Effects of mechanical activation on the HCl leaching behavior of plagioclase, ilmenite and their mixtures

Plagioclase (NaAlSi₃O₈–CaAlSi₂O₈) is one of the dominant impurity minerals in the ilmenite concentrate from the Panxi area of China. The effects of mechanical activation on the structural changes of plagioclase and ilmenite single minerals from Panxi were investigated using X-ray diffraction (XRD), particle size analysis, and scanning electron microscope (SEM). Hydrochloric acid leaching behaviors of mechanically activated plagioclase and ilmenite single minerals and their mixtures were also studied. The results show that with increasing milling time, the crystallite size, lattice strain and the particle size changed continuously but differed between plagioclase and ilmenite. Mechanical activation enhanced the leaching reactivity of plagioclase and ilmenite with 20% HCl at 105 °C, consistent with the lattice disorder and decreased particle size. The leaching of plagioclase was hardly affected by the existence of ilmenite, but the leaching of ilmenite was inhibited when plagioclase co-existed in the sample which is attributed to silica gel produced from leached plagioclase blocking the surface of unleached ilmenite.     

Preparation of synthetic rutile by hydrochloric acid leaching of mechanically activated Panzhihua ilmenite

Dissolution of mechanically activated Panzhihua ilmenite in hydrochloric acid for the preparation of synthetic rutile was investigated. Both the dissolution and its coupled titanium hydrolysis were greatly enhanced by the mechanical pretreatment. Increases in the lattice strain and surface area of ilmenite induced by energetic ball milling were responsible for the enhanced dissolution. The rapid hydrolysis led to formation of quantities of the nanosized primary particles, giving rise to a solid/liquid separation problem. The 15 min milled ilmenite, however, yielded an easy-to-filter hydrolysate due to formation of porous, micron-sized, secondary particles during the dissolution. The crystallization and aggregation behaviour of the primary particles were probably related to both the surface property of the un-reacted solid and the ferric ion concentration in solution. The technology for preparation of synthetic rutile was systematically investigated. The optimum milling and dissolution conditions were as follows: milling in air for 15 min, hydrochloric acid concentration 20%, initial reaction temperature 100 °C, ilmenite/20% acid mass ratio 1 g:5.5 g, reaction time ≥ 6 h. The synthetic rutile prepared under the optimum conditions contained 92% TiO₂ and 2.1% Fe₂O₃ as well as combined CaO and MgO of 0.28%. The results demonstrate that the mechanical pretreatment can take the place of the traditional high temperature pretreatment of ilmenite and avoid the dissolution being conducted under pressurized condition.     

Effect of mechanical activation on the leaching kinetics of pyrrhotite

BET, SEM, and particle size analysis was used for studying the changes in surface and bulk properties of mechanically activated pyrrhotite in a vibrating mill. The results showed that mechanical activation increased microstructure defects and specific surface area of pyrrhotite, and decreased powder particle size. And the formation of aggregates was very obvious. The influence of mechanical activation on leaching kinetics of pyrrhotite by FeCl₃–HCl solutions was investigated. When pyrrhotite was mechanically activated for 10 min, 20 min and 40 min, the apparent activation energy decreased from 133 kJ/mol to 33, 26 and 25 kJ/mol, respectively. Compared with the non-mechanical activation method, mechanical activation greatly improved the activity of pyrrhotite and decreased the apparent activation energy, so that the reaction speed was accelerated remarkably.     

Dissolution studies of mechanically activated Manavalakurichi ilmenite with HCl and H2SO4

The effect of the change in phase constitution, particle size distribution, surface area, crystallite size, strain and lattice parameters introduced by mechanical activation of the altered beach sand ilmenite from Manavalakurichi region, India on the dissolution kinetics of HCl and H₂SO₄ was investigated. The altered ilmenite showed different physico-chemical characteristics and was found to be more resistant to acid leaching than the less altered ilmenite from the Chatrapur beach sands, India investigated earlier. The dissolution behavior was also different in H₂SO₄ and HCl. For sulfuric acid leaching, the dissolution of Fe and Ti increased monotonically with time of milling and showed a continuous increase with time of leaching, whereas hydrolysis of titanium occurs in HCl medium, especially for the activated samples at lower acid concentration, lower solid to liquid ratio and higher temperature leading to lower solution recoveries. The dissolution kinetics in both H₂SO₄ and HCl prior to hydrolysis conforms initially to the reaction rate control model and for higher leaching times to the shrinking core model where diffusion through the product layer is rate controlling. It is postulated that the anatase formed by hydrolysis in milled samples impedes the further progress of leaching. The activation energies for the dissolution of Fe and Ti decreased with time of milling and were marginally lower in HCl than in H₂SO₄. An attempt has also been made to correlate the decrease in activation energy to the increase in the energy input to the material through high-energy milling. The relative contribution of the increase in surface area and structural disorder on the enhancement of the dissolution rates has been evaluated.     

Leaching Kinetics of Willemite in Ammonia-Ammonium Chloride Solution

The leaching kinetics of willemite in ammonia-ammonium chloride solution was investigated. The effects of the ammonia-ammonium ratio, particle size, temperature, and total ammonia concentration on the leaching rate of willemite were determined. The results show that the optimum ammonia-ammonium ratio is 1:2 over the studied range. The zinc extraction increases with the reduction of particle size and with the increase of temperature and the total ammonia concentration. Leaching kinetics indicate that the grain pore model could be adopted to describe the leaching process, and diffusion is the main rate-controlling step. The apparent activation energy was determined to be 54.47 ± 6.39 kJ/mol and a reaction order with respect to NH₃(aq) was 3.16 ± 0.40, both of which are likely a result of the parallel nature of the chemical reaction and diffusion in porous solids, even if the chemical reaction is not the rate-controlling step.     

Leaching behavior of metals from a limonitic nickel laterite using a sulfation–roasting–leaching process

The leaching behavior of metals from a limonitic laterite was investigated using a sulfation–roasting–leaching process for the recovery of nickel and cobalt. The ore was mixed with water and concentrated sulfuric acid followed by roasting and finally leaching with water. Various parameters were studied including the amount of acid added, roasting temperature and time, sample particle size, addition of Na₂SO₄ and solid/liquid ratio in leaching process. More than 88% Ni, 93% Co and < 4% Fe are extracted under the determined conditions. Simultaneously, about 90% Mn and Cu, 70% Mg, 45% Al, 25% Zn, 4% Cr and Ca are extracted respectively. The pH of the leach solution is about 2. The leaching efficiency is independent of sample particle size due to decomposition of ferric sulfate formed during roasting. The roasted mass was characterized by various physico-chemical techniques such as DSC/TGA, XRD and SEM. This process provides a simple and effective way for the extraction of nickel and cobalt from laterite ore.     

机械活化强化铌钽矿碱性水热体系浸出

针对现行铌钽矿HF酸处理工艺氟污染严重的问题,提出以KOH溶液替代高毒性HF介质的铌钽矿碱性水热体系浸出新方法,研究了铌钽矿在KOH碱性水热体系浸出规律.结果表明,在KOH质量分数50%范围内,KOH质量分数和反应温度的提高会促进铌钽矿分解生成可溶性六铌(钽)酸钾,但过高的KOH质量分数和反应温度会使可溶性六铌(钽)酸钾向不溶性偏铌(钽)酸钾转化,造成铌、钽浸出率的下降.在KOH质量分数35%、反应温度200℃、碱矿质量比4:1以及反应时间2 h的最佳浸出条件下,铌和钽浸出率仅为18.73%和9.4%;通过机械活化对铌钽矿进行预处理后,铌和钽浸出率可大幅度提高至95%和60%,说明机械活化可显著强化铌钽矿碱性水热浸出过程.铌钽矿经机械活化后,矿物粒度减小,比表面积增加,晶格畸变增大,无定形化程度增加,内部缺陷程度增加,矿物的反应活性大大增加,铌钽矿的浸出率显著提高.      

Enhancing Physicochemical Properties and Indium Leachability of Indium-Bearing Zinc Ferrite Mechanically Activated Using Tumbling Mill

The synthetic indium-bearing zinc ferrite (IBZF) was activated mechanically using a tumbling mill under different rotation speeds, milling times, media fillings, and ball-to-material ratios. Subsequently, the changes in the physicochemical properties and leaching behavior of IBZF induced by mechanical activation were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectra (FT-IR), M?ssbauer spectrometry, particle size analysis, and leaching tests in sulfuric acid. The results showed that different milling conditions could form different particle size distribution, morphologies, and crystal structures, which influenced indium extraction differently. In addition, the indium extractions from various activated samples were related closely to the changes of physicochemical properties induced by mechanical activation. The strengthening effect of mechanical activation in IBZF decomposition lies mainly in the damage of crystal structure besides the decrease of the particle size because the indium-leaching efficiencies increased significantly with the increase of the damage of the crystal structure when the particle size is kept constant.     

Effect of aging conditions on the leaching of mechanically activated pyrite and sphalerite

The leaching of mechanically activated pyrite and sphalerite exposed to nitrogen (99.999 vol pct) or air at ambient temperature or 573 K was investigated. The results indicate that at the same leaching time, the iron-leaching ratio of mechanically activated pyrite or sphalerite aged in nitrogen at both ambient temperature and 573 K decreases slightly with increasing aging time and remains constant after a certain aging period. The iron-leaching ratio of mechanically activated pyrite exposed to ambient air varies with the exposure period. But, at the same leaching time, the zinc-leaching ratio of mechanically activated sphalerite aged at ambient temperature does not change with the aging atmosphere. The structures of mechanically activated pyrite and sphalerite after being aged were determined. The specific granulometric surface area of mechanically activated pyrite and sphalerite decreases with increasing aging time, but keeps constant after a certain aging period. The X-ray diffraction patterns of mechanically activated pyrites aged in nitrogen do not change with aging time; neither do the X-ray diffraction patterns of mechanically activated sphalerites aged either in air or in nitrogen. For mechanically activated pyrite exposed to ambient air for 3 and 6 months, new phases were found. The lattice distortion and the elemental sulfur content of pyrite and sphalerite mechanically activated in nitrogen were also investigated. The results indicate that the elemental sulfur content of mechanically activated pyrite rises noticeably, and its lattice distortion (ε) rises slightly, with increasing grinding time. The elemental sulfur content of mechanically activated sphalerite remains constant at 0.5 mg elemental sulfur per gram of sphalerite, and its lattice-distortion ratio increases apparently with increasing grinding time. These observations provide further evidence for our opinion that the formation of dangling bonds on the surface of mechanically activated pyrites and the lattice distortion on the surface of mechanically activated sphalerites may mainly result in the enhancement of hydrometallurgical process for corresponding sulfide minerals.     

The oxidation behavior of unactivated and mechanically activated sphalerite

The oxidation behaviors of unactivated and mechanically activated sphalerites were investigated using the thermogravimetry method (TG) in flowing highly pure oxygen at the heating rate of 10 K min⁻¹. It is found that the remaining mass between 400 and 873 K in the TG curves of mechanically activated sphalerites rises with increasing grinding time. The difference in oxidation reactivity of unactivated and mechanically activated sphalerites was also discussed. The specific granulometric surface area (S _G), the structural disorder, and the content of elemental sulfur of unactivated and mechanically activated sphalerites were determined by X-ray diffraction (XRD) laser particle size analysis, X-ray diffraction, and the gravimetric method, respectively. The results show that the specific granulometric surface areas of mechanically activated sphalerites remain almost constant after a certain grinding period. The elemental sulfur contents of unactivated and mechanically activated sphalerites were determined to be 0.5 mg/g, and the lattice distortions (ɛ) increase but the crystallite sizes (D) decrease with increasing grinding time. All the results imply that the mass increase between 400 and 873 K in the TG curves of mechanically activated sphalerites depends mainly on the increase of lattice distortions (ɛ) and the decrease of the crystallite sizes (D) with increasing grinding time. It was concluded that TG is a useful method for characterizing mechanically activated sphalerites.     

Silicon and aluminum removal from ilmenite concentrates by alkaline leaching

In this paper, a hydrometallurgical process for the treatment of ilmenite concentrates is developed, in order to reduce the silicon content to the maximum allowed value for the production of “grade B” ferrotitanium. The process was based on pressure leaching with sodium hydroxide and the effect of the main leaching parameters, namely the temperature, sodium hydroxide concentration and retention time, on the efficiency of silicon removal was studied. Caustic leaching of the ilmenite concentrates resulted in the removal of silicon, as well as of aluminum, without affecting the contents of titanium and iron. Leaching temperature and the retention time were proved as crucial parameters for the effective dissolution of silicon. Besides, these parameters affected directly the secondary precipitation of silicon and aluminum as a zeolitic phase, which polluted the treated ilmenite concentrate. Leaching kinetics determined the feasibility of the process, leading to the development of two optimized alternatives. The first alternative achieved the reduction of silicon and aluminum content to 0.32% and 0.61%, respectively, after 72 h leaching at 120 °C. This alternative necessitated a leached solids washing stage in order to separate the formed precipitate from the treated ilmenite concentrate. The second alternative achieved to reduce silicon and aluminum to 0.29% and 0.59%, respectively, after 1 h leaching at 200 °C, while avoided the formation of the secondary precipitate. Both alternatives achieved the selective leaching of silicon and aluminum without affecting titanium and iron content of the ilmenite concentrate. The applicability of each alternative is a matter of detailed technical and economic studies.     

Enhancement Reduction of Panzhihua Ilmenite Concentrate with Coke and Conglomeration of Metal with Ferrosilicon

The particle size and metallization ratio of iron in reduced ilmenite have an important function in separating the metal from TiO₂‐rich slag in the electric arc furnace process. In this study, an ilmenite concentrate supplied by Panzhihua Iron and Steel (Group) Co. was reduced at 1380°C in an electric resistance furnace. The effects of Fe–Si addition and reduction time on the particle size and metallization ratio of iron in the reduced sample were analyzed. The metallization ratio of iron significantly increased with increasing Fe–Si amount and reduction time, and reached ≈90% after 40 min. However, the metallization ratio of iron was about 85% without Fe–Si addition. Meanwhile, the iron particle size increased with increasing Fe–Si amount; the growth was obvious with the addition of 1% Fe–Si. Moreover, the growth rate of the iron particle size also increased with increasing reduction time. The TG‐DTG curves indicated that the mass loss with Fe–Si addition was less than that without Fe–Si addition, and the temperature at which the maximum rate of mass loss rate was achieved was lower than that without Fe–Si addition.     

热酸球磨浸出攀枝花钛铁矿

在工业矿酸比条件下,研究攀枝花钛铁矿热酸球磨快速浸出的可行性,着重考察了搅拌球磨的转速、球料比、硫酸浓度以及反应温度等因素对酸解的影响。结果表明,与未实施球磨的浸出相比(其它试验条件相同、磨浸60 min),钛的浸出率可提高64%,这是由于搅拌球磨导致钛铁矿晶格畸变以及颗粒显著细化所致。获得了磨浸的优化工艺条件为:搅拌磨的转速700 r/min,球料比5∶1,矿酸比1∶1.6,硫酸浓度70%以及温度120℃。在此条件下磨浸60 min钛的酸解率达到81%,所得钛液稳定性≥550 mL,表明70%硫酸可直接液相酸解钛铁矿,为实现水解废酸循环利用提供了一条可行途径。     

Oxidative acid leaching of mechanically activated sphalerite

The pressure leaching kinetics of mechanically activated sphalerite was investigated in this work. X-ray diffraction and scanning electron microscopy were used to characterise the influences of crystalline structure and morphology, respectively. A laser particle size analyser and specific surface area tester were used to determine the particle size and specific surface area, respectively. Compared to the non-activated sample, the activated samples demonstrated distinct physicochemical properties with higher reaction efficiencies and increased Zn recovery ratios. The activation energy of sphalerite decreased from 69.96 to 45.91, 45.11, and 44.44?kJ?mol^?1 as the activation time increased from 0 to 30, 60, and 120?min, respectively. The reaction orders for the H₂SO₄ solutions of the sphalerite samples activated for 0, 30, 60, and 120?min were 1.832, 1.247, 1.214, and 1.085, respectively, which indicated that the dependency of the sphalerite leaching process on H₂SO₄ could be reduced by means of mechanical activation.     

Rare earth recovery from fluoride molten-salt electrolytic slag by sodium carbonate roasting-hydrochloric acid leaching

Fluorinated rare earth molten-salt electrolytic slag contains a considerable amount of rare earth elements,as well as a variety of heavy metals and fluorides that cause environmental pollution.Therefore,it is of great importance to fully utilise this resource.In this study,the transformation mechanism of fluorinated rare earth molten-salt electrolytic slag roasted with sodium carbonate,and the regulation mechanism of rare earth leaching under different roasting conditions were investigated with ...     

钛精矿球磨活化微波还原试验

研究攀枝花低品位钛精矿的球磨活化-微波还原。采用激光粒度及X衍射研究不同球磨条件下钛铁矿的粒度和物相变化并进行分析,结果表明磨矿活化使矿物颗粒逐渐减小、特征峰宽化、晶粒变细;研究了活化物料的升温和还原行为,并对还原产物微观形貌和物相进行分析,表明活化物料有良好的微波吸收性能和还原效应。证实在反应过程中存在"热点"。球磨8 h的混合物料在温度900℃、反应时间30 m in条件内金属化率超过90%。     

氧化还原—机械活化对攀西钛铁矿浸出行为的影响

研究了"氧化还原—机械活化—盐酸浸出"的方法对钛铁矿中主要杂质离子铁离子浸出行为的影响,并采用XRD、SEM/EDS对处理前后的矿物结构进行分析。结果表明:经过氧化还原—活化处理,钛铁矿的物相明显发生改变,铁迁移至表面,形成了富铁的新表面,表面变得疏松、凹凸不平,出现了大量的微裂缝,铁浸出率有了显著的提高。     

Leaching of silica from vanadium-bearing steel slag in sodium hydroxide solution

The work aims to selectively extract silica from vanadium-bearing steel slag by a leaching process. The effects of the particle size, the ratio of solid to liquid, the concentration of sodium hydroxide solution and the leaching temperature on the leaching behavior of silica from vanadium-bearing steel slag were investigated. The leaching kinetics of silica from vanadium-bearing steel slag in 30-50% w/w NaOH solutions was studied at 240 °C and the shrinking-core model was established to express the leaching kinetics of silica. The data showed that the leaching rate was controlled by the chemical reaction on the system interface and the activation energy for the process was found to be 36.4 kJ mol^− 1. By the leaching process, the majority of silica could be removed effectively from the vanadium-bearing steel slag and a residue with a low SiO₂ content of 4.28% and a high V₂O₅ content of 11.15% was obtained. Under these conditions there was partial dissolution of Al and slight dissolution of Cr, Mn and Ti.     

Leaching of sulfide copper ore in a NaCl–H2SO4–O2 media with acid pre-treatment

A study was made of the leaching of a sulfide copper ore in a NaCl–H₂SO₄–O₂ media after pre-treatment by agglomeration with H₂SO_4(conc) and NaCl. The leaching variables evaluated included the amount of NaCl to be employed, the percentage of solids in the leaching solution, particle size of the raw mineral to be leached, and the preferable method of agitation in the leaching system. Mineralogical characterization of the material to be leached included analysis of the raw ore and of the leached ore residue using reflected-light microscopy, X-ray diffraction, and scanning electron microscopy. The soluble species included djurleite and digenite. The most important parameters in the leaching process proved to be particle size and type of agitation. A total percentage of copper extraction of 70% was achieved using mechanical stirring, which increased to 78% when using compressed air agitation. The best extraction of the copper was achieved when leaching with 3 g/L of chloride, room temperature of 20 °C, and when all particles were < 1.65 mm in diameter.     

Kinetics of copper dissolution during pressure oxidative leaching of lead-containing copper matte

The kinetics of pressure oxidative leaching of lead-containing copper matte with sulfuric acid was investigated. The effects of particle size, leaching temperature, oxygen partial pressure and sulfuric acid concentration on the kinetics and mechanism of copper extraction were studied. It was found that the reaction kinetic model follows the shrinking core model of chemical reaction control and the apparent activation energy was determined as 39.1 kJ/mol. The order of the reaction with respect to total pressure was found to be 0.64. The kinetic equations for the effect of particle size, leaching temperature, total pressure and sulfuric acid concentration were obtained and a mathematical model of copper extraction from lead-containing copper matte was developed as:

This equation estimates the extraction of copper with very good agreement (r = 0.99) between the experimental and calculated values.