Search Results (7)

This article presents the results of a thermodynamic analysis of the oxidation soda conversion reactions of minerals in ilmenite concentrates in the temperature range of 373–2273 K. The thermodynamic parameters of pseudorutile, pseudobrukite, and the new minerals, zhikinite and spessartine, were calculated for the first time. It has been established that the most important criterion relating to the stability of titanium minerals and related elements, as well as the reaction properties of the structural oxides of metals and silicon, is their degree of oxidation. Oxides of silicon (IV) and manganese have the best reactivity in solid-phase oxidizing alkaline environments (VI). Modeling this process scientifically substantiates the mechanism involved in the destruction of minerals in ilmenite concentrates in the low-temperature region in the presence of atmospheric oxygen and sodium oxide of soda ash, which are decomposed through the absorption of heat and the evaporation of moisture during the dehydration of hydrated minerals of iron and manganese and the dehydration of the soda–ilmenite batch. Tests conducted during pilot metallurgical production at the Institute of Metallurgy and Enrichment (PMP of JSC) confirmed the feasibility of processing high-chromium and siliceous rutile leucoxene ilmenite concentrates, which are unsuitable for traditional pyro- and hydro-metallurgical enrichment methods, through single-stage oxidation soda roasting, followed by the leaching of easily soluble sodium salts of iron and associated impurities with water and a dilute hydrochloric acid solution. The proposed energy-saving method ensures the production of high-purity (>98%) synthetic rutile while eliminating the formation of strong deposits on the lining of roasting units. Full article

Karst areas are widespread in China and can be divided into southern karst and northern karst based on the geographical boundary of Qinling Mountains and Huaihe River. In northern karst regions, karst springs are the predominant landform. Previous studies on karst springs have predominantly focused on macroscopic perspectives, such as water chemistry characteristics, with less attention given to the microscopic characteristics of springs. Therefore, this study focused on the Jinan Baotu Spring area, representative of a typical northern karst region, and investigated the natural nanoparticles present in different aquifers at various depths from a microscopic point of view. Through the observation of nanoparticle tracking analyzer (NTA), numerous nanoparticles were identified in the groundwater samples. The particle size range of the particles contained in groundwater is mainly concentrated in the range of 150–500 nm, and the particle concentration is mainly concentrated in the range of 1.5–5.0 × 10⁵ Particles/L. The microstructure, chemical composition, and element distribution of these nanoparticles were analyzed using TEM-EDS techniques. The results unveiled the presence of Ti-bearing nanoparticles in various groundwater layers, including both crystalline and amorphous states, as well as nanoparticles exhibiting the coexistence of crystal and amorphous structures. By comparing the measured lattice spacing with PDF cards, the crystalline Ti-bearing nanoparticles were identified as rutile, brookite, anatase, ilmenite, pseudorutile, and ulvospinel. Furthermore, the main components of the amorphous Ti-bearing nanoparticles predominantly consisted of Ti or a mixture of Ti and Fe. EDS analysis further indicated that the Ti-bearing nanoparticles carried additional metal elements, such as Zn, Ca, Mn, Mo, Cr, and Ni, suggesting their potential role as carriers of metal elements during groundwater transportation. This discovery provided new insights into the migration of metal elements in groundwater and underscores the capacity of nanoparticles to enhance the mobility of inorganic substances within the water environment. Notably, brookite was detected in three different areas, including the direct discharge area, indirect recharge area, and discharge area, which may indicate that some special natural nanoparticles could serve as natural mineral tracer particles in the process of groundwater migration. Full article

One of the most extensively studied topics in dozens of studies is the alteration process of ilmenite, the formation of leucoxene, and the presence of some impurity oxides: SiO₂ and Al₂O₃. The altered Egyptian black sand ilmenite grains of relatively lower magnetic characters are studied using the binocular microscope and the Cameca SX-100 microprobe instrument. Both individual brown- and black-altered grains separated at 0.5 and 1 ampere values are investigated. The detection of the various alteration phases, their molecular formulas and limits, and the role of SiO₂ and Al₂O₃ in alteration mechanisms are detected. The alteration phases include pseudorutile (psr) and leached pseudorutile (lpsr) of different phases in addition to rutile. Few analyzed spots are detected to be leached ilmenite (lilm). Several Excel software are adopted to calculate the chemical formulas of each alteration phase. The contents of TiO₂ and Fe₂O₃ of all the investigated psr/lpsr in the study are in the range of 59.16–86.56% and 37.3–6.68%, respectively. The Ti/(Ti + Fe) ratio for these formulas ranges between 0.60 and 0.88. The psr/lpsr chemical formulas of all the investigated grains range as follows: Fe_2.01-0.50Ti₃O_8.97-4.50(OH)_0.03-4.50. The concluded lowest cationic iron content of the well-defined accepted lpsr phase is 0.5 with a corresponding molecular formula of Fe_0.50Ti₃O_4.5(OH)_4.5. The results revealed that in the region of 68–70 TiO₂%, the mechanism of ilmenite alteration may be changed where neither all the analyzed TiO₂ of the spot nor all the calculated structural water are contained within the molecular formula of lpsr. There are other associated mineral phases containing some TiO₂ and also some structural water which most probably are removed from the lpsr phase. As the analyzed spots are located at highly fissured locations, the alteration process is relatively faster and the lpsr phase can be broken into rutile and hematite. Additionally, as the analyzed TiO₂ and structural and/or molecular water contents increase, the darkness of the BSE image areas of the grain increases; this may reflect the existence of an individual TiO₂ phase, most probably rutile, mixed in homogeneity with the existed lpsr component. As the content of TiO₂ increases, within a definite TiO₂ range (80–85%), the associated contents of Al₂O₃ and SiO₂ increase. When the contents of the structural and/or molecular water contained within the lpsr phases decreases, the total oxides sum is more than 98%, the contents of Al₂O₃ are highly depleted. In the late alteration stages, the lpsr structure does not suddenly collapse but gradually produces other associated mineral phases. The relatively enriched contents of SiO₂ and/or Al₂O₃ in some secondary rutile grains can be explained as most of the SiO₂% is associated with mol water or bearing for mol and/or str water necessary for the leachability of Fe³⁺ from the psr structure. The XRD patterns of the investigated grains before and after roasting at 1100 °C for one hour are detected and interpreted. Full article

Pseudorutile and kleberite are intermediate minerals formed during alteration of ilmenite to rutile. They are difficult to identify, as both have a range of chemical composition and occur as small crystals commonly mixed with other minerals. Reference samples of large crystals of pseudorutile and kleberite, with published X-ray diffraction and chemical analyses, were analysed to establish characteristic Raman spectra. Pseudorutile produced a goethite-like Raman spectrum but with a shift to increased wavenumber. It has characteristic Raman bands with peak positions at 234, 302, 402, 546, 617, 713 and 816 cm⁻¹ and OH stretching over the interval of 3390–3350 cm⁻¹. The 402 and 806 cm⁻¹ bands are the most intense. Kleberite produced a similar spectrum, but with a 10–30 cm⁻¹ greater Raman shift in the goethite-like bands. Its Raman bands have peak positions at 432, 573, 740, and 820 cm⁻¹ and OH stretching at 3390–3350 cm⁻¹. These results were applied to identify pseudorutile formed by diagenetic alteration of detrital ilmenite in Cretaceous sandstones of the Mesozoic Scotian Basin, eastern Canada. These samples showed pseudorutile Raman bands, but some samples are intermixed with residual ilmenite. Raman microspectroscopy thus allows rapid identification of small grains of pseudorutile and kleberite. Full article

Ilmenite is a vital raw material for the production of metal titanium and titanium-containing materials. In this paper, microstructure and chemical transformation of natural ilmenite in air atmosphere were investigated by the analysis of XRF, X-ray diffractometer, and SEM-EDS. Results showed that the untreated ilmenite had three layers after oxidation at 800 °C for 60 min, which were Fe₂O₃, TiO₂ and the inside mixture layer of Fe₂O₃ and TiO₂ in turn. Subsequently, it was roasted at 900 °C, and Fe₂Ti₃O₉ was firstly developed between Fe₂O₃ and TiO₂ layers. With the increase in the roasting time, the Fe₂Ti₃O₉ layer was decomposed into Fe₂TiO₅ and TiO₂, and Fe₂Ti₃O₉ continued to be formed along the diameter direction toward the center of the particle until Fe₂TiO₅ and TiO₂ were formed as the final products in the center of particles. Pseudorutile in natural ilmenite was directly decomposed into TiO₂ and Fe₂O₃ in the roasting process. Full article

In order to have a good understanding of the treatment process and improvement on the market value of ilmenite beach placer sands, knowledge of its mineral composition and phase distribution is fundamental. In this study, a combination of characterization techniques including high-resolution scanning electron microscopy (HR-SEM), high-resolution transmission electron (HR-TEM) microscope, and X-ray diffraction (XRD) techniques was used to understand the mineralogical characteristics of ilmenite beach placer sands obtained from Richards Bay, South Africa. The mineral phase constituents of the ilmenite beach placer sands were studied before pre-oxidation and additive leaching in a chloride environment. During observations using XRD and HR-SEM, the ilmenite beach placer sands exhibited signature rhombohedral crystal form and crescentic pits with evidence of alteration phases. The characterized pre-oxidized ilmenite showed the presence of a ferric oxide film deposit of the particles. The leaching characteristics of both raw and pre-oxidized ilmenite was studied in the presence of additives. The leaching efficiency of the pre-oxidized ilmenite in the presence of additives increased by 20% at atmospheric conditions. The characterized residues show the improved amenability of pre-oxidized leach in chloride media. The formation of new phases containing pseudo-rutile indicated crystallographic disintegration by the movement of atoms during dissolution. Some particles retained the crescentic pit and the subangular grain structure; however, the phase changes were observed at the grain boundaries and grain edges. The leached residue’s EDS results still indicated the presence of pseudo-rutile and some minor unreacted oxides such as SiO₂, Al₂O₃, and other trace metals. The trace metals impurities present in the as-received ilmenite were reduced by 80% in the final residue after the leaching. Full article

The kinetics of the sulfuric acid leaching of altered ilmenite, mechanisms, and process intensification methods were studied. The effect of changing the chemical composition during grinding was determined. The content of ilmenite and pseudorutile decreased from 5.3% to 3.1% and from 90.2% to 63.1%, respectively. Rutile increased from 4.5% to 28.7%, while a pseudobrookite new phase appeared in the amount of 5.1% after 2 h of grinding. It was found that the modification of raw material by sulfuric acid led to the increase of the decomposition rate, and at the same time, decreased when the ore was utilized due to an increase of insoluble TiO₂ content. Isothermal conditions were evaluated with H₂SO₄ concentration varying from 50 to 96%. The data obtained were described with the approximation of the contracting sphere model. It was shown for the first time that H₂SO₄ > 85 wt% causes a sharp constant decrease of titanium. Correlating these phenomena allows for the consideration of H₂SO₄·H₂O as reagents, rather than H₂SO₄ molecules. It was experimentally proven that at a temperature above 190 °C, the Ti leaching degree dropped, which is explained by the formation of polymerized TiOSO₄. Finally, it was shown that adding NaF reduced the activation energy to 45 kJ/mol. Full article