Separation of palladium(II) and platinum(IV) from hydrochloric acid solutions by selective precipitation using dimethylglyoxime

Various methods for the reduction of hexavalent uranium to the trivalent state were examined. It was found that the liquid-zinc-amalgam method is simple and rapid, and gives a high yield with a good reproducibility in hydrochloric, sulfuric, and perchloric acid solutions. The percentage of reduction is over 99% in a 0.5 n hydrochloric acid solution. Next, the stability of trivalent uranium in these media was investigated; it was observed that the trivalent uranium ion is fairly stable in any hydrochloric, sulfuric and perchloric acid solutions at a low concentration of the acids in the absence of atmospheric oxygen, but that it becomes unstable as the acid concentration increases. Both the percentage of reduction by the liquid-zinc-amalgam method and the stability of trivalent uranium are highest in a hydrochloric acid solution, next highest in a perchloric acid solution, and lowest in a sulfuric acid solution.

Objective. To investigate the pressure in the proximal duodenum after intraduodenal injection of 0.1 M hydrochloric acid and sunflower oil solution in patients with chronic biliary pancreatitis and postcholecystectomy syndrome depending on the state of excitation and inhibition in the pancreas. Materials and methods. We examined 316 patients with a clinical diagnosis of chronic biliary pancreatitis and 53 patients with postcholecystectomy syndrome. The pancreatic function was assessed by the method of complex fractional gastroduodenal probing. To assess the state of excitation and inhibition processes in the pancreas, the pressure in the antrum of the stomach was measured during stimulated pancreatic secretion using an open catheter. Results. In patients with chronic biliary pancreatitis and postcholecystectomy syndrome after intraduodenal administration of 0.1 M hydrochloric acid solution and sunflower oil, 4 pressure ranges in the duodenal cavity were observed: 0 – 5, 6 – 13, 14 – 18 and 19 – 42 mm Hg. After intraduodenal injection of 0.1 M hydrochloric acid solution among patients with chronic biliary pancreatitis at a pressure in the antrum of the stomach of 0 – 5 mm Hg. statistically significantly increased the proportion of patients with a pressure of 6 – 13 mm Hg (48.09%) and decreased the proportion of patients with a pressure of 19 – 42 mm Hg. (19.85%) in the duodenal cavity compared to the corresponding figures for unstable pressure in the antrum – 35.59 and 30.51% (p < 0.05) and for pressure in the antrum of the stomach 6 – 9 mm Hg – 32 and 36% (p < 0.025). Among patients with postcholecystectomy syndrome with a pressure in the antrum of the stomach of 0 – 5 mm Hg, the proportion of patients with a pressure of 6 – 13 mm Hg increased statistically significantly (52.94%) and the proportion of patients with a pressure of 19 – 42 mm Hg (11.76%) decreased compared with the corresponding figures for unstable pressure in the antrum – 19.35 and 51.61% (p < 0.01). After intraduodenal administration of sunflower oil among patients with chronic biliary pancreatitis with a pressure in the antrum of the stomach of 0 – 5 mm Hg, the proportion of patients with a pressure of 14 – 18 mm Hg increased statistically significantly (47.33%) and decreased the proportion of patients with a pressure of 19 – 42 mm Hg (40.46%) compared with the corresponding figures for unstable pressure in the antrum – 32.2 and 64.41% (p < 0.01), 6 – 9 mm Hg – 36 and 64% (p < 0.01) and 10 and above mm Hg – 17.65 and 82.35% (p < 0.025). Conclusions. The pressure in the proximal duodenum after administration of 0.1 M hydrochloric acid solution and sunflower oil depends on the state of the excitation process in the pancreas: the pressure in the range of 0 – 5 and 6 – 13 mm Hg after administration of 0.1 M hydrochloric acid solution and 6 – 13 and 14 – 18 mm Hg after administration of sunflower oil indicates normal or reduced pancreatic excitability, pressure in the range of 14 – 18 and 19 – 42 mm Hg after administration of 0.1 M hydrochloric acid solution and 19 – 42 mm Hg after administration of sunflower oil – increased pancreatic excitability.

Leaching of secondary resources containing palladium and platinum metals with HCl solution in presence of oxidizing agents results in solution containing PdCl4 2− and PtCl6 2−. According to hard soft acid base principle, PdCl4 2− is a soft acid compared to PtCl6 2−. By utilizing this difference, the possibility of separating Pd(II) and Pt(IV) from HCl solution by selective precipitation of Pd(II) with a soft base was investigated. For this purpose, NaI and Na2S were employed as precipitants and the precipitation behavior of both metal ions was evaluated as a function of the dosage of the precipitants, HCl concentration, the concentration ratio of the two metal ions, reaction time and temperature. In the HCl concentration ranges to 7 mol/L, Pd(II) was completely precipitated by both NaI and Na2S as long as the molar ratio of the precipitant to Pd(II) was larger than 3. The precipitation percentage of Pt(IV) in the presence of excess precipitants was decreased as HCl concentration increased to 3 mol/L. Optimum conditions were obtained from the results to separate Pd(II) from Pt(IV) by selective precipitation. The purity of PdI2 obtained at the optimum condition was 99.9%, while that of PdS was 99.6%. Owing to thermal stability of solid PdS, Pd(II) was completely precipitated by Na2S at 80°C, while the precipitation percentage of Pd(II) by NaI decreased rapidly at 70°C. Treatment of synthetic leaching solution of spent catalysts with NaI and Na2S at the optimum conditions verified that Pd(II) can be separated from Pt(IV) by selective precipitation.

Molecular characteristics of chitosan in diluted water solutions of acetic and hydrochloric acids were studied by viscometry, dynamic light scattering, and thin layer chromatography. Chitosan molecules were found to undergo destruction in the solutions of hydrochloric acid and its mixtures with acetic acid. The structure of the chitosan films cast from these solvents was studied by DSC, TGA, and SEM. As shown by electron microscopic data, all the films had an amorphous-crystalline structure but the films prepared from chitosan solutions in diluted hydrochloric acid were characterized by a higher degree of crystallinity. It was supposed that a lower molecular mass of chitosan molecules in the hydrochloric acid solutions results in more extended conformations providing a higher capability of self-organization and formation of regular supermolecular structure. The difference in crystal modification in structure of the films cast of these acids was observed. It was found that the films prepared from the mixtures of acids had a spherulite structure and the crystal modification like ones cast from hydrochloric acid, but with a lower degree of crystallinity.

Electrochemical and surface analysis of the Fe-Cr-Ru system in non-oxidizing acid solutions

The adsorption and separation of gold(III) and palladium(II) chlorocomplexes by anion‐exchange and synthesized coordinating resins are evaluated and compared in batch and column operations. New coordinating resins with a functional group based on triisobutyl phosphine sulfide with spacer arms containing coordinating O and/or S atoms are used. For both types of resin, the mechanism of the metal adsorption process is characterized. The highest separation factors at equilibrium conditions are obtained with the coordinating resins. However, the adsorption rate is faster with the ion‐exchange resins. A faster kinetics of the adsorption process is obtained with both types of resin when the temperature is increased, but the total adsorption capacity increases at higher temperatures for the coordinating resins and decreases in the case of ion‐exchange resins. In column operations, the highest separation factors are obtained with the coordinating resin containing ethylene oxide chains as a spacer arm. The quantitative elution of both ions is achieved with all the resins, but it is only possible to obtain a 100% pure palladium fraction with the coordinating resins. These resins are also more selective than ion‐exchange resins, allowing the separation of palladium and gold chlorocomplexes from mixtures containing other noble and base metals.

This article reports on the extraction of palladium(II) from hydrochloric acid (HCl) solutions using polymer inclusion membranes (PIMs) containing tetrabutylammonium bromide (TBAB) as the ion carrier. The membranes were based on cellulose triacetate (CTA) as the polymer support. The main aim of this study is to determine the possibility of TBAB’s application as the effective ion carrier/extractant of Pd(II) from hydrochloric acid solutions. At first, the effect of the hydrochloric acid concentration in the aqueous phase on palladium(II) extraction was investigated. Next, cellulose triacetate membranes with TBAB as the carrier were prepared and applied for the recovery of Pd(II) from HCl solutions. As a result of the investigations, the optimal composition of the receiving phase was determined to be 0.5 M thiourea in 0.1 M hydrochloric acid. The effect of the acid concentration in the source phase was investigated. The results show a linear decrease in the permeability coefficient and initial flux of palladium(II) with an increase in the hydrochloric acid concentration in the source phase. The separation of Pd(II) from Pt(IV) from the hydrochloric acid solution was also studied. The transport rate of Pd(II) was higher than Pt(IV). The separation coefficient SPd/Pt was 1.3. The results show that transport through PIMs with TBAB can be used as an effective method to recover Pd(II) from hydrochloric acid, especially at a low concentration of this acid.

PurposeProposes to investigate preparation of amorphous silica via precipitation reaction from aqueous solution of sodium metasilicate and hydrochloric acid in emulsion medium, focusing on determination to optimise the dispersive and morphological properties of silicas studied.Design/methodology/approachThe silicas obtained were analysed using modern research techniques, such as scanning electron microscopy for studies on particle surface morphology and dynamic light scattering technique for studies on particle structure and their tendency for agglomeration. Moreover, the sedimentation characteristics of the silica powders were evaluated.FindingsThe properties of silicas precipitated from emulsion systems depend on several variables but the amount and concentration of the applied reagents and pH of the emulsion are of critical importance. Using 16, 14 or 12 wt% solution of sodium metasilicate (per SiO2 content) and 5.0, 4.3 or 3.7 wt% solution of hydrochloric acid, the particles obtained were of best dispersive parameters. Mean diameter, polydispersity, shape and sedimentation of particles reflect the applied preparation procedure. Several of the silicas obtained manifest tendency for formation of secondary agglomerates and aggregates. The pH of the solution obtained from two mixed emulsions exerts a pronounced influence on quality and properties of the prepared silica. The best silica is obtained at pH 6‐7. In the cases where the emulsion has been dosed with “pure” sodium metasilicate solution, particles of irregular shape of high mean particle diameters, with a tendency to form large particle accumulations, have been formed.Research limitations/implicationsIn the precipitation reaction, aqueous solution of sodium metasilicate, hydrochloric acid and emulsifiers in the form of non‐ionic surfactants were used as substrates. The organic phase involved cyclohexane. Alternatives could be explored.Practical implicationsThe method developed provides a novel and practical solution to precipitation of hydrophilic/hydrophobic silica fillers.Originality/valueThe method for obtaining amorphous types of silica could find numerous applications, particularly as polymer fillers.

Solvent extraction and separation of palladium(II) and platinum(IV) from hydrochloric acid medium with dibutyl sulfoxide

Corrosion behavior of Hastelloy C22 coating produced by laser cladding in static and cavitation acid solution

The dissolution of aluminium in hydrochloric acid and sodium hydroxide solutions in the presence of semicarbazide, thiosemicarbazide and sym.diphenylcarbazide as corrosion inhibitors has been studied using thermometric, weight‐loss and polarization methods. The three methods gave consistent results. The higher inhibition efficiency of these compounds in acidic than in alkaline madia may be due to the less negative potential of aluminium in hydrochloric acid solution, favouring adsorption of the additive. The adsorption of these compounds were found to obey Frumkin adsorption isotherm.Cathodic polarization measurements showed that these compounds are cathodic inhibitors and their adsorption in the double layer does not change the mechanism of the hydrogen evolution reaction. The results are analysed in terms of both molecular and cationic adsorption.

The dissolution of aluminium in hydrochloric acid and sodium hydroxide solutions in the presence of dimethyltin dichloride as corrosion inhibitor has been studied using hydrogen evolution and thermometric methods. The two methods gave consistent results. The higher inhibition efficiency of this compound in acidic than in alkaline media may be due to the less negative potential of aluminium in hydrochloric acid solution, favouring adsorption of the additive. The adsorption of this compound was found to obey Frumkin adsorption isotherm.

The extraction of mercury (II) from hydrochloric and nitric acid solutions by trioctyl phosphine oxide (TOPO) in benzene has been investigated under different conditions. The organic extracts were examined by infrared, Raman and nuclear magnetic resonance spectroscopies. As the results, it was found that with increasing the concentration of aqueous hydrochloric acid solutions, the distribution coefficient for TOPO decreased below 1 mol dm-3 HCl and rised to a maximum at about 4 mol dm-3 HCl and then fell. The distribution behavior for the extraction of mercury (II) by TOPO from nitric acid solutions was analogous to that from hydrochloric acid solutions, while their extraction efficiencies were in the order of extraction systems HCl > HNO3. Consequently the following equilibrium equations are proposed for the extraction of mercury (II) from hydrochloric and nitric acid solutions by TOPO : for HCl extraction system, HgCl2 (a) + 2TOPO (o) ⇔ HgCl2·2TOPO (o), HgCl42- (a) + 2H+ (a) + 2TOPO (o) ⇔ H2HgCl4 · 2TOPO (o) and when mercury loading increases HgCl2 (a) + TOPO (o) ⇔ HgCl2·TOPO (o) ; for HNO3 extraction system, Hg (NO3)2 (a) + 2TOPO (o) ⇔ Hg (NO3)2·2TOPO (o) and Hg (NO3)42- (a) + 2H+ (a) + 2TOPO (o) ⇔ H2Hg (NO3)4·2TOPO (o).

The recycling of metals from electronic waste (e‐waste) using efficient, selective, and sustainable processes is integral to circular economy and net‐zero aspirations. Herein, we report a new method for the selective precipitation of metals such as gold and copper that offsets the use of organic solvents that are traditionally employed in solvent extraction processes. We show that gold can be selectively precipitated from a mixture of metals in hydrochloric acid solution using triphenylphosphine oxide (TPPO), as the complex [(TPPO)4(H5O2)][AuCl4]. By tuning the acid concentration, controlled precipitation of gold, zinc and iron can be achieved. We also show that copper can be selectively precipitated using 2,3‐pyrazinedicarboxylic acid (2,3‐PDCA), as the complex [Cu(2,3‐PDCA‐H)2]n ⋅ 2n(H2O). The combination of these two precipitation methods resulted in the recovery of 99.5 % of the Au and 98.5 % of the Cu present in the connector pins of an end‐of‐life computer processing unit. The selectivity of these precipitation processes, combined with their straightforward operation and the ability to recycle and reuse the precipitants, suggests potential industrial uses in the purification of gold and copper from e‐waste.

The recycling of metals from electronic waste (e‐waste) using efficient, selective, and sustainable processes is integral to circular economy and net‐zero aspirations. Herein, we report a new method for the selective precipitation of metals such as gold and copper that offsets the use of organic solvents that are traditionally employed in solvent extraction processes. We show that gold can be selectively precipitated from a mixture of metals in hydrochloric acid solution using triphenylphosphine oxide (TPPO), as the complex [(TPPO)4(H5O2)][AuCl4]. By tuning the acid concentration, controlled precipitation of gold, zinc and iron can be achieved. We also show that copper can be selectively precipitated using 2,3‐pyrazinedicarboxylic acid (2,3‐PDCA), as the complex [Cu(2,3‐PDCA‐H)2]n ⋅ 2n(H2O). The combination of these two precipitation methods resulted in the recovery of 99.5 % of the Au and 98.5 % of the Cu present in the connector pins of an end‐of‐life computer processing unit. The selectivity of these precipitation processes, combined with their straightforward operation and the ability to recycle and reuse the precipitants, suggests potential industrial uses in the purification of gold and copper from e‐waste.