Papers by Keyword: Leaching

Abstract: The cathode sediments (CS), obtained as a result of industrial processing of gold-polymetallic raw material with complex chemical and mineral composition, contain a significant amount of impurity metals (copper, lead, zinc, iron, etc.), which leads to a significant increase in the cost of subsequent refining of these materials. The authors carried out experimental work on preliminary acid treatment of CS for the purpose of leaching impurities and increasing the share of precious metals in them. The objects of research were cathodic sediments (bypass solutions of the enterprise) containing copper and lead in the amount,% wt., respectively: 21.29 and 4.11. We tested nitric acid as a solvent in laboratory tests. For the selection of optimal leaching parameters, studies were carried out at various concentrations of the agent (from 50 to 350 kg/m3) and the ratio of L:S - (3-7):1. The duration of the experiments was 2 h, the experiments were carried out with vigorous stirring and standard ambient temperature (25°C). The experimental data processing was carried out with the help of STATISTICA 6.0 software; As factors of variation, we chose: concentration of acid, ratio of liquid and solid phases. It has been determined that nitric acid provides effective purification of CS from impurities. After the chemical enrichment, the content of precious metals in leaching cakes increased, the CS became compliant with the requirements of TU 117-2-3-78. When processing cathode sediments with nitric acid, 99% of silver passes into solution, which then allows it to be recovered from solutions by cementation and, consequently, to obtain alloys of gold and silver separately.

Abstract: In aluminium preparation by means of electrolysis of alumina-cryolite melts one of the largest-scale type of industrial waste is spent pot lining (SPL). Chemical composition of SPL carbon part consists of various elements with fluorine as the main one. One of the solutions of the problem of reducing environmental load by means of storage of waste of this type is extraction of valuable components (such as fluorine), that can be used further for preparation of fluorine entities (cryolite, calcium fluoride), that are brought back to electrolytic process. We have held experiments on extracting fluorine from SPL by caustic liquor leaching under effect of ultrasonic oscillations on a pulp, increasing the degree of fluorine solubilization. By means of mathematical planning method of a factor experiment cross impact of three leaching parameters was stated, maximum concentration of fluorine ions in the solution (20.21 gr/dm³) was achieved in following conditions: NaOH concentration - 2%, solid-liquid ration - 6:1, process length - 90 min. The degree of fluorine extraction from SPL is 69.87%.

Abstract: The problem of processing slimes of galvanic production, formed as a result of neutralization of technological solutions and wastewater containing heavy non-ferrous metals is considered. At present, sludges are transported to disposal area and are not used in any way. Typically, such sludges contain significant amounts of chromium and nickel, which creates environmental hazard. Investigated sludge of Dimitrovgrad Automobile Units Plant (Russia) contains up to 6.6% Ni and up to 7,4% Cr. The hydrometallurgical process is proposed to treatment of these sludges. Solutions of sulfuric acid, ammoniaс chloride and Trilon B were used as lixiviants. It is shown that when using a solution of sulfuric acid with pH=1,5, extraction of up to 93,3% Cu, 70,2 Ni, 90,3 Zn is achieved.

Abstract: Spent catalysts contain metals that have a high added value. From all metals, lanthanum has attracted a lot of attention due to the growing demand in the high-tech. The spent catalyst of the hydrotreatment unit is a material composed of lanthanum-enriched matrix of amorphous aluminosilicates. The experiment was carried out with a spent catalyst with a constant particle size of 90 μm. The treatments were obtained applying of two level factorial design to investigate the effect of following factors: temperature (20 - 60 °C), nitric acid concentration (3 - 6 M), leaching time (1 - 4 h) and percent solids (10 - 20 %). The research is carried out in two steps process: pretreatment of the catalyst and leaching with nitric acid. The leaching results show a yield of lanthanum of 99.44% using the following conditions: temperature (20 °C), nitric acid concentration (3M), leaching time (1 h), percent solids (20%) and 300 rpm. The principal analysis of the spent catalyst was carried out using the X-Ray Fluorescence (XRF) technique, 3.08%, while the percentage of lanthanum recovery in the extract, washing and refining was carried out using the Inductive Coupling Plasma (ICP) technique.

Abstract: The article describes the basic mechanisms of interaction of the components of the concrete mixture, the analysis of a number of components and conducted comprehensive studies for the formation efflorescence on the surface of products made from various concrete mixtures by vibropressed.

Abstract: The present work describes the extraction of lanthanide (rare earth elements, REE) from low grade bauxite using acid leaching method. The aim of this study is to obtain the best condition for extraction of lanthanides from low grade bauxite. The effect of different parameters such as temperatures and concentration of oxalic acid in leaching process were investigated. The content of La, Ce and Y elements were determined using ICP-OES. The experimental result shows that the efficiencies of lanthanide leaching are the temperature-dependent. Increasing leaching temperature from 45°C to 85°C did not improve recoveries of lanthanides. The most optimum condition was found at oxalic acid leaching of 1 mol/L, leaching temperature at 40°C, and time for 2 hours. The obtained results show that the lanthanides can be leached using oxalic axid. This finding may lead to more effective and economical method to separate lanthanides from low grade bauxite.

Abstract: The paper concerns an approach about using environmental technology and hydrometallurgical process to the recovery of valuable metal from waste cathode material produced during the manufacture of lithium-ion batteries. It is noteworthy that the content of nickel, manganese and cobalt from cathode material are in the extraordinary large proportion. In the acid leaching step, the essential effects of H₂SO₄ concentration, H₂O₂ concentration, leaching time, liquid-solid mass ratio and reaction temperature with the leaching percentage were investigated. The cathode material was leached with 2M H₂SO₄ and 10 vol.% H₂O₂ at 70 °C and 300 rpm using a liquid-solid mass ratio of 30 ml/g and the leaching efficiency of cobalt was 98.5%, lithium was 99.8%, nickel was 98.6% and manganese was 98.6% under optimum conditions. Kinetic study demonstrates the activation energies for those analyzed metals with Arrhenius equation and manifests the data with hybrid reaction control mechanism. The process was proved from activation energies ranged from 27.79 to 47.25 kJ/mol. Finally, the valuable metals will be leached in sulfuric acid effectively.

Abstract: Based on the characters of coastal saline-alkali soil in Yellow River Delta, four kinds of soil with the total salt content of 0.13%, 0.24%, 0.86%, 2.07% respectively, were used as the research objects in this study. Leaching experiment of soil improvement were operated by using flue gas desulfurization gypsum and humic acid as the soil amendments through single or combined application. After leaching, the pH values, EC and the total salt content including Na⁺, Ca²⁺ and Mg²⁺ of four times leachate were analyzed. Meanwhile, the sodium adsorption ratio (SAR) was also calculated in order to evaluate the amendment efficiency. The results showed that: the pH values of the leachate of flue gas desulfurization gypsum without (treat A) or with humic acid (treat C) were significantly lower than that of control group (treatment CK) and humic acid (treatment B), while the EC values were significantly higher. For the saline-alkali soil, all of treatment A, B and C could decrease soil pH, exchangeable Na⁺ and soil SAR. Treatment B could decrease the total salt content insignificantly, while treatment A and C could increase the total salt content significantly. By analyzing the results, it was found that treatment C had the most significant improvement effect, comparing with the treatment CK. PH was decreased respectively 0.26%, 0.83%, 1.05% and 1.83%, Na⁺ was decreased respectively 82.4%, 92.6%, 89.1% and 78.6%, SAR was decreased respectively 97.4%, 98.5%, 97.7% and 94.7%. The experimental results demonstrate that a combined application of flue gas desulfurization gypsum and humic acid is a potential method to improve coastal saline alkali soil in Yellow River Delta on the basis of ensuring the irrigation amount.

Abstract: The causes of the global vanadium consumption increase are described and new applications of this metal are given in the article. The main natural sources of vanadium are titanomagnetite, which is a strategic mineral raw material. The current volumes of vanadium extraction from natural raw materials do not match the demand of the market. Therefore there is an urgent need for recycling of secondary and technogenic sources. Partially the basic existing technologies processing vanadium-containing waste are reviewed. The effect of these wastes on the environment and human health is analyzed. The importance of vanadium steel slag recycling for the ecological state of industrial regions, resource-efficiency in expanding the raw material sources of vanadium and reducing the cost of steel production in general is shown. The results of studies on the extraction of vanadium in the form of soluble vanadate of metallurgical vanadium slag using hydrometallurgical processing are demonstrated. The analysis of the received values of the vanadium extraction degree was conducted. The influence of various factors on the completeness of extraction was examined. A significant influence on the vanadium extraction degree of slag chemical composition, the ratio of slag and alkaline additives in the charge, conditions of roasting and leaching was revealed.

Abstract: To improve the efficiency of sustainable recovery of valuable resources (such as copper, gold, uranium), advanced technologies of electrochemistry, surface chemistry and materials characterization, such as Synchrotron X ray-absorption spectroscopy (XAS), X-Ray photoelectron spectroscopy (XPS), and in situ X-ray Diffraction (XRD) have been employed to investigate the interactions between microbes and sulfide minerals in situ to gain a detailed understanding of the chemical reaction mechanisms operating in bioleaching. It has been demonstrated that alternating current Scanning Electrochemical Microscopy (ac-SECM) allows for straightforward characterization of sulfide mineral samples in aqueous solution. With the technology localized electrochemical properties of the mineral surface including the surface current mapping can be achieved. Robust chemical sensors have been developed for real time, in-situ monitoring of key leaching process parameters.