Evaluation of VSK separation in the classification of two mineralogically different iron ore fines

With gradually diminishing Fe grade in tandem with the ever-increasing demand for high-grade iron ores,iron ore industries are now focusing on the beneficiation of low-grade iron ore fines,mainly considered waste.Besides,the scarcity of water at many of the mines’sites and the new water conservation policies of the governments have necessitated research on suitable dry beneficiation routes.In this context,an effort has been made to evaluate the efficacy of a dry classification unit,such as the VSK separator,in upgrading the iron values of two low-grade Indian iron ore fines,named Sample 1 and Sample 2.The mineralogical studies,involving scanning electron microscopy and X-ray diffraction,suggest that Sample 1 is a low-grade blue dust sample(51.2wt%Fe)containing hematite and quartz as the major minerals,while Sample 2(53.3wt%Fe)shows the presence of goethite in addition to hematite and quartz.The experiments,carried out using Box-Benkhen statistical design,indicate that blower speed,followed by feed rate,is the most influencing operating parameter in obtaining a good product in the VSK separator.At optimum levels of the operating factors,a fines product with~55wt%Fe at a yield of~40%can be obtained from Sample 1,while Sample 2 can be upgraded to~56wt%Fe at a yield of~85%.The results suggest that the VSK separator can be employed as an efficient intermediate unit operation in a processing circuit to upgrade the iron contents of iron ore fines.

Microwave-assisted reduction roasting–magnetic separation studies of two mineralogically different low-grade iron ores

The microwave-assisted reduction behaviours of two low-grade iron ores having a similar Fe content of 49wt%but distinctly different mineralogical and liberation characteristics were studied.Their performances in terms of the iron grade and recovery as obtained from statistically designed microwave(MW)roasting followed by low-intensity magnetic separation(LIMS)experiments were compared.At respective optimum conditions,the titano-magnetite ore(O1)could yield an iron concentrate of 62.57%Fe grade and 60.01%Fe recovery,while the goethitic ore(O2)could be upgraded to a concentrate of 64.4%Fe grade and 33.3%Fe recovery.Compared with the goethitic ore,the titanomagnetite ore responded better to MW heating.The characterization studies of the feed and roasted products obtained at different power and time conditions using X-ray diffraction,optical microscopy,vibrating-sample magnetometry,and electron-probe microanalysis explain the sequential reduction in the iron oxide phases.Finally,taking advantage of the MW absorbing character of the titano-magnetite ore,a blend of the same with the goethite-rich ore at a weight ratio of 60:40(O2:O1)was subjected to MW roasting that resulted in a concentrate of 61.57%Fe grade with a Fe recovery of 64.47%.

印度一水硬铝石样品中氧化铁相的矿物学、解离和浸出特性（英文）

利用磁选和浸出技术从印度一水硬铝石样品中除铁,采用扫描电镜、电子探针显微分析仪和X射线衍射等定量矿物学评价技术进行深入的矿物学表征研究。结果表明,极细的赤铁矿颗粒与其他几种矿物相以复杂的方式结合在一起;即使粒度小于38μm,仍有约60%的赤铁矿未被解离出来;这个粒度也是物理分离过程去铁的极限。湿式强磁选研究表明,只有49%的铁可被除去。进一步的草酸浸出研究表明,在固液比0.05:1、温度90°C、时间120 min、酸浓度1 mol/L的条件下,可除去约76%的铁。铁在草酸中的溶解受化学反应控制,计算的活化能为35.15 k J/mol。

Bioleaching of copper from pre and post thermally activated low grade chalcopyrite contained ball mill spillage

Bioleaching of a low grade chalcopyrite （ball mill spillage material） was tested for copper recovery in shake flasks. The original samples （as received） were thermally activated （600℃, 30 min） to notice the change in physico-chemical and mineralogical characteristics of the host rock and subsequently its effect on copper recovery. A mixed culture of acidophilic chemolithotrophic bacterial consortium predominantly entailing Acidithiobacillus fer- rooxidans strain was used for bioleaching studies and optimization of process parameters of both original and thermally activated samples. Mineralogical characteriza- tion studies indicated the presence of chalcopyrite, pyrite in the silicate matrix of the granitic rock. Field emission scanning electron microscopy coupled with Energy dispersive spectroscopy （FESEM-EDS） and X-ray Fluor- escence （XRF） analysis indicated mostly SiO2. With pH 2, pulp density 10% w/v, inoculum 10% v/v, temperature 30~C, 150 r.min-~, 49% copper could be recovered in 30 days from the finest particle size （- 1 ~ 0.75 mm） of the original spillage sample. Under similar conditions 95% copper could be recovered from the thermally activated sample with the same size fraction in 10 days. The study revealed that thermal activation leads to volume expansion in the rock with the development of cracks, micro and macro pores on its surface, thereby enabling bacterial solution to penetrate more easily into the body, facilitating enhanced copper dissolution.