Reverse flotation studies on iron ore slime by the synergistic effect of cationic collectors

ABSTRACT

Objective of this study is to investigate the synergistic effect of dodecylamine kerosene as a collector in the reverse cationic flotation of iron ore slime. The hematite slime used in the investigation contains 56.32% Fe, 5.3% SiO₂, and 5.79% Al₂O₃. Iron recovery could be enhanced to 64.58% by the mixed dodecylamine-kerosene collector at neutral pH. Iron concentrate with 64.58% Fe, 3.98% SiO₂, and 4.16% Al₂O₃ was obtained using 80:20 of DDA-kerosene. Potential of synergism for slimes processing by emulsified reagent (dodecylamine/amine) using Tergitol TMN-10 as an emulsifier are envisaged based on this study.     

Utilization of Iron Ore Slimes: A Future Prospective

In India, iron ores processing industries play a vital role in the Indian economy. During the washing and processing of iron ores, slimes less than 0.15 mm are generated and discarded into the tailing pond. These slimes need processing as they cannot be used directly in blast furnaces. In the present investigation, a typical iron ore slime sample containing 59.22% Fe, 4.76% SiO₂, and 4.57% Al₂O₃ was taken. The desliming operation was carried out by using 2” Mozley hydrocyclone. The process variables used to attain the optimum condition of desliming include the spigot opening, the feed pressure, and the diameter of the vortex finder maintaining the pulp density at 10% solid. The deslimed sample was treated by different techniques including an enhanced gravity separator to achieve iron concentrate with 65% Fe so that it can be used for steel making through pelletization. The yield of the magnetic concentrate is about 46.8% with 65% Fe. To improve the yield, the overflow from 2” hydrocyclone and the rejects from magnetic separation were deslimed and processed to recover the iron values. The final concentrate is 74% yield with 64.8% Fe, 1.76% SiO₂, and 1.8% Al₂O_3.     

Effect of mineral geology, mineral size and settling time on selective dispersion and separation process for recovering iron value from iron ultra fines

The dispersion study was conducted on ultra fines of iron ore collected from two locations, Joda and Noamundi slime ponds in the states of Orissa and Jharkhand (India) respectively using sodium hexametaphosphate as a dispersing agent. The Joda slime has been separated into two parts by using hydro cyclone to identify the effect of particle size on selective dispersion and separation of iron ore slimes. Among the gangue minerals present in the slimes, zeolite is more selective towards separation through dispersion process. Under a particular settling condition, a high grade concentrate containing 67.9 wt.% Fe, 1.2 wt.% Al₂O₃ and 1.25 wt.% SiO₂ with 58% iron recovery is achievable using off grade iron ultra fines containing 57.8 wt.% Fe, 7.55 wt.% Al₂O₃ and 7.15 wt.% SiO₂.The efficiency of selective dispersion process strongly depends on mineral geology and particle size. The iron ore ultra fines collected from the Joda slime pond have better selectivity towards dispersion resulting in better separation of gangue minerals in comparison to iron ore ultra fines collected from Noamundi slime pond. This can be attributed to better liberation of Joda slime and difference in nature of the mineral content in Noamundi slime.     

Alumina-Iron Separation of High Alumina Iron Ore by Carbothermic Reduction and Magnetic Separation

The carbothermic reduction of high alumina iron ore in the absence/presence of sodium carbonate (Na₂CO₃) was carried out for alumina-iron separation by wet magnetic separation. Sodium carbonate is found to be capable of improving the separation of alumina and iron, as well as increasing the particle size of metallic iron significantly. When the high alumina ore briquettes were reduced at 1050°C for 80 min, the average particle size of metallic iron was approximately 100 μm in the presence of sodium carbonate, which is bigger than the size of 50 μm in the absence of sodium carbonate. Compared with the absence of sodium carbonate, the Al₂O₃ content of iron concentrate decreased from 4.33% to 1.29%, while the Al₂O₃ removal rate increased from 43.70% to 83.37% with the addition of 9% sodium carbonate. Experimental evidence showed that Na₂CO₃ reacted with Al₂O₃ and SiO₂ to form sodium silicate, aluminum silicate, and sodium aluminosilicate, and decreased the content of Fe in the slags, which improved the separation between the alumina and iron during the magnetic separation.     

Optimal Recovery of Iron Values from a Low Grade Iron Ore using Reduction Roasting and Magnetic Separation

A low grade iron ore containing 51.6% Fe, 17.6% SiO₂, 4.3% Al₂O₃, and 3.8% LOI was subjected to reduction roasting followed by low intensity magnetic separation studies. The phase transformation of hematite into magnetite and fayalite due to reduction roasting was investigated using reflected microscope and X-ray diffraction (XRD) techniques. The effects of reduction variables such as reduction time (40?175 min), temperature (750?1000°C), and reductant dosage (3?11%) using activated charcoal were studied. The process was optimized by using central composite rotatable design (CCRD) and response surface methodology. Iron grade from 59?66% with recovery of 9.5?87% was achieved using CCRD experiments. Model equations were developed both for Fe grade and recovery and then optimized within the bounds of experimental conditions. The program predicted 63.3% Fe with 79% recovery with the following optimum conditions: temperature: 950°C, time: 53.04 min, and reductant: 3%.     

Recycling of waste lubricant oil into chemical feedstock or fuel oil over supported iron oxide catalysts

The recycling of waste lubricant oil from automobile industry was found to be best alternative to incineration. Silica (SiO₂), alumina (Al₂O₃), silica-alumina (SiO₂-Al₂O₃) supported iron oxide (10 wt% Fe) catalysts were prepared by wet impregnation method and used for the desulphurisation of waste lubricant oil into fuel oil. The extent of sulphur removal increases in the sequence of Fe/SiO₂-Al₂O₃<Fe/Al₂O₃<Fe/SiO₂ and this might be due to the presence of smaller crystalline size (7.4 nm) of Fe₂O₃ in Fe/SiO₂ catalyst. X-ray diffraction results suggest the presence of iron sulphide in the used catalyst. Gas chromatography with thermal conductivity detector analysis confirms the presence of H₂S in gaseous products. In addition, Fe/SiO₂ catalyst facilitated the formation of lower hydrocarbons by cracking higher hydrocarbons (≈C₄₀) present in waste lubricant oil.     

Feasibility of Producing Pellet Grade Concentrate by Beneficiation of Iron Ore Slime in India

Abstract

Beneficiation of low grade iron ore slime from Chitradurga, India was studied with a view to produce pellet grade fines. The slime sample had a feed grade of 49.86% total Fe, 7.93% Al₂O₃, and 10.19% SiO₂. Kaolinite and quartz was found to be the main gangue minerals and they formed porous and friable oxide and hydroxide of iron. Over 54% of the materials in the slime were less than 20 micron and this size fraction contained higher percentage of gangue minerals. Liberation of free gangue minerals was observed to be substantial in all size classes. Beneficiation studies indicated that excellent rejection of silica and alumina could be obtained through physical separation. The low grade slime could be enriched to 66.36% Fe with 1.75% silica, and 1.44% alumina.     

Influence of carbonaceous materials on the interactions among (Al2O3-C)/Fe system with temperature and soaking time

It has practical significance for improving the service life of Al₂O₃-C refractories and reducing its influence on steel quality to reveal the reaction mechanism among (Al₂O₃-C)/Fe system under high temperature. The influence of carbonaceous materials on the interactions among (Al₂O₃-C)/Fe system with temperature and soaking time were studied using thermalgravity method in this paper in order to get a better understanding on the reaction mechanism among (Al₂O₃-C)/Fe system. The weight loss of (Al₂O₃-C)/Fe samples and the formation of Al₂O₃ crystal whiskers along with the change of aluminium and carbon content in iron indicates the mechanism of the effects of carbonaceous materials on the reactions among (Al₂O₃-C)/Fe system under high temperature. The result showed that the aluminium pickup of iron was not only due to the dissolution of Al₂O₃ in molten iron but mostly due to the carbothermic reduction of Al₂O₃ and carbonaceous materials in the presence of molten iron.     

EQUILIBRIUM STUDIES IN THE SYSTEM FeO-AI2O3,-SiO2*

Equilibrium relationships on the liquidus surface in the system Fe0-Al₂O₃SiO₂ have been established by a modified quenching procedure. The crystal phases which separate from melts heated in iron crucibles are fayalite (2FeO·SO₂), hercynite (FeO·Al₂O₃), tridymite and cristobalite (SiO₂), mullite (3Al₂O₃·2SiO₂), corundum (Al₂O₃), and wastite (approximately FeO). A considerable portion of this system is liquid at 1400°C. Diagrams show the isotherms and the index of refraction of the glasses formed. Two quintuple points have been established in this investigation. One point is at the composition, SiO₂ 42% by weight, Al₂O₃13%, and FeO 45%, and is a eutectic involving the phases fayalite, hercynite, and tridymite at 970°C. ± 200C. The preferred composition of the second quintuple point is 48% of SO₂, 23% of Al₂O₃, and 29% of FeO; it is a peritectic, and the crystal phases are mullite, hercynite, and tridyrnite. Crystallization from this melt without a change in the weight composition calls for the resorption of mullite at a temperature of 1100°C. ±20°C.     

Studies on removal of lead ions from aqueous solutions using iron ore slimes as adsorbent

Iron ore slimes, a waste material generated during iron ore mining have been employed for the removal of lead ions from aqueous solutions by a batch adsorption technique. The slime sample contains 45.8% Fe, 13.6% SiO₂, and 13.9% Al₂O₃. It is characterized by X-ray diffraction (XRD) and optical microscopy to determine the presence of different phases such as hematite, goethite, limonite, quartz and kaolinite. It is assumed that the adsorption of lead ions is mainly due to the presence of pores and cavities in goethite mineral. The FTIR studies showed the presence of Si-OH and Fe-OH sites responsible for adsorption. Furthermore, the point of zero charge (pzc) of iron ore slime is shifted from 6.2 to 5.8 due to the adsorption of lead ions. Batch adsorption experiments have been conducted to study the sorption behavior of lead ions on iron ore slime. The effects of agitation time, concentration of lead ions, adsorbent doses, solution pH, other metal ions and temperature on the amount of lead ions adsorbed have been investigated. Lead ion adsorption is fast, and equilibrium could be achieved within 15 minutes of time. The adsorption increased with increase in temperature suggesting an endothermic adsorption. Under the conditions, it is possible to remove 95% lead from an aqueous solution bearing ∼20 mg/l at pH∼5.1. The equilibrium adsorption isotherm data fitted very well to both Langmuir and Freundlich adsorption models.     

Production of sintered high alumina refractories from Turkish bauxite ore

Abstract

Bauxite ore extracted from Seydis¸ehir-Konya in Turkey has been used for the production of sintered bauxite. The high iron and calcium in the bauxite were decreased to low levels by hydrochloric acid leaching. Temperature and acid concentration significantly affected the level of iron extraction from bauxite. The aluminium dissolution during acid leaching at 6M and below 70°C was ≤2%, and calcium dissolution was over 95%. XRD and XRF of leached bauxite revealed that the level of iron within the bauxite was decreased below 2% and that no significant TiO₂ or SiO₂ dissolved during leaching. XRD of leached bauxite sintered at 1400-1700°C for 4 h revealed only corundum (α -Al₂O₃) and mullite (3Al₂O₃.2SiO₂). SEM investigation showed that bauxite grains were in the form of large aggregates. The maximum bulk density obtained at 1700°C was low compared with commercial refractory bauxites and the leached bauxite therefore needed to be sintered for longer times at 1700°C or at higher temperatures.     

Separation and recovery of iron and manganese from high-iron manganese oxide ores by reduction roasting and magnetic separation technique

Sodium salts were used in the reduction roasting and magnetic separation process to separate and recover iron and manganese from the high-iron manganese oxide ores to utilize the complex ores. Results showed that Na₂S₂O₃ was the most effective salt. A magnetic concentrate with 86.39 wt% TFe and 96.21 wt% Fe recovery as well as a nonmagnetic product with 54.84 wt% TMn and 85.96 wt% Mn recovery was obtained when the ore sample was reduced at 1100°C for 100 min in the presence of 7 wt% Na₂S₂O₃. In addition, the effects of roasting and separation parameters on the recovery of manganese and iron and the function mechanism of Na₂S₂O₃ were investigated.     

Highly stable Fe/γ‐Al2O3 catalyst for catalytic wet peroxide oxidation

BACKGROUND: A highly stable Fe/γ‐Al₂O₃ catalyst for catalytic wet peroxide oxidation has been studied using phenol as target pollutant. The catalyst was prepared by incipient wetness impregnation of γ‐Al₂O₃ with an aqueous solution of Fe(NO₃)₃· 9H₂O. The influence of pH, temperature, catalyst and H₂O₂ doses, as well as the initial phenol concentration has been analyzed. RESULTS: The reaction temperature and initial pH significantly affect both phenol conversion and total organic carbon removal. Working at 50 °C, an initial pH of 3, 100 mg L^?1 of phenol, a dose of H₂O₂ corresponding to the stoichiometric amount and 1250 mg L^?1 of catalyst, complete phenol conversion and a total organic carbon removal efficiency close to 80% were achieved. When the initial phenol concentration was increased to 1500 mg L^?1, a decreased efficiency in total organic carbon removal was observed with increased leaching of iron that can be related to a higher concentration of oxalic acid, as by‐product from catalytic wet peroxide oxidation of phenol. CONCLUSION: A laboratory synthesized γ‐Al₂O₃ supported Fe has shown potential application in catalytic wet peroxide oxidation of phenolic wastewaters. The catalyst showed remarkable stability in long‐term continuous experiments with limited Fe leaching, < 3% of the initial loading. Copyright © 2010 Society of Chemical Industry     

Study on Fe–Al2O3 interaction over precipitated iron catalyst for Fischer–Tropsch synthesis

Two model spherical iron catalysts (100Fe/0Al₂O₃ and 100Fe/15Al₂O₃) with free Cu and K promoters were prepared by the combination of co-precipitation and spray drying method for the application of slurry Fischer–Tropsch synthesis (FTS). The effect of Fe–Al₂O₃ interaction on the reduction/carburization behavior in H₂/CO/syngas, surface basicity and the change of phase structure were comparatively studied by means of H₂ or CO temperature-programmed reduction (TPR), CO₂ temperature-programmed desorption (TPD) and Mössbauer effect spectroscopy (MES). The results showed that the catalyst incorporated with Al₂O₃ exhibits a strong Fe–Al₂O₃ interaction, which obviously weakens the surface basicity, stabilizes the FeO phase and inhibits the reduction of iron catalyst in H₂ or syngas. Furthermore, Fe–Al₂O₃ interaction also restrains the carburization of iron catalyst in CO or syngas. In slurry FTS process, it was found that the strong Fe–Al₂O₃ interaction decreases the FTS activity and suppresses the water gas shift (WGS) reaction, but can stabilize the active sites of iron catalyst and improve its run stability. Due to the strong Fe–Al₂O₃ interaction, the weak surface basicity on the catalyst incorporated with Al₂O₃ greatly decreases the selectivity of heavy hydrocarbon products.     

Experimental phase equilibria study and thermodynamic modelling of the PbO-“FeO”-SiO2-ZnO,PbO-“FeO”-SiO2-Al2O3 and PbO-“FeO”-SiO2-MgO systems in equilibrium with metallic Pb and Fe

Phase equilibria of the PbO-“FeO”-SiO₂-ZnO, PbO-“FeO”-SiO₂-Al₂O₃ and PbO-“FeO”-SiO₂-MgO slags with liquid Pb metal, solid or liquid Fe metal and solid oxides (cristobalite and tridymite SiO₂, willemite (Zn,Fe)₂SiO₄, wustite (Fe,Al)O_1+x, spinel (Fe,Al)₃O₄, olivine Fe₂SiO₄, corundum (Al,Fe)₂O₃, mullite Al₆Si₂O₁₃ and pyroxene (Mg,Fe)SiO₃) were investigated at 1125–1670 °C. These conditions correspond to the minimum solubility of PbO in slag in presence of Pb and Fe metals at reducing conditions and represent the limit of lead smelting and slag cleaning process. High-temperature equilibration on silica, corundum or iron foil substrates, followed by quenching and direct measurement of Pb, Fe, Si, Zn, Al and Mg concentrations in the liquid and solid phases with the electron probe X-ray microanalysis (EPMA) was used. Present data can be used to improve the thermodynamic models for all phases in this system.     

The role of Fe on PtPd oxidation catalyst prepared by simultaneous and sequential incipient wetnesses

The roles and effects of Fe on the catalytic performance and physicochemical properties of a PtPd diesel oxidation catalyst prepared by three different methods were investigated by CO oxidation reaction, X-ray diffraction, temperature-programmed reduction (TPR), temperature-programmed oxidation, and BET surface area. It was found that the roles of Fe depended strongly on the sequential order of Fe introduction during the preparation of the PtPd catalyst. The Fe/PtPd/Al₂O₃ catalyst was prepared by introducing Fe onto the PtPd/Al₂O₃, and the PtPd/Fe/Al₂O₃ catalyst was obtained by loading the PtPd onto the Fe/Al₂O₃. The former had a superior activity. From the TPR results, the catalytic activity of CO oxidation was correlated with the oxygen mobility of the iron oxides. For PtPd/Fe/Al₂O₃, the iron interacted preferentially with the alumina support forming FeAlO₃, which resulted in the stabilization of the support and a reduction in the surface area. The major role of Fe was to promote the enhancement of the catalytic activity of PtPd through an intimate interaction between the PtPd and iron oxides, which had lattice oxygens to generate oxygen with oxidation abilities.     

EQUILIBRIUM RELATIONSHIPS ON THE LIQUIDUS SURFACE IN PART OF THE MnO-Al2O3-SiO2 SYSTEM*

The minerals found to have a stability range on the liquidus surface in the system MnO-Al₂O₃-SiO₂ are cristobalite and tridymite, SiO₂; mullite, 3Al₂O₃. 2SiO₂; corundum, Al₂O₃; rhodonite, MnO.SiO₂; tephroite, 2MnO.SiO₂; galaxite, MnO.Al₂O₃; spessartite, 3MnO.Al₂O₃.3SiO₂; and a new compound, 2MnO.2Al₂O₃.5SiO₂. The quintuple points and boundary lines found in that part of the MnO.Al₂O₃.SiO₂ system bounded by the systems 3MnO.Al₂O₃.3SiO₂-SiO₂, 3MnO.Al₂O₃.3SiO₂-Al₂O₃, and Al₂O₃-SiO₂have been determined. Quintuple points and boundary lines involving the area inclosed by the systems 2MnO . SiO₂-3MnO . Al₂O₃ . 3SiO₂, 3MnO . Al₂O₃ . 3SiO₂-SiO₂, and 2MnO.-SiO₂-SiO₂ are indicated. Isotherms and isofracts (lines of equal refractive index) are given for the portion of the system investigated. X-ray data show that crystals of the compound 3MnO.Al₂O₃.3SiO₂ have the same structure as the garnet mineral spessartite (manganese garnet). The compound 2MnO. 2Al₂O₃ . 5SiO₂, which is shown by X-ray data to have a basic structure similar to cordierite, 2MgO.2Al₂O₃.5SiO₂, seldom crystallizes from the glass, but a third substance which has a high extinction angle crystallizes readily from the reheated glass. These high extinction angle crystals are replaced by 2MnO .2Al₂O₃.5SiO₂ when a proper heating cycle is employed, and they are not found again until the product is melted and crystallization is repeated.     

Enhancing the Utilization Potential of a Low Grade Chromite Ore through Extensive Physical Separation

Low grade chromite ore with less than 30% Cr₂O₃ was investigated with a view to enhance its utilization potential. The ore contained olivine, serpentine, and chrysotile as the gangue minerals. The chromite mineral contained alumina, magnesia, and FeO in its lattice. Critical mineralogical assessment indicated that enrichment to a level of 39-43% Cr₂O₃ may be possible. Beneficiation of the ore was undertaken using gravity based methods. Inadequate liberation prevented any significant enrichment at 0.9 mm top size. At 0.3 mm top size, the spiral concentration generated a concentrate with 40.5% Cr₂O₃ from the coarser fraction. The finer fraction was treated in a shaking table to generate another concentrate with 41.6% Cr₂O₃. The final combined concentrate assayed 41.2% Cr2O3 with a Cr/Fe ratio of 2.27. The middling from both treatments were rich in chromite content and were recommended to be included in the concentrates. Chromite recovery from the coarse reject was also beneficial. It was recommended that 8-10% solids content of the reject stream with 0.02 kg/t of Magnafloc flocculant may be used to achieve best settling characteristics of the reject fines.     

The potential of Hazara phosphates for phosphoric acid manufacture

The phosphate reserves in Pakistan are small. The largest ore body (Lagarban area) of Hazara Administrative Division located in the North East of the country has 3.25 (measured) and 6.71 (inferred) million tons phosphates rock of silicious and dolomitic nature with 25.8% average P₂O₅ contents besides high impurities of R₂O₃ (3.3%) and MgO (up to 6%).The deposits are not beneficiable by dry and wet screening due to significant phosphate losses which take place. Phosphate flotation recoveries are also low. Heavy intensity magnetic separation removes iron after the removal of dust from classified fraction. Acid leaching is efficient for removing MgO (up to 84%) with low P₂O₅ losses. However, removal of iron and MgO by these methods is not considered feasible on economic grounds.Laboratories and pilot plant processing trials showed that phosphoric acid of 23–25% P₂O₅ can be manufactured from Lagarban rock. As most of the impurities of the rock Fe₂O₃, Al₂O₃, MgO and part of SiO₂ are washed down during processing the resulting product acid is of poor quality with high viscosity.Triplephosphates prepared from this acid are hygroscopic and have low P₂O₅ availability (86%).To overcome the problem of these objectionable impurities in the product acid, removal of these impurities during the processing of phosphoric acid is required, i.e. aggolomeration with gypsum crystals-Pembrook pocess, Occidental process.     

Rh–Fe/Ca–Al2O3: A Unique Catalyst for CO-Free Hydrogen Production in Low Temperature Ethanol Steam Reforming

Low temperature ethanol steam reforming (ESR) was studied over a series of 1 wt% Rh–x % Fe catalysts with various Fe loading (x = 0–10 wt%) and on different supports (Ca–Al₂O₃, SiO₂ and ZrO₂). The results show that close interaction between Rh and Fe is required to reduce the CO selectivity to almost negligible values. In addition, Rh–Fe supported on Ca–Al₂O₃ exhibits the best performance in terms of CO selectivity and hydrogen yield as compared to other supports. Characterization by XPS and XANES indicates the presence of Fe_xO_y species upon reduction, resulting in the formation of coordinatively unsaturated ferrous (CUF) active sites along the Rh–Fe_xO_y interface. These CUF sites promote water–gas shift reaction during low temperature ESR. Temperature programmed oxidation and Raman spectroscopy of spent catalysts also indicate that the addition of iron oxide reduces coke deposition and forms more reactive coke. Hence, the catalyst lifespan is significantly extended.