Extraction Of Valuable Metals Research Articles

Processes of Extraction of Non-Ferrous and Precious Metals from Alternative Sources of Raw Materials

The presence of precious metals in electronic waste such as gold, silver, platinum and palladium, as well as non-ferrous metals (copper, nickel, zinc, tin, etc.) make it attractive for recycling. In industry, both hydrometallurgical and pyrometallurgical methods are used to extract valuable metals from electronic waste. Universal method for processing of electronic scrap waste does not exist nowadays.

Enhanced anodic dissolution of cupronickel alloy scraps by electro-generated reactive oxygen species in acid media

Recycling of the cupronickel alloy scraps not only solves environmental related issues but also realizes the extraction of valuable metals and saves consumption of primary ore resources. Oxidative dissolution is a critical step for the recycling of valuable metal from the alloy scraps. In order to improve the dissolution kinetics and efficiency, a novel integrated electrochemical dissolution strategy for the sustainable recycling of the cupronickel alloy scraps was first developed, where the in-situ electro-generated reactive oxygen species (ROS) were employed as the indirect oxidative mediator. Much higher dissolved concentration of Ni, Zn, and Cu was reached by the present integrated strategy than that of the direct anodic dissolution process, which is attributed to the in-situ produced oxidative H2O2 and ·OH via oxygen reduction reaction and electro-Fenton-like reaction, respectively. Moreover, the large quantity of ROS can be electro-generated, thus achieving high dissolved concentration, under the optimum condition with the preset potential of 0.3 V (vs. Ag/AgCl) or current density of 2.54 mA/cm2, respectively. This novel synergistic strategy may serve as a promising and cost-effective technique for the alloy scraps recycle and valuable metal extraction.

Effective leaching and extraction of valuable metals from electrode material of spent lithium-ion batteries using mixed organic acids leachant

The present work focuses on simultaneous recycling of Li and Co from crushed products of mixed electrode materials using mixed organic acids, in which benzenesulfonic acid and formic acid were cooperatively used as the leaching reagents. Results show that the optimal leaching efficiency of 97% Co and 99% Li were obtained under the conditions of 1.3mol/L benzenesulfonic acid, 1.5mol/L formic acid, a solid to liquid (S/L) ratio of 30g/L, and 40min reaction time at 50°C. Meanwhile, the leaching of Li and Co fits well to logarithmic rate model with apparent activation energy of 32.7 and 47.0kJ/mol in this given leaching system, respectively. Besides, cobalt was directly recovered from the leach liquor as pure cobalt benzene sulfonic with the recovery efficiency of 99%, and lithium can be entirely precipitated by adding phosphoric acid. Further, the reaction mechanism involves the leaching-hydrating-complexing model of LiCoO2 particles was proposed based on the dissolution behavior of metals and then verified by morphological and phase characterization (i.e. FT-IR, XRD and SEM-EDS) of the recycling product. The whole process is found to be effective and sustainable for recovery of Li, Co and graphite from mixed industrial crushing product of spent LIBs.

Growth effects in tropical nickel‐agromining ‘metal crops' in response to nutrient dosing

AbstractAgromining is an emerging technology that utilizes selected ‘metal crops' (= hyperaccumulator plants) to extract valuable target metals from unconventional resources for profit from mineralised soils. Growth characteristics, shoot metal concentrations, and agrominable locations are important considerations in economic agromining. Globally, the greatest potential for nickel (Ni) agromining exists in the tropics. However, the agronomic systems of tropical ‘metal crops' have not been previously tested. Furthermore, it is currently unknown whether nutrient dosing of prospective tropical agromining Ni ‘metal crops’ could possibly cause a shoot Ni‐dilution effect which may ultimately limit economically viable Ni yields. We undertook a pioneering study on Ni uptake and growth responses to nutrient dosing in two promising tropical ‘metal crops' (Phyllanthus rufuschaneyi and Rinorea cf. bengalensis). The experiment consisted of a large randomised block growth trial in large pots over 12 months in Sabah (Malaysia). At 3‐month intervals, the plants were exposed to soluble treatments that altered available concentrations of nitrogen (N), phosphorus (P), and potassium (K). We found strong positive growth responses to N and P additions in P. rufuschaneyi, whereas K additions had negative growth effects. In R. cf. bengalensis, all treatments had positive growth effects. The increases in biomass in response to nutrient dosing did not significantly reduce shoot Ni concentrations in both species, with the exception of N addition in P. rufuschaneyi. This study reveals that Ni uptake and growth responses to nutrient dosing are species‐dependent, primarily influenced by the ecophysiology of the species. Inorganic fertilization could possibly be an important component of the management of local ‘metal crops' to be used in viable commercial agromining in the tropics, but this needs to be tested in the field with different formulations of N, P, and K.

Microwave-Leaching of Copper Smelting Dust for Cu and Zn Extraction.

Industrial wastes may contain high concentrations of valuable metals. Extraction and recovery of these metals have several economic and environmental advantages. Various studies showed positive effects of microwaves as a pretreatment method before the leaching of minerals. However, there are empty rooms for exploring simultaneous microwave and leaching (microwave-leaching) of industrial waste material for the production of valuable metals. This investigation examined the microwave-leaching method to extract copper and zinc from a copper-smelter dust (CSD). The results of microwave-leaching mechanism were compared with conventional heating leaching based on kinetics modelling. The final Cu recovery in the conventional heating and microwave irradiation was 80.88% and 69.83%, respectively. Kinetic studies indicated that the leaching reactions follow diffusion across the product layer. Based on X-ray powder diffraction (XRD) analyses, during conventional experiments sulfate; components formed with high intensity as an ash layer which prevents reagent access to the solid surface and decreases the Cu dissolution. While the sulfate components did not detect in the microwave-leaching residuals which means that microwave irradiation helped to decrease the ash layer formation. Taking all mentioned results into consider it can be concluded that microwave-leaching can be considered as an efficient method for extraction of valuable metals from waste materials.

Novel extraction of valuable metals from circulating fluidized bed-derived high-alumina fly ash by acid–alkali–based alternate method

The recycling of valuable metals from circulating fluidized bed (CFB)-derived high-alumina fly ash (HAFA) paves the way for ash utilization with high economic benefits. However, obtaining an ideal extraction ratio for metals using a single acid treatment under moderate conditions is difficult. A moderate acid–alkali–based alternate method was used in this study to extract aluminum (Al) from CFB-derived HAFA. The dissolution behavior of lithium (Li), gallium (Ga), and rare earth elements (REY) was investigated. The characteristics of leaching residues were studied by XRD, 27Al and 29Si MAS NMR, BET, and SEM-EDS. Results show that Al in the units with low degree of polymerization distributed on the particle surface was preferentially dissolved in the HCl solution. HCl could not penetrate the particle interior and thus greatly limited the improvement of the Al extraction ratio. NaOH solution effectively removed SiO2 that accumulated on the particle surface and broke the Si–O–Al units in the residues. The exposed and liberated Al was further extracted with the HCl solution. Finally, 78% of Al2O3, 80% of Li, 72% of Ga, and 55% of REY in the ash were extracted with the HCl solution. Moreover, 63% of SiO2 in the ash was dissolved in the NaOH solution. The acid leaching residue presented abundant mesopores and a high specific surface area of 205 m2/g. The findings imply that the proposed method that combines the extraction of valuable metals and the preparation of mesoporous materials provides a new way to utilize CFB-derived HAFA.

Gold extraction from paleochannel ores using an aerated alkaline glycine lixiviant for consideration in heap and in-situ leaching applications

The decreasing grades of some gold deposits combined with the increasing depths, difficult surface topography, socioeconomic and geopolitical pressures often make the processing of such deposits infeasible by conventional mining, comminution and leaching technologies. To overcome these problems, the application of in-place, in-situ, and heap leaching often represent an optimal solution that minimises the capital and operating costs associated with mining and processing operations. Non-toxic, low cost lixiviants that are stable over an extended range of pH and Eh are required to provide any practical solution to in-situ leaching (ISL). Since ISL has the inherent benefit of increased natural rock temperature and pressure, glycine-based systems can be considered to extract valuable metals. Based on earlier studies on glycine leaching of pure gold foil, this research shows that Western Australian paleochannel ores are amenable to glycine-based ISL, at elevated alkalinity. The effects of pH, temperature, free glycine, ferric ions, sodium chloride and solids percentages on the kinetics of gold extraction were assessed. More than 85% of the gold can be extracted from ore with solutions containing 15 g/L glycine at pH 12.5 in 336 h. The presence of ferric ions did not improve the gold extraction, and most of the ferric has been precipitated from the leach solutions, implying that the chosen ferric complex was not sufficiently stable at the operating pH. The impurities dissolution during glycine leach was very low and highly selective leaching of gold over gangue was observed.

Deep eutectic solvents for cathode recycling of Li-ion batteries

As the consumption of lithium-ion batteries (LIBs) for the transportation and consumer electronic sectors continues to grow, so does the pile of battery waste, with no successful recycling model, as exists for the lead–acid battery. Here, we exhibit a method to recycle LIBs using deep eutectic solvents to extract valuable metals from various chemistries, including lithium cobalt (iii) oxide and lithium nickel manganese cobalt oxide. For the metal extraction from lithium cobalt (iii) oxide, leaching efficiencies of ≥90% were obtained for both cobalt and lithium. It was also found that other battery components, such as aluminium foil and polyvinylidene fluoride binder, can be recovered separately. Deep eutectic solvents could provide a green alternative to conventional methods of LIB recycling and reclaiming strategically important metals, which remain crucial to meet the demand of the exponentially increasing LIB production. The ever-increasing applications for Li-ion batteries in markets call for environmentally friendly and energy-efficient recycling technologies. Here the authors report using a deep eutectic solvent to extract valuable components of Li-ion batteries.

Comparison of the Ammoniacal Leaching Behavior of Layered LiNixCoyMn1–x–yO2 (x = 1/3, 0.5, 0.8) Cathode Materials

Recycling of spent lithium-ion batteries has received widespread concern on account of the high content of hazardous and valuable metals contained therein. In this research, ammonia leaching process is adapted to extract valuable metals selectively from LiNixCoyMn1–x–yO2 (x = 1/3, 0.5, 0.8) cathode materials. By employing ammoniacal solution as the leaching agent and sodium sulfite as reductant, Ni, Co, and Li are leached from lixivium either as complexes or metallic ion. Manganese is first leached from lixivium as Mn2+ and subsequently deposited from Mn3O4 to (NH4)2Mn(SO3)2·H2O as sodium sulfite is added. Compared with the agglomerated (NH4)2Mn(SO3)2·H2O tightly wrapped on the surface of the unreacted material, loose and porous Mn3O4 is more favorable to ion diffusion and leaching reaction. Amounts of 93.3% Li, 98.2% Co, and 97.9% Ni can be leached from LiNi1/3Co1/3Mn1/3O2 material by the introduced two-step leaching process, much higher than that with the one-step process. Simultaneously, 94.4% Li, 99.7% Co, and 99.5% Ni can be leached from LiNi0.5Co0.2Mn0.3O2 material, while the leaching efficiency of Li, Ni, and Co reaches 95.0%, 98.4%, and 96.9% for LiNi0.8Co0.1Mn0.1O2 material by a one-step leaching process.

SLAGS OF THE METALLURGICAL PLANTS OF ARMENIA AT FINE GRINDING

In connection with the development of copper and molybdenum production in Armenia, it becomes necessary to develop a technology for processing the slags of the functioning metallurgical plants to extract valuable metals from these slags. It concerns the copper slags of Alaverdi Copper-Smelting Plant with a content of FeO ~50 % and the molybdenum slags of Yerevan “Pure Iron” Plant with a content of SiO2 ~80 %. These slags are obtained at high temperatures (with FeO·SiO2 , CaO·SiO2 , Fe3 O4 ) and, therefore, they are less active to be used later. Meanwhile, the mentioned slags are rich in iron and silicon oxides and can serve as a cheap raw material for producing iron silicides. The iron silicides can be used in micro- and nanoelectronics, as well as in metallurgy as an alloying additive in the production of steels of special physical and chemical properties. The production of such valuable silicides from an inexpensive raw material is important for Republic of Armenia and is of not only economic, but also ecological significance. To obtain iron silicides, a method of combined aluminothermal reduction of primarily mechanoactivated copper and molybdenum slags is proposed. The preliminary mechanoactivation allows to purposefully affect the structure of the reaction mixture and parameters of the self-propagating high-temperature synthesis (SHS), thus ensuring the possibility of regulating the structure and phase composition of the synthesized silicides. This work considers issues on the impact of transformation and phase formation on the morphology of slags of copper and molybdenum production in the functioning Armenian metallurgical plants at mechanochemical activation by the method of fine grinding in a vibromill. It is shown that at fine grinding (up to 10 mcm), the slags, containing small-reactivity complex compounds of iron and silicon (fayalite, magnetite, quarzite) undergo profound chemical changes, transforming into amorphous oxides. The obtained activated oxides can serve as a raw material for producing iron- and silicon-containing alloys – iron silicides.

Extraction of Valuable Metals from High-Iron Zinc Sulfide Concentrate by Reductive Leaching

This study was conducted as part of the development of a new process to recover valuable metals of zinc, copper and indium from high-iron zinc sulfide concentrate (HIZSC) by the reductive leaching of high-iron zinc neutral leaching residue (HIZNLR) with zinc concentrate precipitation of copper with iron powder, neutralization of free sulfuric acid with zinc calcine, precipitation of indium with zinc powder and hematite precipitation to reject iron. Among these stages, reductive leaching is the crucial step, which makes that valuable metals in the materials can be effectively leached and ferric iron in the solution is reduced to ferrous iron. The reductive leachate enables copper, indium and iron separation from the solution in the subsequent process. The results show that by increasing the sulfuric acid concentration, HIZSC addition and prolonging the reaction time, the leaching efficiency of zinc, copper, indium and iron in the sample materials was significantly increased. The maximum metal-leaching efficiency was obtained; 84.3% of the iron was in its soluble ferrous state, and zinc ferrite in the HIZNLR was almost entirely dissolved under the experimental conditions of an H2SO4-to-HIZNLR mass ratio of 1.6, a liquid-to-solid ratio of 11.34 mL/g, a temperature of 90°C, an HIZSC addition of 1.05 times of the stoichiometric amount and a reaction time of 5 h.

Use of poly(vinylidene fluoride-co-vinyl dimethylphosphonate) copolymers for efficient extraction of valuable metals

The radical copolymerisation of vinylidene fluoride (VDF) with vinyl dimethyl phosphonate (VDMP) initiated by various kinds of initiators is presented.

Investigating the Slags of the Metallurgical Plants of Armenia at Fine Grinding

In connection with the development of copper and molybdenum production in Armenia, it becomes necessary to develop a technology for processing the slags of the functioning metallurgical plants to extract valuable metals from the slags. It concerns the copper slags of Alaverdi copper-smelting plant with a content of FeO ∼50% and the molybdenum slags of Yerevan Pure Iron Plant with a content of SiO2 ∼80%. These slags are obtained at high temperatures (with obtaining FeO ⋅ SiO2, CaO ⋅ SiO2, Fe3O4) and, therefore, they are less active to be used later. Meanwhile, the mentioned slags are rich in iron and silicon oxides and can serve as a cheap raw material for producing iron silicides. The iron silicides can be used in micro- and nanoelectronics, as well as in metallurgy as an alloying additive in the production of steels of special physical and chemical properties. The production of such valuable silicides from an inexpensive raw material is important for Republic of Armenia and is of not only economic, but also ecological significance. To obtain iron silicides, a method of combined aluminothermal reduction of primarily mechanoactivated copper and molybdenum slags is proposed. The preliminary mechanoactivation allows to purposefully affect the structure of the reaction mixture and the parameters of the self-propagating high-temperature synthesis (SHS), thus ensuring the possibility of regulating the structure and the phase composition of the synthesized silicides. In this work, issues on the impact of transformation and phase formation on the morphology of slags of copper and molybdenum production in the functioning metallurgical plants of Armenia at mechanochemical activation by the method of fine grinding in a vibromill are considered. It is shown that at fine grinding (up to 10 μm), the slags, containing small-reactivity complex compounds of iron and silicon (fayalite, magnetite, quarzite) undergo profound chemical changes, transforming into amorphous oxides. The obtained activated oxides can serve as a raw material for producing iron- and silicon-containing alloys—iron silicides.

A strong spatial association between e‐waste burn sites and childhood lymphoma in the West Bank, Palestine

A paper in the International Journal of Cancer analyzed Palestinian cancer registry data in the West Bank from 1998 to 2007, showing a cluster of elevated cancer incidence in rural villages in south-west Hebron, with a 4.10 risk ratio for childhood lymphoma (p = 0.0023). The paper called for investigation of the environmental or genetic etiologies of this cluster in an otherwise unremarkable rural area.1 Our research in these same villages shows them to be the center of an extensive informal electronic and electrical waste (e-waste) dismantling industry in Palestine, operating for almost two decades. This entails extensive open-burning of e-waste components to extract valuable metals or dispose of nonvaluable waste, releasing high concentrations of hazardous contaminants, which may be an important factor in the elevated cancer incidence. We offer a first step in assessing this link. We applied a novel multitemporal object-based method to map the prevalence and intensity of e-waste burn sites in the entire Hebron Governorate (1,060 km2 ) between 1999 and 2007. A weighted standard deviation ellipse of cumulative burn activity covers a smaller area (247 km2 ) very closely matching the childhood lymphoma cluster: it contains 85% of the core cluster area (RR of 4.1), and falls almost entirely (95%) within the broader area of elevated risk (RR of 2.8). Extensive international evidence linking informal e-waste processing to elevated cancer incidence and this strong spatial association of e-waste burning activity with a distinct unexplained cancer cluster in the Palestinian context signals the urgent need for investigation and intervention.

The role of CaCO3 in the extraction of valuable metals from low-nickel matte by calcified roasting—acid leaching process

The extraction of valuable metals from low-nickel matte via a calcified roasting-acid leaching process was investigated. The influences of process parameters on the extraction of metals were studied, including the roasting temperature, roasting time and the addition of CaCO3. Under the optimum condition, 92.4% of Ni, 97.1% of Cu, 95.1% of Fe, and 91.2% of Co were recovered. In addition, the removal of iron via goethite precipitation process was studied. The results show that 99.8% of Fe could be removed by goethite process. The reaction mechanism of calcified roasting of low-nickel matte was also studied by XRD and XRF analysis. It was shown that the formation of ferrite can be effectively inhibited by CaCO3 addition, leading to enhancement of the metal recovery.

The Culturing Optimization of Bioleaching of the Lead-Zinc Tailings from Different Depths

This study was a continuation of previous work designed to further explore the effect of different culture condition on the recovery of the valuable metals by bacteria. The experiment focused on the Nandan lead-zinc tailings from different depths. First of all, the study systematically performed multi-elements analysis. Subsequently, the effect of the temperature and agitation speed on the bacterial growth was investigated. The data revealed that the temperature of 35°C and the agitation of 160 rpm were the optimum culture conditions for the bacteria. Finally, the bioleaching experiments were performed to explore the ability of bioleaching the tailings. The study illustrated that the microorganism was able to effectively extract valuable metals from different depths samples.

BIOTECHNOLOGICAL METHODS FOR PROCESSING SUBSTANDARD ORES AND WASTES

The information about using of biotechnological methods for the processing of mineral and technogenic raw materials was analyzed and summarized in the article. A review of the main groups of microorganisms that make up the microbiocenosis of various ecological niches and wastes is given. The leading role of acidophilic chemolithotrophic bacteria in the oxidation process of natural sulphide raw materials is also shown. Basic mechanisms of bacterial leaching of metals and the influence of various factors on the efficiency of oxidation of sulfides are considered. A characteristic of the main methods of bacterial leaching – tanks, underground and heap was given and there were considered their advantages and disadvantages. The article gives the world examples of the use of bioleaching for the production of copper, nickel, gold, uranium. It is noted that there is no practical application of bacterial leaching for processing technogenic raw materials, in particular, coal and energy industry waste for the extraction of valuable metals – germanium, gallium, etc.

Sodium sulfate activation mechanism on co-sulfating roasting to nickel-copper sulfide concentrate in metal extractions, microtopography and kinetics

Due to the complexity of occurrence of valuable metals and high content of alkali gangue in nickel-copper sulfide concentrate, traditional pyrometallurgical processing is not suitable. In this work, a two-stage co-sulfating roasting process was used to selectively extract valuable metals from Chinese nickel-copper sulfide concentrate. A mixture of (NH4)2SO4 and Na2SO4 was selected as the co-sulfating agents. The effect of the dosage of (NH4)2SO4 and Na2SO4, first stage roasting temperature, roasting time and second roasting temperature on metal’s extractions were investigated. XRD, SEM, DTA-TG, and DSC-TG were used to reveal the mechanism of action of Na2SO4 and the mineral phase transformations in the two-stage sulfating roasting process. The results show that nearly all of Ni and Co, Cu, and 1.12% of Fe were extracted at the mass ratio of ammonium sulfate to ore of 3.5, first roasting at 500 °C for 2 h, dosage of sodium sulfate of 4 g (10 g ore), followed by second roasting at 680 °C for 2 h, then water leaching at 95 °C for 2 h. Na2S2O7 generated from Na2SO4 in the roasting process, shrinks the particle size of the ore, decrease the surface area of the roasted product, significantly promotes extent of the sulfating of metals, in particular for Ni. Thermal analysis kinetics indicates that Na2SO4 significantly reduces the apparent activation energy of the sulfating roasting process. The metal bearing mineral phases were transformed into sulfates or sodium double or ternary sulfates in the first roasting process, then the sodium double sulfates of Na3Fe(SO4)3 were decomposed.

Effects of intermittent liquid addition on heap hydrodynamics

Heap leaching is a well-known mineral processing technique, whereby crushed low grade ore is used for valuable metal extraction. The technique is typically used to extract precious and base metals, however, the metal extraction efficiency is relatively low. Even though reaction kinetics are extensively studied in heap leaching, the detailed hydrodynamic studies are still required to understand the underlying flow aspects. Heap hydrodynamics plays an important role in the transport of both leaching reagents and dissolved metal species and thus uniform liquid distribution through the ore mass is required. However, liquid channelling within the heaps has been identified as one of the main contributing factors for non-uniform liquid distribution. Since liquid channelling is supposed to be an inherent property in heap leaching systems, this work was primarily designed to explore the suitable techniques to improve liquid distribution and minimise liquid channelling in heaps. Intermittent liquid addition is employed and its effect on liquid channelling is studied, which has not been reported in the literature despite the application of it in industrial heaps. Both narrowly sized ore (16–20 cm) and realistic ore mixtures (2.36–25 cm) were studied in a pseudo 2-D Perspex column and the effect of rest period in intermittent leaching on liquid channelling was studied using out-flow liquid distribution measurements. The experimental results showed improved out-flow liquid distribution profiles and less channelling flow features in intermittent liquid addition conditions. The liquid out-flow profiles in both the packed bed systems were improved by resulting more flow paths through the particles and reduced features of liquid channelling. The narrowly sized fraction formed a near-Gaussian liquid distribution, which is the expected continuous probability based theoretical flow profile with drip emitter based liquid addition in heaps.

Extraction of valuable metals by microwave discharge in crude oil

Microwave discharges in liquids are a new direction in the physics and chemistry of low temperature plasma. The article describes the results of experiments on the separation of metals from oil when a microwave discharge is created at atmospheric pressure in its volume. It is shown for the first time that the content of metals Al, Co, Cu, Fe, Mo, Ni, V, and Zn in a tree-like structure deposited on the microwave antenna is up to 10 times higher than their content in the initial substance.