METHODOLOGY

· Thorough literature and patent search of various methods and practices of iron ore

beneficiation including comminution, classification, gravity and magnetic separation, froth flotation, dewatering and agglomeration

· Collection of data on geology and mineralogy of iron ores from Jilling-Langalata and

Barsua- Kalta deposits of eastern India.

· Processing and interpretation of chemical data.

· Major and trace minerals using X-ray Fluorescence Spectrometry (XRF)

· Mineralogical characteristics have been established for the lump ore and the slime.

Detailed ore microscopy, image analyzer, Scanning Electron Microscopy- Energy Dispersive Spectroscopy (SEM-EDS) and X-ray Diffractometry (XRD) have been used in the characterization of different types of iron ores and slimes and accordingly the processing parameters designed accordingly.

64 5.2.1 MINERALOGICAL ANALYSIS

Mineralogy of the various samples has been established by synthesizing the integrated results brought out by the following instrumental methods:

5.2.1.1Optical microscopy

Mineral identification is the most important aspect that is needed to be carried out prior to beneficiation. The basic instrument for mineral identification is an optical microscope. The polished surface types of ore samples were prepared using araldite in a mould to study under reflected light microscope. The samples were polished by conventional polishing techniques, cleaned ultrasonically and examined under Orthoplan Microscope (Leitz make). The mineralogy, texture, microstructure and inclusions etc. in respect of ore samples were studied by this method [45].

5.2.1.2Electron microscopy

Unlike optical microscopy where light is the source for image formation. In electron microscope, the image formation is due to the scattering of electron beam scans over the sample. In general, this study i) brings out the size, shape and micro morphology of minerals and iii) their textural patterns.

For Scanning electron microscope (SEM) study, the sample was degreased and dried then cleaned ultrasonically with acetone. After cleaning the sample was blown by using a compressed gas. Samples were compressed into small disks for mounting. Carbon tapes by an ion sputtered JFC-1100 was used for this purpose. The powder sample was sprinkled lightly with a spatula, pressed lightly to seat and then studied under a Japanese make electron microscope (JEOL JSM-6480LV). For this, the working height was kept at 15mm with working voltage ranging between 10 kV to 20 kV. For EDS, polished samples were taken

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and examined at 15 mm working height. The working voltages for study was kept at 25 kV with beam current 100 nA. By this technique, Energy dispersive spectra (EDS) spectra of individual sample showing the semi-quantitative abundance of major and minor elements was brought out.

5.2.1.3 X-ray diffraction

X-ray diffraction technique (XRD) was extensively used for identification of various mineral phases especially the clay minerals and gibbsite for assessing the abundance of each phase in an ore sample. The XRD was carried out using PANalytical X-ray Diffractometer, MODEL D500 having automatic receiving slit, divergence slit, and graphite mono-chrometor assembly. Cu, Kα radiation operating at 40 kv and 20 nA was used for this purpose. A diffraction pattern recording the angle 2θ against the intensity was obtained over a range between 10˚ to 70˚ corresponding to d- values between 20 A and 1.34A. The scanning rate was 2˚ per minute with recorder full scale set in to 2 X 103 counts. Each mineral phase exhibits a characteristic reflection peak corresponding to its d-values. These of D values were matched from the [57] and various minerals were identified. Further the variations in the peak intensities of different mineral phases in the ore sample indicate their relative abundance.

5.2.1.4 Zeta Potential

In flotation, the response of many minerals is often dramatically affected by pH .Adsorption of collectors and modifying reagents in the flotation of oxide and silicate minerals is controlled by the electrical double layer at the mineral-water interface. In systems where the collector is physically adsorbed, flotation with anionic or cationic collectors depends on the mineral surface being charged oppositely. Adjusting the pH of the system can enhance or prevent the flotation of a mineral. Thus, the Iso electric point (IEP) of the mineral is the most important property of a mineral in such systems but raising the pH sufficiently above the IEP can repel

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chemisorbing collectors from the mineral surface. Zeta potentials can be used to delineate this interfacial phenomenon.

5.2.2 CHEMICAL ANALYSIS

The objective of chemical analysis was to determine the chemical composition of the different ore types by different established techniques and distinguish the characteristics of one from the other by chemical means. The major, minor and trace constituents in different samples were taken up by wet chemical methods and using different instrumental techniques such as XRF.

5.2.2.1 X-ray Fluorescence

Major and minor constituents of various slag samples were analysed by XRF spectrometry on Phillips (PW-1400) X-ray spectrometer with Scandium and Rhodium targets using pentaerythritol (Al, Si), Thallium Acid Pathalate (Na, Mg), Germanium (P) and Lithium Fluoride (for heavier elements) as analyzing crystals in vacuum medium. International and in-house standards of appropriate compositions were used for calibration. Both major and minor elements were determined by pressed powered pellet technique. The specific gravity of iron ore samples was measured using picnometer by the standard method.

5.3 BENEFICIATION UNIT OPERATIONS