Process For Recovery Of Metals Research Articles

Environmental Impact Assessment of Hydrometallurgical Processes for Metal Recovery from WEEE Residues Using a Portable Prototype Plant

Life cycle assessment (LCA) was applied to hydrometallurgical treatments carried out using a new portable prototype plant for the recovery of valuable metals from waste electrical and electronic equipment (WEEE). The plant was fed with the WEEE residues from physical processes for the recycling of fluorescent lamps, cathode ray tubes (CRTs), Li-ion accumulators and printed circuit boards (PCBs). Leaching with sulfuric acid was carried out, followed by metal recovery by selective precipitation. A final step of wastewater treatment with lime was performed. The recovered metals included yttrium, zinc, cobalt, lithium, copper, gold, and silver. The category of global warming potential was the most critical one considering the specifications for southern European territories, with 13.3 kg CO(2)/kg recovered metal from the powders/residues from fluorescent lamps, 19.2 kg CO(2)/kg from CRTs, 27.0 kg CO(2)/kg from Li-ion accumulators and 25.9 kg CO(2)/kg from PCBs. Data also show that metal extraction steps have the highest load for the environment. In general, these processes appear beneficial for the environment in terms of CO(2) emissions, especially for metal recovery from WEEE residues from fluorescent lamps and CRTs.

Biosorption of lead using pretreated cells of Aspergillus species

Microbial bioremediation is an emerging technology for environmental cleanup. Application of living biomass for metal binding depends on nutrient type and concentration, environmental conditions and cell age. In addition, living biomass may be subject to toxic effect of heavy metals at elevated concentrations. To overcome the disadvantages; non-viable or dead biomass is preferred. To test these hypothesis three fungal strains were isolated from effluent of chemical and pharmaceutical industry using SDA agar. Identification of the above isolates was carried out and was identified to be predominant strains of Aspergillus i.e. (Aspergillus niger and Aspergillus flavus). Further preliminary test was performed to check the tolerance of the fungi to different metal salts of lead, copper, chromium, zinc, nickel, cadmium using 1mM concentration. All three fungal species showed tolerance to metal salts like lead nitrate, zinc sulphate and cupric sulphate above 20 mM. Furthermore minimum inhibitory concentration was determined against the two above species for the three heavy metals. Pretreatment of live cells of Aspergillus strain was carried out .This dried biomass was then used for optimization of various parameters like concentration of metals, biomass concentration, pH, temperature of incubation and contact time. The filtrate was then analyzed after proper digestion and dilution by Atomic Absorption Spectrophotometer. The availability of variety of biomass and their metal binding potential makes it economical and sustainable option for developing effluent treatment process for removal and recovery of heavy metals.

Effect of Chemical Activation on the Adsorption of Heavy Metals Using Activated Carbons from Waste Materials

The effect of chemical activation on the adsorption of metals ions (Cr2+, Cu2+, Ni2+, Pb2+, Fe2+, and Zn2+) using waste Nigerian based bamboo, coconut shell, and palm kernel shell was investigated. The bamboo, coconut, and palm kernel shell were carbonized at 400°C–500°C and activated at 800°C using six activating agents. Chemical activation had significant effect on the iodine number and invariably increased the micropores and macropores of the activated carbons produced from bamboo, coconut, and palm kernel shell. It also affected the adsorption of metal ions and the type of carboneous material used for activation. The highest metal ions adsorbed were obtained from bamboo activated with HNO3. The cellulose nitrite formed during the activation of bamboo with HNO3 combined with high pore volume and low ash content of bamboo effectively create more reaction sites for adsorption of different metal ions. This shows that waste bamboo activated with HNO3 can effectively be used to remove metal ions from waste streams and in different metal recovery processes than activated carbon from coconut shell and palm kernel shell.

Metal Separations and Recovery in the Mining Industry

Molecular Recognition Technology (MRT) plays an important role in the hydrometallurgical processing dissolved entities in solutions in the mining industry. The status of this industry with respect to sustainability and environmental issues is presented and discussed. The roles of MRT and ion exchange in metal separation and recovery processes in the mining industry are discussed and evaluated. Examples of MRT separation processes of interest to the mining community are given involving gold, cobalt purification by extraction of trace cadmium, rhenium, and platinum group metals (PGMs). MRT processes are shown to be sustainable, economically viable, energy efficient, and environmentally friendly, and to have a low carbon footprint.

Laser-induced breakdown spectroscopy application to control of the process of precious metal recovery and recycling

In this paper, we discuss the application of laser-induced breakdown spectroscopy to precious metal alloys used for the control of the process of recovery and recycling of scraps and waste of industrial processes. In particular, the possibility to obtain sensitivity and trueness comparable to the current systems used in industrial environment in the quantitative determination of the elements of interest was explored. The present study demonstrates that laser-induced breakdown spectroscopy can be considered as a viable alternative to inductively coupled plasma optical emission spectrometry and X-ray fluorescence spectroscopy for the determination of recovered precious metals. The limits of detection obtained are of the order of 0.2mg/g for all the elements considered. The maximum deviation with respect to the nominal concentrations is around 1mg/g at concentrations around 20mg/g (gold) corresponding to a relative error slightly higher than ±5%.

End-of-life and waste management in life cycle assessment—Zurich, 6 December 2011

IntroductionWaste management is a key component in society's strategy to mitigate the adverse effects of its economic activities. Through its comprehensive system approach, life cycle assessment (LCA) is frequently put forward as a powerful tool for the assessment of waste management activities. However, many methodological challenges regarding the environmental assessment of waste treatment systems still remain, and consensus is still far from being reached in areas like the definition of (temporal) system boundaries, life cycle inventory generation, selection and use of environmental indicators, and interpretation and communication of the LCA results.Summary of the topics presented in DF-46The 46th Swiss Discussion Forum on Life Cycle Assessment (DF-46) consisted of three sessions. The first session tried to address policy making and implications for sustainable waste management of consumer products, e.g., information and communication technology, and food packaging. The second session focused on recent methodological developments in LCA for end-of-life treatment (EoL) activities and waste management assessment. The third session was dedicated to E-waste treatment and scarce metal recovery processes. DF-46 closed with short presentations on decision support in the areas of coprocessing, food waste, and after-treatment technologies for municipal waste incineration residues.ConclusionsThe main conclusions drawn from DF-46 are: (a) the option of waste prevention, despite its prominent position in the so-called waste hierarchy, is rarely considered in LCAs on waste and EoL management, (b) although a general problem in many other applications of LCA, the differences in scope definitions and time perspectives, the use of proxies or data of poor quality, allocation, or system expansion procedures, and weighting in the impact assessment are prominent issues in LCAs of waste and EoL management and thus have to be minimized and inventory data must be as transparent as possible, (c) life cycle inventory formats have to be adapted to be able to account for new materials, such as nanoparticles and scarce metals in LCA, (d) the selection of environmental indicators requires clear guidance on their appropriate use and open communication. The selection of a set of complementary indicators is of particular importance in order to avoid that the adverse effects on the environment are merely shifted between impact categories, and (e) useful LCA tools for the environmental assessment of waste management options are currently developed to meet the evolving demands and expectations for support in decision making related to waste and EoL management today and in the future. The presentations from DF-46 are available for download (www.lcaforum.ch).

TG–MS study of the thermo-oxidative behavior of plastic automobile shredder residues

Automobile shredder residues (ASR) are materials that are rejected in the metal recovery process for end-of-life vehicles (ELV). These residues are composed of such materials as plastics, foams, glasses, rubbers, textiles, remaining metals and soils. ASR disposal is a difficult task, due to increasingly restrictive re-use policies. The pyrolytic reuse of ASR is one important option for energy recovery. The gas release behavior of pyrolyzed ASR was measured using a TG–MS apparatus, and this thermo-oxidative process was observed under different N2/O2 volume ratios. The final weight/initial residue weight ratio for pyrolyzed ASR decreased from 43.4% to 10.1% with increasing oxygen concentrations. The production rates of hydrogen, methane and carbon dioxide also varied with different N2/O2 volume ratios. The maximum emission of hydrogen and methane occurred when the thermo-oxidative atmosphere was entirely N2. Temperature had a positive impact on hydrogen production, and the methane emission ratio reached a peak at the second shoulder of the devolatilization stage during which stage organic polymers were emitted. A peculiar characteristic of ASR is its content of nitrogen. The effects of ASR nitrogen content on N2O and NOX emissions were investigated in detail. NH3 was the dominant nitrogen species that was released during ASR pyrolysis. N2O is highly temperature-sensitive and decomposes to N2 at temperatures greater than 900°C.

Treatment of Wastewater from Metals Recovery Process from Spent Catalysts

Treatment of Wastewater from Metals Recovery Process from Spent Catalysts

Development of an Environmentally Friendly Process for Separation and Recovery of Rare Metals from Spent Oil-Desulfurization Catalyst

Development of an Environmentally Friendly Process for Separation and Recovery of Rare Metals from Spent Oil-Desulfurization Catalyst

Recovery of Heavy Metal Using Solvent Impregnated Resin (SIR) Coupled with Donnan Dialysis

A membrane process for metal recovery from aqueous solutions was studied. Metal ions diffused from the feed compartment to the stripping compartment through an hybrid Donnan dialysis which consists to combine two ion exchange membranes with solvent impregnated resin (SIR). The aim of this work is to study the recovery of Pb(II), Ag(I) and Cu(II) from nitrate solutions by using SIR combined with classical Donnan dialysis. The resin has been prepared by impregnating the Amberlite XAD-4 using three different extractants namely: di-2-ethyl hexyl phosphine acide (D2EHPA), tris-octyl phosphine oxide (TOPO) and Diphenylthiourea (DPT). Experiments were performed as a function of nature of the extractant impregnated on the XAD-4 resin as well as the concentration in the resin phase, the stripping pH, the concentration ratio of metal ions in the feed compartment and the nature of the counter ions in strip compartment. The results show that the D2EHPA is the better extractant for the metal ions used in this work, and it’s shown a good selectivity for the separation between ions.

저품위(低品位) 우라늄철(鑛)의 미생물 침출법(浸出法)

본 총설은 광석으로부터 우라늄의 미생물 침출시 사용하는 Acidithiobacillus forrooxidans, Acidithiobacillus thiooxidans 그리고 Leptospirillum ferrooxidans 등에 역할과 침출반응에 관하여 기술하였다. 미생물에 의한 우라늄의 침출반응은 박테리아가 우라늄 광석과 직접 반응하기 보다는 박테리아가 <TEX>$U^{4+}$</TEX>를 산화시키는데 필요한 <TEX>$Fe^{3+}$</TEX>를 공급하고, <TEX>$Fe^{3+}$</TEX>가 우라늄 광석과 반응하는 간접반응기구(indirect mechanism)에 의하여 일어난다. 건식제련법과 같은 전통적인 금속회수 공정에 비하여 환경친화적이고 경제적인 장점 때문에 저품위 광물자원으로부터 유기금속을 회수하는데 미생물 제련법이 널리 활용되고 있다. 현재 우라늄은 heap, dump 그리고 in situ를 이용한 미생물 침출법으로 회수되고 있다. Bioheap의 공기 투입량, 교반반응용기의 디자인 및 조업 개선 분야에서 기술개발이 지속적으로 이루어졌으며 최근에는 미생물 침출반응에 투입된 박테리아의 특성 개선 및 균주수를 제어하기 위한 molecular biology 분야에서 활발한 연구가 진행되고 있다. This review describes the involvement of different microorganisms for the recovery of uranium from the ore. Mainly Acidithiobacillus forrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans are found to be the most widely used bacteria in the bioleaching process of uranium. The bioleaching of uranium generally follows indirect mechanism in which bacteria provide the ferric iron required to oxidize <TEX>$U^{4+}$</TEX>. Commercial applications of bioleaching have been incorporated for extracting valuable metals, due to its favorable process economics and reduced environmental problems compared to conventional metal recovery processes such as smelting. At present the uranium is recovered through main bioleaching techniques employed by heap, dump and in situ leaching. Process development has included recognition of the importance of aeration of bioheaps, and improvements in stirred tank reactor design and operation. Concurrently, knowledge of the key microorganisms involved in these processes has advanced, aided by advances in molecular biology to characterize microbial populations.

Bio hydrometallurgical recovery of metals from Fine Shredder Residues

The leaching step of an integrated hydrometallurgical process for the selective recovery of metals from polymetallic concentrates has been investigated. This concentrate has been produced by physical treatment of Fine Shredder Residues derived from a shredding plant processing a mixed feed of metallic scraps, waste electric equipments and end-of-life vehicles. Bacterially assisted leaching experiments have been carried out using a copper-adapted consortium of mesophilic bacterial strains. The influence of various operating conditions such as stirring speed, temperature (25–50 °C), pulp solids density (5–20%) and initial iron concentration (0–15 g/L) has been studied. Temperature and stirring speed have proved to be the most influential parameter regarding copper dissolution kinetics, while pulp solids density and initial iron concentration have been found to have a subordinate importance. In optimum conditions, 95% extractions of zinc and copper were achieved within 48 h. Bacterial presence has been found beneficial in terms of catalysing copper dissolution.

Removal of Chromium on Polyalthia longifolia Leaves Biomass

Adsorption is an environmental friendly process for removal and/or recovery of heavy metals from wastewater. In recent years, it has been substantiated as a popular technique to treat industrial waste effluents, with significant advantages. In this work, batchwise removal of chromium (III) ions from water by Polyalthia longifolia leaves was studied as a function of adsorbent dose, pH, contact time, and agitation speed. Surface characteristics of the leaves were evaluated by recording IR spectra. The Langmuir, Freundlich, and Temkin adsorption isotherms were employed to explain the sorption process. It was found that one gram of leaves can remove 1.87 mg of trivalent chromium when working at pH 3.0. It has been concluded that Polyalthia longifolia leaves can be used as cost-effective and benign adsorbents for removal of Cr(III) ions from wastewater.

合金化および微粒子化を利用した貴金属の溶解法

The hydrometallurgical recovery process of precious metals involves a great environmental load. This is because strong oxidant and complexing agents such as aqua regia are required to dissolve these metals which have high chemical stability. To enhance the dissolution, alloying with other metals may be effective as is conventionally used in production and refinement of some precious metals. When precious metal alloys are immersed in aqueous solution, the less noble metals in them dissolve preferentially and precious metals form transient particles. Thus, the Gibbs-Thomson effect, which explains the excess free energy of small particles, may contribute to the enhancement. Based on the assumption, an exposure to zinc vapor was proposed as a pretreatment for the leaching of precious metals. Precious metals form alloys or intermetallic compounds with zinc during the pretreatment, and if these products can be dissolved more easily than the pure metals, the environmental load involved in the recovery will be reduced. Dissolution rates of some precious metal-zinc compounds were evaluated quantitatively by channel flow double electrode method to discuss the effect of the pretreatment.

Molecular motion and ion diffusion in choline chloride based deep eutectic solvents studied by 1H pulsed field gradient NMR spectroscopy

Deep Eutectic Solvents (DESs) are a novel class of solvents with potential industrial applications in separation processes, chemical reactions, metal recovery and metal finishing processes such as electrodeposition and electropolishing. Macroscopic physical properties such as viscosity, conductivity, eutectic composition and surface tension are already available for several DESs, but the microscopic transport properties for this class of compounds are not well understood and the literature lacks experimental data that could give a better insight into the understanding of such properties. This paper presents the first pulsed field gradient nuclear magnetic resonance (PFG-NMR) study of DESs. Several choline chloride based DESs were chosen as experimental samples, each of them with a different associated hydrogen bond donor. The molecular equilibrium self-diffusion coefficient of both the choline cation and hydrogen bond donor was probed using a standard stimulated echo PFG-NMR pulse sequence. It is shown that the increasing temperature leads to a weaker interaction between the choline cation and the correspondent hydrogen bond donor. The self-diffusion coefficients of the samples obey an Arrhenius law temperature-dependence, with values of self-diffusivity in the range of [10(-10)-10(-13) m(2) s(-1)]. In addition, the results also highlight that the molecular structure of the hydrogen bond donor can greatly affect the mobility of the whole system. While for ethaline, glyceline and reline the choline cation diffuses slower than the associated hydrogen bond donor, reflecting the trend of molecular size and molecular weight, the opposite behaviour is observed for maline, in which the hydrogen bond donor, i.e. malonic acid, diffuses slower than the choline cation, with self-diffusion coefficients values of the order of 10(-13) m(2) s(-1) at room temperature, which are remarkably low values for a liquid. This is believed to be due to the formation of extensive dimer chains between malonic acid molecules, which restricts the mobility of the whole system at low temperature (<30 °C), with malonic acid and choline chloride having almost identical diffusivity values. Diffusion and viscosity data were combined together to gain insights into the diffusion mechanism, which was found to be the same as for ionic liquids with discrete anions.

Thermodynamic modelling of the formation of zinc–manganese ferrite spinel in electric arc furnace dust

Electric arc furnace dust is generated when automobile scrap, containing galvanized steel, is remelted in an electric arc furnace. This dust is considered as a hazardous waste in most countries. Zinc is a major component of the dust and can be of significant commercial value. Typically, the majority of the zinc exists as zinc oxide (ZnO) and as a zinc–manganese ferrite spinel ((Zn x Mn y Fe 1− x− y )Fe 2O 4). The recovery of the zinc from the dust in metal recycling and recovery processes, particularly in the hydrometallurgical extraction processes, is often hindered by the presence of the mixed ferrite spinel. However, there is a paucity of information available in the literature on the formation of this spinel. Therefore, in the present research, the equilibrium module of HSC Chemistry ® 6.1 was utilized to investigate the thermodynamics of the formation of the spinel and the effect of variables on the amount and the composition of the mixed ferrite spinel. It is proposed that the mixed ferrite spinel forms due to the reaction of iron–manganese particulates with both gaseous oxygen and zinc, at the high temperatures in the freeboard of the furnace above the steel melt. Based on the thermodynamic predictions, methods are proposed for minimizing the formation of the mixed ferrite spinel.

Comparative Study of Metals Recovery Process from Effluent Water of a Metallurgical Refining Process

Comparative Study of Metals Recovery Process from Effluent Water of a Metallurgical Refining Process

Thermodynamic Analysis to Assess the Environmental Impact of End-of-life Recovery Processing for Nanotechnology Products

The objective of this study is to use thermodynamic analysis to evaluate the environmental impact of nanotechnology products during the end-of-life (EOL) material recovery stage. A case study of the high-temperature metal recovery (HTMR) process used to recycle lithium-ion (Li-ion) batteries is presented. Previous research has shown that the melting behavior of nanomaterials may deviate from their corresponding bulk materials. The melting temperature of superheated nanomaterials in Li-ion batteries may exceed the process smelting temperature and result in nanomaterials contaminating the recovered material streams. Therefore, the smelting process must be operated at higher temperatures to ensure the full melting of the nanomaterials, resulting in higher energy consumption and process emissions. The environmental impact from the existing HTMR process is examined as well as the impact associated with operations at the higher smelting temperatures. Thermodynamic analysis, consisting of energy and exergy analyses, provides quantitative information on the resulting environmental impacts and the corresponding overall exergy loss, which may occur when recycling nanomaterial-containing Li-ion batteries.

A combined recovery process of metals in spent lithium-ion batteries

This work proposes a new process of recovering Co from spent Li-ion batteries (LIBs) by a combination of crushing, ultrasonic washing, acid leaching and precipitation, in which ultrasonic washing was used for the first time as an alternative process to improve the recovery efficiency of Co and reduce energy consumption and pollution. Spent LIBs were crushed with a 12 mm aperture screen, and the undersize products were put into an ultrasonic washing container to separate electrode materials from their support substrate. The washed materials were filtered through a 2 mm aperture screen to get underflow products, namely recovered electrodes. Ninety two percent of the Co was transferred to the recovered electrodes where Co accounted for 28% of the mass and impurities, including Al, Fe, and Cu, accounted for 2%. The valuable materials left in 2–12 mm products, including Cu, Al, and Fe, were presented as thin sheets, and could be easily separated. The recovered electrodes were leached with 4.0 M HCl for 2.0 h, at 80 °C, along with concurrent agitation. Ninety seven percent of the Li and 99% of the Co in recovered electrodes could be dissolved. The impurities could be removed at pH 4.5–6.0 with little loss of Co by chemical precipitation. This process is feasible for recycling spent LIBs in scale-up.

Recovery of Cu and Fe from Printed Circuit Board waste sludge by ultrasound: Evaluation of industrial application

The paper presents a novel cleaner process for metal recovery from the Printed Circuit Board (PCB) waste sludge by assistance of ultrasound. The process can effectively recover heavy metals at low cost with high separation and recovery efficiency, produce high quality products and also achieve zero waste discharge with operation at industrial scale. With the PCB waste sludge containing (wet content) 3.14–4.85% copper and 3.71–4.23% iron, copper recovery efficiency of 95.2–97.5% and iron recovery efficiency of 97.1–98.5% were achieved, while the purity of copper sulfate produced by the process was 98.0% and the produced ferric chloride had a satisfied quality for using as a coagulant material for the plant on-site wastewater treatment. The process had been successfully scaled up to the industrial scaled applications in a heavy metal recovery plant in city of Huizhou, China for more than two years. The novel cleaner heavy metal recovery process has a great prospect on the applications of resources recovery and environmental protection practices.