Flocculation, filtration and selective flocculation studies on haematite ore fines using starch

The flocculation and filtration characteristics of typical Indian iron ore fines have been studied using starch as flocculant in the presence of an inorganic electrolyte, namely calcium chloride. The effect of various parameters such as pH, starch and calcium chloride concentrations and pulp density on the settling and filtration rates, turbidity of the supernatant and on residual starch and calcium ion concentrates has been investigated through a statistical design and analysis approach and subsequently optimised on a laboratory scale. The adsorption mechanisms of starch onto haematite have been elucidated through adsorption density measurements, infrared and X-ray photoelectron spectroscopic techniques. The rheological property of the polymer solutions of relevance to flocculations has also been investigated. Further, the role of metal ion-starch interactions in the bulk solution, has been studied. In order to understand the nature of polymer adsorption at the double-layer, electrokinetic studies have been carried out with the iron ore mineral samples using starch and calcium chloride. Based on the above findings, selective floculaation tests on artificial mixtures of iron ore minerals have been carried out to determine the separation efficiencies from the view point of alumina and silica removal from haematite as well as the control of alumina: silica ratio in Indian iron ores.

Studies on interaction of Paenibacillus polymyxa with iron ore minerals in relation to beneficiation

Interaction between Paenibacillus polymyxa with minerals such as hematite, corundum, quartz and kaolinite brought about significant surface chemical changes on all the minerals. Quartz and kaolinite were rendered more hydrophobic, while hematite and corundum, became more hydrophilic after biotreatment. The predominance of bacterial polysaccharides on interacted hematite and corundum and of proteins on quartz and kaolinite was responsible for the above surface-chemical changes. Bio-pretreatment of the above iron ore mineral mixtures resulted in the selective separation of silica and alumina from iron oxide, through bioflotation and bioflocculation. The utility of bioprocessing in the beneficiation of iron ores is demonstrated.

Microbial Aspects of Environmentally Benign Iron Ore

Many types of micro-organisms inhabit iron ore deposits contributing to biogenic formation and conversion of iron oxides and associated minerals. Bacteria such as Paenibacillus polymyxa arc capable of significantly altering the surface chemical behaviour of iron ore minerals such as haematite, alumina, calcite and silica. Differing mineral surface affinities of bacterial cells and metabolic products such as proteins and polysaccharides can be utilised to induce their flotation or flocculation. Mineral-specific bioreagents such as proteins are generated when bacteria are grown in the presence of haematite, alumina, calcite and silica. Alumina-grown bacterial cells and proteins separated from such cells were found to be capable of separating alumina from haematite. Biodegradation of iron ore flotation collectors such as amines and oleates can be effectively utilised to achieve environmental control in iron ore processing mills.

Zeta Potential Studies On Some Iron-Ore Minerals In The Presence Of Starches

Authors perform zeta potential studies on hematite, corundum, and quartz samples using starches to understand the adsorption behavior of polymeric starch flocculants at the oxide mineral-solution interface and to correlate this information with their flocculation characteristics and investigate effects of pH and CaCl#72 on zeta potential of Fe ore minerals.

A Geostatistical Study pf Alumina-Content in Ores of An Indian Iron-Ore Deposit

Mining and blending operations in the high grade iron ore deposit under study are performed to optimize recovery with minimal alumina content while maintaining required levels of other chemical component and a proper mix of ore types. In the present work the regionalisation of alumina in the ores has been studied independently and its effects on global and local recoverable tonnage as well as on alternatives of mining operations have been evaluated. The global tonnage recovery curves for blocks (20m x 20m x 12m) obtained by simulation closely approximated the curves obtained theoretically using a change of support under the discretised gaussian model. Variations in block size up to 80m x 20m x 12m did not affect the recovery as the horizontal dimensions of the blocks are small in relation to the range of the variogram. A comparison of the local tonnage recovery curves obtained through multiple conditional simulations made with that obtained by the method of uniform conditioning of block grades on an estimate of panel 100m x 100m x 12m panel grade reveals comparable results only in panels which have been well conditioned and possesing an ensemble simulation mean close to the ordinary kriged value for the panel. Study of simple alternative sequence of mining on the conditionally simulated deposit shows that concentration of mining operations simultaneously on a single bench enhances the fluctuation in alumina values of ore mined.

Reverse flotation of silica from Kudremukh iron ore .1. Selection of cationic reagents

Four types of cationic collectors were tested and evaluated for their performance in the reverse flotation of silica from the spiral preconcentrate of Kudremukh iron ore. A stagewise flotation was conducted by adding the reagent in three stages. Starch was used to depress hematite. Silica flotation was found to be very sensitive to the amount of cationic reagent added. The performance of the reagents was evaluated based on the percentage of silica and iron in the concentrate and percent recovery of iron obtained in the concentrate. Tests of significance, namely, t-test and F-test were performed to select the best two reagents for further investigations.

Reverse flotation of silica from Kudremukh iron ore .2. Optimization of flotation process

An experimental programme based on statistical analysis was used for optimizing the reverse Rotation of silica from non-magnetic spiral preconcentrate of Kudremukh iron ore. Flotation of silica with amine and starch as the Rotation reagents was studied to estimate the optimum reagent levels at various mesh of grind. The experiments were first carried out using a two level three factor design. Analysis of the results showed that two parameters namely, the concentration level of the amine collector and the mesh of grind, were significant. Experiments based on an orthogonal design of the hexagonal type were then carried out to determine the effects of these two variables, on recovery and grade of the concentrate. Regression equations have been developed as models. Response contours have been plotted using the 'path of steepest ascent', maximum response has been optimized at 0.27 kg/ton of amine collector, 0.5 kg/ton of starch and mesh of grind of 48.7% passing 300 mesh to give a recovery of 83.43% of Fe in the concentrate containing 66.6% Fe and 2.17% SiO2.

Developments in Biotechnology for Environmentally Benign Iron Ore Beneficiation

Biomineralization and biogenesis of iron ore deposits are illustrated in relation to indigenous microorganisms inhabiting iron ore mines. Aerobic and anaerobic microorganisms indigenous to iron oxide mineralization are analyzed. Microbially-induced flotation and flocculation of iron ore minerals such as hematite, alumina, calcite and quartz are discussed with respect to use of four types of microorganisms, namely, Paenibacillus polymyxa, Bacillus subtilis, Saccharomyces cerevisiae and Desulfovibrio desulfuricans. The role of the above organisms in the removal of silica, alumina, clays and apatite from hematite is illustrated with respect to mineral-specific bioreagents, surface chemical changes and microbe-mineral interaction mechanisms. Silica and alumina removal from real iron ores through biobeneficiation is outlined. Environmental benefits of biobeneficiation are demonstrated with respect to biodegradation of toxic reagents and environmentally-safe waste disposal and processing.

Impact of riparian land use on stream insects of Kudremukh National Park, Karnataka state, India

The impact of riparian land use on the stream insect communities was studied at Kudremukh National Park located within Western Ghats, a tropical biodiversity hotspot in India. The diversity and community composition of stream insects varied across streams with different riparian land use types. The rarefied family and generic richness was highest in streams with natural semi evergreen forests as riparian vegetation. However, when the streams had human habitations and areca nut plantations as riparian land use type, the rarefied richness was higher than that of streams with natural evergreen forests and grasslands. The streams with scrub lands and iron ore mining as the riparian land use had the lowest rarefied richness. Within a landscape, the streams with the natural riparian vegetation had similar community composition. However, streams with natural grasslands as the riparian vegetation, had low diversity and the community composition was similar to those of paddy fields. We discuss how stream insect assemblages differ due to varied riparian land use patterns, reflecting fundamental alterations in the functioning of stream ecosystems. This understanding is vital to conserve, manage and restore tropical riverine ecosystems.

Adsorption behaviour of an oxidised starch onto haematite in the presence of calcium

The adsorption behaviour of an oxidised starch AP as well as that of calcium onto haematite have been studied both individually and together. While the adsorption density of starch AP onto haematite is enhanced in the presence of calcium, the adsorption of calcium onto haematite is not promoted by starch AP. Flocculation tests on haematite ore fines in the presence of starch AP and calcium chloride reveal that the sequence in which calcium and starch are added governs the settling rates and turbidity values. Zeta potential, viscosity and conductivity measurements, and calcium ion binding studies with starch AP indicate calcium-starch interactions. Possible mechanisms involved in such interactions with respect to haematite flocculation have been discussed.

Microbially induced selective flocculation of hematite from kaolinite

Microbially induced selective flocculation of hematite from kaolinite has been demonstrated using Bacillus subtilis. Growth of bacterial cells in the presence of kaolinite resulted in enhanced production of extracellular proteins while that of hematite promoted significant secretion of exopolysaccharides. Bacterial cells were adapted to grow in the presence of the minerals and use of hematite-grown and kaolinite-grown cells and their metabolic products in the selective flocculation of hematite and dispersion of kaolinite illustrated. Bacterial cells and extracellular polysaccharides exhibited higher surface affinity towards hematite, rendering it hydrophilic; while significant protein adsorption enhanced surface hydrophobicity of kaolinite. Bacterial interaction with hematite and kaolinite resulted in significant surface chemical changes on the minerals. Due to higher surface affinity towards extracellular proteins, zeta potentials of kaolinite shifted in the positive direction, while those of hematite shifted in the negative direction due to higher adsorption of extracellular polysaccharides. Bacterial interaction promoted selective flocculation of only hematite, while kaolinite was efficiently dispersed. Mineral-specific stress proteins were generated on growing B. subtilis in the presence of kaolinite. Interfacial aspects of microbe-mineral interactions are illustrated to explain microbially-induced selective flocculation of hematite from kaolinite with relevance to clay and iron ore beneficiation. (C) 2013 Elsevier B.V. All rights reserved.

Study the effect of electrical and mechanical shock loading on liberation and milling characteristics of mineral materials

Milling is an energy intensive process and it is considered as one of the most energy inefficient processes. Electrical and mechanical shock loading can be used to develop a pre-treatment methodology to enhance energy efficiency of comminution and liberation of minerals. Coal and Banded Hematite Jasper (BHJ) Iron ores samples were taken for the study to know the effect of shock loading. These samples were exposed to 5 electric shocks of 300 kV using an electric shock loading device. A diaphragmless shock tube was used to produce 3 and 6 compressed air shocks of Mach number 2.12 to treat the coal and Iron ore samples. Microscopic, comminution and liberation studies were carried out to compare the effectiveness of these approaches. It was found that electric shock loading can comminute the coal samples more effectively and increases the yield of carbon by 40% at 1.6 gm/cc density over the untreated coal samples. Mechanical shock loading showed improved milling performance for both the materials and 12.90% and 8.1% reduction in the D-80 of the particles was observed during grinding for treated samples of coal and iron, respectively. Liberation of minerals in BHJ Iron ore was found unaffected due to low intensity of the mechanical shock waves and non conductivity of minerals. Compressed air based shock loading is easier to operate than electrical shock loading and it needs to be explored further to improve the energy efficacy of comminution. (C) 2014 Elsevier Ltd. All rights reserved.

Identification of type and degree of railway ballast fouling using ground coupled GPR antennas

GPR is widely used for ballast fouling identification, however, there are no robust guidelines to find the degree and type of fouling quantitatively. In this study, GPR studies were carried out on model and actual railway tracks using three ground coupled antennas and considering three fouling materials. Three ground coupled antennas viz., 100 MHz, 500 MHz and 800 MHz antennas were used for the initial survey and it was found that the 800 MHz ground coupled antenna is an optimum one to get quality results. Three major fouling materials viz., screened/broken ballast, coal and iron ore were used to construct prototype model sections, which were 1/2 of the actual Indian broad-gauge railway track. A separate model section has been created for each degree and type of fouling and GPR surveys were carried out. GPR study shows that increasing the fouling content results in a decrease in the Electromagnetic Wave (EMW) velocity and an increase in the dielectric constant. EMW velocity of ballast fouled with screened ballast was found to be more than coal fouled ballast and iron ore fouled ballast at any degree of fouling and EMW velocity of iron ore fouled ballast was found to be less than coal and screen ballast fouled ballast. Dielectric constant of iron ore fouled ballast was found to be higher than coal and screen ballast fouled ballast for all degrees of fouling. Average slope of the trend line of screen ballast fouled section is low (25.6 degrees), coal fouled ballast is medium (27.8 degrees) and iron ore fouled ballast is high (47.6 degrees). (C) 2016 Elsevier B.V. All rights reserved.

Laboratory studies on ball wear in the grinding of a hematite-magnetite ore

Marked-ball grinding tests were carried out under different grinding conditions and environments. Three types of balls were used, namely, cast hyper steel, high chrome cast iron and EN-31 (forged), which cover a wide range of chemical composition, microstructure and media hardness. The effect of pulp density on ball wear and grinding efficiency was also studied. Relative pulp viscosities at different percent solids for the ore slurry were also determined. As the Kudremukh ore contained about 0.2% pyrite, the effect of addition of pyrite on ball wear was studied separately. Results of marked-ball grinding tests indicated that ball wear increased with time and showed a sharp increase for wet grinding over dry grinding. Ball wear under wet grinding conditions was also influenced by the gaseous atmosphere in the mill. At 70% solids, the best results in terms of reduced ball wear coupled with satisfactory grinding efficiency were obtained. The influence of oxygen on the corrosive wear of grinding balls was increasingly felt only if sulphide minerals such as pyrite were also present in the ore. The various ball materials could be arranged in the following order with respect to their overall wear resistance: high chrome cast iron > EN-31 (forged) > cast hyper steel.Possible ball wear mechanisms involved in the grinding of Kudremukh ore are discussed.

Ball wear and its control in the grinding of a lead-zinc sulphide ore

Marked ball grinding tests were carried out in the laboratory with a lead-zinc sulphide ore under different experimental conditions using high carbon low alloy steel (cast and forged) and high chrome cast iron balls. Relative ball wear as a function of grinding period and milling conditions was evaluated for the different types of ball materials. The role of corrosion and abrasion-erosion in the wear of grinding media is brought out. Methods to minimise ball wear through control of mill atmosphere and addition of reagents are discussed.