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In view of the complex structure and insoluble problems of platinum-containing group metal ferroalloys, alkali roasting desiliconization pretreatment was carried out to destroy stab! and dense alloy structures. The experimental results show that the optimum roasting conditions are as follows: mass ratio of alkali to material 1. 4, roasting temperature 600 °C, roasting time 2. 0 h, under these conditions, the alloy phase is completely decomposed into NaFeO2 and Na4SiO4 'Na4SiO4 is removed via water leaching and the silicon content in the obtained water leaching residue is reduced to 0. 84%. After desiliconization, the material has loose structure' high activity, and is easy to remove iron via add dissolution, which is conducive to the refining and recovery of platinum group metals. [ABSTRACT FROM AUTHOR]

Insights into the kinetics occurring during the combined blown (top and bottom blowing) oxygen steelmaking process, particularly at the impact and emulsion zones within separate reactors, can provide a deeper understanding of the refining mechanism in steelmaking. A dynamic model has been developed that can predict the contributions of various refining processes such as decarburization, desiliconization, demanganization, and dephosphorization. The model considers gas–metal interactions at the impact zone and slag–metal–gas interactions at the emulsion zone in an oxygen steelmaking converter. The model includes sub-models for lime dissolution and heat loss calculation. FactSage™ software and its macro programming facility were employed to integrate thermochemical and kinetic information into the model. The model predicts the temperature, composition, and volume of several phases involved in the process. The model predictions transient metal and slag compositions and metal bath temperature, were found to be consistent with the plant data. [ABSTRACT FROM AUTHOR]

BACKGROUND: Despite the large reserves of titanium ores, their treatment by basic approaches to obtain titanium products is not always economically feasible due to various factors. One of these problems is the high content of silicon in the ores. RESULTS: The paper considers the desiliconization of a leucoxene concentrate with an aqueous solution of ammonium bifluoride. It was found that at 80 °C the main impurities, such as silicon and iron, pass into solution in the form of corresponding ammonium–fluorine complex compounds. CONCLUSIONS: The degree of desiliconization was up to 99%. Aluminium reacts with ammonium bifluoride, but is almost not leached into solution due to its low solubility. Titanium does not react due to its relatively higher reaction Gibbs energy among other metals in reaction with ammonium bifluoride. The content of titanium oxide in the calcined leaching residue was 85.52 wt%. The resulting residue corresponds to the raw material used in industry for the production of titanium dioxide pigment or titanium metal by the chlorine method. Iron and silicon can be precipitated from the leaching solution. Furthermore, the resulting filtrate can be evaporated in order to regenerate and reuse ammonium bifluoride. © 2022 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

[Display omitted] • SAA can selectively control the surface properties of quartz. • Selective adsorption of SAA on quartz from quartz-magnesite mixtures. • Hydrogen bonding formed between the −N–H group of SAA and the oxygen atom of the O-Si-O group on quartz surface. Reverse flotation desiliconization from magnesite is significant for the exploitation of complex and barren magnesite resources. In this process, a critical issue is to find efficient and selective chemicals as flotation collectors. Herein, a cationic surfactant stearylamine acetate (SAA) was first used as a collector for the separation of magnesite and quartz. Micro-flotation experiments demonstrate that quartz can be separated from magnesite with a high Gaudin's selectivity index of 6.51 at slurry pH 5.0 and 70 mg/L SAA. Measurements of zeta potential and contact angle show that SAA selectively increased the surface charge and hydrophobicity of quartz. Field emission scanning electron microscopy (FESEM/EDS) and atomic force microscope (AFM) imaging indicate greater adsorption density of SAA on quartz than magnesite, with significantly higher nitrogen element content and RMS surface roughness of quartz. We also used surface-sensitive time of flight secondary ion mass spectrometry (TOF-SIMS) and FTIR spectroscopy to characterize the selective adsorption of SAA on quartz from quartz-magnesite mixtures. Apart from electrostatic attraction, it is found that the selective adsorption was attributed to hydrogen bonding formed between the −N–H group of SAA and the oxygen atom of the O-Si-O group on quartz surface. [ABSTRACT FROM AUTHOR]

The results of studying the associated synthesis of calcium hydrosilicates during the hydrometallurgical desiliconization of siliceous titanium concentrates from the Pizhem deposit (Komi Republic) are presented with allowance for the specific form of quartz present in the concentrates and the mineralogical compositions of the latter. The process is based on the selective binding of finely dispersed silica incorporated inside titanium-containing grains with CaO to form calcium hydrosilicate in an autoclave at elevated temperatures and pressures corresponding to the saturated vapor pressure in the presence of an activating NaOH additive. [ABSTRACT FROM AUTHOR]

The article presents the results of a study to determine the optimal conditions for an autoclave desiliconization of a zinc product. According to the plan of a six-factor experiment at 5 levels, the optimal conditions for the process of leaching of silicon dioxide from a zinc product were determined. Based on significant partial dependencies, a generalized multivariate equation was compiled for the degree of extraction of silica in solution. The generalized multifactor equations make it possible to determine the optimal conditions for the desiliconization of a silica-containing zinc product with a combination of different temperatures, the duration of the process, and the initial alkali concentration in the solution.

The average silicon content of the hot metal produced by Corex furnace is 0.6–1.5 mass%, which increases the oxygen blowing time and leads the unsatisfactory dephosphorization, high reblowing rate. The oxidation of carbon and silicon and optimization of dephosphorization during the refining process were studied through industrial practice and theoretical calculation. The results show that the optimum residual content of silicon in liquid steel at first slag making phase is about 0.05–0.07 mass%. The phosphorus content of liquid steel at first deslagging can be controlled at a low level (0.055–0.060 mass %), when the temperature is 1340–1360°C. The slag basicity of first deslagging should be controlled about 1.5, and (FeO) content should be controlled within 15%. In order to control the [P] of molten steel within 0.01mass%, the basicity should be higher than 3.4 and the temperature should be less than 1640°C. [ABSTRACT FROM AUTHOR]

The Corex furnace can produce hot metal without using coke, but the silicon content of the hot metal is abnormal within a week of reopening the furnace. The silicon content of the abnormal hot metal is 2–5.0 mass%. In order to produce with the high silicon hot metal, a new converter steelmaking process is developed. Two converters are used in the operation process. The first converter is used to remove a large amount of silicon of hot metal, and the second converter is used to carry out the decarburization and dephosphorization process. The new converter refining process can treat the high Si content hot metal. But it also brings some new problems. The biggest problem is to control the heat balance of the molten bath. By establishing a regression model and calculation of material and heat balance of BOF 1, the addition amount of slag material and scrap can be obtained under the different conditions of hot metal. After optimization of the new operation, the end point temperature of semi steel is about 1500°C, and the scrap ratio of the whole process is higher than before. The quantity of iron bead taken by per 100 g slag is about 2.3 g, and the T.Fe of slag is less than 5 mass%. On the basis of the same processing time, the optimized new method is more accurate at temperature control of semi steel, more efficient and more reliable. [ABSTRACT FROM AUTHOR]

The dephosphorization process for producing stainless steel hot metal is divided into desiliconization period and dephosphorization period, and the ability to contain phosphorus in the slag is important for the dephosphorization effect of hot metal. The phase structure of the slags during the desiliconization and dephosphorization phases is studied by X‐ray diffraction (XRD), petrographic analysis, and scanning electron microscopy (SEM). The ability of slag to contain phosphorus during the slagging process of calcium ferrite is discussed. The final slag petrographic composition in the desiliconization stage is mainly free calcium oxide, dicalcium silicate and calcium phosphate solid solution, RO phase, calcium ferrite and metallic iron. The final slag petrographic composition in the dephosphorization phase is mainly composed of tricalcium silicate, dicalcium silicate and calcium phosphate solid solution, RO phase, dicalcium ferrite and free calcium oxide. Compared with the desiliconization phase, the crystal phase obtained during the dephosphorization phase is more stable. The terminal ferrous slag phosphorus in calcium ferrite slag system mainly exists in the form of 2CaO⋅SiO2−3CaO⋅P2O5 solid solution, whereas the content in other phases is small. [ABSTRACT FROM AUTHOR]

A new electrosilicothermic method has been proposed in the present paper to produce Ni–Cr ferroalloy, which can be used for the production of 300 series stainless steel. Based on this new process, the Ni–Si ferroalloy is first produced as the intermediate alloy, and then the desiliconization process of Ni–Si ferroalloy melt with chromium concentrate is carried out to generate Ni–Cr ferroalloy. The silicon content in the Ni–Si ferroalloy produced in the submerged arc furnace should be more than 15 mass% (for the propose of reducing dephosphorization), in order to make sure the phosphorus content in the subsequently produced Ni–Cr ferroalloy is less than 0.03 mass%. A high utilization ratio of Si and a high recovery ratio of Cr can be obtained after the desiliconization reaction between Ni–Si ferroalloy and chromium concentrate in the electric arc furnace (EAF)–shaking ladle (SL) process.

The article presents the results of a study to determine the optimal conditions for an autoclave desiliconization of a zinc product. According to the plan of a six-factor experiment at 5 levels, the optimal conditions for the process of leaching of silicon dioxide from a zinc product were determined. Based on significant partial dependencies, a generalized multivariate equation was compiled for the degree of extraction of silica in solution. The generalized multifactor equations make it possible to determine the optimal conditions for the desiliconization of a silica-containing zinc product with a combination of different temperatures, the duration of the process, and the initial alkali concentration in the solution. [ABSTRACT FROM AUTHOR]

This research investigated water leaching of roasted vanadium slag and studied the effects of leaching parameters, such as agitation speed, temperature, liquid-to-solid ratio, and leaching time. Further, solution purification via desiliconization and precipitation of ammonium vanadate were studied using the vanadium solution obtained from the water leaching of roasted vanadium slag. Vanadium solution contains residual silicon (1.67 g/L), which should be removed before ammonium vanadate precipitation. Based on the results, vanadium can be effectively recovered from vanadium slag and a recovery efficiency of 96.9% was obtained under optimal water leaching conditions. During solution purification, silicon can be precipitated with Al 2 (SO 4) 3 to very low levels without any significant vanadium loss. The ammonium vanadate precipitation achieved a high precipitation efficiency of >99%. • Roasted vanadium slag was water leached with the high (96.9%) vanadium yield • Solution has high vanadium content, but also silicon as impurity (1.67 g/L) • Silicon was successfully removed with Al 2 (SO 4) 3 without significant vanadium loss • Finally, ammonium vanadate was precipitated under optimal conditions • Recovery efficiency of 99% was achieved after 300 min of precipitation. [ABSTRACT FROM AUTHOR]

Under laboratory conditions, an optimum regime of operation of a secondary anion-exchange filter filled with AV-17-8 strong basic anionite in the scheme for chemical water desalination was investigated. The paper is concerned with the character of an increase in the concentration of silicic acid in the spent regenerant solution. The dependence of an operating exchange capacity of anionite on the main characteristics is shown when the filter operated in the regime according to the double-flow-counterflow regeneration technology, and the significant advantages of the latter as compared to those of the direct-flow technology are demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: The technology of hot metal pretreatment had tremendous improvements in past decades and was widely used by the overwhelming majority of steelworks in Japan. While, since the first hot metal pretreatment station was established in Taiyuan Iron and Steel Co., Ltd in the later period of 1980s, this process began to be applied in domestic steel plants. And now 30 years have passed, the desilionization and dephosphorization process are still rarely seldom used in China except desulphurization process in most carbon steel plants. So in this paper, the metallurgical principles and effects of hot metal desiliconization were analyzed in great details. Meanwhile, the optimum silicon content of hot metal between iron-making and steelmaking process was summarized and calculated. The necessity of hot metal desiliconizaiton was discussed for the iron and steel companies in China. [Copyright &y& Elsevier]

The article presents a study which discusses the newly developed continuous desiliconization process equipped with a mechanical stirrer in the hot metal runner of a blast furnace. Results of the study for the desiliconization process were determined from small-scale experiments, plant tests, and commercial operations. The study has observed the importance of stirring intensity for the process performance of mechanical stirring method and the improved slag-metal residence time.

Ammonium hydrofluoride was used for fluorination of titanium-silica-containing raw materials (by the example of quartz-leucoxene concentrate of Yaregskoye deposit, South Timan, Russia). The optimum physical and chemical conditions for the processing of quartz-leucoxene concentrates, which allow obtaining a high‑titanium product containing >85% TiO 2 in a mixture of rutile and anatase at relatively low temperatures and a short processing time (300°С for 2 h), are presented. The results of thermodynamic calculations on interaction of NH 4 HF 2 with the components of the leucoxene concentrate were checked in experiments. The main phases formed during the interaction of NH 4 HF 2 with the two components of the leucoxene concentrate have been determined by thermal and X-ray phase analysis methods. The rate of fluorination depending on the amount of ammonium hydrofluoride and the influence of mechanical activation of mineral raw materials was studied. Optimal ratio is SiO 2 :NH 4 HF 2 = 1:4. Material grinding leads to its activation and intermediate products ((NH 4) 3 TiF 7 , (NH 4) 2 SiF 6)) are formed at lower temperatures. This will reduce the consumption of fluorinating component and allow to obtain a high‑titanium product with minimal costs. • Desiliconization of quartz-leucoxene concentrates using ammonium hydrofluoride (NH 4 HF 2) was done. • Based on thermodynamic calculations the stages of intermediate products formation in a multicomponent system were defined. • Desiliconization was carried out by simple thermal treatment at 300 °C. • High‑titanium concentrates containing >85% TiO 2 (a mixture of rutile and anatase) were obtained. [ABSTRACT FROM AUTHOR]

Abstract: The desiliconization reaction in sodium aluminate solution was studied by adding tricalcium hydroaluminate (C3AH6). C3AH6 prepared at 323 K has a relatively high desiliconization capacity. Kinetic results show that the desiliconization reaction is first-order in SiO2 concentration, and the apparent activation energy is estimated to be 96 kJ/mol between 363 and 393 K, which is lower than that from adding Ca(OH)2. During the desiliconization process, SiO2(OH)2 − ions enter the interior of C3AH6 particles and react with them further. As a result, the distribution of SiO2 in the desiliconization product (DSP) is more uniform than that from adding CaO. Also, the SiO2 content in DSP is higher. [Copyright &y& Elsevier]

Chromium sludge is a hazardous solid waste which cannot be effectively treated but only piled up and abandoned, causing serious environment pollution and resource wasting. This work proposes an effective novel process to separately recover all resources in chromium sludge via a sustainable way. The obtained acid solving liquid from chromium sludge is desiliconized by cationic flocculant (PCAM) to induce coprecipitation of polysilicate gel and PCAM, which mixture is calcinated to generate the product of white carbon black in purity of 94.35% with a recovery of 92.58%. After desiliconization, V in the solving liquid is selectively extracted by microemulsion (ME), which is recovered as V 2 O 5 in purity of 99.34% with a recovery of 95.53% by the subsequent procedure of stripping-precipitation-calcination. The Fe3+ in raffinate is reduced to Fe2+ cations by Na 2 SO 3 , and is then recovered by H 2 C 2 O 4 precipitation to generate the FeC 2 O 4 product in purity of 99.12% with a recovery of 98.25%. Cr3+ cations in residual solution are recovered by alkaline precipitation and calcination to generate the Cr 2 O 3 product in purity of 98.25% with a recovery of 92.68%. This work provides fresh penetrations into the synchronous detoxification, resource recovery and value-added utilization of hazardous industrial solid wastes. ga1 • Si from chromium sludge can be recovered as white carbon black in high purity of 94.35%. • 95.53% of V(V) and 92.68% of Cr(VI) in chromium sludge were recovered separately. • All the SiO 2 , V 2 O 5 FeC 2 O 4 and Cr 2 O 3 final products have high purity. • Efficient recovery of Si, V, Fe and Cr resources simultaneously treated the solid waste. [ABSTRACT FROM AUTHOR]

Hollow zeolite single crystals have received extensive attention due to their unique cavities and outstanding catalytic performance. Although many kinds of zeolites have been synthesized with hollow structures, the related synthesis of hollow SSZ-13 zeolites has not been reported yet. In this work, we first synthesized hollow zeolite SSZ-13 single crystals by a simple and economical strategy without additional templates, which involves adjusting the spatial chemistry distribution of elements throughout the crystals to create Al-zoned and forming cavity by selective desiliconization. Furthermore, we doped the synthesized hollow zeolite SSZ-13 with copper, and the hollow Cu-SSZ-13 zeolite exhibits an enhanced catalytic activity of selective catalytic reduction (SCR) of NO x with NH 3 compared with the traditional solid Cu-SSZ-13. Image 1 • Hollow SSZ-13 zeolites are synthesized by one-pot method. • Synthetic process involves creating Al-zoned and selective desiliconization. • The Al-zoned is created by adjusting the spatial distribution of Al elements in the crystal. • NH 3 -SCR activity of hollow Cu-SSZ-13 is better than conventional solid Cu-SSZ-13. [ABSTRACT FROM AUTHOR]