HCl Leaching Research Articles

Photocatalysts market is estimated to cross the $6 bn mark by 2029

It is important to understand low-temperature oxidation to inhibit the spontaneous combustion of lignite for its safe transportation and efficient utilization. The study investigates the effect of temperature on microstructure and mass change during low-temperature oxidation of Shengli lignite (SL) and further explores the promoting effect of iron species. In this work, inherent minerals of Shengli lignite were first demineralized by HCl leaching (SL+), Fe3+ were then loaded by impregnation method (SL+-Fe), and low-temperature (200–300 °C) oxidation was carried out in laboratory-scale fixed bed reactor. The structures of low-temperature oxidation treated coal samples were characterized by SEM-EDS, FT-IR, XPS, XRD and Raman spectroscopy. The low-temperature oxidation experiment results showed that coal displayed noticeable jump in mass change at particular oxidation temperatures (called jump temperature). The jump temperature of SL+-Fe was approximately 20 °C lower than that of SL+. The FT-IR analysis indicated presence of analogous quinone structure that was originating from SL+-Fe after low-temperature oxidation at 200–210 °C, which was approximately 20–30 °C lower than that of SL+. XRD and XPS results revealed that iron species changed from highly dispersed or unknown chemical state to α-Fe2O3 before and after jump temperature. It is deduced that the jump phenomenon of coal samples maybe attributed to the oxidation decomposition of analogous quinone structure, and highly dispersed iron species caused shifts in jump temperature of SL+-Fe to lower values.

Microstructural characteristics of Shengli lignite during low-temperature oxidation and promotion effect of iron species

It is important to understand low-temperature oxidation to inhibit the spontaneous combustion of lignite for its safe transportation and efficient utilization. The study investigates the effect of temperature on microstructure and mass change during low-temperature oxidation of Shengli lignite (SL) and further explores the promoting effect of iron species. In this work, inherent minerals of Shengli lignite were first demineralized by HCl leaching (SL+), Fe3+ were then loaded by impregnation method (SL+-Fe), and low-temperature (200–300 °C) oxidation was carried out in laboratory-scale fixed bed reactor. The structures of low-temperature oxidation treated coal samples were characterized by SEM-EDS, FT-IR, XPS, XRD and Raman spectroscopy. The low-temperature oxidation experiment results showed that coal displayed noticeable jump in mass change at particular oxidation temperatures (called jump temperature). The jump temperature of SL+-Fe was approximately 20 °C lower than that of SL+. The FT-IR analysis indicated presence of analogous quinone structure that was originating from SL+-Fe after low-temperature oxidation at 200–210 °C, which was approximately 20–30 °C lower than that of SL+. XRD and XPS results revealed that iron species changed from highly dispersed or unknown chemical state to α-Fe2O3 before and after jump temperature. It is deduced that the jump phenomenon of coal samples maybe attributed to the oxidation decomposition of analogous quinone structure, and highly dispersed iron species caused shifts in jump temperature of SL+-Fe to lower values.

Determination of the Carbon Dioxide Sequestration Potential of a Nickel Mine Mixed Dump through Leaching Tests

Carbon dioxide sequestration via mineralization is one of the methods that has the capability to efficiently store carbon dioxide in a stable form. A mixed dump sample collected from a nickel laterite mine in Southern Philippines was tested for its carbon dioxide sequestration potential through HCl leaching tests, employing the Face-Centered Cube (FCC) experimental design for Response Surface Methodology (RSM). Mineralogical analysis performed through X-ray diffraction (XRD) analysis suggests the presence of three minerals, namely goethite, khademite and lizardite; additional X-ray fluorescence (XRF) and inductively-coupled plasma optical emission spectroscopy (ICP-OES) results, however, established goethite as the main component due to the dominance of iron in the sample. Morphological analyses performed through a scanning electron microscope (SEM) and the Brunauer–Emmett–Teller (BET) method suggest high accessible surface area despite considerable variability in sample composition. Leaching tests further confirmed the high reactivity of the mixed dump as high extraction rates were obtained for iron, with the maximum iron extraction efficiency of 95.37% reported at 100 °C, 2.5 M, and 2.5 h. The carbon dioxide sequestration potential of the mixed dump was reported as the amount of CO2 that can be sequestered per amount of sample, which was calculated to be 327.2 mg CO2/g sample using the maximum iron extraction obtained experimentally.

High-temperature stability of Mg(Al,Cr)2O4 spinel co-existing with calcium aluminates in air

Abstract Cr2O3 is a well-known corrosion resistant oxide used in refractory applications. However, it can oxidize into toxic and water-soluble Cr(VI) compounds upon reaction with calcium aluminate cement phases in the presence of oxygen, which subsequently causes disposal problems after use. This study describes the extent to which chromium in the spinel Mg(Al,Cr)2O4 phase can be oxidized to Cr(VI) when it reacts with the calcium aluminate cement phases C12A7, CA, CA2 and free CaO at 1300 °C in air, using XRD, XPS and leaching tests (TRGS 613 standard) as analytical tools. On reaction with CaO, the Mg(Al,CrIII)2O4 spinel mainly transformed into hauyne (Ca4Al6CrVIO16) and Ca5Cr3O12 which contains both Cr(IV) and Cr(VI). The reaction of C12A7 and CA with the spinel phase also resulted in the formation of Ca4Al6CrO16. Conversely, the reaction of Mg(Al,CrIII)2O4 spinel with CA2 resulted in the formation of only a trace amount of Cr(VI). Water-soluble Cr(VI) leached in large quantities (>100 mg/L) from samples where the Mg(Al,CrIII)2O4 reacted with either C12A7 or CA. Almost no Cr(VI) leached from the sample when Mg(Al,CrIII)2O4 reacted with CaO, using the standard TRGS 613 leach test, but a significant amount of Cr(VI) was released into solution when leached with a HCl solution for 12 h. Both Cr(IV) and Cr(VI) present in the Ca5Cr3O12 dissolved into acidic solution. Only a small amount of Cr(VI) leached from the sample that resulted when spinel was reacted with CA2, even after a prolonged HCl leach. Cr(III) in spinel Mg(Al,Cr)2O4 is very stable and does not leach in either distilled water or acidic solution.

A Process for the Separation of Noble Metals from HCl Liquor Containing Gold(III), Palladium(II), Platinum(IV), Rhodium(III), and Iridium(IV) by Solvent Extraction

The demand for noble metals is increasing, owing to their excellent chemical and physical properties. In order to meet the demand, the recovery of noble metals with high purity from diverse secondary resources, which contain small amounts of noble metals, is of immense value. In this work, the possibility of the separation of Au(III), Pd(II), Pt(IV), Rh(III), and Ir(IV) by solvent extraction from a synthetic HCl solution is investigated. Only Au(III) was selectively extracted by Cyanex 272 in the HCl concentration range from 0.5 M to 9 M, leaving the other metal ions in the raffinate. The loaded Au(III) in Cyanex 272 was efficiently stripped by (NH2)2CS. The other four noble metals were sequentially separated on the basis of the procedures reported in the previous work. The mass balance showed that about 98% of each metal, except Pt(IV), was recovered by the proposed process. An efficient process for the recovery of the five noble metal ions from the HCl leaching solution of secondary resources containing these metals can be developed.

The influencing factor study on the extraction of gallium from red mud

The extraction of Al from Inner Mongolia (China) fly ash by HCl leaching produced a kind of solid waste called red mud (CRM). This red mud contained a great deal of gallium (Ga2O3, 0.305 wt%) and thus it was a very valuable Ga resource. In this work, an easy hydrothermal alkaline leaching method was developed to extract Ga from CRM. This method mainly solved the separation of Ga and Fe, because they existed in CRM in the form of Ga(OH)3 and Fe(OH)3, and the Fe(OH)3 in CRM had a strong coating effect on Ga(OH)3. In this method, Fe(OH)3 was converted to Fe2O3 in hydrothermal environment with small specific surface area, which weakened the coating for Ga(OH)3 and accelerated the leaching reaction between Ga(OH)3 and NaOH. The influencing factors on the leaching rate of Ga were discussed and the optimal Ga leaching conditions were determined as NaOH concentration of 20 wt%, leaching temperature of 120 °C, leaching time of 12 h, filling degree of 50%, reactor rotating state, and liquid-to-solid ratio of 5 mL/g. The leaching rate of 91.4% was obtained for Ga from CRM at the optimal conditions and the Ga2O3 concentration in leaching solution reached 73.44 mg/L. Fe was not detected in leaching solution using hydrothermal alkaline leaching method and the main component of the leaching residue was α-Fe2O3 with small (average size 3.62 μm) and uniform particle size.

Clinoptilolite foams prepared by alkali activation of natural zeolite and their post-synthesis modifications

Abstract Alkaline activated aluminosilicate materials have been studied mainly in the building industry as a substitute for concretes, ceramic materials and thermal insulations, but their properties predispose them to much greater use in the chemical industry. The aim of this study is to determine whether the alkaline activated natural zeolites can be modified to obtain a suitable chemical and textural properties for catalyst supports or sorbents. The alkaline activated natural zeolites with the clinoptilolite structure were foamed using Al powder and H2O2 solution. The prepared foam pellets were post-synthetically modified by HCl leaching and analyzed to compare their properties by XRF, XRD, N2 physisorption, Hg porosimetry, DRIFT, TGA, SEM and the cutting-edge strength methods. The analysis showed that the clinoptilolite structure of the basic raw zeolite was partially preserved and porous materials had sufficient strength, a density of about 0.8 g/cm3 and a specific surface area up to 160 m2/g making them suitable as catalyst supports or sorbents.

Hydrotalcite and hydrocalumite as resources from waste materials of concrete aggregate and Al-dross by microwave-hydrothermal process

Hydrotalcite (HT) and hydrocalumite (HC) were synthesized from active MgO, CaO and Al2O3 in the presence of K2CO3 using microwave-hydrothermal (M−H) process at 100 °C/1 h. The above active oxides were prepared via HCl leaching of dolomite (fine waste of concrete aggregate) and Al-dross waste, precipitated as hydroxides and then activated by calcination. The prepared materials were characterized via XRD, FTIR and TEM. Results showed that chemical recycling of Al-dross and dolomite wastes produced aluminum, magnesium and calcium hydroxides from which their active oxides produced at 600, 900 and 1000 °C, respectively. The M−H treatment of MgO/Al2O3 (4:1) slurry of the active oxides for 1 h at 100 °C resulted in Mg2Al(OH)7 in amorphous plate-like shape while the CaO/Al2O3 (4:1) slurry under the same conditions provided semi-crystalline multi-phases. These phases were identified through X-ray diffraction (XRD) analysis as Katoite [Ca3Al2(OH)12] and calcium aluminum hydroxides [Ca2Al(OH)7·3H2O]. In the presence of K2CO3, MgO/Al2O3 and CaO/Al2O3 slurries produced nano-sized crystalline hydrotalcite or hydrocalumite as deduced from XRD, FTIR and TEM results.

Decomposition process of bastnaesite concentrate in NaOH[sbnd]CaO[sbnd]H2O system

A novel process of calcification-leaching for bastnaesite concentrate (REFCO3) was proposed. The prior calcification was carried out in the system of NaOHCaOH2O and the lgC-pH pattern for CeFCaCH2O system was drawn. The thermodynamics result indicates that decomposition for bastnaesite requires certain alkaline condition, but excessive alkalinity also causes decomposition of CaF2. XRD and SEM-EDS analyses on the calcification-leaching process reveal that bastnaesite first decomposes into RE (OH)3 and CaF2. Then, by HCl leaching rare earths were extracted, while CaF2 was left in the leaching residue. In addition, effects of temperature, time, NaOH and CaO on the calcification were investigated. The results show that the leaching rate of rare earths (REs) reaches 72.5 wt%, at the same time 99.2 wt% of F is left in leaching residue with 20 wt% NaOH and 38 wt% CaO at 493 K for 180 min.

Kinetic mechanism of aluminum removal from diamond wire saw powder in HCl solution.

Impurity removal is essential for the recovery and regeneration of silicon resources from diamond wire saw powder by metallurgical purification technologies. In this paper, the aluminum was removed from the diamond wire saw powder via a direct HCl leaching method. In order to analyze the removal efficiency of various experimental conditions, certain parameters such as HCl concentration, leaching temperature, reaction time and liquid-solid ratio were also investigated. Particularly, the removal efficiency of Al reached 95.6% under the optimal leaching condition, such as the HCl concentration of 4 mol·L-1, the leaching temperature of 60 °C, the reaction time of 3 h, and the liquid-solid ratio of 10. The shrinking core model and homogeneous model were then respectively utilized to describe the leaching kinetics of the Al removal leaching process. The results indicated that the homogeneous model was more suitable than the shrinking core model. Moreover, the kinetics parameters regarding the reaction orders m=3, n=2.81, the activation energy Ea=97.30kJmol-1, the frequency factor A=1.11×1014 min-1. Furthermore, the leaching mechanism of Al removal was revealed based on kinetic analysis and materials characterization. This work is of great practical value in terms of regenerating silicon resources from the diamond wire saw powder waste materials with efficient and low cost methods.

Rare earth elements and yttrium in coal ash from the Luzhou power plant in Sichuan, Southwest China: Concentration, characterization and optimized extraction

Coal ash is considered as a promising alternative resource for rare earth elements and yttrium (REE + Y or REY) recovery. Coal ash samples (fly ash and bottom ash), as well as corresponding feed coals, collected from the Luzhou coal-fired power plant in Sichuan, southwestern China were analyzed for their chemical and mineralogical characteristics. The fly ash was further tested for its feasibility of REE extraction. The feed coals are characterized as a low-volatile bituminous, medium‑sulfur, and high-ash coal, sourced from the Guxu coalfield (Late Permian Longtan Formation) in Sichuan, SW China. REE and Y, along with high-field-strength elements Zr(Hf) and Nb(Ta), and Li, F, Sc, V, Cr, Co, Cu, Zn, Ga, Ge, Se, Sr, Cd, In, Sn, Hg, Th, U, are all enriched in the feed coal. The mineralogical compositions of the feed coals are dominated by kaolinite and illite/smectite (I/S) mixed layers, followed by the carbonate minerals including calcite, siderite, ankerite, and minor amounts of anatase and jarosite.The combustion of the feed coals produces a Class F fly ash, characterized by an aluminosilicate composition with a low CaO content. The bottom ash is compositionally similar to the fly ash, except that it is more enriched in high-density elements (Fe and Mn), and more depleted in volatile elements. REY are enriched in both the fly ash and bottom ash, although heavy REY (HREY) are notably more enriched in the fly ash. Mineralogical analysis shows that the fly ash consists of >70% amorphous glass and <30% mineral phases such as mullite, quartz and iron oxides. The bottom ash is composed of ~60% amorphous glass but with a more complex mineralogical composition than the fly ash. Dissolution of the fly ash and bottom ash with 4% hydrofluoric acid (HF) showed that ~90% of all the REY are associated with the amorphous glass in the fly ash, whereas <50% of REY in the bottom ash is contained in the glassy component. An alkaline-acid-combined (NaOH-HCl) sequential leaching process was employed to test the extractability of REY in the Luzhou fly ash. The experimental variables, including extractant concentration, liquid-to-solid ratio, leaching temperature and leaching time, were optimized by an orthogonal array design. The optimal NaOH leaching conditions results in 41.10% of active silica removal from the fly ash and 39.43% of REY enrichment. The HCl leaching of desilicated fly ash achieves 88.15% of REY extraction efficiency under the optimal conditions, which is a dramatic increase as compared to the same leaching of raw fly ash. Even though the extraction efficiency may vary between different coal ashes from various sources, a complete REY extraction procedure from fly ash is suggested for future use.

Mechanochemical synthesis and consolidation of nanostructured cerium hexaboride

This study reports on the mechanochemical synthesis (MCS) and consolidation of nanostructured CeB6 powders of high purity. CeB6 powders were prepared via MCS by milling CeO2, B2O3 and Mg powders in a high-energy ball mill for different milling times. The effects of milling time on the formation, microstructure and thermal behaviour of the synthesized powders were investigated and the optimum MCS duration was determined. Purified powders were obtained after HCl leaching by removing MgO by-product. The prepared powders were characterized by a number of techniques including X-ray diffraction, stereomicroscopy, scanning and transmission electron microscopy coupled with energy dispersive spectrometry, differential scanning calorimetry, atomic absorption spectrometry, particle size analysis, surface area analysis and vibrating sample magnetometry. The high-purity CeB6 powders having an average particle size of 86 nm were consolidated by cold-pressing followed by pressureless sintering at 1700 ?C for 5 h. The bulk CeB6 specimen was investigated for its microstructure, density, electrical resistivity, surface roughness and some mechanical properties (microhardness and wear behaviour). The relative density, electrical resistivity, microhardness and wear rate of the bulk CeB6 were determined as 95.2%TD, 57.50 ?W?cm, 11.65GPa and 1.46 ? 10?4 mm3/N?m, respectively.

High-precision measurement of B isotopes on low-boron oceanic volcanic rock samples via MC-ICPMS: Evaluating acid leaching effects on boron isotope compositions, and B isotopic variability in depleted oceanic basalts

Recent analytical advances have made the high precision (2SD, ±≤1‰) determination of boron (B) isotopic ratios in silicate rocks a possibility, but few such data are as yet available, especially for low B (<2 ppm) samples like oceanic basalts, where issues related to cryptic seawater alteration are a concern. This study carefully assesses the reproducibility of B isotope measurement via MC-ICPMS on silicate rocks. Based on repeated measurements of the standard reference materials B-5, B-6, JB-2, JR-2, AGV-2 and JB-3 and nature samples, the external reproducibility of MC-ICPMS measurements on the same solution is generally between 0.1‰ and 0.5‰ (2SD), a similar level of accuracy to that obtained based on long-term measurement of solution standard NIST SRM 951 of 0.4‰ (2SD). For different digestions, the average external reproducibility is 0.6‰ (2SD), which represents the whole procedure reproducibility, including chemical treatment. We have tested an acid leaching experimental procedure for its effects on the B isotope compositions of ~50 Ma boninites collected from a deep ocean setting. Fresh and moderately altered boninite samples were subjected to cold HCl leaching treatments for 1, 3, 5, 7 and 9 h, using 2 N and 6 N HCl, respectively. δ11B values for the fresh sample remained unchanged within error after leaching, suggesting that leaching did not lead to any B isotopic fractionation. δ11B values for different aliquots of an altered boninite sample show lower and uniform δ11B values after 1 h of 6 N HCl leaching, while aliquots leached in 2 N HCl show similar δ11B to the unleached altered sample. These results suggest that changes in B isotopes caused by at least moderate degrees of alteration, and/or adsorption effects in volcanic rocks preserved on the ocean floor can be effectively eliminated through short-duration 6 N HCl leaches before digestion and analysis. B isotope measurements on three documentably fresh, low-B N-type mid-ocean ridge basalt (MORB) glass samples from the Southwest Indian Ridge yield δ11B values from −6.62‰ to −7.39‰, within the range of the recommended global MORB value of ≈−7.1 ± 0.9‰, determined via SIMS methodologies (2SD at ±1.5‰; Marschall and Monteleone, 2015), and the range of four fresh glass samples from the Eastern Pacific Ridge of −7.3 ± 0.8‰, measured by in-situ laser-ablation ICP-MS (2SD at ±0.7–1.0‰; Le Roux et al., 2004).

An electrochemical immunobiosensor for ultrasensitive detection of Escherichia coli O157:H7 using CdS quantum dots-encapsulated metal-organic frameworks as signal-amplifying tags

We report here cadmium sulfide quantum dots (CdS QDs)-encapsulated metal-organic frameworks as signal-amplifying tags for ultrasensitive electrochemical detection of Escherichia coli O157:H7 (E. coli O157:H7). CdS QDs were encapsulated in zeolitic imidazolate framework-8 (ZIF-8) to form CdS@ZIF-8 muti-core-shell particles by in situ growth of ZIF-8 in the presence of CdS QDs. To specifically recognize E. coli O157:H7 cells, CdS@ZIF-8 particles were coated with polyethyleneimine to introduce amino groups on their surfaces, followed by surface modification of anti-E. coli O157:H7 antibody. A sandwich-type electrochemical immunobiosensor for the detection of E. coli O157:H7 was fabricated using CdS@ZIF-8 particles as signal tags. Cd(II) ions were released from CdS@ZIF-8 tags by HCl leaching, enabling the detection of E. coli O157:H7 by differential pulse voltammetry. Under the optimized conditions, the linear range of the biosensor is from 10 to 108 colony forming units (CFU) per mL for E. coli O157:H7 detection, with the detection limit of 3 CFU mL−1 (S/N = 3). The sensitivity of the biosensor for E. coli O157:H7 detection using CdS@ZIF-8 particles as signal tags is 16 times that of a biosensor using CdS QDs as signal tags, because the number of CdS QDs labeled to each bacterial cell increases greatly resulting from a great number of CdS QDs encapsulated in each CdS@ZIF-8 label. This method was successfully used to detect E. coli O157:H7 in milk samples.

Growth control and enrichment of Si crystals from Si-Sn melt by directional solidification

The growth control and enrichment of Si crystals using Si-50 at.% Sn melts via upwards and downwards directional solidification at various moving rates was investigated. As expected, a large area of quasi-bulk Si (98.6% enrichment percentage) was successfully obtained at the 0.01 mm/min upwards moving rate. Moreover, after HCl leaching, the residual at.% of Sn in the enriched Si area was easily reduced to the 0.00132–0.00163 range, which was almost the same as that for the solid solubility of Sn in Si. Furthermore, a model was established to explain the crystal growth process and enrichment mechanism during directional solidification. In conclusion, we chose the upwards moving direction for the follow-up experiments, which solved the most critical first step of using Si-based alloy solvent refining to produce solar grade Si.

Recovery of Gallium from Corundum Flue Dust by Two-Stage Alkali Leaching, Carbonation, Acid Leaching and Solvent Extraction Process

Flue dust generated during the process of manufacturing corundum is a carrier of critical metal gallium. In this study, a process of alkali leaching-carbonation-acid leaching-solvent extraction was developed to recover and enrich gallium from corundum flue dust. Over 93% of the gallium in corundum flue dust could be recovered through a two-stage alkali leaching process, which consists of 120 min of concentrated alkali leaching in NaOH solution and a subsequent 30-min dilute alkali leaching (after dilution), with an alkali-to-ore mass ratio of 1.2:1. Liquid to solid ratios in two alkali leaching stages were 1.5:1 and 8:1, respectively. The carbonation process was employed to remove high-level Si in alkali leachate. After carbonation and HCl leaching, over 96% of gallium in the NaOH leachate could be dissolved into acid solution. After extracting gallium from the HCl leachate using N235 as extracting agent, 1% NaOH solution was used to strip gallium from the organic phase. The extraction and stripping efficiency of gallium was over 99% and 97%, respectively.

Synthesis of LaB6–Al2O3 nanocomposite powders via ball milling-assisted annealing

In this study, LaB6–Al2O3 nanocomposite powders were synthesized via ball milling-assisted annealing process starting from La2O3–B2O3–Al powder blends. High-energy ball milling was conducted at various durations (0, 3, 6 and 9 h). Then, the milled powders were annealed at 1200 °C for 3 h under Ar atmosphere in order to obtain LaB6 and Al2O3 phases as reaction products. X-ray diffractometry (XRD), scanning electron microscopy/energy-dispersive spectrometry (SEM/EDS) and transmission electron microscopy (TEM) techniques were utilized to carry out microstructural characterization of the powders. No reaction between the reactants was observed in the XRD patterns of the milled powders, indicating that high-energy ball milling did not trigger any chemical reactions even after milling for 9 h. LaAlO3 and LaBO3 phases existed in the annealed powders which were milled for 0, 3 and 6 h. LaBO3 phase was removed after HCl leaching. 9-h milled and annealed powders did not exhibit any undesired phases such as LaAlO3 and LaBO3 after leaching step, and pure nanocrystalline LaB6–Al2O3 composite powders were successfully obtained. TEM analyses revealed that very fine LaB6 particles (~ 100 nm) were embedded in coarse Al2O3 (~ 500 nm) particles.

Mechanochemically synthesized Fe2B nanoparticles embedded in SiO2 nanospheres

This study reports on the preparation of diiron boride (Fe2B) powders via mechanochemical synthesis (MCS) followed by a purification step and on the embedment of pure Fe2B nanoparticles into silica (SiO2) nanospheres. Fe2O3, B2O3 and Mg powders used as starting materials were blended in stoichiometric amounts and mechanochemically synthesized up to 7 h in a high-energy ball mill. As-synthesized powders were purified from the undesired Mg-based by-products by HCl leaching. After that, pure Fe2B nanoparticles with sizes of smaller than 40 nm were embedded in SiO2 nanospheres using a tetraethyl orthosilicate (TEOS) and ammonia (NH3) containing solution. Characterization investigations of the as-synthesized, leached and SiO2-embedded powders were carried out using X-ray diffractometer (XRD), scanning electron microscope/energy dispersive spectrometer (SEM/EDS), particle size analyzer (PSA), transmission electron microscope (TEM), Fourier transform infrared spectrometer (FTIR) and vibrating sample magnetometer (VSM). The average particle size of the Fe2B incorporated SiO2 nanospheres was measured as about 330 nm. Magnetic measurements revealed that pure Fe2B powders and their SiO2-embedded samples had soft ferromagnetic behaviour with coercivity of 125 and 168 Oe, respectively.

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.

Lithium Recovery by Precipitation from Impure Solutions – Lithium Ion Battery Waste

AbstractHydrochloric acid (HCl) leaching solutions were investigated with the aim of recovering the lithium present in industrial battery waste. The lithium‐rich solution after HCl leaching of battery waste contains major impurities such as iron, nickel, cobalt, manganese, aluminum, and copper. This composition was used as a model system to prepare a synthetic solution for lithium recovery by precipitation. The precipitation results indicated that the feeding rate of carbonate and stirring rate had an effect on particle size distribution. Uniform particles were obtained with a semi‐batch process. A faster carbonate feeding rate can result in a smaller particle size due to the high supersaturation degree and chemical reaction rates.