Vanadium Titanium Magnetite Research Articles

A novel chitosan–vanadium-titanium-magnetite composite as a superior adsorbent for organic dyes in wastewater

In this research, a novel chitosan (CS)–vanadium-titanium-magnetite (VTM) composite was designed and synthesized. The interaction between CS-VTM and Congo red (CR) dye conformed to a pseudo-second-order model to support the potent involvement of chemisorption. The effects of adsorbent dosage, reaction temperature, and initial solution pH on adsorption of CR were investigated. Approximately 99.1% of CR (100 mg/L) was adsorbed at a CS-VTM dose of 2.0 g/L or above, while such a reaction was favored at temperatures of 65 °C and pH of 6.0. Thermodynamically, the adsorption of CR proceeded spontaneously (ΔG < 0) above 35 °C. According to scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer, and zeta potential analysis, its adsorption on CS-VTM can be attributed to electrostatic attraction and hydrogen bonds. The prepared CS-VTM exhibited superior adsorption performance on removal of CR as evidenced by significantly large partition coefficient of 108.3 mg g−1 μM−1 (equilibrium adsorption capacity of 62.2 mg/g at CR dose of 100 mg/L). Overall, the CS-VTM proved to be a promising and environmentally friendly adsorbent for the highly efficient and effective removal of organic dyes among the comparable sorbents studied to date.

Effect of B2O3 Content on the Sintering Basic Characteristics of Mixed Ore Powder of Vanadium-Titanium Magnetite and Hematite

The sintering basic characteristics of iron ore play a key role in the process of sintering. In this study, the effects of B2O3 on the assimilation characteristics, softening temperature, fluidity of liquid phase, compressive strength of bonding phase, and microstructure of the mixed fine powder of hematite and vanadium-titanium magnetite (H-VTM) are studied. Results show that B2O3 content from 0%–5% (wt%) could improve the assimilation characteristics of the H-VTM and increase the amount of the liquid phase. The liquidity of the bonding phase index (LBPI) of the H-VTM increases from 3.7 to 24.2. When B2O3 content exceeds 2%, the diameter of the pore in the H-VTM sintered samples enlarges. However, the compressive strength gradually decreases. Boron and calcium-magnesium-aluminium elements are abundant in the bonding phase, which can reduce the formation of calcium silicate and perovskite in H-VTM sintered samples.

Ultrasonic assisted dispersive liquid-liquid microextraction combined with flame atomic absorption spectrometry for determination of trace gallium in vanadium titanium magnetite

A new method of ultrasonic assisted dispersive liquid-liquid microextraction (USADLLME) combined with flame atomic absorption spectrometry (FAAS) was developed to determinate trace gallium in vanadium titanium magnetite. In the proposed approach, 1-(2-pyridineazo)-2-naphthol was selected as a complexant of gallium and chlorobenzene was chosen as extractant. The processes of complex formation and microextraction were influenced by the following factors: dosage of complexant, complex pH, extractant and its dosage, extraction temperature and time, etc. Under optimal conditions, the linear range of working curve was 0.1–1 μg/mL with detection limit of 0.07 μg/mL, and the enrichment factor of gallium was 124. 0.5 μg/mL gallium standard solution was parallelly extracted using USADLLME and determined by FAAS for 7 times and the relative standard deviation (RSD) was 13.54%. The presented method was simple, fast, sensitive and low cost, which had been successfully applied to the quantitative determination of gallium in vanadium titanium magnetite with complex matrix.

Overall utilization of vanadium–titanium magnetite tailings to prepare lightweight foam ceramics

Vanadium–titanium magnetite tailings (VTMT) are a common industrial waste in China, which are harmful to the environment and economic development. The efficient utilization of this industrial waste is urgently needed. Herein, foam ceramics were successfully prepared as partition materials using VTMT as the main raw material. In this work, the effects of VTMT and SiC content on the properties and microstructure of foam ceramics were investigated. Properties like rate of linear expansion, bulk density, water absorption and average pore size were analyzed. Furthermore, the foaming mechanism was further explained. Results showed that the rate of linear expansion of the samples first increased from 35.0% to 53.3% and then decreased with increasing VTMT content. Bulk density decreased, and the average pore size gradually increased from approximately 0.86mm to 2.56mm with increasing SiC content. Finally, the optimum foam ceramics were formed with 55wt.% VTMT and 0.10wt.% SiC sintered at 1130°C. Such samples had a bulk density of 0.78g/cm3, a water absorption of 14.3%, and a uniform pore size distribution. More importantly, this potential recycling process shows benefits to the environmental management and sustainable development of enterprises.

Effect of Basicity on Sintering Behavior and Metallurgical Properties of High-Chromium Vanadium-Titanium Magnetite

Basicity has an important effect on the behavior of high-chromium vanadium-titanium magnetite (HCVTM) sinter. The effect of basicity on sintering, reduction, and softening-melting properties was investigated in an experiment-scale sinter pot. The results showed that with the basicity increasing from 1.7 to 2.5, the vertical sinter speed, the productivity, the particle size, the reduction disintegration index (RDI), and the reducibility index (RI) increased. The yield increased first and then decreased, while the tumble index (TI) had the opposite trend. The perovskite content increased first and then stabilized, and the silico-ferrite of calcium and aluminum (SFCA) increased from the basicity of 2.3. The HCVTM sinter had a better tendency of the softening behavior with the basicity increase. In addition, the melt droplet comprehensive index S increased, which indicated that the increase in basicity negatively affected the droplet performance. As the basicity increased, the comprehensive index value increased. Considering the adverse effect of basicity on softening-melting properties, the best recommended value is 2.3.

Softening–melting Properties and Slag Evolution Behavior of High Titanium Sinter

Vanadium–titanium magnetite (VTM) is an important strategic resource, and now the process of Blast Furnace (BF) is the dominate route for smelting VTM. However, the difficulties of smelting VTM by BF inhibited further increase of VTM proportion in furnace burden due to its complex behavior in cohesive zone. The objective of this study is to reveal the softening–melting behavior of a high titanium sinter. The results indicated that the softening–melting properties of the experimental high titanium sinter were relatively worse than that of ordinary sinter due to its wider melting temperature interval and bad gas permeability in melting stage. The melting temperature interval of 225°C was obtained, and the permeability index (S value) of 1917 kPa·°C was calculated correspondingly. A second increase in pressure drop was observed in the softening–melting process, which may be ascribed to great difference of melting point between pig iron and slag. The mechanism on slag evolution was also clarified by interrupting the softening–melting process at characteristic temperatures. The XRD patterns indicated that initial slag phase mainly consisted of wustite, silicates and perovskite, of which the wustite content decreased gradually during the softening–melting process. The content of wustite was a crucial factor that affected the phase transformation during slag evolution.

Slag formation path in converter smelting process of semi-steel containing chromium

ABSTRACT Aiming at the high-efficiency utilization of vanadium–titanium magnetite with high chromium content, a slag formation path in the converter smelting process of semi-steel containing chromium was proposed. The influences of MnO and Cr2O3 on the melting characteristics of converter slag were calculated through FactSage. The effects of components and temperature on the equilibrium distribution ratio of P, Cr between molten CaO–SiO2–FeO–MgO–MnO–Cr2O3–P2O5 slags and molten steel was obtained by the indirect experimental method and the regular solution model. The results show that the liquidus region and the proportion of liquid phase decrease with the increase of Cr2O3 content in steel slag. The increases of basicity conduces to dechromization and dephosphorization. The L Cr increased continuously with increasing FeO content and the influence of the oxidization of steel slag on the L Cr is greater than L P. Both L P and L Cr decrease distinctly with the increase in temperature. The slag formation path for the smelting process of semi-steel containing chromium is as follows: 17wt-%CaO–16wt-%SiO2–67wt-%FeO→25wt-%CaO–20wt-%SiO2–55wt-%FeO→57wt-%CaO–17wt-%SiO2– 6wt-%FeO.

Experimental Study on Strengthening Carbothermic Reduction of Vanadium-Titanium-Magnetite by Adding CaF2

The effects and reduction mechanisms of carbothermic reduction of vanadium–titanium–magnetite were studied by adding various mass fractions of CaF2 ranging from 0%, 1%, 3%, 5% to 7%. The results showed that the proper CaF2 addition could strengthen the carbothermic reduction of vanadium–titanium–magnetite while the excessive amounts will weaken the promotive effect, hence the appropriate dosage was determined to be 3 mass%. The CaF2 was favorable for the carbon gasification reaction, where it increased the partial pressure of CO inside briquette and caused the lattice distortion of vanadium–titanium–magnetite. The reaction improved the reduction process and accelerated the reduction rate. The appearance of 3CaO·2SiO2·CaF2 and other complex compounds with low melting point facilitated the aggregation and growth of the slag and the iron, which increased the concentration of iron grains and the aggregation level of the slag.

Process Mineralogical Characteristics and Ore Value of Typical Vanadium Titanium Magnetite in China

Process Mineralogical Characteristics and Ore Value of Typical Vanadium Titanium Magnetite in China

The decolorization of methyl orange by persulfate activated with natural vanadium-titanium magnetite

Magnetite activating persulfate to produce sulfate radicals was received immense importance for its potential to destroy organic pollutants in wastewater. Herein, the Vanadium Titanium Magnetite (abbreviated as VTM) was characterized and applied in treatment of Methyl Orange (abbreviated as MO) pollutants containing solution for its availability and low cost, which exhibited its ideal activity in decolorization performance. The effects of initial pH, temperature, MO initial concentration, VTM dosage and PDS dosage on MO decolorization efficiency were all investigated through batch decolorization studies. MO is degraded by SO4− which is produced by activation of persulfate with Fe (II) provided by VTM. The MO decolorization rate (%) was increased from 75.20% to 97.82% with the VTM dosage increased from 1 g/L to 4 g/L and increased from 11.94% to 98.73% with the PDS concentration varied from 0 to 16 mM. When VTM or PDS continued to increase, MO decolorization rate decreased, which due to the mutual quenching of SO4− and the consumption of SO4− by Fe2+ and S2O82−.This study would create a lower cost approach for the decolorization of Methyl Orange containing wastewater activated by the VTM, which was a kind of low cost and available catalyst.

Green one-step roasting method for efficient extraction of vanadium and chromium from vanadium-chromium slag

An effective and environment-friendly method based on one-step sodium hydroxide roasting was proposed to extract vanadium and chromium from vanadium-chromium slag. In optimal conditions (roasting temperature 800 °C and NaOH addition dosage 30%), vanadium spinel was converted into NaVO3 while chromium spinel was converted into Na2CrO4 and CaCrO4. Leaching efficiencies of vanadium and chromium reached 94.87% and 80.51%, respectively. During sodium roasting, Na also reacted with Si, Fe, Ti and Al to produce sodium salts of high melting points, which inhibits sintering of reaction mixture and facilitates the formation of vanadates and chromates. The leaching residues consist mainly of Fe2O3, which can be recycled to converter as flux of slagging materials to achieve resource recycling and zero-discharge of solid wastes. This work has provides a simple green way to extract vanadium and chromium from vanadium-chromium slag, which puts forward the green comprehensive utilization of vanadium-titanium magnetite ores with high chromium contents.

Rhizobia population was favoured during in situ phytoremediation of vanadium-titanium magnetite mine tailings dam using Pongamia pinnata

Mine tailings contain toxic metals and can lead to serious pollution of soil environment. Phytoremediation using legumes has been regarded as an eco-friendly way for the rehabilitation of tailings-laden lands but little is known about the changes of microbial structure during the process. In the present study, we monitored the dynamic change of microbiota in the rhizosphere of Pongamia pinnata during a 2-year on-site remediation of vanadium-titanium magnetite tailings. After remediation, overall soil health conditions were significantly improved as increased available N and P contents and enzyme activities were discovered. There was also an increase of microbial carbon and nitrogen contents. The Illumina sequencing technique revealed that the abundance of taxa under Proteobacteria was increased and rhizobia-related OTUs were preferentially enriched. A significant difference was discovered for sample groups before and after remediation. Rhizobium and Nordella were identified as the keystone taxa at genus rank. The functional prediction indicated that nitrogen fixation was enhanced, corresponding well with qPCR results which showed a significant increase of nifH gene copy numbers by the 2nd year. Our findings for the first time elucidated that legume phytoremediation can effectively cause microbial communities to shift in favour of rhizobia in heavy metal contaminated soil.

Production of ferrotitanium alloy from titania slag based on aluminothermic reduction

At present, the titanium resource from vanadium-titanium magnetite (VTM) has not been used very effectively. With the aim of addressing this urgent problem, the titania slag with over 40 wt% TiO2 was obtained from VTM through gaseous reduction and melting separation in the previous work. In this study, the aluminothermic reduction for the ferrotitanium alloy production was conducted in order to develop a new utilization way for the titanium resource from VTM. CaO and Fe2O3 are extra added to ensure the slag fluidity, alloy quality, and sufficient physical heat. And the addition ratios of Al are optimized by the thermodynamic calculation. At last, the ferrotitanium alloy with 30.5 wt% Ti, 8.4 wt% Al, 3.2 wt% Si content is successfully prepared. However, the macro analysis indicates that some alloy particles with different contents are dispersedly distributed among the slag, and the slag consists of three different phases. It is mainly associated with the reaction intensity and thermodynamic stability, which is detailedly discussed in this paper as well.

Observation of diffusion behavior between Cr2O3 and calcium ferrite based on diffusion couple method at 1373 K

The existence of Cr2O3 has an effect on the quality of high-chromium vanadium-titanium magnetite sinter. In order to investigate the influence of Cr2O3 on the quality of sinter in the solid-phase reaction stage of sintering process, the solid-phase reactions of Cr2O3-calcium ferrite (CF) system at 1373 K in air at different times were studied by diffusion couple method. The change of diffusion interface and the migration of Ca, Cr and Fe were observed by emission scanning electron microscopy. The results show that in the process of diffusion, the diffusion thickness of Ca2+ in CF layer was 10.22 μm, and that of Ca2+ in Cr2O3-CF diffusion couple was 57.65 μm at 1373 K for 8 h. The relationship between the thickness of the product layer and time at 1373 K for 0 h–20 h was obtained. The diffusion of Ca2+ to the Cr2O3 layer is the driving force of the solid phase reaction, and the diffusion of Ca2+ in the ferrite layer is the limiting link of the solid phase reaction, the order of magnitude of diffusion coefficient of Cr2O3-CF diffusion couple was 10−11 cm2 s−1. Ca2+ in calcium ferrite is likely to combine with Cr3+ to form CaCr2O4. The production of calcium ferrite will be reduced when Cr2O3 is present in sintering material. Meanwhile, the solid phase product CaCr2O4 in the diffusion process has the properties of high melting point and difficult reduction. The shortage of liquid phase due to high melting point and the difficulty in reduction may affect the quality of sinter.

High-Temperature Interactions Between Vanadium-Titanium Magnetite Carbon Composite Hot Briquettes and Pellets Under Simulated Blast Furnace Conditions

The high-temperature interactions between vanadium-titanium magnetite carbon composite hot briquettes (VTM-CCBs) and pellets were systematically investigated under simulated blast furnace conditions with respect to the reduction behavior, softening–melting–dripping characteristics, gas permeability, and Ti(C, N) precipitation mechanisms. The results showed that VTM-CCB charging can promote the reduction of the pellet in the packed bed and decrease the compressive strength of the pellet after reduction. The compressive strength of the VTM-CCB after reduction decreased with increasing temperature when the FC/O ratio (the ratio of the fixed carbon mol(C) in coal to the reducible oxygen mol(O) in iron oxides) was higher than 1.0. With an FC/O ratio lower than 1.0, the compressive strength of the VTM-CCB initially decreased and then increased. The FC/O ratio has a significant influence on the softening–melting interaction mechanism between the VTM-CCB and the pellet. With an FC/O ratio of 0.8, the bonding layer at the interface between the pellet and the VTM-CCB (consisting of molten fayalitic slag) can promote the softening process, thereby decreasing the softening start and end temperatures. By increasing the FC/O ratio to 1.4, a dense metallic iron shell with relatively high strength formed at the interface and restricted the collapse of the packed bed, thereby increasing the softening start and end temperatures and ensuring the transport of the reduction gas through the packed bed. The melting point of the primary slag phase increased with increasing FC/O ratio due to a decrease in the FeO content, which resulted in an increase in the melting start temperature from 1273 °C to 1294 °C (1546 K to 1567 K). The gas permeability in the cohesive zone increased with an increasing FC/O ratio of the VTM-CCB due to a combination of the skeletal role performed by the residual VTM-CCB and the decrease in the liquid slag proportion. In addition, as the FC/O ratio increased to 1.4, unconsumed carbon promoted the precipitation of Ti(C, N) at the slag–carbon and slag–metal interfaces, which resulted in a substantial increase in the dripping temperature and deterioration of the dripping behavior of the packed bed. Therefore, to suppress the precipitation of Ti(C, N) and improve the dripping behavior of the packed bed, the FC/O ratio of the charged VTM-CCB should be controlled within an appropriate range.

Investigations of MgO on Sintering Performance and Metallurgical Property of High-Chromium Vanadium-Titanium Magnetite

High-chromium vanadium-titanium magnetite (HCVTM) in the Hongge region has been used as an essential mineral resource in ironmaking. The effects of MgO on sintering performance and metallurgical properties were investigated by sintering pot tests, X-ray diffraction (XRD), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). HCVTM sinters with varying MgO contents (2.7–3.5%), which was achieved by adding dolomite, were tested for yield, strength, reduction degradation index (RDI), reduction index (RI), and softening-melting properties. The productivity and the comprehensive index were evaluated. The results show that yield and productivity increased, while the vertical sintering speed and the tumbler index (TI) initially increased then decreased with the increase of MgO content. The mineral structure of HCVTM sinter changed from a non-uniform state to a uniform state with increased MgO content. Most of the Mg2+ entered the magnetite lattice, while a small amount entered the perovskite and the calcium silicate. The increase of MgO content improved RDI and softening-melting properties while reducing RI. The best recommended amount of MgO was 3.3% from the comprehensive index.

Effect of coke breeze content on sintering mechanism and metallurgical properties of high-chromium vanadium-titanium magnetite

ABSTRACT The coke ratio has an important effect on the behaviour of high-chromium vanadium–titanium magnetite (HCVTM) sintering. The effect of coke breeze content on sintering properties and mechanism of HCVTM was investigated in an experimental-scale sintering pot. And the softening-melting test was carried out to study the metallurgical properties of sinter. The results showed that with increasing coke breeze content from 4.0% to 6.0%, the mineral phase grains of HCVTM sinter refined. Further, the mineral content of FeO, silicate, perovskite, and magnetite increased while calcium ferrite and haematite decreased. The vertical sintering speed (VSS), tumble index (TI), productivity, and reduction disintegration index (RDI) increased while yield and reducibility index (RI) of HCVTM sinter decreased, and the softening-melting behaviour of HCVTM sinter improved with the increasing of coke breeze content.

Reaction sequence and formation kinetics of perovskite by calcium ferrite–titania reaction

Controlling the generation of perovskite (CaO·TiO2, CT) during sintering with vanadium–titanium magnetite (VTM) is the key to improve the strength and yield of VTM sinters. This study determined whether adding pre–formed calcium ferrite (CaO·Fe2O3, CF) effectively prevents the formation of CT during sintering with VTM. The formation behavior of CT in the CF–T system was investigated using X–ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Phase composition analysis by XRD indicates that CT is formed significant quantities in the CF–T system when the temperature is higher than the melting temperature of CF. DSC analysis shows that the CF–T samples undergo two reaction stages in continuous heating. Namely, CF first melts and forms its liquid phase, then TiO2 substitutes Fe2O3 in liquid CF to produce CT. SEM images confirm that CT could be generated at regions with a high concentration of CF. Non–isothermal DSC measurements on the formation kinetics of CT indicate that its activation energy reaches 252.00 kJ/mol and that the model function is f(α)=(1–α)2, revealing a second–order reaction based on Malek analysis. The kinetics equation of CT formation can be expressed by ln(dαdt)=2ln(1−α)−216805+70382αRT+16.71+10.33α. Quantitative calculation on enthalpy change by DSC curves shows that raising heating rates enhance the consolidation ability of CF–T samples as the melting of CF increases and the formation of CT decreases.

Comparative Study on Metallurgical Performance of Different Vanadium-Titanium Magnetite Burdens

Comparative Study on Metallurgical Performance of Different Vanadium-Titanium Magnetite Burdens

Effect of B2O3 on the carbothermal reduction of vanadium titanium magnetite

The effect of B2O3 on the carbothermal reduction of vanadium titanium magnetite was investigated under different temperatures by isothermal experiments. XRD analysis, SEM analysis and kinetic analysis were used to reveal the mechanism of B2O3 in the reduction process. The results showed that B2O3 could accelerate the reduction rate of vanadium titanium magnetite, and the suitable addition amount was 3%. B2O3 was easy to melt during carbothermal reduction, B3+ diffused into the crystal lattice of ferrotitanium compound, resulting in a decrease in binding energy and an increase in lattice parameters. B2O3 had also an erosion effect on the surface of the iron ore, and the contact area between reducing agent CO and vanadium titanium magnetite increased, thereby promoting the reduction. Low melting point compound CaO ∙ B2O3 formed after adding B2O3, which could improve the fluidity of the system and change the melting point of non-ferrous phase to further promote the growth and aggregation of iron particles. The reduction process was firstly limited by the first-order chemical reaction, then it was controlled by three-dimensional diffusion of reactants. The activation energy calculated by the best model was smaller than that of without adding B2O3.