Inorganic Acid Solutions Research Articles

Inorganic Acid Resistance Performances of Magnesium Phosphate Cement: A Two-Year Observation.

Magnesium phosphate cement (MPC), a cementitious material that hardens through an acid-base reaction, is theoretically expected to exhibit strong acid resistance. However, studies on the durability of MPC in acidic environments remain limited. This study aims to systematically evaluate the acid resistance of MPC in common inorganic acid solutions across various pH levels. By measuring changes in compressive strength, mass loss, apparent changes, pH changes, and the microstructure evolution of MPC under acidic conditions, the mechanisms and influencing factors of its acid resistance are revealed. The results indicate that at pH levels of 1.0 and 2.0, MPC's resistance to H2SO4 and HCl erosion is markedly superior compared to its performance against H3PO4, as evidenced by compressive strength retention, mass loss, and visible erosion. At pH levels above 2.0, MPC demonstrates robust resistance to all tested corrosive media, with compressive strength retention ranging from 68.9% to 86.9%, irrespective of the acid source. Although new corrosion products form in these acidic environments, the adverse effects of NH4/P loss from struvite, along with the redissolution of corrosion products due to their higher solubility, increase porosity and subsequently reduce the mechanical strength. Nevertheless, considering that strength retention is significantly higher than that of other cement-based materials reported in the literature, MPC still exhibits good acid resistance and is suitable for environments requiring enhanced resistance to acid corrosion.

Dissolution process and mechanism of montmorillonite in oxalic acid and sulfuric acid media at various pH levels

The dissolution of silicate minerals plays a crucial role in many natural geological processes. In order to better comprehend the reaction mechanisms and dissolution characteristics of montmorillonite in different acidic systems, the effects of interfacial reactions of montmorillonite with oxalic and sulfuric acid solutions at various pH levels on the ionic dissolution, crystal structure, and micro-morphology were studied, and the morphology of aluminum and saturation index of secondary mineral were simulated. It was shown that the dissolution amounts of Mg2+, Al3+ and Si4+ in montmorillonite structure decreased with the increase of pH value, which reflected the dependence of montmorillonite dissolution on the pH value of solution. The dissolution percentages of Mg2+, Al3+ and Si4+ after the reaction of montmorillonite with oxalic acid solution were greater than those in sulfuric acid solution, and the highest dissolution rate of Al3+, indicated that both ligands and protons attacked the surface sites of montmorillonite and accelerated the dissolution of ions. Moreover, oxalate ligands exerted specific binding effects on Al3+ ions. While reacting with oxalate and sulfate, the tetrahedral, octahedral and interlayer cations of montmorillonite exhibited the non-stoichiometric and inconsistent dissolution. The oxalate ligands have a strong complexation effect on Al3+, so that Al3+ in oxalate solution exists in the form of aluminum oxalate complex, which reduces the effective concentration of Al3+ in solution and promotes the dissolution of Al3+ in montmorillonite structure. The Mg2+ ions settled at octahedral substitution sites possessed weak stability, while those from the interlayer featured strong interlayer interchangeability, demonstrating the dissolution percentage up to 10.85 % and 8.62 % even in oxalic and sulfuric acid solutions at pH of 6.5. All secondary mineral phases in the solution were undersaturated, making the montmorillonite dissolution difficult to balance. Montmorillonite has a high cation exchange capacity, which makes it have a strong buffer capacity to exogenous acids. This study helps to explain the dissolution process of montmorillonite in inorganic and organic acid solutions at different pH value.

Green solutions for desalinated water drip irrigation systems: Organic acids outperform inorganic acids in fouling control

Desalinated saline water (DSW) has been widely applied in many fields due to global water scarcity. However, fouling formation in desalinated saline water distribution systems (DSWDS) raises serious technical concerns. The conventional approaches (e.g., inorganic acids) for DSWDS fouling control is not only ineffective sometimes but also lead to serious environmental and health risks. Accordingly, this study introduces a greener method utilizing organic acids for antifouling in DSWDS. The performances and influences of three types of inorganic acids (hydrochloric acid (HCl), phosphoric acid (H3PO4) and hydrofluoric acid (HF)) and three types of organic acids (citric acid (C6H8O7), formic acid (CH2O2) and oxalic acid (H2C2O4)) on DSWDS fouling control were investigated and compared. The obtained results indicated that in general, organic acids exhibited higher antifouling capacities than inorganic acids. Among the selected six acids, CH2O2 was the most effective, followed by H2C2O4, H3PO4, C6H8O7, HCl, and HF. In comparison with the most commonly used inorganic HCl, the fouling dry weights in the samples treated with C6H8O7, CH2O2, and H2C2O4 reduced by an average of 8.9 %, 45.3 %, and 33.2 %, respectively. Despite the higher acidity of inorganic acid solutions compared to organic acids, the latter exhibited a stronger chelating capacity for cations (e.g., Ca2+, Mg2+) in DSW, showing a lower tendency to form precipitation in their treated groups. Moreover, organic acids could increase the crystal cell volume and change the chemical bond length of chemical precipitation, resulting in lattice distortions. Furthermore, organic acids can slow down the flocculation and settling of suspended particulate matter, thereby alleviating the formation of particulate fouling. Overall, these findings suggest that the application of organic acids is a more effective and environmental-friendly approach for fouling control compared to inorganic acids, which provides qualitative and quantitative insights into developing greener antifouling protocol for DSW delivery in actual field practices.

Pervaporation performance and characterization of hydrophilic ZSM-5 zeolite membranes for high inorganic acid and inorganic salts

The hydrophilic ZSM-5 zeolite membranes are applied to separate the inorganic acid solutions and inorganic acid/inorganic salt mixtures by pervaporation, and the membrane presents good stability, dehydration and desalination performance. Influences of inorganic acid type (H2SO4, H3PO4, HNO3 and HCl), H2SO4 concentration (1–6 mol·L–1), test temperature (60–90 °C) and inorganic acid/inorganic salt type (2 M H2SO4 and sulfate, 2 M H3PO4 and phosphate) on the pervaporation performance are investigated in this work. Either for concentrating 3% (mass) H2SO4 solution or consecutive dehydrating 20% (mass) H2SO4 solution, the hydrophilic ZSM-5 zeolite membrane has a good dehydration performance and stability. Even though the H2SO4 concentration and test temperature are increased to 6 M and 90 °C, only H2O molecules could pass through the membrane and pH value of the permeation is kept neutral. Besides, the membrane has good dehydration and desalination performance for H2SO4/sulfates and H3PO4/phosphate mixtures, the rejection of natrium salt, molysite, and magnesium are almost 100 %.

Extraction of gallium from carbon concentrate - Aluminum industry waste

A complex approach to the extraction of gallium from a carbon concentrate (CC), a waste product of the aluminum industry, was considered. Ashing of CC made it possible to remove the main component - carbon and obtain ash, which is an oxide mineral-like compound, from which gallium was leached with solutions of inorganic acids and their mixtures. The maximum degree of leaching (98%) of gallium was achieved with 6 M HCl for ash after ashing the CC at 600 °C. It was shown that Purolite anion exchangers with highly basic tertiary and quaternary ammonium base groups recovered gallium(III) from 2 to 10 M HCl, where the sorption equilibrium was attained after 60 min. The maximum extraction was observed from 6 M HCl. Under optimal conditions, the maximum sorption capacities for gallium(III) were achieved for Purolite A300 (2.7 mmol g−1) and Purolite A500 (2.2 mmol g−1) sorbents. Gallium(III) was quantitatively (99%) eluted from the sorbents with distilled water. Sorption of gallium(III) and its subsequent desorption with water made it possible to separate it from the predominant amounts of transition metal ions: Fe(III), Ni(II), Co(II), Zn(II), V(V) and other cations: Al3+, Ca2+, Mg2+, Na+ and K+. The addition of sodium hydroxide to the concentration of 200 g L−1 resulted in the cementation of gallium on aluminum gallama (liquid gallium‑aluminum alloy).

ХИМИЧЕСКАЯ СТАБИЛЬНОСТЬ, СТРУКТУРА И ТОПОЛОГИЯ ПОВЕРХНОСТИ ОТЕЧЕСТВЕННОЙ КОМПЛЕКСНО СТАБИЛИЗИРОВАННОЙ ДИОКСИДЦИРКОНИЕВОЙ КЕРАМИКИ В МОДЕЛИРУЕМЫХ АГРЕССИВНЫХ СРЕДАХ

Subject of the study is the chemical stability of a complex stabilized zirconium dioxide system of 3 mol.% Y2O3 15 mol.% CeO2 in simulated aggressive media (1 and 10% NaOH; 1 and 10% HCl; 1, 10 and 40% CH3COOH.
 The goal – to study the effect of various aggressive media on the structural and chemical stability of domestic comprehensively stabilized zirconium dioxide ceramics under experimental conditions.
 Methods. The tests were carried out on experimental samples of ceramic grinders (40 pcs.) of the same area and shape: the experimental group (20 pcs.) – stabilized zirconium dioxide ceramics, the control group (20 pcs.) – zirconium dioxide ceramics without stabilizing additives. The presence, severity and features of the reaction of zirconium dioxide ceramics to aggressive media were evaluated in a comparative aspect by changing the mass of samples, the microstructure of their surface and the Raman spectra.
 Results. The interaction of complexly stabilized zirconium dioxide with alkaline solutions does not lead to a statistically significant decrease in the mass of samples, under the action of solutions of organic and inorganic acids, a statistically insignificant (p<0.5) increase in total mass is observed. Scanning electron microscopy of ceramic samples of both groups after exposure to aggressive media did not reveal ultrastructural changes in the surface. Raman spectra of light before exposure in aggressive media showed more favorable values of Raman intensity for stabilized zirconium dioxide, which indicates its better degree of crystallization. After exposure to aggressive media, changes in the crystal lattice of the control samples were determined, for stabilized zirconium dioxide, the ratio I260/I320 did not change.
 Conclusions and Relevance. Stabilized zirconium dioxide of the system 3 mol.% Y2O3 15 mol.% CeO2 has increased resistance in aggressive environments, which is of practical importance when choosing a ceramic material for the manufacture of dentures, which are exposed to aggressive biological environments of the oral cavity during the entire service life.

Microwave-sustained inductively coupled atmospheric-pressure plasma (MICAP) for the elemental analysis of complex matrix samples

Microwave induced plasma optical emission spectrometry (MIP-OES) has gained widespread attention in the last few years for trace elemental analysis. Among the new generation of MIPs it is worth to mention the microwave-sustained inductively coupled atmospheric-pressure plasma (MICAP) for which previous works have shown similar detection capabilities to those afforded by ICP-OES. Nevertheless, this instrument has not been applied yet to complex matrix sample analysis. Therefore, the goal of this work is to evaluate MICAP-OES performance (e.g., analytical figures of merit, matrix effects, etc.) for elemental analysis of samples of different nature (e.g., environmental, food and polymers). To this end, both spectral and non-spectral interferences were investigated for 19 elements (Ag, Al, As, B, Ca, Cd, Co, Cr, Cu, Fe, Ga, In, Mg, Mn, Ni, Pb, Sr, Tl, Zn) in the presence of inorganic acid, organic and saline solutions and compared to a 5 % w w−1 HNO3 solution. Unlike previous MIPs, experimental data showed that the optimum nebulizer gas flow rate for a given emission wavelength was mostly independent of matrix characteristics. Regarding matrix effects, this device was highly robust operating both inorganic acid and organic matrices. Interestingly, when operating saline matrices, changes on emission signal by easily ionizable elements were less significant than those early reported by alternative MIP cavities. Moreover, due to MICAP spectrometer design employed allows real-time simultaneous analysis, Rh, Pd, Sc and Y were suitable internal standards to minimize non-spectral interferences. Finally, MICAP-OES can be successfully applied to the elemental analysis of different complex matrix samples (i.e., CRM-DW1 Drinking water; BCR-146 Sewage sludge industrial; BCR-185 Bovine liver; BCR-278R Mussel tissue; NIST-1549 Non-fat milk powder; ERM-EC681k Polyethylene (high level) and BCR-483 Sewage sludge amended soil).

The study on distribution coefficient of polonium between tri-octylphosphine oxide (TOPO) and tri-butylphosphate (TBP) in toluene and cyclohexane and selected inorganic acids

In this work the distribution coefficients (D) of polonium between 0.1 mol dm−3 TOPO/toluene; TOPO/cyclohexane; TBP/toluene and TBP/cyclohexane and aqueous solutions of inorganic acids (HCl, HNO3, H2SO4 and H3PO4) were determinated. The molarities of inorganic acids were between 0.5 and 12.0 mol dm−3. The activity of extracted Po-209 was measured by means of liquid scintillation counting. The best result was obtained for TOPO/toluene and 2 mol dm−3 H2SO4 system (D = 62 ± 9). The most stable conditions of extraction were found for TOPO/toluene-HCl system.

Green extraction of berberine from Coscinium fenestratum (Gaertn.) Colebr. using ultrasound-assisted aqueous solutions of organic acids, polyalcohols, and deep eutectic solvents

Berberine displays many potential bioactivities and is found in several medicinal herbs, such as Coscinium fenestratum. The extraction of berberine from biomass was carried out using volatile organic solvents, inorganic acid solutions, and more recently, ionic liquids and deep eutectic solvents. In order to develop more efficient and sustainable extraction processes, this study used inexpensive green solvents, such as carboxylic acid and polyalcohol aqueous solutions, to extract berberine from Coscinium fenestratum. Initial screening was performed to compare the berberine extraction performance of various solvents, including aqueous solutions of carboxylic acids, polyalcohols, and their deep eutectic solvents. The obtained results showed that lactic acid was a potential solvent for extracting berberine. After optimizing the process using response surface methodology (RSM), the optimal ultrasound-assisted extraction conditions were determined to be a lactic acid concentration of 60 % (w/w), a liquid-to-solid ratio of 17.25 mL/g, an extraction time of 20 min, and an extraction temperature of 66 °C. This resulted in an extraction efficiency of 38.23 ± 0.69 mg/g, corresponding to a berberine concentration of 2.22 ± 0.04 mg/mL. Additionally, the use of lactic acid as the extraction solvent yielded superior extraction efficiency and berberine purity compared to conventional volatile organic solvents, and inorganic acids, bases. The recovery of berberine was achieved using macroporous resins, allowing for the recovery of 99.52 ± 0.67 % of berberine from aqueous lactic acid solutions. The lactic acid solvent and the AB-8 resin were successfully recovered and reused for a minimum of three consecutive extraction cycles, maintaining their full effectiveness throughout the entire process. The recovered berberine from the lactic acid extract exhibited stronger antibacterial activity than the extracts obtained using ethanol, methanol, and acetone, as well as berberine recovered from the limewater and sulfuric acid extracts. Furthermore, the lactic acid solvent and its extracts demonstrated no cytotoxicity toward the human embryonic kidney cell line. The findings of this investigation establish a foundation for future studies utilizing eco-friendly solvents for alkaloid extraction from medicinal plants. This lays the groundwork for implementing a large-scale extraction process of natural active compounds in a safe and environmentally conscious manner.

Recovery of Nickel and Cobalt Metal Powders from the Leaching Solution of Spent Lithium-Ion Battery by Solvent Extraction and Chemical Reduction

ABSTRACT Spent lithium-ion batteries (LIBs) contain some valuable metals. Smelting reduction of spent LIBs produces metallic alloys containing Co, Cu, Fe, Mn, and Ni. Leaching of the metallic alloys with inorganic acid solutions and subsequent separation of Cu(II), Fe(III) and Mn(II) results in a solution containing Co(II) and Ni(II). In this work, solvent extraction and chemical reduction experiments were performed to recover pure metals from this solution. Cobalt(II) was first separated from Ni(II) by solvent extraction with saponified Cyanex 272. Batch simulation experiments based on the McCabe-Thiele diagram for the extraction of Co(II) verified the complete separation of Co(II) from Ni(II). Hydrazine was then employed as a reducing agent for Co(II) and Ni(II) from the stripping solution and the raffinate, respectively. The effect of several variables on the reduction such as the molar ratio of hydrazine to metal ion, reaction time, temperature, and solution pH was investigated. It was found that the reduced metals could be dissolved owing to the oxidizing action of hydrazonium in acidic solution. Addition of NH4Cl was effective in suppressing the dissolution of the reduced metals. Especially, there was an optimum molar ratio of NH4Cl at which maximum reduction of Co(II) was obtained. The recovery percentages of Co and Ni powder were higher than 99.1% and 99.9%, respectively, and the purity of the reduced metals was higher than 99.9%.

Reduction of ZrO2 in LiCl-Li2O Melt During Electrolysis

Reduction of spent nuclear fuel (SNF) components to metals during the electrolysis of the LiCl-Li2O melt at 650 °C is extremely important in the framework of the development of fuel reprocessing technology. In the present paper the ZrO2 reduction by lithium during the electrolysis of the LiCl-Li2O melt at 650 °C was studied. Cathode processes on a molybdenum substrate in contact with different ZrO2 samples (powder, pressed pellet, dense ceramic) were analyzed using cyclic voltammetry and electrolysis. It was shown that the appearance of ZrO2 near the molybdenum cathode leads to increasing cathode currents and decreasing lithium oxidation current. Both effects indicate the consumption of reduced lithium for the reduction of ZrO2 samples. In order to analyze the reduction products X-ray phase analysis and scanning electron microscopy were used, and to estimate the reduction degree of ZrO2 samples three methods were tested: dissolution of samples in inorganic acid solution, dissolution of samples in EtOAc/Br2 solution, and carbothermal reduction. It was shown that during the electrolysis of dense samples only the lithium zirconate (Li2ZrO3) was formed at their surfaces, whereas the electrolysis of ZrO2 powder samples resulted in the formation of Li2ZrO3, Zr3O, and ZrO phases.

Selective Dissolution of Nd2O3 from the Mixture with Fe2O3 and Ga2O3 by Using Inorganic Acid Solutions Containing Ethylene Glycol

Rare earth elements (REEs) are strategically critical in the manufacture of advanced materials. Red mud and end-of-life NdFeB magnets can be good secondary sources for REEs, but recovery is difficult due to the high iron oxide content and small amount of REEs. Oxide mixtures whose composition of Fe, Nd, and Ga was similar to that in red mud were employed in experiments. In this study, a relatively inexpensive non-aqueous system was used to selectively dissolve Nd2O3 in a mixture with Fe2O3 and Ga2O3. The addition of ethylene glycol (EG) to HCl and H2SO4 solution depressed the dissolution of Fe2O3 and Ga2O3 from the mixtures, and thus selective dissolution of Nd2O3 was possible. The optimum conditions were as follows: (a) 1.0 M HCl in EG, 25 °C ± 1 °C, 50 g/L pulp density, 120 min, 200 rpm; and (b) 0.05 M H2SO4 in EG, 25 °C ± 1 °C, 50 g/L pulp density, 60 min, 300 rpm. Under these conditions, Nd2O3 was completely dissolved, whereas no Fe2O3 or Ga2O3 was dissolved by the H2SO4 system, and the dissolution percentage of these two oxides by the HCl system was less than 1%. Due to the selective dissolution of Nd2O3 from the oxide mixtures, it is simple to recover Nd. An efficient process can be developed for the recovery of REEs from red mud and end-of-life NdFeB magnets by applying our results.

Effect of Crystallization Additives on Durability of Cement Composites in Aggressive Environments

This article analyses the effect of crystallization additives on the long-term durability of self-compacting concretes (SCCs) in relation to specific types of chemically aggressive environments. The effect of both an inorganic acid solution and the aggressive solutions produced during plant ensilage were tested, while the effect of diesel on these modified concretes was also investigated. Attention was given to the effect of crystallization additives on the characteristically capillary porous structures of self-compacting concrete, specifically in terms of the long-term durability of SCCs in relation to the above-stated chemically aggressive solutions. The effect of aggressive environments was evaluated through a set of physical-mechanical trials and physical-chemical analyses.

Stratigraphic analysis of intercalated graphite electrodes in aqueous inorganic acid solutions

A detailed stratigraphic investigation of the intercalation mechanism when graphite electrodes are immersed inside diluted perchloric (HClO4) and sulfuric (H2SO4) electrolytes is obtained by comparing results when graphite crystals are simply immersed in the same acid solutions. By combining time-of-flight secondary ion mass spectrometry (ToF-SIMS) and in-situ atomic force microscopy (AFM), we provide a picture of the chemical species involved in the intercalation reaction. The depth intensity profile of the ion signals along the electrode crystal clearly shows a more complex mechanism for the intercalation process, where the local morphology of the basal plane plays a crucial role. Solvated anions are mostly located within the first tens of nanometers of graphite, but electrolytes also diffuse inside the buried layers for hundreds of nanometers, the latter process is also aided by the presence of mesoscopic crystal defects. Residual material from the electrolyte solution was found localized in well-defined circular spots, which represent preferential interaction areas. Interestingly, blister-like micro-structures similar to those observed on the highly oriented pyrolytic graphite (HOPG) surface were found in the buried layers, confirming the equivalence of the chemical condition on the graphite surface and in the underneath layers.

Recovery of Co, Ni, and Li from solutions by solvent extraction with β-diketone system

A method of recovering cobalt, nickel, and lithium from mixed solutions was proposed based on β-diketone solvent extraction using benzoyltrifluoroacetone (HBTA), trioctylphosphine oxide (TOPO), and green kerosene. The effective metal recovery and separation parameters such as solution pH, saponification degree, extraction time, and phase ratio were evaluated experimentally. The results indicated that cobalt and nickel were recovered through 2-stage cross-current extraction at different phase ratios and that lithium was recovered through three-stage countercurrent extraction. The metal-loaded organic phase was stripped using an inorganic acid solution to obtain cobalt-, nickel-, and lithium-concentrated solutions. The Co/Ni and Ni/Co molar ratios in the cobalt- and nickel-concentrated solutions were 54.4 and 164, respectively, and the lithium concentration reached 1.78 × 104 mg L−1 in the lithium-enriched solution. The extraction mechanism was studied, and the results revealed that Co2+ and Ni2+ were extracted by ion exchange in which two moles of H+ or Na+ had been replaced by divalent metal ions. The Li+ extraction stoichiometry was studied by cultivating single crystals. Because cobalt, nickel, and lithium were recovered by single extraction, no other organic substances were required. This work provides a sustainable, environmentally friendly, and versatile method of recovering valuable metals from spent lithium batteries.

Leaching of a Mixture of Palladium and Zinc Metal Using Hydrochloric and Sulfuric Acid Solutions

Spent electroplating solutions contain small amounts of Pd(II). Cementation of Pd(II) with zinc metal powder is practiced to concentrate the Pd. Dissolution of the cemented Pd metal is necessary to recover pure Pd metal or compounds. In this work, the leaching behavior of Pd metal in inorganic acid solutions (hydrochloric and sulfuric acid) in the presence of an oxidizing agent such as H2O2, NaClO3, or NaClO was investigated. To determine the optimum conditions for Pd leaching, experiments were conducted by adjusting the concentration of the acids and oxidizing agents, reaction temperature and time, and pulp density. Complete leaching of Pd was possible using a hydrochloric acid solution with 3 kinds of oxidizing agents, whereas only NaClO was effective in the leaching with sulfuric acid solution. The chloride ions of HCl and NaClO3/NaClO play an important role in enhancing the leaching of Pd, due to the formation of Pd chlorocomplexes and by decreasing the reduction potential of Pd(II). Compared to H2O2, NaClO3 and NaClO showed some merits as oxidizing agents in terms of reaction time, temperature and low acid concentration. Based on the optimum leaching conditions of single Pd metal, the conditions for the complete leaching of Pd and Zn from the metallic mixtures were obtained.

Extraction Behavior of Indole from Simulated Wash Oil Using Halogen-Free Ionic Liquids.

Indole is an important raw material in the chemical industry, and more than 1 wt % indole is contained in wash oil. Therefore, the extraction of indole from wash oil is of much importance. The conventional separation methods generally cost much money, pollute the environment, and corrode the metallic devices due to the use of large amounts of inorganic acid and alkali solutions, and therefore, new methods should be proposed. In this work, a solvent extraction process for separating indole from simulated wash oil by five halogen-free ionic liquids (HFILs) has been designed, and the extraction behavior of indole has been evaluated. All the studied HFILs presented excellent extraction behavior for indole, and the whole separation process took no more than 5 min. For the same HFIL, the minimum residual indole contents remained the same, even if the initial indole contents changed. Among the HFILs, 1-butyl-3-methylimidazolium dimethyl phosphate ([Bmim][DMP]) has attracted more attention than other HFILs. The results showed that [Bmim][DMP] could extract over 96.9 wt % indole from the simulated wash oil, and the minimum residual indole content was as low as 2.1 g/dm3. For indole, [Bmim][DMP] presented a maximum distribution coefficient of 201, which was much improved compared to other methods. The HFILs could be regenerated by using diethyl ether with ease. The regenerated HFILs could be reused, and the extraction behavior remained the same as the original HFILs. Based on FT-IR results, a mechanism of hydrogen bonds forming between HFILs and indole was proposed. In addition, the superiorities of HFILs over other separation agents in reusability, amounts needed, distribution coefficient for indole, and chemical structure were proved by comparison.

Leaching of Cobalt and Nickel from Metallic Mixtures by Inorganic and Organic Acid Solutions

Leaching of Cobalt and Nickel from Metallic Mixtures by Inorganic and Organic Acid Solutions

Dissolution of Palladium Metal in Solvent Leaching System with the Presence of Oxidizing Agent

Platinum group metals (PGMs) are important for the manufacture of advanced materials in the field of catalysts and electronic devices. Since the chemical properties of PGMs are very similar to each other, hydrometallurgical processes should be employed to recover PGMs with high purity from either ores or secondary resources. In hydrometallurgical processes for PGMs, the first step is the dissolution of PGMs. For this purpose, inorganic acid solutions with oxidizing agents are generally employed. In this work, nonaqueous solvent leaching systems with a relatively cheap price were employed to investigate the dissolution of pure palladium (Pd) metal. The solvent leaching systems consisted of concentrated hydrochloric acid solution and commercial extractants such as tributyl phosphate (TBP), 7-hydroxydodecan-6-one oxime (LIX 63), and di-n-octyl sulfide (DOS) in the presence of H2O2 as an oxidizing agent. Among the three systems, TBP showed the best efficiency for the dissolution of Pd. The effect of several parameters like TBP concentration, temperature, time, stirring speed and the weight ratio of Pd to TBP/HCl/H2O2 was explored. The dissolution percentage of Pd by the HCl–H2O2–TBP system was higher than by the HCl–H2O–H2O2 system at the same concentration of HCl and H2O2. The role of TBP in enhancing the dissolution of Pd was discussed on the basis of the interaction between HCl and TBP. Compared to aqueous systems, mass transfer is important in the dissolution of Pd metal by the solvent leaching system. Optimum conditions for the complete dissolution of Pd were obtained.

An exploratory study of recovery of rare-earth elements from monazite in mild conditions using statistical-mixture design

Monazite is a phosphate mineral, considered an essential source of light rare-earth elements (REE). The present work sought to evaluate different methods of solubilization of REE through the use of different concentrations of inorganic acids (H2SO4, HCl, and HNO3) and organic acids (citric, oxalic, and lactic) in mild conditions at room temperature. According to the results, the inorganic acid solutions favored the solubilization in order of Ce3+, La3+, Nd3+, Pr3+, and Sm3+ elements, while organic acid solutions only favored the solubilization of Ce3+ and La3+. Nitric acid was the more efficient leaching agent for the first group. In the case of organic acids, lactic acid solubilized Ce3+, while mixtures of lactic and citric acids appeared to solubilize La3+.