Thermal expansivity of geikielite and ilmenite utilizing in-situ synchrotron X-ray diffraction at high temperature

The unit-cell parameters and volumes of geikielite(MgTiO_(3))and ilmenite(FeTiO_(3))were investigated at high temperatures up to 700 K and ambient pressure,using in-situ angle-dispersive synchrotron X-ray diffraction.No phase transition was detected over the experimental temperature range.Using(Berman in J Petrol29:445-522,1988.10.1093/petrology/29.2.445)equations to fit the temperature-volume data,the volumetric thermal expansion coefficients at ambient conditions(α_(V0))of MgTiO_(3) and FeTiO_(3) were obtained as follows:2.55(6)×10^(-5)K^(-1)and 2.82(10)×10^(-5)K^(-1),respectively.We infer that the larger effective ionic radius of Fe^(2+)(Ⅵ)(0.78 A)than that of Mg^(2+)(Ⅵ)(0.72?)renders FeTiO_(3)has a larger volumetric thermal expansivity than MgTiO_(3).Simultaneously,the refined axial thermal expansion coefficients under ambient conditions areα_(a0)=0.74(3)×10^(-5)K^(-1)andα_(c0)=1.08(5)×10^(-5)K^(-1)for the aaxis and c-axis of MgTiO_(3),respectively,andα_(a0)=0.95(5)×10^(-5)K^(-1)andα_(c0)=0.92(12)×10^(-5)K^(-1)for the aaxis and c-axis of FeTiO_(3),respectively.The axial thermal expansivity of MgTiO_(3) is anisotropic,but that of FeTiO_(3) is nearly isotropic.We infer that the main reason for the different axial thermal expansivity between MgTiO_(3) and FeTiO_(3) is that the thermal expansion mode of the Mg-O bond in MgTiO_(3) is different from that of the Fe-O bonds in FeTiO_(3).

An in situ ATR-FTIR study of mixed collectors BHA/DDA adsorption in ilmenite-titanaugite flotation system

This paper researched the enhanced flotation separation performance of ilmenite and titanaugite using the mixed collector benzhydroxamic acid/dodecylamine(BHA/DDA).The interface assembly mechanism was mainly investigated through in situ attenuated total reflectance Fourier transform infrared(ATRFTIR)spectroscopy combined with the two-dimensional correlation spectroscopy(2D-COS)and X-ray photoelectron spectroscopy(XPS).It has been found that BHA/DDA mixed collectors successfully separate ilmenite from titanaugite at a molar ratio of 8:1.Zeta potential experiments suggested that,in the presence of mixed collector system,the BHA-DDA complex adsorbed on the ilmenite surface via the chemically adsorbed BHA and the electrostatically adsorbed DDA,however,the complex adsorbed on the surface of titanaugite unstably.According to in situ ATR-FTIR combined with 2D-COS and XPS results,the interface assembly mechanism of BHA/DDA is summarized as:the function group of BHA molecules first binds to the metal sites on minerals to form bidentate ligand,then DDA co-adsorbed with BHA on the surface of minerals through hydrogen bonding.DDA may change the adsorption modes of some BHA on the ilmenite surface from four-membered ring to five-membered ring,while the modes on the titanaugite surface is true opposite.Finally,recommended adsorption configurations of the BHA/DDA complex on the two mineral surfaces are proposed.

Phase transformation and reduction kinetics during the hydrogen reduction of ilmenite concentrate

The reduction of ilmenite concentrate by hydrogen gas was investigated in the temperature range of 500 to 1200℃. The microstructure and phase transition of the reduction products were studied by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and optical microscopy （OM）. It was found that the weight loss and iron metallization rate increased with the increase of reduction temperature and reaction time. The iron metallization rate could reach 87.5% when the sample was reduced at 1150℃ for 80 min. The final phase constituents mainly consist of Fe, M305 solid solution phase （M=Mg, Ti, and Fe）, and few titanium oxide. Microstructure analysis shows that the surfaces of the reduction products have many holes and cracks and the reactions take place from the exterior of the grain to its interior. The kinetics of reduction indicates that the rate-controlling step is diffusion process control with the activation energy of 89 kJ.mo1-1.

Mossbauer Spectrum Study on Hydrogen Reduction of Preoxidized Ilmenite

Reduction behavior of preoxidized synthetic ilmenite was studied by means of Mossbauer spectra. In the course of reduction, iron component in the samples is reduced in stepwise: Fe 3+ →Fe 2+ →Fe 0, and some intermediate compounds, such as Fe 3O 4, Fe 2TiO 4 etc . and their solid solution may be generated besides Fe 2O 3 and FeTiO 3. If the reduction temperature is higher than 1173 K, the metallization needs only half time of the case when the temperature is lower than 1073 K.

Beneficiation of Titanium Oxides From Ilmenite by Self-Reduction of Coal Bearing Pellets

The study on the beneficiation of titanium oxides from Panzhihua ilmenites by reduction of coal bearing pellets was carried out. The iron oxides in pellets were efficiently reduced to metal iron, and titanium oxide slag beneficiated was separated from metal iron. The effect of temperature, flux and coal blending ratio on the reduction and separation was investigated, and rational parameters were determined. A new process for the beneficiation of titanium oxides by rotary hearth furnace （RHF） was proposed.

Removal of iron from ilmenite by KOH leaching-oxalate leaching method

Oxalic acid was used for the removal of iron from the intermediates of ilmenite leached by KOH liquor. Various parameters, such as pH, temperature, initial oxalate concentration, and illumination were investigated. Meanwhile, it was found that orthorhombic crystal Ti2O2（OH）2（C2O4）-H2O formed as the leaching proceeded. Scanning electronic microscope （SEM） images implied that the formation of Ti2O2（OH）2（C2O4）.H2O with good crystallinity proceeded through three stages. Calcining Ti2O2（OH）2（C2O4）·H2O, anatase （350℃） or mtile （550℃） type TiO2 was obtained, respectively. Element analysis found that the calcined product contained 94.9% TiO2 and 2.5% iron oxide, but only about 1600 ppm dissolvable iron oxide was left, which indicates that oxalic acid was comparatively effective on iron oxide removal from the intermediates. Finally, an improved route was proposed for the upgrading of ilmenite into mtile.

MICROWAVE-ASSISTED CARBOTHERMIC REDUCTION OF ILMENITE

The microwave-assisted carbothermic reduction of ilmenite was investigated by thermogravimetric analysis under argon atmosphere. A comparison between microwave assisted reduction and the conventional one was made. It was demonstrated that the instantaneously volumetric heating of microwaves could significantly enhance the overall reduction process. By microwave application, the reduction could take place at much lower temperatures and the activation energy for the process could be lowered.The mechanism of the reduction was discussed according to the experimental data.

Combustion synthesis of fine TiFe series alloy powder by magnesothermic reduction of ilmenite

Fine TiFe series alloy powder was fabricated by magnesothermic reduction of ilmenite as main raw material. Adiabatic temperature of the FeTiO3-Mg system was studied through thermodynamic analysis. Meanwhile, the characteristics of TiFe series alloy were described by XRD, SEM and grading analysis. It is shown that combustion synthesis of the FeTiO3-Mg system can carry out due to its strong exothermic reaction through adiabatic temperature calculate. Ultrafine TiFe series alloy powder after leached for 5 h has reasonable phases and morphology with the particle distribution of 0.2 to 1 μm. It indicates that in-situ magnesothermic reduction of natural ilmenite is a feasible way to fabricate ultrafine powder with a relatively lower cost.

Effect of Temperature on Carbothermic Reduction of Ilmenite

The reduction of ilmenite (FeTiO_3) has been studied extensively. Temperature for the carbothermic reduction of ilmenite ranges from 900 ℃ to 1 400 ℃, and the reduction degree of Panzhihua ilmenite increases with increasing temperature. X-ray diffraction analysis and SEM analysis were used to identify the phase before and after reduction, and to identify the morphology of reduced samples respectively. It is found that the reaction initiates at about 860 ℃. The reaction rate varies with temperature simultaneously. Impurities in Panzhihua ilmenite decrease the reduction degree. Magnesium and calcium oxide-rich zone is formed preventing complete reduction of Fe 2+. In general, the reaction products are iron, Ti_3O_5 and carbon.

Innovative pre-concentration technology for recovering ultrafine ilmenite using superconducting high gradient magnetic separator

To achieve the utilization of the abandoned ultrafine ilmenite(-20 μm) produced in the titanium magnetite processing plant in Panzhihua,the superconducting high-gradient magnetic separation(SMS) technology was proposed in this study.After optimizing the conditions of magnetic intensity,feeding and pulsation,an SMS concentrate with TiO_(2) grade of 16.03% and TiO_(2) recovery of 66.39% was obtained through one roughing-one cleaning pre-concentration flowsheet.The specific magnetic force and magnetic force were calculated and analysed to illustrate the pre-concentration mechanism,and the results revealed that the combination of high magnetic field and strong pulsating resulted in the effective preconcentration of the ultrafine ilmenite in the SMS process.In addition,the magnetic force analysis indicated that the high magnetic intensity and high magnetic gradient are the key factors of the SMS technology.Furthermore,the EDS-Mapping detection certified that the ultrafine ilmenite was concentrated from the gangue minerals using SMS technology.

Ti leaching from activated ilmenite–Fe mixture at different milling energy levels

Mechanical activation processes on ilmenite concentrate were performed in three different energy levels. Iron powder as a reducing agent was added to ilmenite in the milling stage and the mechanically activated mixture was subjected to acid leaching. The leaching experiments were designed using the Taguchi method, and the optimum ranges were obtained. Furthermore, response surface methodology(RSM) was used to optimize the critical parameters in the leaching system to achieve the highest titanium(Ti) leachability. Based on the inductively coupled plasma-optical emission spectrometry(ICP-OES) results, maximum leaching recovery of Ti(80%) was obtained using activated Ti concentrates at a medium activation energy level, which is calculated to be 25.38 kJ/g, using 15 vol% hydrochloric acid(HCl), a temperature of 70°C, leaching time of 3 h, and a solid-to-liquid ratio of 0.05 g×mL^(–1). Intensifying the milling energy from a low to high level led to a decrease in the mean crystallite size and also structure homogenization at the high energy level. According to the transmission electron microscopy(TEM) images, the mean grain size of the ilmenite/Fe nanocomposite was about 30 nm at the medium energy level sample. Finally, solvent extraction by tributyl phosphate(TBP) was performed on the leach liquor to separate dissolved Fe(the major impurity) from Ti, which led to 83% extraction recovery of Ti.

Reagent types and action mechanisms in ilmenite flotation:A review

Ilmenite is an essential mineral for the extraction of titanium.Conventional physical separation methods have difficulty recovering fine ilmenite,and dressing plants have begun applying flotation to recover ilmenite.The interaction of reagent groups with Ti and Fe sites on the ilmenite surface dramatically influences the ilmenite flotation.However,the investigation on Fe sites has received more attention because the activity of Ti is lower than that of Fe.For the activators on ilmenite flotation,most are metal ions but typically lead ions.The metal ions of activators promote ilmenite flotation by increasing the active sites on the ilmenite surface.Combined reagents have a better selective separation of ilmenite than single reagents due to their synergistic effect.Combining the lead ion(Pb^(2+))and the benzyl hydroxamic acid(BHA)into a Pb-BHA complex has a marked effect on ilmenite flotation,which puts forward a new idea of developing combined reagents for ilmenite flotation.This review considers reagent types and action mechanisms in ilmenite flotation.On the basis of the analysis of previous research,a brief future outlook of reagent types and action mechanisms in ilmenite flotation is also proposed in this study.

Extraction behaviours of titanium and other impurities in the decomposition process of ilmenite by highly concentrated KOH solution

To effectively utilize ilmenite and recycle KOH solution, the extraction behaviours of titanium and other associated impurities in the decomposition process of ilmenite by highly concentrated KOH solution were studied. Experiments on the extraction behaviours of tita- nium as well as other associated impurities of ilmenite such as iron, silicon, calcium, and aluminium were carried out. The effects of various parameters, including reaction temperature, KOH concentration, reaction time, alkali-to-ore mass ratio, and particle size on the extraction rate of titanium and other impurities were examined. When the finely ground ore （58-75 ~tm） reacted with KOH solution （80wt%） in an al- kali-to-ore mass ratio of 7：1 at 260~C for 60 min, almost complete extraction of titanium was achieved, while the extraction rate of aluminium was 78% and that of other impurities was less than 22%. Moreover, high purity （98.2wt%） TiO2 with the anatase structure could be gained in the purification process.

Triboelectric properties of ilmenite and quartz minerals and investigation of triboelectric separation of ilmenite ore

Triboelectric separation, as an entirely dry technology, is a prospective method to process fine minerals.The aim of this paper is to investigate the performance of triboelectric separation of ilmenite and quartz minerals in a lab unit and to get ready for the separation of ilmenite ore. A tribocharge measurement system was used to test the triboelectric properties of ilmenite and quartz particles with tribochargers respectively made of PVC, PPR, PMMA, Teflon, copper, stainless steel and quartz glass. The results show that the ilmenite particles charged positively while quartz charged negatively when tribocharged with PVC tribocharger. The mixture of 12% ilmenite and 88% quartz was prepared for the triboelectric separation. The recovery of ilmenite increases with the increase of airflow rate, decreases with the increasing feed rate, and grows up firstly and then decreases with the increasing voltage. A maximum ilmenite recovery of 51.71% with ilmenite content 32.72% was obtained at 40 m^3/h airflow rate, 6 g/s feed rate and 20 kV voltage. According to the optimal parameters of the separation of ilmenite and quartz mixture,fine ilmenite ore with 7.55% Ti content was beneficiated using the unit and the Ti content increased to 12.32% in concentrate product.

Isothermal reduction kinetics of Panzhihua ilmenite concentrate under 30vol% CO–70vol% N2 atmosphere

The reduction of ilmenite concentrate in 30vol% CO–70vol% N_2 atmosphere was characterized by thermogravimetric and differential thermogravimetric(TG–DTG) analysis methods at temperatures from 1073 to 1223 K.The isothermal reduction results show that the reduction process comprised two stages;the corresponding apparent activation energy was obtained by the iso-conversional and model-fitting methods.For the first stage,the effect of temperature on the conversion degree was not obvious,the phase boundary chemical reaction was the controlling step,with an apparent activation energy of 15.55–40.71 k J·mol^(–1).For the second stage,when the temperatures was greater than 1123 K,the reaction rate and the conversion degree increased sharply with increasing temperature,and random nucleation and subsequent growth were the controlling steps,with an apparent activation energy ranging from 182.33 to 195.95 k J·mol^(–1).For the whole reduction process,the average activation energy and pre-exponential factor were 98.94^(–1)18.33 k J·mol^(–1) and 1.820^(–1).816 min^(–1),respectively.

A simple and novel synthetic route to prepare anatase TiO2 nanopowders from natural ilmenite via the H3PO4/NH3 process

A simple and novel technique for the preparation of anatase TiO2 nanopowders using natural ilmenite(FeTiO3)as the starting material is reported.Digesting ilmenite with concentrated H3PO4 under refluxing conditions yields a whiteα-titanium bismonohydrogen orthophosphate monohydrate(TOP),Ti(HPO4)2·H2O,which can be easily isolated via gravity separation from unreacted ilmenite.The addition of ammonia to the separated TOP followed by calcination at 500°C completes the preparation of anatase TiO2.Calcination at temperatures above 800°C converts the anatase form of TiO2 to the stable rutile phase.The removal of iron from ilmenite during the commercial production of synthetic TiO2 is problematic and environmentally unfriendly.In the present study,the removal of iron was found to be markedly simple due to the high solubility of iron phosphate species in concentrated H3PO4 with the precipitation of TOP.The titanium content of the prepared samples on metal basis with silica and phosphorous as major impurities was over 90%.Prepared TiO2 samples were characterized using X-ray fluorescence,Fourier-transform infrared spectroscopy,Raman spectroscopy,ultraviolet–visible diffuse reflectance spectroscopy,high-resolution transmission electron microscopy,and X-ray diffraction analyses.The photocatalytic potentials of the commercial and as-prepared TiO2 samples were assessed by the photodegradation of rhodamine B dye.

Benefciation studies on recovery and in-depth characterization of ilmenite from red sediments of badlands topography of Ganjam District,Odisha,India

This paper deals with the recovery of ilmenite mineral from red sediments of badlands topography and suggested flowsheet with material balance.The results of these investigations reveal that the red sediment samples contain 33.2%total heavy mineral,in which ilmenite mineral concentrate is 28.71%(by weight).The ilmenite concentrate recovered from red sediment sample by physical benefciation process,which included scrubbing,desliming,gravity concentration,magnetic and electrostatic separation,contains 99.41%grade with 97.3%recovery.The ilmenite mineral concentrate recovered from red sediments is also suitable for industrial applications.The characterization studies on ilmenite reveal that the TiO2percentage is marginally increasing from 46.69%to 47.86%with increasing magnetic intensity from0.46 to 1.55 T.

Catalytic Mechanism of KCl during Carbothermic Reduction of Pre-Oxidized Ilmenite

As alkali additive,KC1 catalyzes effectively the carbothermic reduction of pre-oxidized ilmenite,and the catalytic effect becomes more remarkable as the amount of KC1 increases.During the carbothermic reduction,the gaseous product consists mainly of CO,and the partial pressure of which increases with reaction temperature.The EPMA and XPS of the partially reduced ilmenite ore and that of the used graphite as reductant showed that the potassium ions enter both ilmenite particles and graphite powders during reduction.The above-mentioned phenomena result in the distortion of ilmenite and carbon structure by potassium ions and reaction activity of carbon and ilmenite was enhanced.As a result,the overall carbothermic reduction was catalyzed by KC1.

Effects of mechanical activation on the digestion of ilmenite in dilute H_2SO_4

The commercial sulfate process for pigment production uses concentrated sulfuric acid(N 85 wt% H_2SO_4) as feeding material and discharges 8–10 tons of spend dilute acid(20 wt% H_2SO_4) per ton of product. Re-using spend acid to leach ilmenite can cut the waste emission and save fresh feeding acid. However, the leaching reaction with dilute acid is very slow and the digestion efficiency is fairly low. This paper describes a wet-milling process to enhance the dilute-acid leaching of ilmenite that makes it possible to produce TiO_2 pigment in a more environmentally benign routine. The leaching kinetic study of unmilled ilmenite, dry milled 60 min ilmenite and wet milled 60 min ilmenite was conducted by revision of the shrinking core model(SCM), incorporation of particle size distribution(PSD) into SCM. The results revealed that mechano-chemical activation method significantly increased the leaching efficiency of titanium from 36% to 76% by reducing the particle size and increasing the reaction contact area. On the other hand, the milling process increased the lattice deformation and amorphization of crystalline, which lowered the activation energies in the leaching process. Compared with dry milling operation, wet milling is more effective, the particle size distribution of wet-milled ilmenite was much narrower, smaller, and more uniform. Wet milling of ilmenite makes the leaching reaction with dilute acid(60 wt% H_2 SO_4) practicable and the re-use of spend acid becomes possible and economical.

Synthesis of titanium oxycarbonitride by carbothermal reduction and nitridation of ilmenite with recycling of polyethylene terephthalate (PET)

An innovative and sustainable carbothermal reduction and nitridation(CTRN) process of ilmenite(FeTiO_3) using a mixture of polyethylene terephthalate(PET) and coal as the primary reductant under an H_2–N_2 atmosphere was proposed. The use of PET as an alternative source of carbon not only enhances the porosity of the pellets but also results in the separation of Fe from titanium oxycarbonitride(TiOxCyNz) particles because of the differences in surface tension. The experiments were carried out at 1250°C for 3 h using four different PET contents ranging from 25wt% to 100wt% in the reductant. X-ray diffraction(XRD),scanning electron microscopy(SEM) in conjunction with energy-dispersive X-ray spectroscopy(EDX),and LECO elemental analysis were used to study the phases and microstructures of the reduced samples. In the case of 75wt% PET,iron distinctly separated from the synthesized Ti OxCyNz phase. With increasing PET content in the sample,the reduction and nitridation rates substantially increased. The synthesis of an oxycarbonitride with stoichiometry of TiO_(0.02)C_(0.13)N_(0.85) with minimal intermediate titanium sub-oxides was achieved. The results also showed that the iron particles formed from CTRN of FeTiO_3 exhibited a spherical morphology,which is conducive for Fe removal via the Becher process.