Leaching kinetics of scheelite in hydrochloric acid solution containing hydrogen peroxide as complexing agent

Cobalt and molybdenum are valuable metals whose presence in nature is very limited. The consumed catalyst, which is abundantly available in the petroleum refinery industry, is a potential source of those metals. A hydrometallurgical process using acid as a leaching agent is usually used to extract and separate the metals more effectively. This method is considered capable of yielding recovery of a higher percentage of metal. In this study, hydrochloric acid solutions at various concentrations of 1.0, 1.5 and 2 M were used. The consumed catalyst was obtained from Pertamina Refinery Unit IV, Cilacap, Indonesia. Leaching experiment was carried out for 300 minutes and sampling was undertaken at 1, 3, 5, 15, 30, 90 and 300 minutes. The particle size and agitation speed were fixed at 200 mesh and 400 rpm. Samples of consumed catalyst were analyzed using EDXRF before the leaching process. Samples of solution were analyzed using ICP-EOS. Experimental results have shown that the recovery of cobalt and molybdenum increases with the increase of either concentration of hydrochloric acid or temperature. The highest recoveries in cobalt and molybdenum were 34.66% and 5.03%, respectively, obtained at a concentration of hydrochloric acid of 2 M and temperature 60°C.

Determination of solubility of ZnCl2 in hydrochloric acid solutions for 68Ga production in liquid target

Calcium ion selectivity and isotope effects studied by using benzo-18-crown-6 resins

The partitions of uranium (vi) and thorium between hydrochloric acid solutions and solutions of tri‐n‐butyl phosphate (TBP) in benzene or kerosene have been investigated at different concentrations of hydrochloric acid and solvent, and at different temperatures. An infra‐red spectral study has also been made of the organic solutions obtained in the extraction of uranium. The effect of organic solvent on the extractions has also been examined.

Microgram amounts of iron(III), gallium(III), thallium(III), antimony(V), and antimony(III) were collected by adsorption on activated carbon from hydrochloric acid solutions. The extent of adsorption was determined radiochemically or spectrophotometrically. The hydrochloric acid concentrations that gave the highest recoveries (_??_90%) were: 7M for gallium, 1M for thallium(III), 9M for antimony(V), and 3M for antimony(III). Thallium(I) was not adsorbed, but it was oxidized to thallium(III) by air in the presence of activated carbon. Iron(III) was adsorbed more satisfactorily from 0.1M hydrochloric acid-(6-12)M lithium chloride solutions than 6-10M hydrochloric acid solutions. Probably the metals are adsorbed as chloro-complexes. Iron and gallium in aluminum alloys were determined spectrophotometrically after adsorptive separation.

In this work, hydrochloric acid is used to remove iron impurities in the bauxite ore contained in the diasporite mineral located in the Sari region. The bauxite ore was calcined at different temperatures and times, and then dissolved in a hydrochloric acid solution. After determining the optimum calcination conditions in 1 h at 900 °C, the response surface methodology (RSM) with four factors in five levels was employed in order to evaluate the effects of calcination temperature, calcination time, acid concentration, and leaching time on the iron leaching efficiency. A quadratic model is proposed using this methodology to correlate the leaching variables. The test results indicate that the model is consistent with the experimental data, and that the most important varriables involved are the acid concentration, leaching time, and squared term of calcination temperature (A2). The maximum iron recovery was 94.97%, and the Fe grade in the solids remained was 2.35% at the calcination temperature of 900 °C, a calcination time of 1 hour, and a leaching time of 2 h in hydrochloric acid (6 mM).

Direct mercury determination in aqueous slurries of environmental and biological samples by cold vapour generation–electrothermal atomic absorption spectrometry

Investigation of thermodynamic and kinetic regularities of asbestos waste leaching processes

The stability of porcine insulin (PI) in various concentrations of hydrochloric acid was investigated by use of high-performance liquid chromatographic (HPLC) method. Separation and determination of PI and its degradation products were achieved on a column of LiChrosorb RP-18 with a mixture of acetonitrile and 0.1 M phosphate buffer (pH 5.0) (29 : 71) containing 50mM sodium sulfate and 0.2mM cethyltrimethylammonium bromide as a mobile phase at 30°C. The decomposition of PI in hydrochloric acid was greatly affected by the concentration of hydrochloric acid and temperature, and followed a good pseudo-first order reaction. In 0.001 and 0.01 N hydrochloric acid, PI was stable at 0°C for 28 d, but it decomposed quickly at 30 and 60°C, and gave almost one degradation product. In 0.1 and 0.3 N hydrochloric acid, PI was slightly decomposed at 0°C, but decomposed rapidly at 30°C and gave many degradation products. HPLC method was very useful for the mutual separation of PI and its degradation products in various concentrations of hydrochloric acid.

In ores, chalcopyrite is usually associated with other sulfide minerals, such as sphalerite, galena, and pyrite, in a dispersed form, with complex mineralogical structures. Concentrates obtained by flotation of such ores are unsuitable for pyrometallurgical processing owing to their poor quality and low metal recovery. This paper presents the leaching of chalcopyrite concentrate from the location “Rudnik, Serbia”. The samples from the flotation plant were treated with hydrogen peroxide in sulfuric acid. The influences of temperature, particle size, stirring speed, as well as the concentrations of hydrogen peroxide and sulfuric acid were followed and discussed. Hence, the main objective was to optimize the relevant conditions and to determine the reaction kinetics. It was remarked that the increase in temperature, hydrogen peroxide content, and sulfuric acid concentration, as well as the decrease in particle size and stirring speed, contribute to the dissolution of chalcopyrite. The dissolution kinetics follow a model controlled by diffusion, and the lixiviant diffusion controls the rate of reaction through the sulfur layer. Finally, the main characterization methods used to corroborate the obtained results were X-ray diffraction (XRD) as well as qualitative and quantitative light microscopy of the chalcopyrite concentrate samples and the leach residue.

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.

Background: The tooth bleaching treatment can cause structural changes in the surfaces of the teeth; these changes can increase the absorption of staining agents. Purpose: This study assessed surface morphological changes and predisposition to staining in dental enamel bleached with different hydrogen peroxide (HP) concentrations, with or without the use of a light source (LS). Methods: 25 bovine incisor specimens were divided into five groups (n = 5): Control- no treatment; HP35 - hydrogen peroxide 35%; HP35+LED - hydrogen peroxide 35% + light emission; HP20 - hydrogen peroxide 20%; and HP7 - hydrogen peroxide 7,5%. Twenty days after bleaching, the specimens were immersed in staining solutions four hours a day for 28 days. The morphological alterations of the bovine enamel surface were evaluated by means of scanning electron microscopy, X-ray dispersive energy spectroscopy and predisposition to the staining of the brightened enamel by means of colorimetry. Results: ANOVA with Tukey's test (p<0.05) showed that HP7 had the highest ΔL values (p=0.176) (brightest), with a better lightening effect. The bleached groups exhibited morphological changes in the enamel. The groups did not exhibit significant changes in oxygen, calcium, and phosphorus values (p=0.020). The presence or absence of light was not significant (p=0.007) for the predisposition to staining in bleached teeth. Conclusion: The time of exposure to the staining solution was significant for staining bovine dental enamel. High concentrations of HP were not necessary for achieving effective bleaching. HP caused an increase in enamel porosity and depressions. The light source did not influence bleaching.

The paper provides the results obtained in the study of the features of metallic platinum, rhodium and iridium dissolution in hydrochloric acid solutions under hydrothermal autoclave conditions. Hydrogen peroxide was used as an oxidizing agent. Solid and liquid phases were brought into contact after reaching a predetermined temperature, which is critically important in the study of rhodium black and platinum plate dissolution kinetics due to the high rates of these processes. The concentrations of metals in solutions were determined by atomic absorption spectroscopy and inductively coupled plasma mass spectrometry. The forms of rhodium, iridium, and platinum chlorocomplexes in solutions were determined using the spectrophotometric method. As a result of the experiments, the conditions of platinum plate and rhodium quantitative dissolution (in the form of affined powder and a plate) were determined and it was shown that at 210 °C in 6M hydrochloric acid as a medium with the addition of 5 vol.% hydrogen peroxide, iridium taken in the form of affined powder went into the solution by 50 % within more than 50 h, while the platinum plate dissolved completely at 130 °C in about 120 min. Kinetic data analysis using the shrinking core model showed that rhodium black and affined rhodium and iridium powders dissolve under autoclave conditions in a kinetic mode. The results obtained can be used both in analytical chemistry for the quantitative determination of inert platinum metals and in refining production to improve the technology for processing raw materials containing platinum group metals (PGMs) and to optimize approaches to the synthesis of pure chlorocomplex compounds of PGMs.

1.(1) Hydrogen peroxide and silver nitrate, and possibly other soluble noble metal salts acting on a photographic plate after exposure and before development increase the developability of the light-exposed portion above its normal developability and in greater proportion than that of the unexposed portion. This we have called intensification of the latent image.2.(2) Hydrogen peroxide and the salts just mentioned seem to be unique among the numerous substances we have used for producing intensification of the latent image, in that they are the only ones which give a strong intensification when the concentration is low enough not to produce objectionable fog. This effect is, however, approximately equivalent in degree to that produced by a brief flash exposure of the plate to light before or after the principal exposure.3.(3) With the same concentration of hydrogen peroxide and time of treatment, the latent image on the fast plates which we have used was affected to a greater extent than on medium-speed plates, while on the process and desensitized plates used it was not affected at all. Eastman portrait and N. C. films behaved like the process plates.4.(4) The latent image on the process plates, desensitized plates, and the film just mentioned could be intensified to a certain extent by increasing the hydrogen peroxide concentration, or by lengthening the time of treatment over that used for the fast plates.5.(5) It was possible to produce no more than a slight latent fog with hydrogen peroxide, i.e., with no light exposure, on desensitized plates, no matter what concentration or time of treatment were used.6.(6) Water caused an apparent intensification of the latent image. This is explained as partly due to swelling of the gelatin, allowing more rapid penetration of developer.7.(7) The ratio of gamma of the peroxide-treated to the untreated plates usually increased with increasing development time.8.(8) Intensification of latent image in most cases increased somewhat with increasing development time when measured as a density effect and decreased when measured by H. and D. speed difference.9.(9) Experiments have shown that as little as I part hydrogen peroxide in 10,000,000 of water can be determined to within 20 to 30 per cent. by the latent image intensification method, when it is known that other intensifying agents and oxidizing substances are not present.10.(10) The hypothesis, previously stated by Wightman, Trivelli and Sheppard, that light produces not only a developable but also an undevelopable latent image, and that the peroxide action makes this latter image developable in producing latent image intensification is supported by the present work. An extension of this hypothesis has been found necessary to explain the action on the latent image of fast, medium and slow plates, namely, that there is less undevelopable image formed by light in the medium and slow plates and desensitized high-speed plates and it is for this reason that the same concentration of peroxide and same time of treatment give different degrees of intensification on these plates of different speed.

Leaching chalcopyrite with sodium chlorate in hydrochloric acid solution