Extraction Of Valuable Metals Research Articles

The extraction of valuable metals and phase transformation and formation mechanism in roasting-water leaching process of laterite with ammonium sulfate

Ammonium sulfate roasting-water leaching technology is a potential cleaner production process with low energy consumption, minor equipment corrosion and high selectivity contrasted with the traditional metallurgy process. Thermodynamic analysis showed that the main mineral of serpentine and magnesium iron ore in raw ore could react with ammonium sulfate, and the analysis through XRD and EDS also proved that most mineral phases were (NH4)3Fe(SO4)3, (NH4)2Mg2(SO4)3, Fe2O3, and SiO2 as roasting products. With the decomposition of original mineral in roasting process, valuable metals of nickel, cobalt and manganese disseminated in other host minerals could be released to react with ammonium sulfate and produce metal sulfate which could be leached into the water. However, the iron mainly existed in iron oxide was water-insoluble and remained in residues. The conditions of the ammonium sulfate roasting-water leaching process, such as ammonium sulfate dosage, roasting temperature, roasting time, leaching temperature, and leaching time have been investigated here. The roasting temperature (only 400 °C) is lower than other pyrometallurgical process, which leads to less energy consumption and equipment corrosion. The leaching of Ni, Co, Mn and Fe could be 90.8%, 85.4%, 86.7% and 9.98% at the optimal condition, and the selectivity extraction can be achieved.

Chemo-biohydrometallurgy—A hybrid technology to recover metals from obsolete mobile SIM cards

The exponential increase in the cellular networking and advancement in the related technology has led to an increase in obsolete SIM cards. Elemental composition of obsolete SIM waste (SIMW) of particle size 355–700μm was 75.84% Cu, 0.42% Au, and 0.01% Ag. SIMW can be used to extract valuable metals. A chemo-biohydrometallurgy approach was employed for metals recovery from SIMW. Bioleaching experiments were performed in 150ml Erlenmeyer flasks with 50ml of Luria broth medium at pH 9, glycine concentration 5g/L, rpm 150, temperature 30° C and pulp density 10g/L. Two step bioleaching of untreated SIMW using Chromobacterium violaceum yielded poor metals mobilization of copper (13.79%), gold (0.44%) and silver (2.55%). Acidic pretreatment of SIMW recovered 72% of copper, as its high concentration cause hindrance for leaching and solubilization of other metals like Au, and Ag. Subsequent, two-step bioleaching of pretreated SIMW at alkaline pH using Chromobacterium violaceum solubilized 70.61% of the remaining Cu within 4days of incubation period. Therefore, a hybrid technology can be applied to efficiently recover Cu and other metals from SIMW. To the best of authors’ knowledge, this is the first report of using hybrid technology to leach out Cu and other metals from SIMW.

Pyrometallurgical Treatment of High Manganese Containing Deep Sea Nodules

The steadily growing demand for critical metals and their price increase on the world market makes the mining of marine mineral resources in the not too distant future probable. Therefore, a focus lays on the development of a sustainable, zero-waste process route to extract valuable metals from marine mineral resources such as manganese nodules. These nodules contain industrially important metals like nickel, copper and cobalt in substantial amounts. However, the development of a general metallurgical process route is challenging due to varying nodule compositions. Especially challenging is a high Mn content, since the liquidus temperature of a smelted slag phase directly correlates with Mn content. This paper presents thermodynamic models created in FactSage™ 6.4, which support direct reduction smelting of manganese nodules in an electric arc furnace. Thermodynamic modeling has never been applied to the metallurgical treatment of manganese nodules, and therefore, represents a significant advantage over previous studies. Furthermore, these calculations were verified in lab scale experiments. The nodules were supplied by BGR, German Federal Institute for Geosciences and Natural Resources, and have origin in the German licensed territory of the Clarion Clipperton Zone in the Pacific Ocean.

Extraction of copper, zinc and cadmium from copper–cadmium-bearing slag by oxidative acid leaching process

An intensified oxidative acid leaching of copper–cadmium-bearing slag featuring using high-efficient oxygen carrier, such as activated carbon, was investigated to achieve high leaching rate of valuable metals. The effects of leaching variables, including agitation rate, sulfuric acid concentration, temperature, slag particle size, activated carbon and cupric ion concentration, were examined. It is found that leaching rates of cadmium and zinc both exceed 99 % in a very short time, but for copper, leaching rate of 99 % is achieved under the optimized leaching parameters, which are agitation rate of 100 r·min−1, sulfuric acid concentration of 15 wt%, leaching temperature of 80 °C, slag particle size of 48–75 μm, activated carbon concentration of 3 g·L−1, liquid-to-solid ratio of 4:1, oxygen flow rate of 0.16 L·min−1, and leaching time of 60 min. The macro-leaching kinetics of copper metal was analyzed, and it is concluded that the inner diffusion is the controlling step, with apparent activation energy of 18.6 kJ·mol−1. The leaching solution with pH value of 2–4 can be designed to selectively extract valuable metals without neutralization, and the leaching residue can be treated by prevailing Pb smelting process. The phase compositions of the leaching residue are PbSO4 and CaSO4. And the chemical composition analysis result shows that about 13 % Pb is contained in the residue, which can be recycled by Pb smelting technology in an Isa furnace. The way is that the Pb-containing concentrate and the PbSO4-containing leaching residue can be mixed and placed in the furnace.

Global response of Acidithiobacillus ferrooxidans ATCC 53993 to high concentrations of copper: A quantitative proteomics approach

Acidithiobacillus ferrooxidans is used in industrial bioleaching of minerals to extract valuable metals. A. ferrooxidans strain ATCC 53993 is much more resistant to copper than other strains of this microorganism and it has been proposed that genes present in an exclusive genomic island (GI) of this strain would contribute to its extreme copper tolerance. ICPL (isotope-coded protein labeling) quantitative proteomics was used to study in detail the response of this bacterium to copper. A high overexpression of RND efflux systems and CusF copper chaperones, both present in the genome and the GI of strain ATCC 53993 was found. Also, changes in the levels of the respiratory system proteins such as AcoP and Rus copper binding proteins and several proteins with other predicted functions suggest that numerous metabolic changes are apparently involved in controlling the effects of the toxic metal on this acidophile. SignificanceUsing quantitative proteomics we overview the adaptation mechanisms that biomining acidophiles use to stand their harsh environment. The overexpression of several genes present in an exclusive genomic island strongly suggests the importance of the proteins coded in this DNA region in the high tolerance of A. ferrooxidans ATCC 53993 to metals.

A novel process to effectively extract values from a manganese-bearing Au-Ag ore by pretreatment with iron scrap as reductant

A novel process was developed to improve the extraction of valuable metals from a manganese-bearing gold-silver ore. Before cyanidation, a reductive sulfating leaching pretreatment process was adopted to preferentially dissolve manganese from the primary ores, according to mineralogy of the ores and possible leaching thermodynamic calculations of manganese minerals, and iron scrap was firstly introduced as reductant because of its low cost and wide source in China. In pretreatment tests, the effects of iron scrap concentration, sulfuric acid concentration and leaching temperature were studied, and the results indicated that manganese could be rapidly leached out to a complete degree even at room temperature. Then the reduced residue was suggested to the cyanidation process for silver and gold extraction, and the effect of cyanide concentration was also addressed. Based on the above study, pilot tests were finally conducted in Beiya 50 t/d concentrator to correctly evaluate the whole leaching process in the case of continuous production, and the gold and silver extractions in the novel process were up to 92.16 and 82.33%, respectively, corresponding to an increase of 9.08 and 45.97% compared to those in the direct cyanidation process, which are of great implications for future commercial operations of these refractory manganese-bearing gold-silver ores.

Investigating the Structurization Process of Iron Monosilicide Powders Obtained by High-Temperature Synthesis from the Preliminarily Mechanoactivated Burden

Raising the efficiency of production, for the most part depends on the use of secondary material resources, particularly such wastes as metallurgical slags of the operating plants. Huge quantity of such slags generates an urgent problem of their reasonable utilization with maximum extraction of valuable metals. The objective of the thesis is the development of an efficient technology for obtaining powder iron-monosilicon alloy by means of processing of iron and silicon containing dump slags on the basis of out-of-furnace aluminothermic reduction. Thus, structure of the obtained alloy strоngly depends on the state of the initial slags, on their correlation and on the amount of components contained in the complement of the burden. The structurization processes of the iron powder-like silicide obtained by the method of self-propagating high-temperature synthesis of the preliminarily mechano activated burden are investigated. The combination of these two methods allows to form unique materials and alloys, significantly reducing the power expenditure by applying the exothermal effect of the reactions, and to obtain a product with special physico-chemical properties. The results of the investigation are to obtain monophase iron silicide by preliminary mechano-chemical activation of the burden, containing a mixture of wastes of a certain composition obtained from metallurgical production—the Alaverdi copper-smelting and the Yerevan molybdenum factories, as well as KNO3 and CaO by combined aluminothermal reduction in the SHS regime. By the X-ray fluorescent method of analysis, the structurization process of the obtained alloy is studied. It is shown that, at the expense of preliminary mechano-chemical activation of the burden, a finer and homogeneous structure of powder-like iron silicide is formed.

Research on Reusing Technology for Disassembling Waste Printed Circuit Boards

Waste printed circuit boards (WPCBs), which have lots of highly valuable components and toxic substances, are important subjects for disposal of waste electric and electronic equipment (WEEE). Nowadays material recycling and components reusing are still the main disposal methods of WPCBs. Increased crushing-sorting separation technology to extract valuable metals from WPCBs usually produce large amounts of resin powder which result in seriously secondary pollution. The study aims to the disassembly acceleration and separation of components without damage on WPCBs. The components reuse-oriented disassembly technology is studied, in which the key technologies of leaching and sealing-off. Fluoboric acid/ Hydrogen peroxide leaching system is discussed in detailed including solution concentration, reaction time and metal leaching rate. The experiments realize the dismantling of WPCBs by selectively dissolve solder and offer a new way to recycle valuable materials from WPCBs and prevent the environmental pollution effectively.

Selective recovery of valuable metals from nickel converter slag at elevated temperature with sulfuric acid solution

Abstract High pressure oxidative acid leaching (HPOXAL) was employed to extract valuable metals from nickel converter slag. Parameters such as sulfuric acid concentration, temperature, liquid/solid (L/S) ratio, leaching time, oxygen partial pressure and particle size were investigated to optimize the solubility of metal values and improve the solid–liquid separation characteristics of the leaching slurry. A highly selective leaching of valuable metals with extraction of >97% for cobalt and nickel, >95% for copper and 2 h. The residue containing hematite, silica and

State-of-the-art of recycling e-wastes by vacuum metallurgy separation.

In recent era, more and more electric and electronic equipment wastes (e-wastes) are generated that contain both toxic and valuable materials in them. Most studies focus on the extraction of valuable metals like Au, Ag from e-wastes. However, the recycling of metals such as Pb, Cd, Zn, and organics has not attracted enough attentions. Vacuum metallurgy separation (VMS) processes can reduce pollution significantly using vacuum technique. It can effectively recycle heavy metals and organics from e-wastes in an environmentally friendly way, which is beneficial for both preventing the heavy metal contaminations and the sustainable development of resources. VMS can be classified into several methods, such as vacuum evaporation, vacuum carbon reduction and vacuum pyrolysis. This paper respectively reviews the state-of-art of these methods applied to recycling heavy metals and organics from several kinds of e-wastes. The method principle, equipment used, separating process, optimized operating parameters and recycling mechanism of each case are illustrated in details. The perspectives on the further development of e-wastes recycling by VMS are also presented.

Extraction of metals from automotive shredder residue: Preliminary results of different leaching systems

The study is focused on the extraction of valuable metals from automotive shredder residue (ASR) by different leaching solutions. First, ASR samples were roasted at 600°C to simulate a thermal treatment processing. Distilled water, citric and sulphuric acid were preliminarily investigated, thus two further full factorial systems entailing H2SO4–H2O2 and H2SO4–H2O2–Fe3+ were tested. The preliminary experimental results showed that 0.1mol·L−1 H2SO4 solution extracted 100% of Cu, Fe and Zn, whereas citric acid leached 100% of Zn and Pb, 59% of Fe and 62% of Cu; whereas, H2SO4–H2O2 and H2SO4–H2O2–Fe3+ (Fenton's) leaching media showed that Cu, Fe and Zn can be extracted simultaneously and completely from the ASR ashes before final disposal.

Extraction of niobium, yttrium, and cerium from a low-grade niobium-bearing ore by roasting (NH4)2SO4-Na2SO4-H2SO4 system

A novel process of extracting niobium, yttrium, and cerium from a low-grade niobium-bearing ore by the roasting (NH4)2SO4-Na2SO4-H2SO4 system was experimentally studied. The influences of various factors, such as roasting temperature, roasting time, mass ratio of agents-to-ore and particle size fraction on the extraction of valuable metals were comprehensively investigated. It is found that the roasting Na2SO4-H2SO4 system is effective to extract the niobium, yttrium, and cerium. The obtained optimum conditions for the extraction of Nb, Y, and Ce are roasting temperature of 300 °C, roasting time of 3 h, mass ratio of Na2SO4:H2SO4:Ore of 0.5:1.0:1.0, and particle size fraction of −74 μm (~95 %). Under the optimum condition, the maximum recovery of Nb, Y, and Ce can reach 90.53 %, 92.15 %, and 98.04 %, respectively. All the results generated from this study will provide the fundamentals for Nb, Y, and Ce extraction from a niobium-bearing ore with low-grade.

Isolation and characterization of a novel Acidithiobacillus ferrivorans strain from the Chilean Altiplano: attachment and biofilm formation on pyrite at low temperature

Microorganisms are used to aid the extraction of valuable metals from low-grade sulfide ores in mines worldwide, but relatively little is known about this process in cold environments. This study comprises a preliminary analysis of the bacterial diversity of the polyextremophilic acid River Aroma located in the Chilean Altiplano, and revealed that Betaproteobacteria was the most dominant bacterial group (Gallionella-like and Thiobacillus-like). Taxa characteristic of leaching environments, such Acidithiobacillus and Leptospirillum, were detected at low abundances. Also, bacteria not associated with extremely acidic, metal-rich environments were found. After enrichment in iron- and sulfur-oxidizing media, we isolated and identified a novel psychrotolerant Acidithiobacillus ferrivorans strain ACH. This strain can grow using ferrous iron, sulfur, thiosulfate, tetrathionate and pyrite, as energy sources. Optimal growth was observed in the presence of pyrite, where cultures reached a cell number of 6.5·107 cells mL−1. Planktonic cells grown with pyrite showed the presence of extracellular polymeric substances (10 °C and 28 °C), and a high density of cells attached to pyrite grains were observed at 10 °C by electron microscopy. The attachment of cells to pyrite coupons and the presence of capsular polysaccharides were visualized by using epifluorescence microscopy, through nucleic acid and lectin staining with Syto®9 and TRITC-Con A, respectively. Interestingly, we observed high cell adhesion including the formation of microcolonies within 21 days of incubation at 4 °C, which was correlated with a clear induction of capsular polysaccharides production. Our data suggests that attachment to pyrite is not temperature-dependent in At. ferrivorans ACH. The results of this study highlight the potential of this novel psychrotolerant strain in oxidation and attachment to minerals under low-temperature conditions.

Alkali extraction of valuable metals from spent Mo–Ni/Al2O3 catalyst

Extraction of metal values from the spent Mo–Ni/Al2O3 catalyst containing complex oxides was investigated in this work. Aiming at studying selective extraction of metals, a sequential recycle process is conceived as follows: First, acidic oxide MoO3 is selectively extracted by alkali leaching. Then amphiprotic Al2O3 is dissolved by caustic soda autoclaving. Al(OH)3 is obtained by seeding precipitation and used to prepare the support of new catalysts. Besides, Ni(OH)2 remains in the digestion residue as “green mud” of the modified Bayer process. In the light of the idea, alkali leaching experiments were conducted, using several common basic leaching agents. The results show that caustic autoclaving at low NaOH/Mo ratio could selectively extract Mo without significant dissolution of the matrix. Under the optimum operating conditions of temperature 160°C, NaOH dosage 1.2 times the stoichiometric amount, solid/liquid ratio 1:4, retention time 120min and stirring rate 300rpm, over 96% of Mo was recovered while less than 0.2% of Al was dissolved. After leaching of Mo, the Al2O3 matrix was dissolved completely by caustic soda autoclaving at 160°C. Sodium aluminate solution was purified by CaO and Ba(OH)2. The overall Mo and Al extraction yields were up to 99%.

A TECHNICAL METHOD OF EXTRACTION OF GOLD FROM E-WASTE: A MULTI-SENSOR BASED METHOD USING MICROCONTROLLER

The disposal of e-wastes into the environment is hazardous as they contain chemicals. The conventional methods of disposing these ewastes are irrelevant and have adverse effect on the environmental conditions which is a threat to life. The objective of this paper is to describe the recycling of e-wastes and extraction of valuable metals like gold and silver from it. The aquaregia solution based method of extraction is the oldest and conventional method. The steps and procedures that are followed and practiced are to be done manually which seems to be quite risky as it is a chemical process. But the aquaregia solution method of extraction can be easily automated for precise and faster extraction. The intension of our paper is to propose an idea of an automation system for the recovery of gold from E-waste. This system for gold recovery is solely controlled by the microcontroller. There is use of several types of sensors, which are in turn act as input providers to the microcontroller, in order to control the whole process. There is great advantage if it is implemented practically. It can create a sort of industrial solution as e-waste is global problem. A new trend in the recycling industry will be created which will be a revolutionary step. The only thing is that the initial investment will be quite more. But once implemented it can be used for long terms and for cost effectiveness.

Biogenic catalysis in sulphide minerals' weathering processes and acid mine drainage genesis.

Bioleaching and biogenesis are the main outputs from a large group of environmental processes participating in the natural material cycle, used in raw materials processing. Bio-oxidation reactions are the main basis for bioleaching procedures, often participating in parallel leaching processes. During the leaching processes of polycomponent sulphide substrates, the factor of process selection also plays an important role, being in direct relation to the electric properties and galvanic effect occurring between the individual components of the leaching substrate. This work gives a summary of the results of a research focused on the possibilities of using biotechnological procedures for treatment of Slovak sulphide ores. The object of the research is extraction of valuable metals, undesirable admixtures and degradation of crystal lattice of sulphides for subsequent chemical leaching processing of precious metals. The results of experiments on the existence of biogenic processes in situ on waste dumps from exploitation containing residual sulphides are also presented. The processes result in acid mine drainage water generation. These waters are strongly mineralised (over 48 g/L) and of low pH; that is why they are very caustic. The arsenic content (2.558 mg/L) in outflowing waters from old mines is high and over the limits set by the law.

Extraction of Valuable Metals from Red Mud

The reason of comprehensive utilization of red mud is that it contains recycled oxides and a variety of valuable metals. In this paper, the basic characterization of red mud is described. The current developments of extraction of Fe, Ti, Sc, rare earth and valuable metals from red mud are summarized with some emphasis. In addition, the technological features of each process route are analyzed briefly. It can be concluded that it is practiable to extract Fe, Ti, Sc, rare earth and valuable metals from red mud. However, in order to realize recycling of red mud, the key is that an economic, energy saving, environment friendly and widely applicable process has to be found.

Comprehensive Utilization of Red Mud Remaining in Alumina Production

Red mud is a solid waste which is generated in the process of alumina production and is of highly alkaline. Red mud has very complex compositions, but contains a variety of rare and valuable metals. In addition, its high alkalinity is a severe pollution to water, land, air and environment, which has been one of the main factors to affect the sustainable development of aluminum industry. The characterization of red mud, the extraction of valuable metals from red mud, the utilization of red mud in construction materials, environmental restoration materials and other fields are introduced in this paper.

Extraction of metal values from waste spent petroleum catalyst using acidic solutions

The extraction of molybdenum and cobalt from spent petroleum catalyst (Co–Mo/Al2O3) was investigated using sulphuric and nitric acid solution. Direct leaching of spent catalyst with sulphuric acid was not effective, whereas the combination of sulphuric and nitric acid was significant for the recovery of both molybdenum and cobalt. The effect of experimental factors such as reaction time, acid concentration, temperature, solid–liquid ratio and particle size were studied to determine the best conditions for the solubilisation of metal values. The parameters, temperature and nitric acid concentration are found to be critical factors especially on leaching of molybdenum from the spent catalyst. Under optimum conditions (pulp density 10% (w/v), [H2SO4] 0.5M, [HNO3] 4.0M, particle size 51–70μm, temperature 50°C and time 5h), about 99.7% of molybdenum and 99.6% of cobalt could be extracted with 14.9% extraction of aluminium.

Extraction of valuable metals from manganese–silver ore

A combined novel process was developed to extract valuable metals from manganese–silver ore. The preferential dissolution of manganese from the primary materials was achieved through reductive leaching in dilute sulfuric acid medium with sodium sulfite as the reductant. Silver, which was enriched in the reductive leaching residue, was leached by complexation dissolution with hydrochloric acid and calcium chloride solution. Effects of process parameters on manganese extraction in the reductive leaching process were investigated, including the average particle size, the amount of sodium sulfite addition, sulfuric acid addition, liquid/solid ratio, leaching temperature and time. As for the silver extraction, the effects of Cl− concentration, hydrochloric acid addition, leaching temperature and time were also addressed. The results suggested that the extraction of manganese and silver could reach 99% and 92% respectively at the optimum conditions, while the high silica-containing product was obtained as the final residue.