Study On Aluminum-Iron Separation Of Limonite Ore With High Aluminum Content

With the rapid development of iron & steel industry of China and decrease of easy processing iron ore,it is of significance to exploit refractory iron ore resource.Limonite with high alumina content is one of the typical intractable iron ores,this kind of resources can be found in Guangxi province and Southeast Asia countries,and they are not effectively utilized yet.In this paper,Aluminium-iron separation of the refractory limonite ore by magnetite roasting and sodium roastingleaching were studied based on investigation on mineralogy,and the mechanisms on Aluminum-iron separation was studied by using XRD and SEM etc..Mineralogical analyses indicate that aluminum minerals are mainly dispersed among the iron ore in a manner of superfine grains of which content is 40.4%or aluminum scatters into the iron minerals in isomorphism,thus magnetic separation and floatation are unable to remove aluminum from the ore effectively.The results of magnetic roasting show that magnetic roasting is ineffective to remove aluminum from iron ores,and the total iron grade is 63.28%,Al₂O₃ content is 10.3%when roasting temperature is 850℃, roasting time is 60min,concentrate of CO is 8%,magnetite intensity is 1000Oe,and it can not break the complex structure of alumiuum and iron, because some magnetite grains of iron concentrate contain high Al₂O₃, and some aluminum minerals also enwrap some magnetite,it causes aliminium can not be remove by magnetic separation.The results of sodium roasting-leaching show that aluminum can be effectively removed from the ore by sodium roasting followed acid leaching processing.Al₂O₃ content decreases from 8.16%in raw ore to 3.62%in iron concentrate,and the total iron grade increases from 48.92% to 62.72%correspondingly under the conditions that roasting temperature is 950℃,roasting time is 15min,weight content of sodium carbonate is 9%,bed height is 300mm,leaching temperature is 90℃,leaching time is 5min,leaching L/S ratio is 5/1,acid-leaching temperature is 60℃,acid-leaching time is 15min,concentration of sulfuric acid is 4.5%, acid-leaching L/S ratio is 5/1. The results of mechanisms on aluminum-iron separation indicate that the phase composition of aluminum and iron varies with the Na₂CO₃ dosage.When Al₂O₃,SiO₂,Fe₂O₃ occurs simultaneously,Na₂CO₃ firstly reacts with Al₂O₃,SiO₂ and react with Fe₂O₃ until Al₂O₃,SiO₂ can not use up.When weight content of sodium carbonate is 9%,aluminum in the ore is transformed to sodium aluminate,sodium alumosilicate andα-Al₂O₃, among which sodium aluminate and sodium alumosilicate can be leached by acid solution in turn,whileα-Al₂O₃ remains in iron concentrate in a manner of superfine grains.Hematite,gothite and magnetite are transformed to hematite and some magnetite,they are unable to dissolve into acid liquorg and enriched in the iron concentrate.