| The content of iron carbonate in Donganshan carbonate-containing iron ore increases with further exploitation of the ore.Most of the iron carbonate refers to siderite.It is a kind of easy grinding mineral.The flotation of the iron ores was severely deteriorated because of the adsorption of fine-grained siderite on quartz and hematite.For this kind of iron ore,a new technology called "stepped-flotation" was proposed by some researchers in NEU.Even though a better result was received,the problem about low recovery of iron still hangs in the balance.Based on large numbers of related literatures at home and abroad,"stepped-flotation" of microfine-grained siderite with selective flocculation was put forward to improve recovery of iron concentrate in direct flotation.Both grade and recovery of the concentrate in the subsequent process of reverse flotation can also be improved.Different dispersants has different dispersion actions on microfine-grained siderite.It has been confirmed by the results of sedimentation test.It showed that the dispersing actions of citric acid and sodium silicate are the best.The dispersing ratio of siderite can be improved from 5.75%to 47.00%and 48.00%respectively.On the basis of flotation solution chemistry and electrochemistry,and by means of electrokinetic potential,solutions with optimum dosage of citric acid and sodium silicate were studied.It turned out that negative charged ions which are generated by ionization of dispersants attach on the surface of minerals.Then dispersion of minerals can be enhanced by increasing electronegativity of mineral surface.When the pH value of the slurry was 6.70 and the dosage of sodium oleate was 200mg/L,the best flotation effect of single mineral flotation could be received with recovering 73.0%siderite.By comparing flocculating effect of different flocculants,acetylated starch,cationic starch and pre-gelatinized starch are the best.And recovery of siderite can be increased by 11.50%,13.50%and 14.50%respectively.Both apparent size of siderites and viscosities of slurry were increased with the impact of three kinds of flocculants above,which verified different flocculation actions.Flotation of artificial-mixed mine of siderite,quartz and hematite were carried out.And comparative tests of dispersants and flocculants and condition tests of "stepped-flotation"were included.The result showed that 4mg/L citric acid,9mg/L pre-gelatinized starch and 4mg/L sodium oleate of direct flotation and pH value of 11.5,6mg/L corn starch and 60mg/L CaCl2 of reverse flotation was the optimum processing condition.Then iron concentrate with grade up to 58.38%and recovery up to 79.97%could be received.Apparent size of siderites with the impact of both dispersants and flocculants showed that dispersants had little effect on flocculation actions.Molecular dynamics simulation of interaction of reagents and mineral showed that citric acid,pre-gelatinized starch and sodium oleate had different interaction energies with siderite,which were-10.45 kJ/mol,-22.59 kJ/mol and-83.47kJ/mol respectively.Interaction energy between citric acid and siderite after being treated by pre-gelatinized starch was-23.22kJ/mol.Citric acid had little effect on the interaction energy with the impact of both sodium oleate and pre-gelatinized starch.Interaction energy between sodium oleate and siderite after dispersion and flocculation was-54.04kJ/mol.It showed that was sodium oleate still had excellent flotation performance on siderite being treated by citric acid and pre-gelatinized starch. |
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