Extraction of Valuable Metals from Titanium-bearing Blast Furnace Slag by Acid Leaching

To realize the resource utilization of the valuable metals in the titanium-containing blast furnace slag,the process route of “hydrochloric acid leaching-electrolysis-carbonization and carbon dioxide capture-preparation of calcium carbonate” was proposed.In this study,the influences of process conditions on the leaching rates of calcium,magnesium,aluminum,and iron and the phases of the leaching residue were investigated for the leaching process.The experimental results show that the HCl solution could selectively leach the elements from the titanium-containing blast furnace slag.The better leaching conditions are the HCl solution concentration of 4 mol/L,the leaching time of 30 min,the ratio of liquid volume to solid gas of 10 mL/g,and the stirring paddle speed of 300 r/min.Under the conditions,the leaching rates of calcium,magnesium,aluminum,and iron can reach 85.87%,73.41%,81.35%,and 59.08%,and the leaching rate of titanium is 10.71%.The iron and the aluminum are removed from the leachate to obtain iron-aluminum water purification agents,and the magnesium is removed from the leachate to obtain magnesium hydroxide.The leaching residue phase is dominated by perovskite,followed by magnesium silicate and tricalcium aluminate,and the titaniumrich material could be obtained from the leaching residue by desiliconization.

Preparation of Ti-rich material from titanium slag by activation roasting followed by acid leaching

A method of activation roasting followed by acid leaching using titanium slag was introduced to prepare Ti-rich material. The effects of HaPO4 dosage, roasting temperature, and roasting time on TiO2 grade were investigated. A Ti-rich material containing 88.54% TiO2, 0.42% （CaO＋MgO） was obtained when finely ground titanium slag was roasted with 7.5% H3PO4 at 1000 ℃ for 2 h, followed by a two-stage leaching in boiling dilute sulfuric acid for 2 h. The XRD patterns show that the product is titanium dioxide with a rutile structure. Mechanism studies show that structures of anosovite solid solution and silicate minerals are destroyed in the roasting process. As a result, titanium components in titanium slag are transformed into TiO2 （futile） while impurities are transformed into acid-soluble phosphate and quartz.

φ-pH diagram of V-Ti-H_2O system during pressure acid leaching of converter slag containing vanadium and titanium

To analyze the thermodynamic characteristics of leaching process of converter slag, φ-pH diagram of V-Ti-H2O system at oxygen partial pressure of 0.5 MPa, ionic mass concentration of 0.1 mol/kg and temperatures ranging from 60 to 200 ℃ was obtained by recently published critically assessed standard Gibbs energies and activity coefficients of various species. When pH2, stable regions of V3＋, VO2＋ and VO2＋ exist in the stable region of TiO2. The pH values of stable regions of vanadium and titanium decrease and redox potentials become more positive with the temperature increasing. Vanadium and titanium could be separated by one-step leaching based on thermodynamics. The experiment results of pressure acid leaching of converter slag show that leaching rates of vanadium and titanium are 96.87% and 8.76% respectively, at 140 ℃ of temperature, 0.5 MPa of oxygen partial pressure, 0.055-0.075mm of particle size, 15：1 of liquid to solid ratio, 120 min of leaching time, 500 r/min of stirring speed and 200 g/L of initial acid concentration. Vanadium and titanium could be selectively separated in the pressure acid leaching process, and the experiment result is in agreement with thermodynamic calculation result.

Reaction kinetics of roasting high-titanium slag with concentrated sulfuric acid

A novel method of roasting high-titanium slag with concentrated sulfuric acid was proposed to prepare titanium dioxide, and the roasting kinetics of titania was studied On the basis of roasting process. The effects of roasting temperature, particle size, and acid-to-ore mass ratio on the rate of roasting reaction were investigated. The results showed that the roasting reaction is fitted to a shrinking core model. The results of the kinetic experiment and SEM and EDAX analyses proved that the reaction rate of roasting high-titanium slag with concentrated sulfuric acid is controlled by the internal diffusion on the solid product layer. According to the Arrhenius expression, the apparent activation energy of the roasting reaction is 18.94 kJ/mol.

Extraction of vanadium from vanadium slag by high pressure oxidative acid leaching

To extract vanadium in an environment friendly manner, this study focuses on the process of leaching vanadium from vanadium slag by high pressure oxidative acid leaching. Characterizations of the raw slag, mineralogy transformation, and the form of leach residues were made by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The result shows that the vana-dium slag is composed of major phases of fayalite, titanomagnetite, and spinel. During the high pressure oxidative acid leaching process, the fayalite and spinel phases are gradually decomposed by sulfuric acid, causing the release of vanadium and iron in the solution. Meanwhile, unreacted silicon and titanium are enriched in the leach residues. With the initial concentration of sulfuric acid at 250 g·L^-1, a leaching tem-perature of 140℃, a leaching time of 50 min, a liquid-solid ratio of 10：1 mL·g^-1, and oxygen pressure at 0.2 MPa, the leaching rate of vana-dium reaches 97.69%.

Remediation of Steel Slag on Acidic Soil Contaminated by Heavy Metal

The technology of in situ immobilization with amendments is an important measure that remediates the soil contaminated by heavy metals, and selecting economical and effective amendments is the key. The effects and mechanism of steel slag, the silicon-rich alkaline byproduct which can remediate acidic soil contaminated by heavy metal, are mainly introduced in this paper to provide theory reference for future research. Firstly, the paper analyzes current research situation of in situ immobilization with amendments. Then, it introduces the main physicochemical properties of steel slag, and the effect on soil pH value as well as heavy metal activity. Besides, the paper elaborates the promoting effect on silicon-requiring plant and the strengthening mechanism for its resistant capability of heavy metal. According to the analysis, the application of steel slag could be a potential valuable strategy to remediate acidic soil contaminated by heavy metal by modifying the transformation of heavy metals in both soil and plant, so that the translocation of heavy metal in food chain is reduced.

Leaching of iron concentrate separated from kiln slag in zinc hydrometallurgy with hydrochloric acid and its mechanism

It is taken as a novel prospective process to treat iron concentrate from hydrometallurgical zinc kiln slag forcomprehensive utilization of valuable metals by a hydrochloric acid leaching-spray pyrolysis method.The leaching mechanism ofdifferent valuable metals was studied.The results revealed that the leaching rates of Ag,Pb,Cu,Fe,As and Zn were99.91%,99.25%,95.12%,90.15%,87.58%and58.15%,respectively with6mol/L HCl and L/S ratio of10:1at60°C for120min.The actionof SiO2in leaching solution was also studied.The results showed that the precipitation and settlement of SiO2(amorphous)adsorbedpart of metal ions in solution,which greatly inhibited the leaching of Cu,Fe,As and Zn,so it is crucial to control the precipitation ofamorphous SiO2.

Extraction of metals from a zinc smelting slag using two-step procedure combining acid and ethylene diaminetetraacetic acid disodium

A two-step leaching method in combination of acid and ethylene diaminetetraacetic acid disodium （EDTA-Na2） was applied to extract metals such as Cd, Cu, Fe, Pb and Zn from a zinc smelting slag. The results show that the extraction rates of Cd, Cu, Fe and Zn in slag reach 88.3%, 54.1%, 69.6% and 54.7%, respectively, while the extraction rate of Pb is only 0.05% leached with 1.25 mol/L sulfuric acid under the conditions of the ratio of slag to liquid of 100 g/L, 65 ℃ and 120 r/min for 2 h. However, Pb extraction rate from 1.25 mol/L sulfuric acid leached residue reaches as high as 66.5% by using 0.1 mol/L EDTA-Na2 solution. The results indicate that two-step sequential extraction procedure combining 1.25 mol/L sulfuric acid and 0.1 mol/L EDTA-Na2 solution can extensively extract Cd, Cu, Fe, Pb and Zn from zinc smelting slag.

Recovery of titanium,aluminum,magnesium and separating silicon from titanium-bearing blast furnace slag by sulfuric acid curing-leaching

An energy-efficient route was adopted to treat titanium-bearing blast furnace slag(TBBFS)in this study.Titanium,aluminum,and magnesium were simultaneously extracted and silicon was separated by low temperature sulfuric acid curing and low concentration sulfuric acid leaching.The process parameters of sulfuric acid curing TBBFS were systematically studied.Under the optimal conditions,the recovery of titanium,aluminum,and magnesium reached 85.96%,81.17%,and 93.82%,respectively.The rapid leaching model was used to limit the dissolution and polymerization of silicon,and the dissolution of silicon was only 3.18%.The mechanism of sulfuric acid curing-leaching was investigated.During the curing process,the reaction occurred rapidly and released heat massively.Under the attack of hydrogen ions,the structure of TBBFS was destroyed,silicate was depolymerized to form filterable silica,and titanium,magnesium,aluminum,and calcium ions were replaced to form sulfates and enriched on the surface of silica particles.Titanium,aluminum,and magnesium were recovered in the leaching solution,and calcium sulfate and silica were enriched in the residue after leaching.This method could effectively avoid the formation of silica sol during the leaching process and accelerate the solid-liquid separation.

Sulfuric Acid Resistance of Concrete with Blast Furnace Slag Fine Aggregate

The deterioration of concrete by sulfuric acid attack in sewage environments has become a serious problem for many existing sewage structures. In this study, the properties of concrete using the blast furnace slag have been examined. It was shown that by using the blast furnace slag fine aggregate and blast furnace slag fine powder, it is possible to enhance the resistance of mortar and concrete to sulfuric acid. The resistance to sulfuric acid of mortar and concrete can be improved by using a blast-furnace slag fine aggregate in the total amount of fine aggregate. When mortar or concrete reacts to sulfuric acid, dihydrated gypsum film is formed around the particulate of the fine aggregate. This dihydrated gypsum film could retard the penetration of sulfuric acid, thus, improving the resistance to sulfuric acid. Furthermore, it has been proved that the relationship between the erosion depth by sulfuric acid attack and the product of immersion period and concentration of sulfuric acid can be expressed linearly. However, this relationship is dependent on the type of materials of concrete.

Ladle Slag of Electric Steelmaking as Alkaline Agent on Controlling of Acid Mine Drainage Generation

Commercial coal production in the southern region of Brazil (comprising the Paraná, Santa Catarina, and Rio Grande do Sul states) has been occurring since the beginning of the twentieth century. Regarding the Santa Catarina coalfields, about 60% - 65% of the ROM coal is discharged at dump deposits as waste. These wastes can lead to the formation of acid mine drainage (AMD), a source of ground and surface water pollution. One of the technologies used for preventing AMD consists of the alkaline additive method. Thus, the aim of this work was to study, at laboratory scale, the DAM control by blending coal waste with a metallurgical slag. A coal-tailing sample was collected from a coal mine, and the slag was obtained from a semi-integrated steel plant. Static tests were carried out by the acid-base account method to determine the balance between the acid-producing and acid-consuming (neutralizing) mineral components of the samples. Kinetic tests were conducted in humidity cells, following the ASTM D 5744-96 method, for a period of 80 weeks. The results showed that the coal tailing generates AMD. However, environmental problems can be minimized by mixing the coal waste with the metallurgical slag in 1:1 or 1:1.5 proportions. The kinetic experiments proved that, in this condition, the lixiviation presents a higher pH and a lower concentration of acidity, metals, and sulfate. Finally, it is possible to conclude that the blending slag in coal tailing deposits can be a viable alternative for DAM control in coal mining.

Study of cryolite preparation from fluoride-containing acid slag in aluminium industry

A new process of cryolite preparation is studied in this work by selecting a proper system of reaction and weeding impurity technology. The quality of artifial cryolite reaches and exceeds the first level of national standard. The utilization efficient of fluoride-containing acid slag is above 99.5%. It brings considerable economic benefit, and the environment is improved.

Extraction of vanadium from molten vanadium bearing slag by oxidation with pure oxygen in the presence of CaO

A novel process of vanadium extraction from vanadium slag in its molten state was conducted at the laboratory scale by oxidation with pure oxygen in the presence of CaO. The effect of mass ratio of CaO to V2O5 on the recovery of vanadium was studied. The sintered samples were leached by H2SO4 solution and characterized by XRD, XPS, SEM and EDS techniques. Compared with the roasting process, the energy saving effect of the proposed process was also discussed. The results showed that vanadium-rich phases were formed and vanadium mainly existed in the forms of CaV2O5 and Ca2V2O7. The formation mechanism of calcium vanadates in the molten vanadium bearing slag was explained. The XRD and XPS results implied that there was a limit to the oxidation reaction of V(IV) to V(V) under the high temperatures even though oxygen-supply was sufficient. An increase in the CaO content led to an increase in the formation of Ca2V2O7. About 90%of the vanadium recovery was obtained under optimal experiment conditions (mass ratio of CaO to V2O5 of 0.6, particle size 120 to 150μm, leaching temperature 90 °C, leaching time 2 h, H2SO4 concentration 20%, liquid to solid ratio 5:1 mL/g, stirring speed 500 r/min). The energy of 1.85×106 kJ could be saved in every 1000 kg of vanadium bearing slag using the proposed process from the theoretical calculation results. Recovery of vanadium from the molten vanadium bearing slag and utilisation of its heat energy are important not only for saving metal resources, but also for energy saving and emission reduction.

钒渣酸浸提铁工艺优化及复合光催化剂的制备

钒渣来自转炉钒渣,含有大量铁元素,它的二次利用具有重大的经济价值与现实意义。本文以H2SO4为酸浸液,利用响应面法优化酸浸工艺参数,后通过煅烧-水热法成功制备出ɑ-Fe_(2)O_(3)/Bi_(2)WO_(6)复合光催化剂,在模拟可见光作用下光降解染料废水甲基橙(MO)。结果表明,响应面优化酸浸实验的最佳工艺参数为H2SO4浓度2.8mol/L、酸浸温度98℃、酸浸时间138min、固液比1∶4.2,钒渣中Fe的浸出率为71.0%;以钒渣为铁源,采用沉淀-煅烧法制备出α-Fe_(2)O_(3)后,通过水热法合成VS-Fe_(2)O_(3)/Bi_(2)WO_(6),其光降解性能明显优于商业Fe_(2)O_(3)/Bi_(2)WO_(6),VS-Fe_(2)O_(3)的最佳掺杂量为10%,当H2O2投加量为19.58mmol/L、p H=6.5、催化剂投加量为0.4g/L、MO初始浓度为10mg/L、光反应6h时,MO去除率达96%,COD去除率为88.4%,出水COD为13.34mg/L,符合《污水综合排放标准》一级标准,光反应速率常数为纯相Bi_(2)WO_(6)的4.8倍;MO的降解机理主要为H2O2协同VS-Fe_(2)O_(3)/Bi_(2)WO_(6)作用下的光芬顿反应。本文可为钒渣高效、清洁的资源化利用及其在光催化领域的资源化利用提供参考。

铅锌冶炼废水中和渣中有价元素综合回收

铅锌冶炼废水中和渣回收价值大、处理难度高,其湿法处理工艺是未来发展的主流趋势。基于中和渣特性,提出采用逆流酸浸工艺回收其中的有价金属,并探究不同反应条件对浸出效果的影响。结果表明,在液固比为3∶1、渣酸比为1.67、初始硫酸浓度200 g/L、熟化硫酸浓度98%、室温(自热浸出)和浸出时间30 min的条件下,中和渣中锌、锰、锗的浸出率大于95%,镁的浸出率大于85%。该技术可将中和渣中的钙转变为石膏渣产品,将砷转变为砷酸铁固砷产物,同时获得了可外售的活性氧化锌和碱式碳酸镁产品,可为我国企业的绿色化生产提供支撑。

酸碱协同从钢渣中分离回收钙硅试验研究

研究了采用酸碱协同分离法回收钢渣中的钙、硅元素,考察了浸出剂浓度、温度、浸出时间及液固体积质量比对钙、硅元素浸出率的影响,探究了其在不同浸出条件下的浸出规律。结果表明:浸出剂浓度、浸出时间、液固体积质量比对钙、硅元素浸出率有较大的影响,而温度对钙、硅元素的浸出率影响不明显;在盐酸浓度0.75 mol/L、浸出时间30 min、温度25℃及液固体积质量比10∶1条件下,钙浸出率为53.74%,所制得的草酸钙纯度可达98.94%;在氢氧化钠浓度1.5 mol/L、温度95℃、浸出时间120 min及液固体积质量比20∶1条件下,二氧化硅浸出率为43.22%,所制得二氧化硅纯度可达80.85%。该法能有效分离回收钢渣中钙、硅元素,实现资源化利用。

酸浸法富集含钒钢渣中铁/钒元素研究

本试验通过酸浸法对含钒钢渣中铁/钒元素进行富集,研究了醋酸浓度(体积分数,下同)、液固比、酸浸时间、酸浸温度对铁/钒氧化物富集的影响。结果表明,液固比是影响酸浸渣中铁/钒氧化物含量的主要因素,醋酸浓度次之,酸浸时间和酸浸温度影响较小。在醋酸浓度为5%,液固比为20 mL/g,酸浸温度为30℃,酸浸时间为1 h的条件下,酸浸渣中Fe_(2)O_(3)、V_(2)O_(5)富集效果最佳,分别达到52.06%和2.15%;此时,酸浸渣中CaO含量降至19.42%。在此条件下得到的酸浸渣碱度系数R为1.3,处于钢铁冶炼要求的推荐渣性区间,将其直接熔融还原,铁、钒氧化物还原率分别达到了91.84%和66.51%。

Recovery of vanadium from vanadium slag by composite roasting with CaO/MgO and leaching

A novel process of composite roasting with CaO/MgO and subsequent acid leaching was proposed to improve the recovery rate of vanadium from Linz–Donawiz(LD)converter vanadium slag.The effects of the MgO/(CaO+MgO)molar ratio and the roasting and leaching parameters on the recovery of vanadium were studied.The results showed that the leaching efficiency of vanadium decreased from 88%to 81%when CaO was replaced completely by MgO;however,it could be improved by roasting with the composite of CaO/MgO.The maximum vanadium leaching efficiency of 94%was achieved under the optimum MgO/(CaO+MgO)mole ratio of 0.5:1.The results from X-ray diffractometry(XRD)and scanning electron microscopy with energy-dispersive X-ray spectroscopy(SEM−EDS)confirm that the formation rate of acid-soluble vanadates can be enhanced during roasting with the composite of CaO/MgO and that the leaching kinetics can be accelerated owing to the suppression of calcium sulfate precipitation.

Stabilization effects of surplus soft clay with cement and GBF slag

Utilization of industrial waste and surplus construction soft clay as construction material was recommended, and many attempts at geotechnical waste utilization were undertaken. This study aimed at the application of cement and a kind of industrial wastes, i.e. granulated blast furnace slag, on stabilization of surplus soft clay. The results showed that the cement and slag can successfully stabilize Ariake clays even though this high organic clay fails to be stabilized by lime and cement. Addition of slag in cement for stabilization induces higher strength than cement alone for longer curing time. The application of the cement with slag is more suitable than cement alone for stabilization because of economical consideration.

铁尾矿-钢渣-锂渣混凝土耐酸侵蚀性能研究

目的在混凝土中掺入铁尾矿、钢渣、锂渣,分析混凝土的耐酸侵蚀性能,实现铁尾矿、钢渣、锂渣高效资源化利用。方法将铁尾矿、钢渣、锂渣作为掺合料替代部分水泥,铁尾矿碎石和铁尾矿砂作为粗、细骨料制备混凝土;对制备的混凝土标准养护28 d后进行为期60 d的酸侵蚀试验;通过改变水胶比和水泥替代率分析其质量损失率、抗压强度损失率及侵蚀深度,利用MIP、SEM探究铁尾矿-钢渣-锂渣混凝土耐酸侵蚀的机理。结果掺入铁尾矿、钢渣、锂渣可以降低混凝土的质量损失率、抗压强度损失率和侵蚀深度;其中掺量为30%时,质量损失率为0.12%、抗压强度损失率为-7.8%、侵蚀深度为0.6 mm,均达到最低值;混凝土的质量损失率、抗压强度损失率和侵蚀深度随着水胶比的增大而升高。结论铁尾矿-钢渣-锂渣混凝土中铁尾矿、钢渣、锂渣发挥的填充作用和与水泥发生的二次水化反应使混凝土体系更加致密,很大程度上阻碍了酸的侵入;同时,二次水化消耗了易与酸反应的CH,生成了更稳定的C-S-H凝胶,表现出更好的耐酸侵蚀性能。