Removal of magnesium and calcium from electric furnace titanium slag by H3PO4 oxidation roasting–leaching process

H₃PO₄ oxidation roasting followed by HCl acid leaching was proposed to remove magnesium and calcium from electric furnace titanium slag containing 3.12% MgO and 0.86% CaO. XRF, XRD and SEM techniques were used to characterize the composition, mineral phase component and microstructure of the titanium slag. The H₃PO₄ oxidation thermodynamic, mineral phase transformation, microstructure, element distribution in titanium slag during H₃PO₄ oxidation process and leaching process were investigated. The thermodynamic analysis indicated that H₃PO₄ could promote the decomposition of MgTi₂O₅ and CaSiO₃. The results indicated that H₃PO₄ could effectively promote the transformation of titanium-bearing mineral to rutile and enrich the impurities in M_xTi_3–xO₅ into phosphate which could be removed by acid leaching process. Under the studied conditions, the leaching rates of magnesium and calcium reached 94.68% and 87.19%, respectively. The acid leached slag containing 0.19% MgO and 0.13% CaO (mass fraction) was obtained.     

废弃SCR脱硝催化剂与废NaCl盐焙烧回收催化剂中的钛、钒、钨（英文）

通过废弃选择性催化还原(SCR)脱硝催化剂与废NaCl盐焙烧,可以将催化剂中的钨和钒与钛分离。在最佳浸出条件下(焙烧温度900℃,焙烧时间3 h,废盐与废催化剂的质量比为0.5,浸出温度80℃,反应时间60 min),钨和钒的浸出率分别达到84.63%和66.42%,同时钛的损失率仅为1.3%。废NaCl盐和焙烧温度可以促进锐钛矿型TiO₂转化为金红石型TiO₂,反应后得到了金红石型TiO₂。金红石型TiO₂中的钛的价态为四价,晶格氧和化学吸附氧分别占57.26%和42.74%。该方法可以同时解决2种废弃物的处置问题。     

Effect of rutile crystal shapes on its settlement

The effect of rutile crystal shapes on its settlement in a modified slag was studied by theoretical analysis, FactSage simulation, X-ray diffraction and scanning electron microscopy. The results show that the settling velocities of spherical rutile crystals are faster than those of other shapes of rutile crystals under the same volume conditions, and the shape transformation of rutile crystals from rod to sphere can be achieved by adding titanium slag to Ti-bearing blast furnace slag. The volume fractions of the rutile crystals in the upper and lower parts of the modified slag are 30% and 71% when the added titanium slag increases to 278 g, indicating that rutile settling is obvious. Due to the rutile settling, half shaker sorting task is saved, and the recovery rate of TiO₂ is significantly increased. The TiO₂ content of rutile is greater than 93%, and the total content of CaO and MgO is less than 0.4%, meeting the requirements for the raw materials of titanium white in the chloride process.     

Extraction of valuable metals from Ti-bearing blast furnace slag using ammonium sulfate pressurized pyrolysis–acid leaching processes

A novel method of extracting valuable metals from Ti-bearing blast furnace slag (TBBF slag) via pressure pyrolysis of recyclable ammonium sulfate (AS)–acid leaching process was proposed. The results show that when pressurized roasting at an AS-to-slag mass ratio 3:1 and 370 °C for 90 min, the extraction rates of titanium, aluminum and magnesium reached 94.5%, 91.9% and 97.4%, respectively. The acid leaching solution was subjected to re-crystallization in a boiling state to obtain a titanium product having a TiO₂ content of 94.1%. The above crystallization mother liquor was adjusted to pH=6 and pH≥12.2, respectively, and then qualified Al₂O₃ and MgO products were obtained. The analysis through XRD and SEM–EDS proves that the main phases in roasted samples were NH₄AlSO₄, CaSO₄ and TiOSO₄. The thermodynamic analysis presents that the main minerals of perovskite, spinel and diopside in raw ore could spontaneously react with the intermediate produced by AS under optimal conditions.     

废旧锂离子电池火法冶炼富锰渣中锰和锂的提取（英文）

开展富锰渣硫酸化焙烧-水浸选择性提取锰和锂的试验,采用XRD、TG-DSC和SEM-EDS详细分析锰和锂的提取机理。结果表明,在酸浓度为82%(质量分数)、酸矿质量比1.5:1、焙烧温度800℃和焙烧时间2 h时,Mn和Li的浸出率分别达到73.71%和73.28%。焙烧过程中,富锰渣首先与浓硫酸反应形成Mn SO₄、MnSO₄·H₂O、Li₂Mg(SO₄)₂、Al₂(SO₄)₃和H₄SiO₄。随着焙烧温度的升高,H₄SiO₄和Al₂(SO₄)₃依次分解,并形成莫来石和尖晶石相。莫来石的形成有利于降低Al和Si的浸出率而增加Li的浸出率;而尖晶石的形成则会降低Mn和Li的浸出率。     

Leaching of Titanium and Silicon from Low-Grade Titanium Slag Using Hydrochloric Acid Leaching

Acid-leaching behaviors of the titanium slag obtained by selective reduction of vanadium-bearing titanomagnetite concentrates were investigated. It was found that the optimal leaching of titanium and silicon were 0.7% and 1.5%, respectively. The titanium and silicon in the titanium slag were firstly dissolved in the acidic solution to form TiO²⁺ and silica sol, and then rapidly reprecipitated, forming hydrochloric acid (HCl) leach residue. Most of the silicon presented in the HCl leach residue as floccules-like silica gel, while most of the titanium was distributed in the nano-sized rod-like clusters with crystallite refinement and intracrystalline defects, and, as such, 94.3% of the silicon was leached from the HCl leach residue by alkaline desilication, and 96.5% of the titanium in the titanium-rich material with some rutile structure was then digested by the concentrated sulfuric acid. This provides an alternative route for the comprehensive utilization of titanium and silicon in titanium slag.     

Appropriate titanium slag composition during smelting of vanadium titanomagnetite metallized pellets

The suitable titanium slag composition with high titanium content for electric furnace smelting of vanadium titanomagnetite was investigated through thermodynamics and related phase diagram analysis. According to the thermodynamic results, low-melting-point regions and MgTi₂O₅ primary phase area in the phase diagrams, the suggested titanium slag composition for the present vanadium titanomagnetite metallized pellets should consist of 50% TiO₂, 8%–12% MgO and 13% Al₂O₃ (mass fraction) with a binary basicity of 0.8–1.2. Finally, the verified smelting experiments were conducted and successful separation of the molten iron from the titanium slag is obtained. The obtained vanadium-containing molten iron contains 0.681% V and 0.267% Ti, and the obtained titanium slag contains 52.21% TiO₂ (mass fraction), in which MgTi₂O₅ is the primary phase. The titanium resource in the final titanium slag production could be used to produce TiO₂ pigment by acid leaching methods.     

改性含钛高炉渣中铁、钒和钛的回收

提出两段氧化—碱浸—酸浸工艺来回收改性含钛高炉渣中的铁、钒和钛.较佳的提铁实验条件为一段氧化时间40 s和保温时间8 min,铁的回收率为89.93％.较佳的提钒实验条件为总氧化时间126 s、NaOH浓度4.0 mol/L、浸出温度95℃、浸出时间90 min和碱浸循环次数4,钒的浸出率为92.13％.较佳的提钛实验...     

Molybdenite–limestone oxidizing roasting followed by calcine leaching with ammonium carbonate solution

Oxidizing roasting of molybdenite with lime can significantly reduce SO₂ pollution compared with the traditional roasting without lime. However, the calcine is subsequently leached by sulfuric acid, resulting in serious equipment corrosion and abundant non-recyclable CaSO₄ slag. In this work, a novel process, in which the molybdenite was roasted with CaCO₃ followed by (NH₄)₂CO₃ solution leaching, was proposed to improve the art of lime roasting–sulfuric acid leaching. Oxidizing roasting of molybdenite with CaCO₃ was investigated through thermodynamic calculation, thermogravimetric analysis and roasting experiments. The results show that the products of the oxidizing reaction of MoS₂ in the presence of CaCO₃ and O₂ are CaSO₄, CaMoO₄ and CO₂ at 573–1000 K. The MoS₂ conversion rate achieves approximately 99% and the sulfur-retained rate attains approximately 95% with a CaCO₃-to-MoS₂ molar ratio of 3.6 at 500 °C for 1 h by adding 5% mineralizer A (mass fraction). The leaching results show that the leaching rate of Mo reaches 98.2% at 85 °C for 7 h with a (NH₄)₂CO₃ concentration of 600 g/L and a liquid–solid ratio of 10 mL/g. The results presented are potential to develop a novel cleaner technique for ammonium molybdate production.     

Upgrading ilmenite into a high-grade synthetic rutile

Titanium, the ninth most abundant element, occurs mainly in minable form as ilmenite (95%) and rutile (5%) minerals. The current world consumption of these minerals is used mainly to produce titanium dioxide pigments, with the balance in welding rod flux and titanium metal. Ilmenite is currently being mined in annual quantities eight times larger than rutile. In the past 35 years, an increasing percentage of the pigments have been produced via the chloride method, which requires rutile. This has caused the need to produce a synthetic rutile of more than 90% TiO₂ content and large amounts of an 85% TiO₂ slag from ilmenite. The direct chlorination of 61% TiO₂ ilmenite is being done on a large scale in the United States.     

Preparation of titanium mineral from vanadium titanomagnetite concentrates by hydrogen reduction and acid leaching

Titanium mineral was prepared from vanadium titanomagnetite concentrates by hydrogen reduction and acid leaching. The leaching behaviors of elements like Fe, V, Mn, Al, Mg, Ca, and Si were highly related to the reduction degree. The phase compositions of the reduced materials and the leached residues were analyzed by XRD to identify the effect of reduction degree on the leaching mechanisms. The results showed that the concentrates were reduced to iron metal and titanomagnetite at 800?1000 °C for 0.5 h, and the above elements of Fe and impurities were easily leached. Deeper reduction led to the formation of ilmenite and Mg?Al spinel, which hindered leaching. Mg-bearing anosovite appeared in the further reduced materials, and the leaching rates of impurities became much lower. An upgraded titanium mineral with a normalized TiO₂ grade of 70.3% was achieved by H₂ reduction at 850 °C for 0.5 h and acid leaching, which is a satisfactory Ti resource for the preparation of titanium oxide by sulfate process.     

Phase conversion and removal of impurities during oxygen-rich alkali conversion of high titanium slag

In order to achieve high-efficiency alkali conversion and impurity removal of high titanium slag under the condition of low alkali concentration, a new way of oxygen-rich alkali conversion in KOH solution was proposed. The conversion law of element occurrence state and the influence of the conversion conditions on the titanium conversion rate and removal rate of silicon and aluminum were studied. The results showed that the KOH solution converted the titanium oxide in high titanium slag into whisker-like potassium titanate. Silicon and aluminum elements were dissolved into the solution. Under the following conditions, KOH concentration of 6 mol/L, conversion temperature of 260 °C, initial oxygen partial pressure of 2 MPa, liquid?solid ratio of 35 mL/g, conversion time of 4 h, and high titanium slag particle size of 48?74 μm, the conversion rate of titanium was 97.0%, and the removal rates of silicon and aluminum were 90.2% and 76.2%, respectively. Oxygen-rich alkali conversion product was converted to rutile with a TiO₂ grade of 99.1% by acid hydrolysis conversion.     

Comparison of Ultrasound-Assisted and Regular Leaching of Vanadium and Chromium from Roasted High Chromium Vanadium Slag

Ultrasound-assisted leaching (UAL) was used for vanadium and chromium leaching from roasted material obtained by the calcification roasting of high-chromium–vanadium slag. UAL was compared with regular leaching. The effect of the leaching time and temperature, acid concentration, and liquid–solid ratio on the vanadium and chromium leaching behaviors was investigated. The UAL mechanism was determined from particle-size-distribution and microstructure analyses. UAL decreased the reaction time and leaching temperature significantly. Furthermore, 96.67% vanadium and less than 1% chromium were leached at 60°C for 60 min with 20% H₂SO₄ at a liquid–solid ratio of 8, which was higher than the maximum vanadium leaching rate of 90.89% obtained using regular leaching at 80°C for 120 min. Ultrasonic waves broke and dispersed the solid sample because of ultrasonic cavitation, which increased the contact area of the roasted sample and the leaching medium, the solid–liquid mass transfer, and the vanadium leaching rate.     

Reduction roasting–magnetic separation of vanadium tailings in presence of sodium sulfate and its mechanisms

Reduction roasting with sodium sulfate followed by magnetic separation was investigated to utilize vanadium tailings with total iron grade of 54.90 wt% and TiO_2 content of 17.40 wt%. The results show that after reduction roasting–magnetic separation with sodium sulfate dosage of 2 wt% at roasting temperature of 1150 °C for roasting time of 120 min, metallic iron concentrate with total iron grade of 90.20 wt%, iron recovery rate of 97.56 % and TiO_2 content of 4.85 wt% is obtained and high-titanium slag with TiO_2 content of 57.31 wt% and TiO_2 recovery rate of 80.27 % is also obtained. The results show that sodium sulfate has a catalytic effect on the reduction of tailings in the novel process by thermodynamics, scanning electron microscopy(SEM) and X-ray diffraction(XRD) and reacts with silica and alumina in the tailings to form sodium silicate and sodium aluminosilicate. Migration of elements and chemical reactions destroy the crystal structures of minerals and promote the reduction of vanadium tailings, resulting in that iron grains grow to large size so that metallic iron concentrate with high total iron grade and low TiO_2 content is obtained.     

Dissociation of Ti2O3 from titania slag under mechanical activation

In this present study, the effects of mechanical activation on the characterization of titania slag were systematically investigated. The crystal structures, surface chemical functional groups, and microstructure of the samples were characterized before and after mechanical activation using XRD, FT-IR, and Raman spectroscopy techniques, respectively. It was found that untreated titania slag under mechanical activation was mainly composed of Fe₃Ti₃O₁₀ and rutile TiO₂, but that of being treated by mechanical activation was mainly composed of Fe₃Ti₃O₁₀, Ti₂O₃ and rutile TiO₂. Ti₂O₃ is transformed partially from Fe₃Ti₃O₁₀ under moderate mechanical activation conditions for 12 h. The demonstration of mechanical activation techniques can be applied effectively and efficiently to the treatment processing of titania slag.     

热喷涂法制备的La3+掺杂纳米TiO2粉末的表征

采用等离子热喷涂法以钛酸四丁酯为主要原料制备出稀土离子掺杂的纳米TiO2光催化剂.通过XRD,XPS,TEM,UV-Vis等检测手段对样品进行表征,同时检测了其光催化性能,并分析了掺杂对TiO2的影响机理.结果表明,所制备的La3 掺杂纳米TiO2是锐钛矿相和金红石相混晶结构,粒径分布在10～50nm之间;La3 掺杂能够促进锐钛矿向金红石的转变,同时抑制TiO2晶粒的长大;La3 掺杂使TiO2紫外-可见吸收光谱发生红移;适量La3 掺杂能显著提高TiO2的光催化活性,最佳掺杂浓度为0.5%(与Ti原子摩尔比),甲基橙降解率在90min内可达到82.4%.比纯TiO2高出13.2%.     

Synthesis of As-Cast Ti-Al-V Alloy from Titanium-Rich Material by Thermite Reduction

We present a novel methodology for preparing as-cast Ti-Al-V alloy directly from titanium-rich material through a thermite reduction. The new method is shown to be feasible through a thermodynamics and dynamics analysis. The as-cast Ti-Al-V alloys synthesized from titanium dioxide, rutile, and high-titanium slag were analyzed by an x-ray diffractometer, a scanning electron microscope, an inductively coupled plasma emission spectrometer, and an oxygen/nitrogen/hydrogen analyzer. The results indicate that the alloy is composed of a Ti-Al-V matrix and Al₂O₃ inclusions. The Al and V contents in the matrix are close to the mass ratio of Ti-6Al-4V (Al: 5.5–6.8 wt.%, V: 3.5–4.5 wt.%). The Si and Fe in the alloys synthesized from rutile and high-titanium slag can be used as alloying elements in low-cost titanium alloys. The present method is expected to be useful for preparing Ti-Al-V alloys at a low production cost.     

Extraction of molybdenum and nickel from roasted Ni–Mo ore by hydrochloric acid leaching,sulphation roasting and water leaching

To extract molybdenum and nickel from the roasted Ni–Mo ore, a process of hydrochloric acid leaching, sulphation roasting and water leaching was investigated. The results showed that this process could get a high leaching rate of Mo and Ni. Under the optimum conditions of hydrochloric acid leaching (roasted Ni–Mo ore leached with 0.219 mL/g hydrochloric acid addition at 65 °C for 30 min with a L/S ratio of 3 mL/g), sulphation roasting (51.9% sulfuric acid addition, roasting temperature 240 °C for 1 h), followed by leaching with the first stage hydrochloric acid leaching solution at 95 °C for 2 h, the leaching rates of Mo and Ni reached 95.8% and 91.3%, respectively.     

Immobilization of Cd and Pb in soils by polymeric hydroxyl ferric phosphate

A polymeric hydroxyl ferric phosphate (PHFP) was prepared by using a byproduct of titanium dioxide containing ferrous sulfate and phosphates under alkaline condition. The PHFP was used to immobilize lead (Pb) and cadmium (Cd) in soils. Fourier transform infrared spectra, X-ray diffraction were applied to revealing the characteristics of PHFP, and the modified Tessier sequential extraction and column leaching experiment with simulated acid rain were used to assess the effectiveness of immobilization of Cd and Pb in soils by PHFP. The results showed that PHFP was indeed a polymer with complicated OH—Fe—P structure and consisted of Fe₆(OH)₅(H₂O)₄(PO₄)₄(H₂O)₂ and Fe₂₅(PO₄)₁₄(OH)₂₄. Moreover, the removal rates of DTPA-extractable Cd and Pb in soils reached up to 33% and 45%, and the water-soluble Cd and Pb decreased by 56% and 58%, respectively, when PHFP was added in soils at 4% dosage. In addition, the immobilization of Cd and Pb contributed to transforming water soluble, exchangeable and carbonate-bonded fractions to Fe and Mn oxides-bonded, organic-bonded and residual fractions. Under leaching with simulated acid rain, Cd and Pb release amount in PHFP amended soil declined by 53% and 52%, respectively, as compared with non-treated soil. The result implied that PHFP had a potential application for the remediation of Cd- and Pb-contaminated soils.     

Formation of a wear-resistant nanocrystalline layer strengthened by TiO2 (Rutile) particles on the surface of titanium

The effect of a thermomechanical treatment including severe plastic deformation under dry sliding friction conditions and subsequent heating in air to 350–650°C with further holding for 1 h on the structure and wear resistance of commercial titanium of grade VT1-0 has been studied. It has been shown that the deformation by friction leads to the formation of a nanocrystalline structure with α crystals 20–100 nm in size in a surface layer of titanium of about 10 μm thick. The heating of titanium deformed by friction at temperatures of 450–650°C for 1 h in air leads to the formation in the surface layer of this material ～10 μm thick of nanocrystalline particles of the titanium oxide TiO₂ (rutile), the volume fraction of which reaches tens of percents, while the dimensions are ～10 nm. The presence in the surface layer of titanium of a nanocrystalline two-phase (α-Ti + rutile) structure leads to a significant increase in the wear resistance of the VT1-0 titanium in pair with steel 40Kh13. This is explained by the enhanced strength of the arising nanocrystalline layer and its positive influence (as of a transition layer) on the reduction of the level of internal stresses that exist at the interface between the titanium oxide TiO₂ and the host metal.