Enhancing copper recovery from copper minerals via sulfuric acid leaching

The article describes results of research on copper recovery from low-grade copper ore by heap bioleaching method. The objects of investigation are ores of the Benkala deposit. Results of chemical analysis by atomic-emission spectrometric method and chemical phase analysis present ores element composition and identify copper and iron forms existing in the ores. Ores were subjected to bioleaching by chemolithotrophic bacteria, which oxidizes sulfur and iron compounds. Acidithiobacillus ferrooxidans FT-24 and BF, Acidithiobacillus thiooxidans BS, Acidithiobacillus ferrivorans SU-8 and Sulfobacillus thermosulfidooxidans ST-12 strains were used in the research. It was modeling the process of bacterial heap leaching of low-grade ore in percolation columns. Comparison of efficiency of sulfuric acid and bacterial leaching in percolation columns shows advantage of bioleaching. The copper yield was 47 % at using conventional sulfuric acid leaching, while utilizing bacterial leaching increased the copper recovery up to 86 % during 90 days of the experiment. The values of oxidation-reduction potential (ORP) at sulfuric acid and bacterial leaching of copper ore presented are in accordance with yield of copper. The values of ORP at standard sulfuric acid leaching are between 330-360 mV, at bacterial leaching more high and are 480-550 mV due to high content of ferric iron. During the extraction of copper, the effect of the organic reagent LIX 984N in concentrations 50 and 250 mg/L on the activity of microorganisms was studied. As a result, the extraction reagent has a little effect on the growth of microorganisms and the extraction of copper. Without adding the extraction reagent, the total copper recovery was about 83 %, while the addition of the extraction reagent with concentration 250 mg/L decreased it to 81 %. So using bioleaching technology allows deep processing of copper ore due to oxidation of copper sulfide minerals.

Natural graphite is classified as a strategic critical raw material by the European Union due to its strategic significance. The demand is steadily increasing, but the current purification methods are not environmentally sustainable, highlighting the need for greener alternatives. This study investigates the effects – sulfuric acid (H2SO4) leaching, thermal treatment, and their combination – on natural graphite from a flotation pilot plant. In the sulfuric acid leaching, the influences of reaction time (60–300 min), temperature (70–100°C), sulfuric acid concentration (0.5–3 mol/L), and liquid-to-solid ratio (10–20 mL/g) were systematically studied using experimental design. Leaching effectively removed 91.4% iron and 52.9% aluminum, but was ineffective against silicon-containing phases. A short 15 min thermal treatment at 2400°C in an argon atmosphere using induction annealing eliminated most silicon phases and other impurities, although residual 2.65 mg/g iron and 1.27 mg/g silicon remained. The combined approach reduced iron and silicon contents to 0.24 and 0.25 mg/g, respectively, and increased the carbon content from 78.4 to 97.6 wt% to near commercial battery-grade levels (98.0 wt%). Additionally, the combination-treated graphite exhibited the lowest degree of structural defects, offering a more sustainable route for purifying natural graphite to high-purity levels compared to conventional halogen-containing techniques.

Physico-chemical nature and leaching behaviour of goethites containing Ni, Co and Cu in the sorption and coprecipitation mode

Inherent problems of oxidized gold-bearing copper ores processing and a comparison of hydrometallurgical methods, applied for such materials, are discussed in this article. Studies on sulfuric acid and cyanide leaching have been carried out, using the following sample of oxidized ore from one of the copper deposits (Kyrgyzstan), %: 15 Mg O, 45.6 SiO2, 0.1 S, 20 Ca O, 12.1 Fe2O3, 0.86 Cu, 1.78 Au, 9.61 Ag. Studies have been carried out. Agitation sulfuric acid leaching able to extract up to 29.9% of copper. At the same time, column sulfuric acid leaching able to extract up to 78.5% of total copper and 85.23% of copper presented by acid-soluble compounds. In case of precious metals, the agitation cyanide leaching is able to extract up to 97.6% of gold in 24 h. Increasing the grinding fineness up to 90% - 74 μm reduces cyanidation duration down to 12 h. The consumption of sodium cyanide is 4.8 kg/t of ore. At the same time, column cyanide allows to extract 73.5% Au and 81.9% Ag during 111 days, whereas 52.4% of gold is recovered in the first 10 days. Consumption of sodium cyanide is 5.45 kg/t. The most efficient ways for processing of such materials are proposed.

Highly selective separation of vanadium over iron from stone coal by oxalic acid leaching

Gossan discarded from mining processes result in metal resource wastage, and its long-term stacking causes environmental hazards. Therefore, this article considers zinc-containing gossan as the research object. The ore was roasted to prepare primary zinc ferrite products and sulfuric acid leaching was performed for purification. Then, XRD analysis was performed to characterize the purified products. The results indicated that the effect of sulfuric acid concentration on the purification of the products was related to its zinc ferrite content. Furthermore, the effect of leaching temperature on the purification of zinc ferrite products was related to sulfuric acid concentration; the lower the sulfuric acid concentration, the more considerable the effect of leaching temperature. The conditions suitable for purifying the products through sulfuric acid leaching are as follows: sulfuric acid concentration of 140 g/L, liquid–solid ratio of 4:1, leaching temperature of 80 °C, leaching time of 120 min, and stirring speed of 300 rpm. This article determines the factors affecting the purification of zinc ferrite by sulfuric acid leaching along with the optimal purification conditions. The findings presented herein provide a theoretical foundation for the development of new processes for preparing zinc ferrite, which has considerable industrial application value.

Rare earth element recovery in molten salt electrolysis is approximately between 91 and 93%, whereof 8% is lost in waste molten salt slag. Presently, minimal research has been conducted on the technology for recycling waste rare earth molten salt slag, which is either discarded as industrial garbage or mixed with waste slag into qualified molten salt. The development of a new approach toward the effective treatment of rare earth fluoride molten salt electrolytic slag, which can recycle the remaining rare earth and improve the utilization rate, is essential. Herein, weak magnetic iron separation, sulfuric acid leaching transformation, water leaching, hydrogen fluoride water absorption, and cycle precipitation of rare earth are used to recover rare earth from their fluoride molten salt electrolytic slag, wherein the thermodynamic and kinetic processes of sulfuric acid leaching transformation are emphatically studied. Thermodynamic results show that temperature has a great influence on sulfuric acid leaching. With rising temperature, the equilibrium constant of the reaction gradually increases, and the stable interval of NdF3 decreases, while that of Nd3+ increases, indicating that high temperature is conducive to the sulfuric acid leaching process, whereof the kinetic results reveal that the activation energy E of Nd transformation is 41.57 kJ/mol, which indicates that the sulfuric acid leaching process is controlled by interfacial chemical reaction. According to the Nd transformation rate equation in the sulfuric acid leaching process of rare earth fluoride molten salt electrolytic slag under different particle size conditions, it is determinable that with the decrease of particle size, the reaction rate increases accordingly, while strengthening the leaching kinetic process. According to the equation of Nd transformation rate in the sulfuric acid leaching process under different sulfuric acid concentration conditions, the reaction series of sulfuric acid concentration K = 6.4, which is greater than 1, indicating that increasing sulfuric acid concentration can change the kinetic-control region and strengthen the kinetic process.

Comparison and evaluation of vanadium extraction from the calcification roasted vanadium slag with carbonation leaching and sulfuric acid leaching

Ammoniacal leaching and sulfuric acid leaching were explored separately to recover copper from smelter slag. The overall 75% copper recovery was achieved from the smelter slag under optimum condition using ammoniacal leaching. The low copper recovery in this process is directly related to the complex slag mineralogy and dissolution kinetics. To overcome such problems, sulfuric acid leaching was applied separately. This method provided an overall 89% copper recovery under atmospheric condition. The use of sulfuric acid as the leaching agent was found to be more advantageous than ammonia due to the complex interlocking nature of copper bearing particles and different reaction kinetics of the slag.

Physical treatment and chemical treatment of spent lithium-ion battery were studied in our research team. Especially we developed two types of acidic leaching for crushed powders containing LiCoO2 of spent lithium ion battery. One of them is sulfuric acid leaching with H2O2 as a reducing agent. The leaching rates of cobalt, lithium and the other metals were above 99 % at the condition of 2 M H2SO4, 10 vol. % H2O2, 75°C, 300 rpm agitation speed, 250 g/5L solid liquid ratio and 75 minutes reaction time. And the other leaching process is the oxalic acid leaching. In this process more than 99% of Li and less than 1% of Co were dissolved at the condition of 3M oxalic acid, 80°C reaction temperature, 300rpm agitation speed, 50g/L initial solid/liquid ratio and 90min extraction time. Each process has its advantage and disadvantage. In sulfuric acid leaching, leaching reagent is very cheap and cobalt could be recovered into cobalt hydroxide. On the other hand, oxalic acid is more expensive than sulfuric acid but lithium could be dissolved selectively. Also cobalt could be recovered into cobalt oxalate and it could be changed into cobalt oxide after heat treatment. In order to select the effective recycling process, recovery rate and purity of cobalt hydroxide and cobalt oxalate were compared and it was investigated which process was more environment-friendly and economical.

In this paper, the conventional physical separation method such as flotation, gravity separation, magnetic separation, alkaline leaching and sulfuric acid leaching were studied. The effects of grinding fineness, amount of agent, magnetic intensity, roasting temperature, roasting time, the leaching agent and leaching time on the leaching of zinc were investigated, respectively. The results show that the leaching rate of zinc is below 50% in the conventional alkaline leaching, and the leaching rate of zinc is below 85% and the leaching rate of iron is above 35% in sulfuric acid leaching. Compared with XRD pattern of the raw ore, the different diffraction peaks of smithsonite is off in alkaline leaching products. In sulfuric acid leaching, the different diffraction peaks of smithsonite are off in the leaching products when sulfuric acid concentration is less than 60 g/L. After 60 g/L, the different diffraction peaks of smithsonite and siderite are off in the leaching products.

In this paper, the conventional physical separation method such as flotation, gravity separation, magnetic separation, alkaline leaching and sulfuric acid leaching were studied. The effects of grinding fineness, amount of agent, magnetic intensity, roasting temperature, roasting time, the leaching agent and leaching time on the leaching of zinc were investigated, respectively. The results show that the leaching rate of zinc is below 50% in the conventional alkaline leaching, and the leaching rate of zinc is below 85% and the leaching rate of iron is above 35% in sulfuric acid leaching. Compared with XRD pattern of the raw ore, the different diffraction peaks of smithsonite is off in alkaline leaching products. In sulfuric acid leaching, the different diffraction peaks of smithsonite are off in the leaching products when sulfuric acid concentration is less than 60 g/L. After 60 g/L, the different diffraction peaks of smithsonite and siderite are off in the leaching products.

Separation of arsenic and extraction of zinc and copper from high-arsenic copper smelting dusts by alkali leaching followed by sulfuric acid leaching

In this paper, sulfuric acid leaching was carried out to assess the effect of several parameters on metal extraction in a low grade complex gossan ore in which the grade of zinc and iron is 13% and 40.2%, respectively. Parameters, such as sulfuric acid concentration, liquid to solid ratio and leaching temperature, were studied. The results show that the zinc leaching rate is almost 80%, while the iron leaching rate is about 45% used strong acid with 200g/L. It can be seen from the results that sulfuric acid leaching could not effectively recover zinc from gossan ores studied in this paper because of iron dissolving greatly.

Enhanced process route to remove fluorine and uranium from copper concentrades by selective sulfuric acid leaching