Mineral Acid Solutions Research Articles

Extraction and sorption recovery of rhenium(VII) using oligodentate β-аminophosphoryl compounds

The interphase distribution of microquantities of ReO4– between aqueous solutions of mineral acids and solutions of oligodentate β-aminophosphoryl compounds in organic solvents was studied. The stoichiometry of the extracted complexes was determined, the influence of the concentration of HClO4, HNO3, HCl and H2SO4 in the aqueous phase, the structure of the extractant and the nature of the organic solvent on the efficiency of the transition of ReO4– ions into the organic phase was considered. The possibility of selective extraction and concentration of Re(VII) with a complexing sorbent obtained by non-covalent attachment of tris[bis(2-diphenylphosphorylethyl)aminoethyl]amine on the surface of the macroporous polymer Amberlite XAD7HP was demonstrated.

STABILIZING ADDITIVE FOR CRUSHED STONE-MASTIC ASPHALT CONCRETE BASED ON A LOW-GRADE PRODUCT AND WASTE FROM THE PRODUCTION OF CHRYSOTILE ASBESTOS

The results of a study of adsorption activity for bitumen and the physical and mechanical characteristics of the additive for crushed stone-mastic asphalt concrete (SMA), made on the basis of low-grade chrysotile and dusty waste from the enrichment of chrysotile-asbestos production, are presented. Structuring of the surface of layered magnesium silicates 3MgO 2SiO2 2H2O by treatment with dilute solutions of mineral acids is proposed, in which magnesium dissolution occurs only from the surface layers of magnesium silicate. At the same time, due to the structural features of the tubular structure - multilayering, the initially fibrous structure of magnesium hydrosilicate is preserved, and a layer enriched with silicon is formed on the surface of the fibers. As a result, the surface acquires a more amorphous state, which causes an increase in adsorption activity for bitumen. Based on the results of establishing the physical and mechanical characteristics of an additive made from low-grade chrysotile and powdered waste chrysotile-asbestos in the prepared crushed stone-mastic asphalt concrete mixture (ShchMAS-20), it is shown that the selected composition meets all the requirements of GOST 31015-2002 “Asphalt concrete mixtures and crushed stone asphalt concrete - mastic. Technical conditions".

Acid Leaching of CIGS Solar Cells: A Focus on Silver and Indium

Solar electricity from photovoltaics (PV) contributed to about 4.5 % of the global electricity production in 2022 and is expected to continue increasing by 2050 [1]. Therefore, both manufacturing waste and end of life waste are expected to reach a considerable volume in the upcoming decade. However, recycling methods for this type of waste are still at a very early stage of development. The thin film CIGS PV technology achieves high energy conversion efficiencies [2] and it is also used in promising newer technologies, namely multijunction solar cells. However critical elements like indium (In) and gallium (Ga), and often valuable silver (Ag) as conductive grid, are essential for the achievement of such efficiencies. Therefore, environmental, economic and resource depletion reasons demand the recovery of these elements.In industrial scale, there is currently no established recycling activity on CIGS containing materials. In lab scale, research mainly focuses on recycling of pure CIGS material production waste, which are free of any other element except for their 4 constituent elements in contrast to the real solar cells or PV. However, monitoring and controlling the impurity levels in the recycling of complex waste is of outmost importance, since the higher the purity of the recovered materials, the more economically viable their recycling business becomes. At the same time, the existing literature on the recycling of pure CIGS waste suggests the use of strong mineral acid solutions and high temperatures for the recovery of their elements. The case is similar for Ag, with some studies on its recovery only from another PV technology, namely silicon PV, being available and describing similarly harsh recovery conditions. Although such conditions can be efficient in many cases, they are not environmentally friendly and can be costly for the industry as well. To the best of our knowledge, the only available research work on the recovery of valuable elements from CIGS solar cells (Ag, In and others) using more benign recovery conditions compared to the ones that have been investigated so far (i.e. lower acid concentrations and room temperature), is our recent research work on leaching with nitric acid (HNO3) [3].In our current work we investigated the leaching of flexible CIGS solar cells with a stainless steel substrate production waste at room temperature and acid concentrations no higher than 2 M. The leaching efficiency of Ag and In was studied under different leaching times, acid leaching agents and concentrations, as well as geometrical surface area to liquid ratios (A:L). The elemental composition of all the elements that were likely to be present in the solar cell was measured in all the leachates with ICP-OES. The solid materials left on the cell’s surface after the treatment were characterized in terms of morphology and elemental composition with SEM-EDS, when necessary.The results proved that the choice of the leaching agent plays an important role in the recovery of the different elements present in the cell. It was also confirmed that higher acid concentrations achieve higher leaching recoveries for the same leaching conditions, as expected. As far as the A:L ratio is concerned, in many cases, higher A:L ratios achieved higher efficiencies, probably due to better oxygenation of the solutions.An example of the efficiency of the method is presented in Fig. 1, in which the Ag grid line of the untreated sample (Figure 1a, b) looks white under SEM due to the presence of Ag particles. After the acid treatment of the cell with 2 M HNO3 for 24h, the Ag particles of the Ag grid lines have disappeared, making the line look black (Figure 1c).In total, two important conclusions were drawn: a) selective leaching of various elements for achievement of higher purity products is possible by adjusting the leaching parameters and b) a complete recovery of Ag is possible within one day with more environmentally friendly conditions than the ones suggested so far.

Hydrate-Anion Complex of Proton [H(H2O)n]+А− as the Basis of the Complex Acidity Function Н0w of Aqueous Solutions of Strong Mineral Acids in Excess of Water

Hydrate-Anion Complex of Proton [H(H2O)n]+А− as the Basis of the Complex Acidity Function Н0w of Aqueous Solutions of Strong Mineral Acids in Excess of Water

TRAITEMENT DU PHOSPHATE NATUREL DE LA TAPOA (NIGER) PAR DES ACIDESMINERAUX ET ORGANIQUES

This study propose away for the development of hardly soluble natural phosphate. Thusitwascarried out, the dissolution of natural phosphate from Tapoa (Niger) in solutions of mineralacids (nitricacid and sulfuricacid) and in solutions of organicacids (citricacid and ethylene diamine tetraacetic EDTA) in function of pH and attack time. The resultsobtainedshowedthat the maximum rate of dissolvedphosphorus as a percentage of phosphoric anhydride (P2O5) is 14.08% and 15.99% respectively in solutions of nitricacid and sulfuricacid at the concentration of after 7 hours of attack. In organicacid solutions, the dissolution rate is 4.67% and 5.17% respectively in citricacid and EDTA solutions at the same concentration. In addition, the dissolution rate decreaseswhen the acid concentration decreaseswhileit tends to increasewith the attack duration regardless of the acid solution used (mineral or organic). Also, this dissolution rate isalmostzero in solutions of organicacidswhen the concentrationis.

Neodymium sorption on the Na-form of Transcarpathian clinoptilolite

The sorption properties of Na-modified Ukrainian Transcarpathian clinoptilolite towards neodymium aqueous solutions under dynamic conditions have been investigated. The sorption capacity of the Na-from of Transcarpathian clinoptilolite towards Nd(III) significantly depends on the concentration of neodymium salt, the pH of the solution, and the heat treatment temperature of the sorbent. Nd(III) is most efficiently sorbed from slightly alkaline solutions (pH 8.5), mainly by adsorption of neutral hydrolyzed forms of Nd(OH)3 on the surface of Na-clinoptilolite samples preheated at 75 °C. During the passage of an Nd(III) solution with a concentration of 1 μg mL−1 through the sorbent at a rate of 3 mL min−1 under optimal conditions, the sorption capacity of Na-clinoptilolite is 7.2 mg g−1, which is in 4 and 2.3 times higher than that of natural and acid-modified forms of this zeolite. It is shown that under the experimental conditions with an increase in the flow rate, the thickness of the stationary surface layer decreases, which leads to a decrease in the sorption capacity of Na-clinoptilolite. The best Nd(III) desorbents are solutions of mineral acids and acidified solutions of alkali metal salts (except NaCl), which provide 93–98 % extraction of lanthanide from the zeolite matrix. The method for neodymium trace amounts preconcentration from aqueous solutions in a solid-phase extraction mode with a further determination of this rare earth element by a spectrophotometric method was developed. The detection limit of this method is 0.75 ng mL−1 and the linearity was evaluated in the range of 2.5–500 ng mL−1.

Synthesis and study of bismuth(III) oxalates precipitated from mineral acid solutions

Bismuth oxalates of the compositions BiOH(C2O4), Bi2(C2O4)3·6H2O, Bi2(C2O4)3·7H2O, and Bi2(C2O4)3·8H2O were obtained by precipitation from bismuth solutions in perchloric, nitric, and hydrochloric acids with addition of oxalic acid. Compound compositions were confirmed by X-ray powder diffraction and chemical analysis, IR and Raman spectroscopy, and thermogravimetry. It has been shown that in the composition of bismuth(III) oxalate hydrates Bi2(C2O4)3· х H2O bismuth cation is coordinated by the oxygen atoms of carboxyl groups of oxalate ions and water molecules in the same way, and compositions, taking into account the structural features, are described by the general formula {[Bi2(C2O4)3(H2O)4]∙( x -4)H2O} n . Conditions for the oxidative thermolysis of BiOH(C2O4) and Bi2(C2O4)3·7H2O to yield the tetragonal modification of bismuth oxide β-Bi2O3 were determined.

Synthesis and Study of Bismuth(III) Oxalates Precipitated from Mineral Acid Solutions

Synthesis and Study of Bismuth(III) Oxalates Precipitated from Mineral Acid Solutions

Investigation of Acid-Catalyzed Hydrolysis of 4-Nitrophenyl-N-Acetyl-4-Methylbenzenesulfonimidate in Dioxane-Water Solutions

The hydrolysis of 4-nitrophenyl N-acetyl-4-methylbenzenesulfonimidate in aqueous 20%, 40%, and 60% (v/v) dioxane solutions of mineral acids was investigated. Rate maxima are observed for both perchloric and sulfuric acids since hydrolysis was studied over a wider range of acidity in 20%, and 40% (v/v) dioxane. Similarly, rate maxima are observed perchloric and hydrochloric acid in 60% (v/v) dioxane at high acid concentration. Analyses of the data by the Cox–Yates excess acidity method and temperature effects indicate hydrolysis by an A-2 mechanism.

Catalytic synthesis of N-substituted allylarylamines

Some N-substituted allylarylamines, for example, N-(1-methyl-2-butenyl) aniline (N-MBA) form, upon isomerization, not only ortho-, but also para- and 2,6-disubstituted derivatives, which does not fit into generally accepted theory. The amino-Claisen rearrangement (ACR) of N-MBA is catalyzed by Lewis acids, cationites, and arylamine hydrochlorides. This work presents the results of studies of ACR N-MBA in solutions of mineral acids. It was found that the reaction must be carried out in dilute solutions. At H2SO4 concentrations of 0.5 mol/L and below, three parallel reactions are observed with the formation of aniline, 2-(1-methyl-2-butenyl) aniline (2-MBA) and 4-(1-methyl-2-butenyl) aniline (4-MBA). The main product in all cases is 2-MBA, the content of which in the reaction mixture exceeds the amount of 4-MBA and aniline by 7 times, which are formed in approximately equal amounts. Prolonged refluxing of 2-MBA under the reaction conditions does not lead to its isomerization to 4-MBA, i.e., the para-isomer is formed directly from N-MBA. The formation of 2,6-di-(1-methyl-2-butenyl) aniline (DMBA) was not observed. In the presence of palladium catalysts, 2-MBA cyclizes to 2,4-methyl quinoline, which indicates the ortho-arrangement of its substituents; 4-MBA does not cyclize under these conditions. The obtained compounds are of interest in the synthesis of nitrogen-containing heterocycles and other polyfunctional organic compounds.

COMPARATIVE ASSESSMENT OF DIGESTION METHODS FOR SOIL SAMPLES DURING THE RADIOCHEMICAL DETERMINATION OF <sup>239+240</sup>Pu

A great many nuclear tests of different types and yields were conducted at the Semipalatinsk Test Site (STS). That has lead to the formation of radioactively contaminated areas within it, which differed from one another in the pattern, levels and the isotopic composition. At the same time, technogenic radionuclides are oftentimes in the soil cover of STS in tightly bound and slightly soluble forms, which hampers their complete extraction from samples for a subsequent quantitative analysis. Typically, the extraction process is carried out in open systems using solutions of hydrofluoric acid (HF) and other mineral acids. However, this technique is time-consuming, requires a great many reagents and may result in the loss of elements to be assayed as well as in a possible cross contamination of samples. Autoclave digestion can be an alternative to acid digestion in open systems. This method, on the one hand, is devoid of the disadvantages inherent in open decomposition, on the other hand, it has an undoubted advantage, which consists in accelerating the decomposition process due to an increase in the boiling point of acids. As demonstrated by experimental findings, measurements of 239+240Pu activity concentration in soil samples obtained from a complete acid and autoclave decomposition, in most cases, agree well enough with one another (the existing discrepancies are within the measurement error). Analysis of a radioactivity reference standard using the autoclave decomposition technique showed satisfactory results. The deviation from a certified value was in the order of 5%.

О переработке ловозерского эвдиалитового концентрата методом сорбционной конверсии

The results of research on the development of the scientific foundations of the complex technology of processing Lovozersky eudialyte concentrate are summarized. The features of the concentrate composition are reported. The regularities of concentrate decomposition by sorption conversion with low-concentration solutions of mineral acids, desorption of metals from sulfocationite, stepwise hydrolytic deposition from eluates of concentrates of rare elements, the use of silicic acid transferred to solutions with simultaneous recirculation of acid solutions were studied. The outlines of the technology of complex processing of eudialyte concentrate are outlined, which provides for the production of concentrates of rare metals and the use of the main part of the silica and alkali metals contained in the concentrate.

Some aspects of the mechanism of steel protection in mineral acid solutions by propargyl alcohol and propargyl chloride

Some aspects of the mechanism of steel protection in mineral acid solutions by propargyl alcohol and propargyl chloride

Protection of Low-Carbon Steel in Solutions of Mineral Acids by Inhibitor of the IFKhAN-29 Series

Protection of Low-Carbon Steel in Solutions of Mineral Acids by Inhibitor of the IFKhAN-29 Series

Dissolution of metallic iridium powders in hydrochloric acid oxidizing media

Iridium is one of the most chemically inert platinum group metals. It is extremely resistant to many reagents, including alkaline and mineral acid solutions. This, combined with the physical properties of iridium, defines the spectrum of its practical applications. This paper demonstrates that metallic iridium powders of various dispersion degrees can be dissolved in hydrochloric acid media in one stage in the presence of hydrogen peroxide. The morphology, as well as the phase and chemical compositions were studied by means of transmission and scanning electron microscopy, X-ray diffraction analysis, adsorption measurements of specific surface area and chemical analysis. The study looked at refined (30–150 μm particles), highly dispersed (150–200 nm) and nanocrystalline (8–15 nm) iridium. It also examined the dissolution kinetics of iridium(0) with different specific surface areas at the temperatures of 190 to 210 oC. For all the studied samples, the dissolution process was established to be of kinetic nature, and the obtained experimental data can be perfectly described with the shrinking core model. The dissolution activation energy for refined, highly dispersed and nanocrystalline iridium(0) in hydrochloric acid solutions in the presence of hydrogen peroxide is 145, 108 and 88 kJ/mol, correspondingly. This way, it was proved that the activation energy tends to go down as the particles get smaller. It was confirmed that iridium is present in solutions in the form of chloride complexes of quadrivalent iridium. Thus, metallic iridium was converted into chloride forms in an environmentally friendly way, which makes it easier to perform analysis for refining purposes, as well as further synthesis of iridium complexes. This research was carried out as part of a governmental assignment allocated to the Institute of Chemistry and Chemical Technology at the Siberian Branch of the Russian Academy of Sciences (Project 0287-2021-0014) and using the equipment of the Krasnoyarsk Regional Shared Knowledge Centre, a part of the Krasnoyarsk Science Center of the Siberian Branch of the Russian Academy of Sciences.

Separation of rare earth metals in countercurrent extraction cascades using binary extractants

The use of binary extractants (BE) in schemes of countercurrent extraction cascades designed for the separation of rare earth metals (REMs) has been studied. It has been shown that the main difference between the use of BE and cation-exchange extracts (CE) is the possibility of using deionized water in the re-extraction cascades, rather than solutions of mineral acids. When optimizing the REM separation scheme, a mathematical model was used to dynamically calculate the distribution of separated metals over the stages of counterflow extraction cascades. The modeling of cascades was carried out on the basis of the physicochemical description previously obtained by the authors of the processes of extraction of REM nitrates with various BE compositions prepared on the basis of industrial cation- and anion-exchange extractants. Calculation of the balance of lanthanides during successive separation by stages of cascades was performed for the initial mixture of REM nitrates with the ratio of elements corresponding to the composition of the ore of the Chuktukonskoe rare metal deposit. A scheme of cascades is proposed for isolating in pure form the five REMs of light and light/medium groups (Pr, Nd, Sm, Eu, Gd) most demanded by the industry, concentrate of La, Ce, and concentrate of REM of medium/heavy and heavy groups. The scheme includes 10 countercurrent extraction cascades with a total number of extraction stages of 390. The scheme uses BE based on di-(2-ethylhexyl)phosphoric acid, synthetic fatty acids, tri-n-octylamine, and an industrial diluent. For the proposed scheme, mineral acid is used only at the stage of obtaining REM nitrates from the initial oxides; 1.8 kg (65%) of nitric acid is consumed per 1 kg of REM oxides. For the precipitation of REM carbonates from re-extracts, the consumption of sodium carbonate is approximately 1 kg per 1 kg of the initial REM oxides. The use of BE in comparison with CE makes it possible to significantly reduce the consumption of mineral acids and bases during the separation and production of individual REMs. The work was carried out within the framework of the state task of the Institute of Chemistry and Chemical Technology of the Siberian Branch of the Russian Academy of Sciences (project 0287-2021-0014) using the equipment of the Kranoyarsk Regional Center for Collective Use of the Federal Research Center of the KSC of the Siberian Branch of the Russian Academy of Sciences.

Защита металлов ингибиторами коррозии в растворах различных кислот

The current state of research in the field of inhibitor protection of metals and alloys in solutions of mineral and organic acids has been summarized and analysed. Acid solutions in modern industry are widely used at oil-and-gas facilities, metallurgy, housing-and-communal services, where they can be in contact with metal parts of industrial equipment for a long time, without the use of additional protection measures, causing its destruction. The specificity of the corrosive effect of acid solutions on metallic materials is analysed. Various groups of metal corrosion inhibitors (CIs) for these media and the features of the mechanism of their protective action were discussed. Among the various groups of CIs that protect metals in acidic media, various azole derivatives deserve the most attention. The industrial use of azoles is promising in the form of mixtures with other compounds. Promising lines of research in the field of inhibitory protection of metals in acidic media are associated with the wider application of the possibilities of electrochemical methods (voltammetry and electrochemical impedance spectroscopy). When determining the thermodynamic parameters of CIs adsorption, one should be guided by determining their true values, and not effective values. In the development of mixed CIs, a thorough theoretical study of these issues is required, taking into account prospects of such developments for the industrial use. Prospects for the industrial application of environmentally friendly («green») CIs for the protection of metals in acidic environments are considered. At present, the practical application of such products is limited by the lack of data on their compliance with the tight requirements of modern industries for CIs. The bibliography includes 129 references.

Особенности коррозии и ингибиторной защиты сталей в растворах кислот, содержащих соли железа (III). Обзор

A critical analysis of literature data on corrosion of steels in solutions of mineral acids containing Fe(III) salts and the possibility of inhibitory protection of steels in these environments has been carried out. The accumulation of Fe(III) salts in acid solutions during their operation at metallurgical, oil and gas enterprises, objects of housing and communal services is a result of dissolution of mineral deposits, scale, thermal scale, and rust containing Fe (III) compounds in them. In addition, additional oxidation of Fe(II) salts in acid solutions to Fe(III) compounds is possible. The effect of the redox potential, determined by the ratio of the content of Fe(III) and Fe(II) cations in them, as well as mobility of Fe(III) cations, on the corrosivity of the systems under consideration was examined. The reasons for the accelerating and retarding action of Fe(III) salts on corrosion of steels in acidic media were analyzed. Modern concepts of the mechanism of corrosion of steels in these environments are discussed. The low efficiency of the inhibitory protection of steels in mineral acids containing Fe(III) salts is demonstrated. It is noted that it is possible to increase the protective effect of some corrosion inhibitors (CI) in these environments by reducing their overall aggressiveness. It can be achieved by introducing H3PO4 into them, which is capable of binding Fe(III) into strong complexes that have a lower oxidizing capacity than Fe(III) aqua complexes and mobility in an aggressive environment. The CI used in an aggressive environment must be effective in slowing down not only the cathodic reduction of protons and anodic ionization of iron, but also significantly suppress reduction of Fe(III) cations, which is realized with the diffusion control. These requirements are met by composite CI based on triazoles, which in H2SO4 + H3PO4 and HCl + H3PO4 solutions containing Fe(III) salts are effective in slowing down the corrosion of low-carbon steel.

Removal of aluminum from chloride leach solutions of rare earths using 3-((bis(2-ethylhexyloxy))phosphoryl)-3-phenylpropanoic acid (PPPA)

The extraction and separation of Al3+ from a chloride solution of rare earths was studied using 3-((bis(2-ethylhexyloxy))phosphoryl)-3-phenylpropanoic acid (PPPA) as the extractant. The effects of factors such as initial pH value (pHini), temperature and saponification degree were investigated. The extraction is a cation exchange process deduced by the slope analysis method. Increasing the temperature facilitates the separation of aluminum from rare earths. Stripping of the loaded Al3+ can be achieved by mineral acid solutions of concentrations of 1.0 mol/L or higher. A cascade extraction process was used to remove Al3+ from a chloride liquor of the concentrate of ion-adsorption type rare earth ore. The Al3+ concentration in the aqueous solution decreased from 304.5 mg/L to 4.35 mg/L, and the recovery of rare earths was 95.6% after 5 stages of extraction and 2 stages of scrubbing.

Снижение окислительной способности растворов минеральных кислот, содержащих соли железа (III), добавками уротропина

A potentiometric study of 2,0 M HCl; 2,0 M H2SO4; 2,0 M H3PO4 and their mixtures (20−95 °C), containing cations Fe(III) and Fe(II), made possible to examine details of the protective action mechanism of a composite inhibitor, containing 3-substituted 1,2,4-triazole (IFKhAN-92), KNCS and urotropin, on the corrosion of low-carbon steels in acid solutions containing Fe(III) salts. It has been found out that a decrease in the oxidizing ability of such systems is observed with the simultaneous presence in their composition of phosphoric acid and urotropine. A decrease in the oxidizing ability of such systems is a result of the binding of Fe(III) in complex compounds with phosphate anions and urotropine. Such Fe(III) complexes have a low oxidizing ability. Inhibitory protection of steels in solutions of mineral acids, in the case of accumulation of an additional oxidizer, namely Fe(III) cations, is possible under the following conditions. First, the oxidizing ability of Fe(III) cations must be reduced by binding them in complex compounds by anions formed during acid dissociation. Individual H3PO4 or mixtures thereof with other acids can be used as such an acid. Second, it is necessary to use an effective inhibitor of acid corrosion, which is capable of simultaneously appreciable slowing down the reduction of protons and Fe(III) complex compounds with anions of acid residuals. Composite inhibitors based on triazole derivatives and sulfur-containing compounds correspond to this property.