Hydrofluoric Acid Research Articles

Comparison of Microleakage of Monolithic Zirconia after Surface Treatment and Thermal Cycles Using Data Analysis Software

Objective: The aim of this study was to investigate the microleakage of monolithic zirconia after different surface treatments using computer software. Materials and Methods: Three different monolithic zirconia ML (Multilayered), STML (Super Translucent Multilayered), UTML (Ultra Translucent Multilayered) were prepared as discs with a diameter of 15 mm and a thickness of 1.2 mm. Four different surface treatments (Hydrofluoric acid, Tribochemical silica coating, Hydrofluoric acid application + Tribochemical silica coating, Milling + Tribochemical silica coating + Hydrofluoric acid application) were applied to the prepared samples according to their groups (n=8). Samples, Group C: Control group, Group HF: Hydrofluoric acid application, Group T: Tribochemical silica coating, Group HF+T: Hydrofluoric acid application + Tribochemical silica coating, Group F+HF+T: Milling + Tribochemical silica coating + Hydrofluoric acid application, then adhesive system was applied to all specimens and repaired with resin cement. The specimens were thermocycled for one year aging and then immersed in basic fuchsin solution to evaluate microleakage. The specimens were separated with a micro-cut device and evaluated under a stereomicroscope. The dimensions of the images were measured in Python program and the permeability and surface treatments of the zirconia samples were compared. Statistical analysis was performed by two-way ANOVA (p<0.05). Results: UTML F+HF+T showed the lowest microleakage (12.15 ± 1.69), while ML C showed the highest microleakage (73.93 ± 1.59). Among the zirconia specimens, the highest adaptation was obtained in the UTML zirconia (37.59 ± 23.58). Conclusion: According to the data obtained, milling + tribochemical silica coating + acid application surface treatments are recommended for the repair of monolithic zirconia restorations. The sintering temperature and Yttrium Oxide (Y2O3) content of the monolithic zirconia used are effective factors in microleakage after repair.

Synergy of Artificial SEI and Electrolyte Additive for Improved Performance of Silicon Electrodes in Li-Ion Batteries.

Maintaining the electrochemically and mechanically stable solid electrolyte interphase (SEI) is of highest importance for the performance of high-capacity anode materials such as silicon (Si). Applying flexible Li-ion permeable coatings to the electrode surface using molecular layer deposition (MLD) offers a strategy to improve the properties of the SEI and greatly contributes to an increase in the cycle life and capacity retention of Si electrodes. In this study, the long-term cycling of Si electrodes with an MLD alucone coating is investigated in the context of more stable SEI formation. When the joined strategy introducing both MLD coating and anFEC electrolyte additive was realized, high performance of Si anodes was achieved, capable of delivering more than 1500 mAh g-1 even after 400 cycles. The reason for the significantly improved longevity is the ability of the alucone layer to react with HF present in LiPF6-based electrolytes already under OCV-like conditions, fluorinating most of the available -OH groups in the alucone structure. This reaction not only partially scavenges hydrofluoric acid but also does not disturb the confining effect of alucone-like fluorinated artificial SEI. This study shows the significance of searching for synergetic solutions, such as a combination of electrode surface modification and electrolyte composition, for maximizing the capacity retention of Si as an active material or as a capacity-enhancing additive to graphite electrodes, and as well can be applied to other high-energy battery materials with large volume changes during cycling.

Faster and Safer "In situ" Synthesis of Germanane and Silicane.

Germanane (GeH) and silicane (SiH), members of the Xanes family, have garnered significant attention as 2D materials due to their diverse properties, which hold promise for applications in electronics, optoelectronics, energy storage, and sensing. Typically, highly concentrated hydrochloric acid (HCl) or hydrofluoric acid (HF) is employed in the synthesis of these Xanes, but both routes are problematic due to slow kinetics and safety concerns, respectively. Here for the first time, a faster and safer method is demonstrated for Xanes synthesis that harnesses the generation of HF "in situ" using a solution of HCl and lithium fluoride (LiF) salt, overcoming the key challenges of the conventional methods. A variety of characterization techniques to establish a baseline is utilized for both Xanes and to provide a holistic knowledge regarding this method, the possible consequences of this approach, and the possibility of applying it to other layered Zintl phases. The novel synthesis protocol results in high-quality GeH and SiH with bandgaps (Eg) of 1.75 and 2.47eV respectively, highlighting their potential suitability for integration into semiconductor applications.

Self-Etching Ceramic Primer Affects Surface Topography and Roughness of Two Zirconia-Reinforced Lithium Silicate Ceramics.

This article evaluates the etching efficacy of a self-etching ceramic primer (SECP) on zirconia-reinforced lithium silicate (ZLS) ceramics. Celtra Duo (DeguDent GmbH, Hanau-Wolfgang, Germany) and Vita Suprinity (Vita Zahnfabrik, Bad Säckingen, Germany) were used in this study. A total of 36 ceramic slices were prepared from each ceramic material and randomly distributed into three groups according to the surface treatment applied (n = 12 per group). Group 1 (polished) was polished with silicon carbide paper discs and did not undergo any surface treatment; group 2 (SECP) was surface treated with SECP (Monobond Etch and Prime, Ivoclar Vivadent, Schaan, Liechtenstein); group 3 (hydrofluoric acid [HF]) was surface treated with 4.7% HF etching. Half of the specimens (n = 6) from each group were gold-sputtered, and the surface topographic alterations were evaluated by scanning electron microscopy at magnifications of 5,000× and 10,000 × . The surface roughness of the other half (n = 6) from each group was tested using a three-dimensional optical profiler. Data were statistically analyzed using two-way analysis of variance and Tukey's multiple comparisons test. Both SECP and HF etching surface treatments resulted in a statistically significant increase (p < 0.05) in the surface roughness of both ceramic materials, compared to that of their respective control group specimens (polished). HF etching resulted in a significant dissolution of the glassy phase of each ceramic. SECP can effectively etch ZLS ceramics. The etching patterns created after the application of SECP were mild compared to those produced by HF etching. The topographic surface features of ceramics are affected by both, surface treatment and material composition.

High Sensitivity Bi2O3/Ti3C2Tx Ammonia Sensor Based on Improved Synthetic MXene Method at Room Temperature.

The MXene Ti3C2Tx was synthesized using hydrofluoric acid and an improved multilayer method in this study. Subsequently, a Bi2O3/Ti3C2Tx composite material was produced through hydrothermal synthesis. This composite boasts a unique layered structure, offering a large surface area that provides numerous contact and reaction sites, facilitating the adsorption of ammonia on its surface. The prepared Bi2O3/Ti3C2Tx-based sensor exhibits excellent sensing performance for ammonia gas, including high responsiveness, good repeatability, and rapid response-recovery time. The sensor's response to 100 ppm ammonia gas is 61%, which is 11.3 times and 1.6 times the response values of the Ti3C2Tx gas sensor and Bi2O3 gas sensor, with response/recovery times of 61 s/164 s at room temperature, respectively. Additionally, the gas sensitivity mechanism of the Bi2O3/Ti3C2Tx-based sensor was analyzed, and the gas sensing response mechanism was proposed. This study shows that the sensor can effectively enhance the accuracy and precision of ammonia detection at room temperature and has a wide range of application scenarios.

A Study on Acid Dissolution Characteristics and the Permeability Enhancement of Deep Coal Rock

In order to reveal the acidification and dissolution characteristics of deep coal rock, core acidification and dissolution experiments are carried out based on low-field nuclear magnetic resonance technology to study the dissolution characteristics of different acid types when applied to coal rock, and to quantitatively evaluate the dissolution characteristics of acid solutions when applied to different-scale pore throats and the karst corrosion characteristics of primary fractures. This will help to further understand the dissolution rate and pore volume growth rate of coal powder under the action of different acid types. Improving the seepage effect of coal seams is of great significance. The results show that 15% acetic acid has the best effect with regard to karst erosion and permeability. The pore volume growth rate is 442.49%, and the permeability increases by up to 31 times. With large pores, the rapid dissolution stage of mud acid, hydrochloric acid, and mixed acid mainly occurred in the first 36 h, and the rapid dissolution stage of acetic acid and hydrofluoric acid applied to the core mainly occurred at 36–72 h. The dissolution rate of acid solution is strongly correlated with porosity and permeability, and the higher the acetic acid concentration, the larger the permeability increase.

Pd nanoparticles on DUT-67-PZDC-derived N-doped carbon for efficient H2 generation from formic acid dehydrogenation

It is important to develop heterogeneous catalysts with high efficiency and stability to catalyze formic acid (FA, HCOOH) dehydrogenation. Herein, through pyrolysis of DUT-67-PZDC and etching in a hydrofluoric acid (HF) solution, the HF-etched N-doped carbon (HNDC) carrier was obtained. Palladium nanoparticles (Pd NPs), with an average particle size of 3.0 nm, were prepared on the HNDC support using a simple chemical co-reduction method. The optimized Pd/HNDC catalyst demonstrates excellent catalytic activity, the initial turnover frequency (TOF) value is 6001 h−1 at 50 °C with the incorporation of sodium formate (SF) as an additive, and the FA conversion and hydrogen (H2) selectivity could be up to 100%, which is comparable to the majority of MOF-derived heterogeneous catalysts published to date. Additionally, the Pd/HNDC can maintain good stability in five consecutive FA dehydrogenation runs with only a slight decrease. Such remarkable catalytic performance of Pd/HNDC is mainly ascribed to the unique structure of HNDC support with high surface area and hierarchical pore characteristic, the strong synergistic interaction between Pd NPs and the N sites on HNDC, as well as the ultrasmall size and high dispersion of Pd NPs as the catalytic active site. This work offers an efficient method for assembling highly active catalysts for FA dehydrogenation.

Evaluation of the immune response of peripheral blood mononuclear cells cultured on Ti6Al4V-ELI polished or etched surfaces.

While titanium and its alloys exhibit excellent biocompatibility and corrosion resistance, their polished surfaces can hinder fast and effective osseointegration and other biological processes, such as angiogenesis, due to their inert and hydrophobic properties. Despite being commonly used for orthopedic implants, research focuses on developing surface treatments to improve osseointegration, promoting cell adhesion and proliferation, as well as increasing protein adsorption capacity. This study explores a chemical treatment intended for titanium-based implants that enhances tissue integration without compromising the mechanical properties of the Ti6Al4V substrate. However, recognizing that inflammation contributes to nearly half of early implant failures, we assessed the impact of this treatment on T-cell viability, cytokine production, and phenotype. Ti6Al4V with extra low interstitial (ELI) content discs were treated with hydrofluoric acid followed by a controlled oxidation step in hydrogen peroxide that creates a complex surface topography with micro- and nano-texture and modifies the chemistry of the surface oxide layer. The acid etched surface contains an abundance of hydroxyl groups, crucial for promoting bone growth and apatite precipitation, while also enabling further functionalization with biomolecules. While cell viability remained high in both groups, untreated discs triggered an increase in Th2 cells and a decrease of the Th17 subset. Furthermore, peripheral blood mononuclear cells exposed to untreated discs displayed a rise in various pro-inflammatory and anti-inflammatory cytokines compared to the control and treated groups. Conversely, the treated discs showed a similar profile to the control, both in terms of immune cell subset frequencies and cytokine secretion. The dysregulation of the cytokine profile upon contact with untreated Ti6Al4V-ELI discs, namely upregulation of IL-2 could be responsible for the decrease in Th17 frequency, and thus might contribute to implant-associated bacterial infection. Interestingly, the chemical treatment restores the immune response to levels comparable to the control condition, suggesting the treatment's potential to mitigate inflammation by enhancing biocompatibility.

High activity of cobalt-atomically dispersed catalyst on mesoporous carbon for rechargeable Zn-air batteries via effective removal of the hard template

The use of oxygen from air in Zn-air batteries requires the smart design of materials with bifunctional activity for oxygen reduction and evolution reactions (ORR/OER), and with a porous structure to facilitate the diffusion of oxygen gas to active sites. Kit-6 template-assisted porous structures have been proposed to this end; however, traditional methods for the removal of Kit-6 templates are highly aggressive and environmentally harmful. In this study, we present the synthesis of a cobalt atomically dispersed catalyst (Co-ADC) with interlayer engineering using mesoporous Kit−6 templates, focusing on two removal strategies: sodium hydroxide (0.5, 1, and 2 M) and hydrofluoric acid (15, 30, and 45 %). Physicochemical results indicated that Co-ADC-containing nanoparticles were obtained using the proposed methodology, while the use of HF promoted the loss of cobalt in the catalyst. During the activity evaluation for the ORR, and it was found that 0.5 M NaOH and HF at 15 % displayed similar activity, which could be related to the effect of carbon material as co-catalyst, but the first enabled a close 4e− pathway, and thus, the Co-ADC presented a ΔEOER-ORR of 640 mV. This optimized ADC displayed improved functionality owing to diffusion improvements by the mesoporous structure, presenting a maximum power density of 130.6 mW cm−2 and 30 % higher specific activity than the Pt + IrO2/C reference material. Rechargeability was evaluated, yielding a ΔV = 0.87 V at 5.175 mA cm−2 with a round-trip efficiency of 57.5 %. Nonetheless, the optimized material presented higher rechargeability, displaying no significant round-trip changes after 100 cycles, while Pt + IrO2/C presented changes due to OER issues after only 48 cycles.

Electrolysis destroyed the O-containing bonds of muscovite for the purification of natural flake graphite and its applications

The muscovite is arranged in parallel and tightly combined with the natural graphite layer, which forms a stable structure and impedes the diffusion of hydrofluoric acid in graphite. It requires large quantities of hydrofluoric acid and long diffusion time for effective purification of natural graphite, which leads to increased production costs and significant environmental impact. Therefore, it is necessary to reduce the amount of hydrofluoric acid used and improve purification efficiency. In this work, electrolysis was used to enhance acid leaching purification process and destroy the structure of muscovite to reduce the amount of hydrofluoric acid used. After hydrochloric acid leaching and heat treatment, the purity of natural flake graphite was increased from 95.27 % to 96.60 %, and the remaining impurities were mainly muscovite and quartz. Through electrolysis, the interlayer spacing of muscovite was increased, and the C-O bond between graphite and muscovite was destroyed, making it easier for hydrofluoric acid to enter and react with the muscovite layers. Compared with acid leaching, 99.9 % high-purity graphite was obtained by electrolysis, and the ratio of 40 wt% hydrofluoric acid to natural graphite was decreased from 1.0 mL/g to 0.7 mL/g, reducing the amount of hydrofluoric acid used by 30 %.

A robust polymetallic-coated sheathless interface with high acid and alkali resistance for coupling capillary electrophoresis with mass spectrometry

A robust interface for coupling capillary electrophoresis (CE) to mass spectrometry (MS) was critical to maintain high separation efficiency of CE while achieving high sensitivity of MS. Current interfaces often suffer from problems such as reproducibility and ruggedness. For this purpose, a new polymetallic-coated sheathless interface was developed for the coupling of CE with MS. The electrical contact of the interface was achieved by etching one end of the fused silica capillary into a tapered tip using hydrofluoric acid (HF) solution, and then depositing a thin layer of chromium followed by a layer of platinum on it via physical vapor deposition technique. The performance of the new sheathless interface was systematically evaluated for the effect of flow rate and electrospray ionization (ESI) voltage on MS signal intensity, as well as the sample loading volume on CE separation efficiency and repeatability by using peptide standards and tryptic digest of bovine serum albumin (BSA). The interface was capable of generating stable electrospray even at ultra-low flow rate of 12.2 nL/min. In addition, the acid and alkali resistance of the polymetallic- coated emitter was tested by immersing it into 1M HCL and 1M NaOH solution, respectively. The results showed that polymetallic coating was still intact even after continuous immersion in the alkaline solution for 8 days (192 h) and a longer period in the acidic solution, indicating its excellent chemical stability. All the experimental results indicated that the sheathless interface fabricated by the new method in this study was robust and stable, making it promising for both sensitive and robust CE-MS sample analysis.

Influence of dealloying on wetting behavior and adhesion properties of Cu-Zr-Al-Ag glassy ribbons

Abstract This research aims to clarify the correlation between dealloying conditions, surface chemistry, and wettability behavior in Cu-based metallic glassy ribbons. Investigating the influence of dealloying on the wettability of Cubased glassy ribbons is the focus of this study. Glassy ribbons composed of the Cu-Zr-Al(-Ag) alloy family were dealloyed in hydrofluoric acid (HF) solution, with molarities ranging from 0.01 M to 0.5 M for durations between 2 and 10 minutes, followed by a thorough cleaning in distilled water. The impact of dealloying parameters on water droplet adhesion was evaluated together with the droplets’ ability to resist detachment after mechanical disturbances. Such insights are pivotal for the development of novel superhydrophobic or superhydrophilic materials, which could find applications in diverse fields such as microfluidics and oil-water separation technologies. The research demonstrates the substantial effects of dealloying on Cu-Zr-Al(-Ag) glassy ribbons, showing significant alterations in surface morphology, elemental composition, and wettability, all influenced by dealloying conditions

Highly enhanced fluoride removal from aqueous systems via solvent extraction utilizing trialkyl phosphine oxide as an efficient extractant

Solvent extraction (SX) has been recognized as an efficient approach for the large-scale removal of impurities, demonstrating considerable potential for fluoride extraction in industrial applications. However, existing fluoride extraction methods typically require the incorporation of additives to form complexes with fluoride for its removal. Due to the excessive additive requirements for efficient fluoride removal, these methods inevitably result in secondary contamination of feed solution, necessitating additional purification efforts to remove them. In this study, four extractants (trioctyl amine, tributyl phosphate, trioctyl phosphate, and trialkyl phosphine oxide (TRPO)) were investigated for fluoride removal via hydrogen bonding with hydrofluoric acid (HF). Various parameters, including the concentrations of extractants and stripping agents, pH values, extraction time, and temperature were initially optimized. It was found that TRPO exhibits the highest extraction efficiency for HF, with a single-stage extraction rate exceeding 70 %. Complete fluoride removal (> 99.9 %) was achieved through a consecutive four-stage extraction process. Further experiments, including maximum loading and slope analysis, combined with FT-IR and 19F NMR characterization, and DFT calculations elucidate the mechanism of the extraction. The transfer of HF into the organic phase is accomplished by the formation of a 1:1 hydrogen-bonded complex with TRPO. The loaded fluoride in the organic phase can be easily stripped by a base to get a fluoride salt. This study paves the way for the construction of novel SX systems to remove fluoride as HF.

Coal-based Si self-doped disordered porous carbon for supercapacitor electrodes

In preparing activated carbon for coal-based supercapacitors, silicon in coal usually requires removal with hydrofluoric acid, which is neither economical nor environmentally friendly. However, silicon can be used as the anode in lithium batteries due to its high theoretical capacity. So silicon was retained to study its effect on supercapacitors. By retaining silicon without hydrofluoric acid treatment and activating at lower temperature, the prepared Si-doped activated carbon achieved a high specific capacitance of 318.3F/g at 0.5 A/g in the three-electrode test system. Omitting hydrofluoric acid treatment increased the specific capacitance by 49 %. Experimental results show that this 4.92 % silicon doping, mainly CSiO3, is the main reason for the enhancement. Density functional theory (DFT) simulations confirmed that CSiO3 improves double-layer capacitance by localizing surface charge and enhancing electrolyte ion adsorption, while also boosting quantum capacitance. High activation temperatures increase coal-activator reactions but also decrease disorder of the carbon, reducing specific capacitance. Temperature experiments show that the specific capacitance increases and then decreases in the range of 600 ∼ 950 °C, and reaches a peak at 650 °C. This study presents a simple, effective method to enhance supercapacitor performance with silicon-carbon precursors and provides detailed explanation on the capacitance enhancement mechanism for the first time.

Shear Bond Strength of Five Different Repair Systems to Three Different Ceramic Materials.

The purpose of the current study was to investigate the shear bond strength of composite resin in five different ceramic repair systems for three different ceramic materials. 225 monolithic zirconia (Zr) and lithium disilicate (LDS) and cobalt chromium (CoCr) specimens with feldspathic porcelain (FP) veneer were fabricated (N=75 per material). The specimens underwent thermo-cycling and were randomly divided into five groups for the following intra-oral repair systems (n=15): 1) Clearfil Ceramic Primer Plus, Kuraray Noritake, Japan; 2) Ibond Intraoral Repair Kit, Kulzer, Germany; 3) VOCO Cimara, VOCO GmbH Germany; 4) Ivoclar Vivadent, Ceramic Repair System Kit, IvoclarVivadent, Liechtenstein; 5) Ultradent Porcelain Repair Kit, Ultradent Products Inc, USA. After surface conditioning, composite was applied using a cylindrical mold and a second round of thermocycling was performed. Each specimen was then subjected to shear load until failure. Microshear bond strength was compared using analysis of variance (one-way ANOVA, Tukey's test, a <0.05). Type of porcelain repair kit significantly affected the shear bond strength. For Zr, the repair systems from Kulzer and VOCO had significantly higher shear bond strength than the other systems (p<0.001) without significant difference between Kulzer and VOCO. For the LDS and CoCr with FP, hydrofluoric acid had the highest shear bond strength (p<0.001). For zirconia, a 10-Methacryloyloxydecyl dihydrogen phosphate (10-MDP) system should be used. The results also suggest that a cleaning bur may be beneficial. For glass-based ceramics and feldspathic porcelain, etching with hydrofluoric acid remains the product of choice.

Box-Behnken design optimization of 2D Ti3C2Tx MXene nanosheets as a microwave-absorbing catalyst for methylene blue dye degradation

The 2D MXene Ti3C2Tx was synthesized from the precursor MAX phase Ti3AlC2 by etching the Al layer using hydrofluoric acid. Different Characterization techniques were employed to investigate the properties of the synthesized Ti3C2Tx. The degradation of methylene blue (MB) dye under microwave irradiation in the presence of the prepared 2D MXene was studied. It was found that the synthesized Ti3C2Tx was an excellent microwave catalyst for MB dye degradation, and results obtained were promising. Using this approach, the dye was almost wholly degraded with a degradation efficiency of 99.85 % in only 10 min without adding any oxidant. The degradation was found to follow the pseudo-first-order kinetic model, and the rate constants obtained varied from 0.10 and reached up to 0.67 min−1. The effect of pH, initial MB concentration and catalyst dosage on the MB dye degradation rate has been studied. It was found that carrying out the reaction at pH values ranging from 2 to 10 did not obviously affect its rate. On the other hand, lower initial MB dye concentrations and higher catalyst dosages significantly increased the degradation rate. The high degradation efficiency was found to be maintained for up to five successive catalytic cycles, ensuring the high stability of the synthesized 2D MXene Ti3C2Tx as a catalyst. Optimization of parameters affecting the degradation process was studied using response surface methodology (RSM). According to the Box-Behnken design, the optimal degradation efficiency (99.92 %) could be achieved by adding 21.24 mg of 2D Ti3C2Tx MXene catalyst and using an initial MB dye concentration of 53.06 ppm (mg/L) during a reaction time of 11.93 min.

Manufacturing lithium-ion anodes from silicon recovered from end-of-life solar panels

With the rapid growth of solar energy, the recycling or re-use of used solar panels has become a key issue. Recycling high-value photovoltaic silicon from solar cells is an important step towards achieving “carbon neutrality.” In this paper, an efficient and high-value recycling strategy is employed to convert recycled silicon from discarded solar cells into lithium-ion anode materials. In this case, the recycled PV silicon is etched with hydrofluoric acid (HF) to create a porous silicon structure. This structure is designed to withstand the expansion stress of the electrodes. After surface modification with citric acid and carbon nanotubes to enhance the electrical conductivity of the recycled silicon and buffer the electrode from stress expansion during lithium storage and release, lithium difluorooxalate borate was added to pre-treat the surface of the recycled photovoltaic silicon through heat treatment. This process creates a robust and fast lithium-ion conductive interface enriched with LiF, Li2C2O4, LiBO2, and Li2B4O7. Density Functional Theory (DFT) calculations were performed to investigate the electronic structure of the synthesized materials, revealing their remarkable electronic conductivity and atomic bonding characteristics. When used as an anode for Li-ion batteries, W-pSi@C/CNTs exhibited high initial coulombic efficiency with stable cycling, demonstrating a capacity of 2040 mAh/g at 0.2 A/g for 200 cycles. In addition, this high-value recycling will help promote the development of renewable energy in an economically and environmentally sustainable manner.

Optimization of Tantalite Ore Dissolution Using Hydrofluoric-sulphuric Acid and Shrinking Core Model

Aim: This study investigates the dissolution of tantalite mineral from granitic pegmatite in Okpella, Northern Edo State, Nigeria. Study Design: Elemental and mineral composition analysis of tantalite ore sample from Okpella was carried out using X-ray fluorescence and X-ray diffraction. Response Surface Methodology (RSM) and the shrinking core model were used in designing the study while the effects of temperature, stirring speed, particle diameter, and mixed acids concentrations were investigated in the dissolution rates of the mineral. Duration of Study: 50 experimental runs were designed using RSM Central Composite Design (CCD) to optimize variables including HF concentration (1-8 M), H2SO4 concentration (0.5-3 M), temperature (32-82°C), stirring speed (0-500 rpm), and particle size (0.1-0.3 mm), with a constant contact time of 240 minutes. Methodology: Pulverized tantalite samples (0.1-0.3 mm) were reacted with varying concentrations of hydrofluoric and sulphuric acids (1-8 M and 0.5-3.0 M, respectively) for 240 minutes, with stirring speeds between 0-500 rpm and temperatures from 32 to 82°C. The mixture was stirred in a water bath with 50 ml of mixed acids solution and 2 g of ore. After the reaction, the solution was decanted, and the residual ore was washed, dried at 60 °C, and weighed. The difference between the initial and final weights indicated the amount of undissolved tantalite ore. Results: Ore characterization results revealed high concentration of tantalum (34.17%), iron (12.55%), niobium (8.38%), and titanium (6.01%), with other elements present in smaller amounts. Optimal conditions were found to be 8 M HF, 0.5 M H2SO4, 82°C, 500 rpm stirring speed, and 0.1 mm particle size, resulting in 97.28% dissolution of tantalite ore. Regression analysis demonstrated model robustness with an F-value of 16.70 and a P-value of 0.0001, indicating HF concentration and stirring speed as the most impactful factors. The model’s R² value of 0.9201 and adjusted R² of 0.8650 confirm its predictive accuracy. Analysis using the shrinking sphere model showed that film diffusion control is the primary limiting step with t/τ=0.999, while reaction control resulted in slightly lower conversion with t/τ=0.973, highlighting film diffusion as the main constraint but with high conversion efficiency. Conclusion: The findings from this investigation not only reveal the dissolution of tantalite ore through a detailed experimental approach, identifying optimal conditions -8 M HF, 0.5 M H2SO4, 82 oC, 500 rpm stirring speed and 0.1 mm particle size- that achieve a 97.28% dissolution, but they also enhance our understanding of mineral processing. These understanding are crucial for mineral dissolution up scaling technologies in industrial applications, which will potentially leads to a more efficient extraction method that could significantly reduce costs and environmental impacts in the mining sector. This research could drive advancements in sustainable resource recovery and contribute to sourcing of critical minerals.

INVESTIGATION OF RARE AND RARE-EARTH ELEMENTS LEACHING PROCESSES FROM THE WEATHERING CRUST ORES OF THE KUNDYBAY DEPOSIT

The weathering crust ore of the Kundybay deposit is a hard-enriched ore that contains such minerals as cherchite, bastnesite, kaolinite, etc., which are embedded in the matrix structure of other silicate rocks. These minerals contain rare earth (RE) and rare earth elements (REE). The multi-component structure and dense packing of minerals in the aluminosilicate matrix of the ore make it difficult to be blocking out. Determination of the optimal ore blocking method in order to extract RE and REE is an urgent task for today. The purpose of this work is to develop an effective method of leaching RE, REE and "white soot" from the weathering crust ores of the Kundybay deposit. Methods. Processing with soluble ammonium, magnesium and aluminium salts will allow estimation of the state of RE and REE in the ore. The indicator of RE and REE blocking out during leaching with sodium hydroxide is the transfer of silica into solution, due to which RE and REE form their own hydroxides, which can be subsequently transferred into solution by acid treatment. Acid leaching with sodium pyrosulfite, hydrofluoric acid and sulfuric acid will allow the RE and REE to be immediately transferred into solution. Results and Discussion. The main characteristics of the Kundybay deposit weathering crust ore were determined, such as: silica content, moisture content, base metals, RE and REE. Conclusion. The degree of extraction of RE and REE by soluble salts of ammonium, magnesium and aluminium did not exceed 2%, which indicates the existence of RE and REE in the form of their own minerals. Leaching with sodium hydroxide showed low recovery of silica, with RE and REE remaining in a difficult-torecover form. Leaching with a mixture of sodium pyrosulfite, hydrofluoric and sulfuric acids is a promising method for RE and REE recovery due to the complex effect of the components of this mixture.

Energy-efficient synthesis of Ti3C2Tx MXene for electromagnetic shielding

Traditional methods for synthesizing two-dimensional Ti3C2Tx MXenes such as hydrofluoric acid (HF) or LiF/HCl based etching can be time-consuming, complex, and often result in low yields. They generally involve multi-step processes involving >40 h of preparation time that can expose the materials to harsh conditions. In this study, we demonstrate a rapid single-step microwave (MW) synthesis method that significantly reduces production time to 90 min, achieving a 90 % yield and cutting energy consumption by 75 %. For the first time, synchrotron x-ray pair distribution function (PDF) analysis conducted on MW-synthesized MXene (MW-Ti3C2Tx) indicates greater structural fidelity in local atomic ordering, indicating high-quality which is comparable to conventionally synthesized counterparts (CO-Ti3C2Tx). This method achieves similar or greater structural quality in less time while also enhancing electromagnetic interference shielding (EMI SE) performance. A 15 μm MW-Ti3C2Tx film demonstrated an impressive EMI SE of ∼67 dB in the X-band, compared to the ∼63 dB achieved by CO-Ti3C2Tx. The enhanced EMI SE performance is attributed to the presence of fluorine terminations, which provide oxidation resistance, increased conductivity and improved absorption of EM waves. The MW-induced shocks during irradiation not only help remove O2/OH groups, preventing oxidation, but also tunes the functional groups, enhancing charge transport and effective EM wave attenuation. The MW synthesis method presents a fast, efficient, and scalable approach for producing high-quality MXene nanosheets, paving the way for advancements in EMI shielding and other applications.