizes is-74 ?m.The optimal conventional magnetic separation process is the coarse grinding magnetic tail-fine grinding that determined by experiment.Under conditions of grinding fineness of 93.50% passing 30 ?m,the iron concentrate with 61.54% iron grade,74.04% iron recovery and 32.46% discarding tailings rate can be obtained through magnetic separation.The result showed that part of the magnetite is too fineto be recovered by magnetic separation but lost in the tailings,the total recovery of iron concentrate is low.The beneficiation indexes could be optimized by selective flocculation-low intensity magnetic separation process.Adding 750 g/t of carboxymethyl starch(CMS)as flocculation to finely pulp and stir for 10 minters in 400r/min.The concentrate with iron grade of 62.82%,recovery of 79.12% iron was obtained through magnetic concentration and the intensity of magnetic is 47.76 kA/m.Compared with conventional magnetic separation,iron grade and recovery rate increased by 1.28% and 5.08% respectively.Mechanism analysis showed that the Fe 2p binding energy of magnetite shifting 0.57 e V toward decrease after flocculation due to the CMS adsorbed on the surface of magnetite by hydrogen bond.So the average particle size of coarse concentrate increase to 38.37 ?m and increase by 14.07 ?m through CMS selective adsorption on magnetite particle surface.But the hydrogen bond-forming effect was unable not overcome electrostatic repulsion to cause adsorption between CMS and quartz.So the process has reached the target of selective flocculation,and increased the dressing indices.