Abstract
Washing of iron ore fines and slime (10% and 25% w/v, slurry concentrations) with two types of surface-active agents (sodium humate (synthesized) and AD 200 (commercial)) at varying concentrations at pH 8 was conducted for ascertaining the efficacy of dispersants in beneficiating the low-grade iron ores. The beneficiation process follows the “selective dispersion-cum-settling technique.” The process results in the formation of a dispersed phase rich in gangue minerals and a settled phase of predominantly active hematite mineral. The stability of dispersed phase (DP) was evaluated by determination of the percentage solid content in the DP. Settling tests were performed. First-order kinetic models have been applied to the dispersion-cum-settling behaviour of both the samples, and evaluated kinetic parameters were found to have good agreement with experimental data. Removal of gangue minerals from iron ore depends on the pH of the slurry, concentration of the slurry, and concentration of the surface-active agent used. The surface-active agents at pH 8 produce ∼1.2–1.5 times more stable suspension in the case of iron ore fines and slimes than that of without surface-active agent. They significantly remove gangue minerals and increase the iron value ∼2–7% with ∼58–74% recovery depending on the experimental conditions. The concentrates collected satisfy the required specifications (Al203/Fe < 0.05 and Al203/Si02 < 1). The gangues in the dispersed phase as characterised by “SEM-EDXA” are mostly clay-bearing minerals like kaolinite, goethite, chlorite, and alumina-silicate minerals. Heat treatment causes distortion of clay minerals present in the dispersed phase and also indicates the complex nature of the gangue minerals.
Highlights
Upgradation of iron ore is an essential step to meet the quality norms of the feed for the blast furnace in the iron and steel industry
India is rich in iron ore reserves, consisting of around 14 billion tonnes [2]. e principal plants are situated in the states of Jharkhand, Orissa, Goa, Karnataka, and Chhattisgarh [3]. e quality of the iron ore is generally soft in nature associated with high amount of clay minerals [4]. e Indian iron ore processing industry is discarding about 8 to 10 million tons of iron per annum at ∼50–60% iron in the form of slimes that results in huge loss of iron value including threat to the environment [5]. e generated lowgrade iron ore fines and slime are considered as waste
Increasing iron value and simultaneous lowering of gangue minerals in iron ore are of prime concern for the industry. e iron ore fines and slime having an alumina-to-silica ratio typically >1 create severe operational problems during sintering and subsequent smelting in the blast furnace
Summary
Upgradation of iron ore is an essential step to meet the quality norms of the feed for the blast furnace in the iron and steel industry. E surface-active agent, either simple or complex, adsorb onto hematite surfaces of iron ore, resulting in flocculation of hematite particles and dispersion of gangue minerals rich in alumina and silica. In this context, the beneficiation of iron ore tailings with sodium hexametaphosphate as dispersant and starch as flocculant using ultrasonication technique was significant as it produces concentrate with 65% Fe and 91% recovery from a feed assaying 50.5% Fe with high gangues [20]. Characterization of the dispersed phase of iron ore slime slurry is essential for proper information of the gangue mineral phases as this in turn helps in selection of suitable beneficiation techniques [21]. The DRIFT spectroscopic characterization of the dispersed phase is extended by thermal treatment on the same and the XRD results are supported by SEM-EDXA analysis
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