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A review of recovery of metals from industrial waste
Abstract
Due to rapid industrialization the demand for heavy metals is ever increasing, but the reserves of high-grade ores are diminishing. Therefore there is a need to explore alternative sources of heavy metals. The rapid industrialization generates a variety of industrial wastes. These industrial wastes possess toxic elements such as heavy metals. Improper disposal of these wastes becomes a key factor in metal contamination and thus when leached into atmosphere cause serious environmental problem. These metals exert wide variety of adverse effects on human being. Some of the metals have extremely long biological half-life that essentially makes it a cumulative toxin. Also some metals are carcinogenic in nature. Among the wastes, electronic scraps, medical waste, metal finishing industry waste, spent petroleum catalysts, battery wastes, fly ash etc., are some of the major industrially produced wastes. These solid wastes mostly contain Au, Ag, Ni, Mo, Co, Cu, Zn, and Cr like heavy metals in it. Hence these waste materials which are causing serious environmental problems, can act as potential source for heavy metals. In this sense these industrial wastes can act as artifitial ores. The valuable metals can be recovered from these industrial wastes. There are varieties of methods in use for recovery of heavy metals. These include pyrometallurgical, hydrometallurgical and bio-hydrometallurgical methods. Pyrometallurgical recovery consists of the thermal treatment of ores and metal containing wastes to bring about physical and chemical transformations. This enables recovery of valuable metals. Calcining, roasting, smelting and refining are the pyrometallurgical processes used for metal recovery. The hydrometallurgical recovery uses mainly the leaching process. It involves the use of aqueous solutions containing a lixiviant which is brought into contact with a material containing a valuable metal. Further the metals are concentrated and purified by using precipitation, cementation, solvent extraction and ion exchange. The metals are finally recovered in pure form by using electrolysis and precipitation methods. Biohydrometallurgy is one of the most promising and revolutionary biotechnologies. This technique exploits microbiological processes for recovery of heavy metal ions. In last few decades the concept of microbiological leaching have played a grate role to recover valuable metals from various sulfide minerals or low grade ores. Now the microbiological leaching process has been shifted for its application to recover valuable metals from the different industrial wastes. There are many microrganisms which play important role in recovery of heavy metals from industrial wastes. Among the bacteria Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Leptospirillum ferrooxidans, and Sulfolobus sp., are well known for the bioleaching activity while Penicillium, and Aspergillus niger are some fungi those help in metal leaching process. The process of recovery makes sense only if the cost of recovery is much less than the value of the precious metal. The restrictions imposed on waste disposal and stringent environmental regulations demand eco-friendly technologies for metal recovery. This paper reports a review of number of industrial processes that generate metal containing waste and the various methods in use for recovery of metals from these wastes. This will help in selection of a proper method for recovery of heavy metals from industrial wastes.
... Every year, many waste metals are discharged into nature from various industrial fields such as electronics, metallurgy, mining, metal processing, and electroplating. Metals produced as waste from various industrial fields are shown in Table 1 below (Jadhav & Hocheng, 2012). ...
... Waste Metals Released by Various Industries (Jadhav & Hocheng, 2012) Since heavy metals are toxic and tend to accumulate in living organisms, it is vital to remove them from nature and wastewater. Therefore, it becomes a necessity in the industry to recover wastes as toxic or valuable components (González-Muñoza et al., 2006). ...
... In addition, recovered metals contribute to the economy of countries. Morever, decreasing ore reserves due to the increasing population necessitates the recovery of metals (Jadhav & Hocheng, 2012). ...
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... Synthesis of various metals using wastes and non-waste materials had been reported previously [25][26][27][28][29][30][31][32]. Jamieson et al. [25] separated red sand into a high iron oxides fraction, silica, and a mixture of iron and silica by using low and high magnetic separators. ...
... Zhu et al. [26] reported the extracting of various metals from red mud using acid leaching, solvent extraction, polymerization process, alkali leaching with pressure, and the aging process. Jadhav and Hocheng [27] have reported on extracting metals from several types of wastes using sulfuric/citrus/oxalic acids and microbiological leachants. Wei et al. [28] utilized silicon cutting waste (SCW) from the diamond wire sawing process by mixing it with aluminum powder and heated at temperatures of 1000-1500 • C. The production of Al-Si alloys can be synthesized by a one-step smelting process [28]. ...
... The presence of liquid steel in the system acts as a metallic solvent to trap the reduced Al in the system [32]. These studies on extracting or recovering metal from waste, non-waste, and industrial byproducts are still to a moderate extent [25][26][27][28][29][30][31][32]. Some of these used several steps and/or high temperatures to extract the metals, and thus have a small or moderate economic worthiness. ...
Mill scale and aluminum dross are the industrial wastes from steel and aluminum industries, which have high concentrations of Fe2O3 and Al2O3, respectively. This paper reports the conversion of reducible metal oxides in scale and dross into an alloy via carbothermic reduction at 1550 °C. Scale and dross were mixed with graphite into three different C/O molar ratios of 1, 1.5, and 2 to produce a pellet. The pellets were heated at 1550 °C for up to 6 h under an argon atmosphere. By this method, carbothermic reductions were found to proceed and formed Fe–Si–Al–C alloy that consists of Fe3Al and Fe3Si phases. The presence of Si in the alloy came from the reduction of SiO2 in aluminum dross. Levels of Al and Si in the alloy increase with increasing C/O molar ratios. However, the Si level in the alloy was found to stabilize since 3 h, while the Al level increases with increasing time up to 6 h. Unreacted oxides in the wastes had an insignificant effect on the ferroalloy formation. These results provide evidence for carbothermic reduction of the Fe2O3-Al2O3-SiO2 system at 1550 °C and show the novel method to upcycling aluminum dross and mill scale toward a circular economy.
... For pyrometallurgical methods, the need for a lot of energy and equipment, the dispersion of dust particles and gases in space, the need for gas collection devices, and cleaning systems, and the difficulty of controlling operations can be mentioned. Also, for the hydrometallurgical method, the large volume of organic acids used, the expense of the process, and secondary pollution can be expressed (Jadhav and Hocheng 2012). Biohydrometallurgy (Bioleaching) is a technique to convert solid compounds into extractable compounds based on the use of biological agents (Jadhav and Hocheng 2012). ...
... Also, for the hydrometallurgical method, the large volume of organic acids used, the expense of the process, and secondary pollution can be expressed (Jadhav and Hocheng 2012). Biohydrometallurgy (Bioleaching) is a technique to convert solid compounds into extractable compounds based on the use of biological agents (Jadhav and Hocheng 2012). Recently, bioleaching has become popular due to its simple process, low cost, high recovery efficiency, and environmental compatibility (Gu et al. 2018). ...
Incinerated sewage sludge ash contains significant amounts of phosphorus. This research optimized the phosphorus extraction process using ultrasonic and leaching processes and determined the most suitable process conditions by the Response Surface Methodology (RSM). This was done by evaluating the effect of different parameters such as the lemon juice (10 to 70% v/v), sewage sludge density (0.2 to 4% w/v), ultrasonic power (50 to 200 W), and time (0 to 120 min). Central Composite Design (CCD) defined a reduced cubic model with R² and Adjusted R², 0.947 and 0.904, respectively. In the optimal conditions including sewage sludge density of 1.17% w/v, lemon juice of 55% v/v, ultrasonic power was 87 W, and 34 min the highest phosphorus extraction was received to 94%. In addition, these studies show that leaching process significantly contributes to detoxification, and reuse of sewage sludge.
Graphical abstract
... Emphasizing the importance of recycling and valorization of industrial by-products or waste, precious metal recovery has become a crucial point for waste minimization and sustainable development [1,2]. Among the wastes related to hydrometallurgical production of zinc, nickel, cobalt and copper, jarosite has attracted great interest, being an important iron oxide (40-50%wt.) ...
... The material collected after the drops was sieved, and the weight fraction inside each sieve was weighted and evaluated as mass percentage with respect to the initial briquette mass. The sieves average opening sizes were 6.7 mm, 5.6 mm, 4 mm, 2 mm, 1 mm, 0.5 mm and 0.125 mm and they were normalized according to the biggest one for the size stability calculation, the size stability factor (s) of the briquettes was than calculated as visible in (2). The Impact Resistance Index (IRI) and the Adjusted Impact Resistance Index (AIRI) were calculated according to (3), (4) and (5). ...
Jarosite and blast furnace sludge (BFS) are two of the main wastes from hydrometallurgical zinc production and iron production by blast furnace, respectively. Jarosite is a hazardous material that can, however, be reused in the steel industry after the recovering of the iron contained within it through carbothermal reduction in which BFS is exploited as a reducing agent. Yet, both wastes have a powdery nature that makes it necessary to agglomerate them for industrial use. On the other hand, despite the advantages of producing a self-reducing product, the particle size of the starting powders and the level of gelatinization of the binder could play a crucial role on the mechanical and metallurgical performance and, consequently, on the industrial applicability of the briquettes. Accordingly, two powder particle sizes (very fine sand vs. coarse silt) and three degree of corn starch binder retrogradation (10%, 30% and non-gelatinized starch) were used to produce briquettes, and their influence was studied by experimental and statistical investigation. The results showed that gelatinization plays the main role on the mechanical properties of briquettes, while particle size affects both density and reduction behavior; in particular, although all the mixtures were able to recover iron at 950 °C the most optimal mixture were obtained by using a granulometry of 63–125 µm for jarosite and less than 63 µm for BFS, while the local maximum of mechanical performance was obtained for a 30% starch retrogradation level.
Graphical Abstract
... Rapid industrialization is the lifeline for the future growth of developed and developing countries, and historically, it has been associated with modern societies and their higher living standards. The demand for natural resources is everincreasing due to rapid industrialization, but the supplies of top-notch natural resources are running out (Jadhav and Hocheng 2012). Rapid industrialization produces various kinds of industrial by-products or wastes. ...
... Rapid industrialization produces various kinds of industrial by-products or wastes. Industrial by-product acquires large areas of land for dumping and contains harmful organic content, high alkalinity, and toxic elements such as heavy metals, which leads to environmental pollution (Jadhav and Hocheng 2012;Lini Dev and Robinson 2015;Wang et al. 2018;Do et al. 2019). In recent years, numerous pieces of research have been conducted successfully for the utilization and recycling of industrial wastes such as fly ash, thermally treated oil sand waste, alum sludge, blast furnace slag, incinerated sewage sludge, dredge sediment, and paper sludge incorporated in CLSM (Yan et al. 2014;Wu et al. 2016;Park et al. 2017;Mneina et al. 2018;Wang et al. 2018;Ghanad and Soliman 2021). ...
There is a recognized need to address the mismanagement of industrial by-products, as their accumulation severely threatens the environment. Efficient reutilizing of industrial waste is indispensable in realizing environment-friendly sustainable development. Towards this end, supervised adoption of controlled low-strength materials (CLSM) can be a solution. CLSM are cement-based materials which are environmentally safe, with self-levelling and self-consolidating properties. CLSM’s long-term sustainable applications exclusively depend on its geo-environmental properties during and after the construction phase. This comprehensive review explores the impact of geo-environmental properties on the plastic and in-service properties of industrial by-products used for CLSM creation. It critically examines various geo-environmental properties of CLSM comprising interlaced aspects of chemical composition, mineralogical composition, leaching behavior, pH value, and thermal conductivity. It is shown that the geo-environmental properties of CLSM are determined mainly by the characteristics and content of raw materials, wastes, and the quantity of water used in the final blend. Further, the review accentuates the geo-environmental properties’ detrimental effects on the plastic and in-service properties of CLSM. The comprehensive review can aid in effectively utilizing CLSM to reduce environmental concerns while achieving sustainable development.
... These processes are some of the most commonly used but they have some limitations, such as environmental problems or high costs [9]. Recently, Jadhav and Hocheng [10] studied the recycling metals from industrial wastes; however, on the contrary to lead, tin or indium, the possibility of recovering gallium from industrial waste is quite difficult. ...
... Expensive Cheap Dosage (g/L) 10 10 Particle size (mm) Powder 0.8 mm Time to reach the equilibrium 15 min Around 1 day q sat (mg/g) 6.5 4.9 ...
In this research, the adsorption of gallium onto natural zeolite (clinoptilolite) and two mesoporous-activated carbons were compared and evaluated. The clinoptilolite was treated with HCl (HCPL), while mesoporous-activated carbons (MCSG60A and MCO1) were synthesized by replica method, using sucrose as the carbon precursor and silica gel as the template. These carbonaceous materials showed large pore sizes and mesoporous surface, as well as a suitable surface chemistry for cation adsorption, which promotes a high negative charge density. On the other hand, zeolites have narrower pore sizes, which hinders the material diffusion inside the particle; however, its strength is their ion exchange capacity. Regarding the gallium kinetic studies, it is described by Pseudo-second order model for both sorts of adsorbents. MCO1 is the best carbonaceous adsorbent studied, with a capacity of 4.58 mg/g. As for zeolites, between the two zeolites studied, HCPL showed the best results, with a gallium adsorption capacity of 3.1 mg/g. The gallium adsorption mechanism onto MCO1 material is based on physisorption, while HCPL is mainly retained due to an ion-exchange process. Regarding the Giles classification, MCO1 isotherm described an H-4 pattern of high affinity and characteristic of multilayer adsorption. The Double-Langmuir model fits properly within these experimental results. In the case of zeolites, HCPL adsorption isotherm followed an L-2 pattern, typical of monolayer adsorption—the Sips model is the one that better describes the adsorption of gallium onto the zeolite.
... Thermal operations find application in the treatment of both primary [9] and secondary [10,11] resources to induce chemical modifications in the treated materials. These modifications are sometimes simple temperature-induced crystal structure rearrangements [12] while, more often, are actual chemical reactions such as roasting, calcination, reduction, etc. [13]. ...
... In both types, the metal ion is exchanged with the hydronium ion or the ammonium ion of the functionalizing anionic group, which determines a decrease in the pH of the solution. While weak acidic resins are active across a narrower pH range (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) than strong acidic resins, they are more advantageous for the recovery of the adsorbed metals via elution. Due to the relatively low selectivity and high cost of the resins, the need to regenerate and replace them as well as the intrinsic batch nature of the ion-exchange operation, the purification by ion-exchange finds application only in relatively low-throughput processes and/or in those processes addressing the recovery of high value materials such as precious and platinum group metals [53]. ...
This white paper covers the fundamentals of hydrometallurgical process synthesis, design, and economic evaluation. Metallurgical and Materials Engineering students and engineers with limited process design experience find it particularly useful. It features theory on process synthesis and analysis, material on hydrometallurgical process simulation, and presents a thorough methodology for estimation of capital and operating costs. It also includes the following five detailed process examples modeled and analyzed with SuperPro Designer: 1) Extraction of Lithium from Spodumene Ore, 2) Bio-Hydrometallurgical Recovery of Copper and Gold, 3) Recycling of Solar Photovoltaic Panels, 4) Hydrometallurgical Recycling of Lithium-Ion Batteries and 5) Manufacturing of NMC 811 Cathode Material for Lithium-Ion Batteries. For additional hydrometallurgical examples of SuperPro Designer, please visit https://www.intelligen.com/industries/metallurgy/
... It can be expected that the further development of various industries and transport industries, as well as the uncontrolled expansion of cities, will lead to an even greater aggravation of the problems associated with the need to isolate metals from solutions. Also, one of the main problems of industry is the resource productivity of the extraction and selective isolation of precious metals from poor polymetallic ores and waste from other industries [4]. More than 50% of metals such as silver, gold, palladium, rhodium and platinum, intended for decorative, protective and other coatings, are lost with electroplating wastewater. ...
Bis-N,N-(3-triethoxysilylpropyl)thiosemicarbazide 3 was obtained by the condensation of 3-aminopropyltriethoxysilane 1 with thiosemicarbazide 2. Ethyl ether N-[3-(triethoxysilyl)propyl]-b-alanine 5 was obtained by the interaction of an equimolar amount of aminopropyltriethoxysilane 1 and ethyl acrylate 4 (aza-Michael reaction). Synthesized functional organosilanes 3 and 5 were successfully immobilized on the surface of natural zeolite Z (Chankanai deposit, Kazakhstan). Compounds and materials have been studied by NMR and IR Fourier spectroscopy and X-ray diffraction analysis. The elemental composition and morphology of modified zeolites Z3 and Z5 were studied using SEM-EDX analysis. The modification of zeolite by organosilanes 3 and 5 leads to changes in the surface structure of the material: with the enlargement of particles and agglomerates, the surface becomes more homogeneous and less porous. This indicates a high degree of zeolite coverage by the modifier layer. The study of the sorption characteristics of the initial Z and modified zeolites (Z3 and Z5) showed a high sorption capacity relative to Ag(I) and Co(II) (static sorption capacity, SSC = 35.85–23.92 mg/g), whereas the SSC values for Z were SSC = 20.63 and 16.64 mg/g. The adsorption of Ag(I) and Co(II) ions was studied in solutions prepared using Co(NO3)2·6H2O, AgNO3 and distilled water. The choice of the initial concentration of metal ions, as well as the pH of the solutions, corresponded to the composition of wastewater from real electroplating production. Zeolites Z3 and Z5 can be used in various sectors of industry, in ecology and for medical purposes as inexpensive and effective adsorbents (enterosorbents) of heavy and noble metals.
... A very common process applied for the recovery of noble metals is cementation [4,5]. It allows noble metals to be retrieved from various materials after leaching them from a solid phase. ...
This study explores the impact of nitrate ions on the efficiency of cementing noble metals from diluted waste solutions at a temperature of 30 °C. The research involved measuring the effectiveness of different cementing metals (such as Zn, Al, Mg, and Fe) in the presence of nitrate ions by assessing the change in metal ion concentrations before and after the cementation process using spectrometric analysis. Initial concentrations of noble metals ware Pt = 5 ppm, Au = 7.5 ppm, Pd = 5 ppm, and Rh = 1 ppm. Kinetic studies revealed that 24 h is adequate to achieve apparent equilibrium in solutions with pH 2 and 1 M nitrate ion content. The study identified significant recovery losses for gold and platinum in nitrate solutions, underlining the necessity of nitrate-free solutions in recycling. Zinc and magnesium were effective in cementing Pd and Rh, while aluminum was efficient for Pt reduction in each condition. Complete removal of Au was not achieved with any tested metal, indicating a need for alternative methods.
... Metal recovery is achieved through hydrometallurgy, a chemical reaction process involving leaching, solution concentration and purification, and metal recovery. Studies have shown the recovery of molybdenum and vanadium from SPC ammonia leaching residue (Chen et al. 2006), dissolution of precious metals from waste hydrotreating catalysts (Valverde Jr, Paulino, and Afonso 2008), and recovery of metals from used hydrodesulfurization catalysts using fluidized bed electrolysis and acidleaching approaches (Jadhav and Hocheng 2012;Lai et al. 2008). Figure 1 illustrates the experimental setup. ...
... Bioleaching has been commercially utilized for the recovery of metals from tailings (Morin and d'Hugues, 2007) and metallurgical side streams (Gericke et al., 2022). However, bioleaching approaches are still at laboratory scale for other waste streams (Jadhav and Hocheng, 2012;Srichandan et al., 2019). Various chemolithoautotrophic and heterotrophic microorganisms have been tested in laboratory scale to bioleach metals from waste materials, such as electronic waste, catalysts, sludges, slags and ashes (reviewed by Srichandan et al., 2019). ...
... Electrochemical repair techniques are expensive and require complex operations [49]. However, bioleaching is considered as a convincing technology for the recovery of valuable metal elements from mine tailings due to the low cost and simple infrastructure, with broad development prospects [50,51]. Moreover, under anaerobic conditions, At. ferrooxidans can also effectively recover Ni, Co, Mn, and rare-earths from mine tailings [20,39]. ...
The accumulation of mine tailings on Earth, generated from the extraction, processing, and utilization of mineral resources, is a serious environmental challenge. The importance of the recovery of valuable elements and rare-earth elements, together with the economic benefits of precious and base metals, is a strong incentive to develop sustainable methods to recover metals from tailings. Currently, researchers are attempting to improve the efficiency of valuable elements and rare-earth elements recovery from tailings using bioleaching, a more sustainable method compared to traditional methods. In this work, we report the research status of the application of Acidithiobacillus ferrooxidans (At. ferrooxidans) anaerobic reduction in tailings disposal. Recent advances in the anaerobic characteristics of At. ferrooxidans recovery process and technical difficulties are further described. We found that current research has made significant progress in anaerobic recovery. This is of great significance for the development of bioleaching technologies and industrial production of heavy metals in tailings. Finally, based on the perspectives and directions of this review, the present study can act as an important reference for the academic participants involved in this promising field.
... The recovery of catalysts usually requires multistep treatment processes by mechanical, chemical, and thermal unit operations [8]. Various techniques are already used at the industrial scale to recover precious metals from spent catalysts [9,10], which mainly consist of pyrometallurgy, hydrometallurgy, and leaching methods [11][12][13][14]. However, these processes require very high temperatures (>1273 K) or generate large amounts of leaching solvents. ...
Precious metals such as palladium (Pd) have many applications, ranging from automotive catalysts to fine chemistry. Platinum group metals are, thus, in massive demand for industrial applications, even though they are relatively rare and belong to the list of critical materials for many countries. The result is an explosion of their price. The recovery of Pd from spent catalysts and, more generally, the development of a circular economy process around Pd, becomes essential for both economic and environmental reasons. To this aim, we propose a sustainable process based on the use of supercritical CO2 (i.e., a green solvent) operated in mild conditions of pressure and temperature (p = 25 MPa, T = 313 K). Note that the range of CO2 pressures commonly used for extraction is going from 15 to 100 MPa, while temperatures typically vary from 308 to 423 K. A pressure of 25 MPa and a temperature of 313 K can, therefore, be viewed as mild conditions. CO2-soluble copolymers bearing complexing groups, such as pyridine, triphenylphosphine, or acetylacetate, were added to the supercritical fluid to extract the Pd from the catalyst. Two supported catalysts were tested: a pristine aluminosilicate-supported catalyst (Cat D) and a spent alumina supported-catalyst (Cat A). An extraction conversion of up to more than 70% was achieved in the presence of the pyridine-containing copolymer. The recovery of the Pd from the polymer was possible after extraction, and the technological and economical assessment of the process was considered.
... Malaysia is an emerging nation that relies on modern efficiency as one of its monetary donors. Different types of wastes are produced in industrial processes, including chemical effluents, industrial plants waste, paper waste, metals, concrete, sludge, electronic devices wastes, etc. [59]. A number of significant materials (e.g., graphite, Cu, Fe, and Zn) from industrial waste can be recuperated utilizing a hydrometallurgical technique called leaching [60]. ...
It is no secret that graphene, a two-dimensional single-layered carbon atom crystal lattice, has drawn tremendous attention due to its distinct electronic, surface, mechanical, and optoelectronic properties. Graphene also has opened up new possibilities for future systems and devices due to its distinct structure and characteristics which has increased its demand in a variety of applications. However, scaling up graphene production is still a difficult, daunting, and challenging task. Although there is a vast body of literature reported on the synthesis of graphene through conventional and eco-friendly methods, viable processes for mass graphene production are still lacking. This review focuses on the variety of unwanted waste materials, such as biowastes, coal, and industrial wastes, for producing graphene and its potential derivatives. Among the synthetic routes, the main emphasis relies on microwave-assisted production of graphene derivatives. In addition, a detailed analysis of the characterization of graphene-based materials is presented. This paper also highlights the current advances and applications through the recycling of waste-derived graphene materials using microwave-assisted technology. In the end, it would alleviate the current challenges and forecast the specific direction of waste-derived graphene future prospects and developments.
... The isolation and separation of metal ions, especially critical ones, both from natural raw materials and from industrial waste, are among the main priorities of the world economy [1][2][3]. One of the most powerful tools in this direction is extraction processes [4][5][6][7][8][9][10][11][12]. The correct selection of ligands for each specific object is a major factor in achieving high efficiency and, therefore, the efforts of a huge number of scientific groups are directed towards the development of new effective organic molecules [13][14][15][16][17][18]. ...
The novel compound 3-methyl-1-phenyl-4-thioacetylpyrazol-5-one is obtained in excellent yield via a thionation of the corresponding oxygen analogue. The product is isolated in pure form using column chromatography and is characterised using 1D and 2D NMR experiments, ATR IR and HRMS spectra, and single-crystal XRD.
... The valuable target component(s) are either those that can be separated from the bulk material (direct recovery e.g. by leaching), or the residual bulk material, after removal of contaminants that prevent reuse (indirect recovery), or a combination of both (see Sapsford et al., 2017). There exists a very large body of research on hydrometallurgical, biohydrometallurgical and pyrometallurgical processes for extraction of valuable resource from mineral-rich industrial and mining wastes (see for example reviews by Jadhav and Hocheng, 2012;Sethurajan et al, 2018;Gunarathne et al, 2022). However, the sustainability (using the definition based on maintenance of genuine wealth, Arrow et al., (2004)) and economic viability of many of these processes requires careful consideration. ...
Many countries face serious strategic challenges with the future supply of both aggregates and critical elements. Yet, at the same time, they must sustainably manage continued multimillion tonne annual arisings of mineral-dominated wastes from mining and industry. In an antithesis of Circular Economy principles, these wastes continue to be landfilled despite often comprising valuable components, such as critical metals, soil macronutrients and mineral components which sequester atmospheric CO 2 . In this paper, the authors aim to introduce a new concept for value recovery from mineral-rich wastes where materials are temporarily stored and cleaned in landfill-like repositories designed to be mined later. The time in storage is utilised for remediating contaminated materials and separating and concentrating valuable components. It is proposed that this could be achieved through engineering the repository to accelerate “lithomimetic” processes, i.e. those mimicking natural supergene processes responsible for the formation of secondary ores. This paper summarises the concept and justifications and outlines fundamental aspects of how this new concept might be applied to the design of future repositories. The proposed concept aims to end the current “linear” landfilling of mineral-rich wastes in favour of reuse as aggregates and ores.
... Cr is released into the environment through natural processes or human activities, and it poses significant health risks to humans (Xiang et al. 2021). The rapid increase in environmental Cr (III) is associated with the fast expansion of the leather, textile, and steel industries (Xia et al. 2019), and Cr (VI) is discharged into natural water through electroplating, metallurgy, leather, dye manufacturing, chrome mining, and from other industries (Cocârţă et al. 2016;Jadhav and Hocheng 2012;Jobby et al. 2018;Pandey et al. 2017;Oskui et al. 2019b). Cr (VI) affects air quality through coal manufacturing, and it eventually causes water and soil pollution (Hassan and Garrison 2015). ...
A novel plant cathode-sediment microbial fuel cell (P-SMFC) was constructed to treat Cr-containing wastewater, and the effects of the plants used, initial concentrations of Cr(VI) employed, and the external resistance on the treatment of wastewater and generation of electricity were investigated. The results showed that the system achieved the best performance when Acorus calamus was the cathode plant, the external resistance was 2000 Ω, and the initial Cr (VI) concentration of the overlying water of is 230 mg/L. A maximum power density of 40.16 mW/m2 was reached, and Cr (VI) and COD removal efficiencies in the overlying water were 99.94% and 98.21%, respectively. The closed-circuit installation promoted the attachment of many microorganisms to the cathode, anode and sediment, increased species abundance, and reduced species diversity. The P-SMFC is inexpensive to construct, it consumes no energy, and it can generate bioelectricity; it thus has great application development value as a chromium-containing wastewater treatment method.
... Other primary sources, such as Moroccan cobalt-arsenic ores, account for the remaining 15% (Mills, 2014). As a result of ever-increasing consumption, the production of base metals must not only be from high-grade primary resources but the recovery of these metals from metallurgical wastes must also be explored (Jadhav and Hocheng, 2012). ...
Copper slag has long been the subject of metal recovery. However, it has become apparent that copper slag flotation tailings can meet resource requirements under certain circumstances. Besides copper, zinc and cobalt can also be obtained from slag tailings. This study investigated the potential of copper slag tailings alongside global metal supply and demand dynamics. It has been emphasized that, such as copper slag, slag tailings can be a new potential resource for global base metals, considering global and domestic copper production, consumption, and base metal prices. In addition, its economic and environmental sustainability was evaluated from a waste management perspective.
... Organic acids, as opposed to inorganic acids, are nearly natural and sustainable, and some organic acids can be employed as a reductant, precipitant, or chelating agent during the active cathode material recovery process (Li et al. 2017). Organic acids are not regarded as potential environmental contaminants because they are formed by microorganisms (Jadhav and Hocheng, 2012). Utilizing organic acids as effective and environmentally friendly leaching agents would prevent secondary emissions, delay equipment corrosion, provide less of a risk to operators, and allow for the selective leaching of certain metals (Horeh et al., 2016). ...
Recycling cathodic materials from spent lithium-ion batteries (LIBs) is crucial not just for the environmental aspects but also for the supply of precious raw materials such as cobalt and lithium. As a result, developing a leaching process with low acid consumption, cost-effectiveness, low environmental impact, and high metal recovery is essential. In this article, the sustainable hydrometallurgical route for recovery of Li and Co from spent LIBs using DL-lactic acid as lixiviant is proposed. The different leaching parameters were studied to optimize the leaching conditions. With increasing lactic acid concentration from 0.1 mol/L to 1.0 mol/L, the leaching efficiency of Li and Co increased from 23% to 41% and 2% to 14%, respectively. The reductant H2O2 has a major role which reduced Co3+ to Co2+ and increasing the leaching efficiency of Co from 15.2% (1% H2O2) to 73.4% (6% H2O2). The maximum leaching efficiency of Li (99.8%) and Co (99%) was attained with 1.0 mol/L lactic acid, 6% H2O2, 60 °C, S/L ratio of 10 g/L, and 60 min leaching duration. The R2 values for the surface chemical reaction model were greater than 0.98, indicating that the lactic acid leaching process was controlled by the surface chemical reaction model. With 1.0 mol/L 70% saponified Cyanex 272, a solvent extraction study showed a higher separation factor (βCo/Li) of 35.7 compared to other saponified and nonsaponified organophosphorus extractants. Using the precipitation method, 99.9% of Co and 99% of Li were precipitated as and with a purity of 99.4% and 98.3%, respectively.
... Additionally, the main way to obtain mineral resources over the years, until now, has been through mining extraction activities. However, such activities seem to be attached to a clock due to new regulations around the world, which are demanding to diminish environmental impacts; consequently, ways to obtain metals are no longer focused exclusively on mining, but also in their recoveries through other sources, like e-wastes [9,26,27,37,54,57,60] or industrial residues, such as spent catalysts [8,20,40,50,59,71,81]. Regarding traditional mining techniques, pyrometallurgy is mainly used in high-grade ores [14,42], leaving aside the low-grade deposits due to cost issues. ...
Minerals have been important throughout history, but nowadays, their use has increased, as well as their extraction needs. Therefore, due to the growing demand for metals, and both the depletion of high-grade ores and their related environmental concerns, the mining industry has been forced to leave behind the past traditional techniques of metal recovery (use of inorganic acids), and adopt eco-friendlier alternatives, such as the utilization of weaker leaching agents, such as organic acids. Thus, the present review is focused on the use of microbially-produced organic acids as a promising alternative to conventional techniques in the mining industry, with emphasis on the following topics: a) the advantages and disadvantages of the use of organic acids for leaching purposes, b) the main microorganisms studied for the production of these organic acids, c) a summary of the latest reports on bioleaching as well as a comparison of the existent techniques; d) the explanation of leaching mechanisms where organic acids may be involved, to fulfill metal recovery; and, e) interactions between metallic ions and organic acids. The review of the current knowledge regarding the use of organic acids for leaching purposes seeks the visualization of relevant strategies that may be improved for metal-recovery processes, intending to develop circular economy practices that may have the potential to be implemented at an industrial scale.
... This century has seen a significant increase in the production of industrial waste. Toxic components in these industrial wastes will contaminate the environment and create disposal issues [1]. Having said that, some of the wastes contain precious metals such as gold and platinum which can be used for other purposes [2]. ...
Conventional methods for recovering heavy metals from industrial waste stream often involve significant energy consumption and chemical use. Hence, using microalga as a biosorbent material can be a low-cost and eco-friendly solution. Galdieria sulphuraria is a red microalga which is known to be capable of recovering heavy metals. This algal species is resistant to extreme temperatures and acidic environment. It is also well-established that light emitting diodes (LED) is effective at promoting algal growth. Our research objectives were to study the effects of LED lightings (red, blue, green, and white) on the growth of G. sulphuraria and to compare the growth in indoor and outdoor cultivations. In this work, the culture medium was the modified 2x Allen’s with pH 2.5. To promote the rapid growth of G. sulphuraria , the culture medium was supplemented with 2% CO2. Algal growth was determined by measuring the optical density at 750nm (OD750) using UV-vis spectrophotometer. Results have shown that in indoor cultivation, the growth rate of G. sulphuraria was highest under red light (μ= 0.06 day ⁻¹ ) and lowest under blue light (μ= 0.02 day ⁻¹ ). For outdoor cultivation, algal growth rate increased by 2 to 6-fold higher compared to that in indoor cultivation. Algal cultivation in outdoors was best with white light (OD = 2.46 ± 0.09; μ = 0.13 day ⁻¹ ). Although the use of LEDs enhanced algal growth, we found it did not make a significant difference statistically when compared to the set without LEDs. This may be attributed to the Malaysia’s environment (photoperiods, temperatures, etc.). This paper will serve as a foundation for future research on cultivating G. sulphuraria indoors and outdoors using various LED lights.
... Hence, it is indispensable to find a facile recycling method to process the aluminum deposits. Several research groups have garnered to process the aluminum deposits and to recover by different recovery strategies like smelting, density separation method, plasma assisted recovery, and acid/alkaline leaching method [13][14][15][16] although some of these methods have some major limitations like need of high cost instruments, recovery involving very high temperature, protracted process, usage of expensive and hazardous/carcinogenic chemicals involved in processing the waste [17][18][19][20]. The major limiting factor of these methods is the formation of hazardous by products in the course of recovery process. ...
Energy has become an unavoidable part of our day-today life; it can be generated from renewable sources of energy, avoiding the depletion of fossil fuels. Electrochemical energy stored is the most efficient and clean form of energy. The choice of electrode material plays a crucial role in the performance of batteries and supercapacitors. The energy storage devices can be made more sustainable and cost-effective if derived from waste. Rising demand of vaccines in this pandemic eon has accumulated the wastes, which need to be recycled promptly to avoid environmental pollution. In this study, the dumped vaccine-bottle caps which are made up of aluminum have been recovered successfully by leaching method, also in order to enhance the performance of the generated residue, it was supported by carbon to improve the conductivity of the derived metal oxides. The physical and electrochemical properties of the synthesized materials were analyzed by various advanced technologies. The re-synthesized Al 2 O 3 /C particles have been applied as electrode in Na 2 SO 4 electrolyte for supercapacitor application. The Al 2 O 3 /C electrode delivered a specific capacity of 147 C g −1 in Na 2 SO 4 at a current density of 1 A g −1. The Na-ion capacitor was fabricated with Al 2 O 3 /C and vulcan carbon (VC) electrodes then the device performance was optimized. A wide potential window of 2 V with good long-term stability was achieved for the aqueous Na-ion capacitor in 1 M Na 2 SO 4 electrolyte. The device was found to deliver an energy density of 21 W h kg −1 at a power density of 8064 W kg −1. Thus, recycling and reuse of Al 2 O 3 /C electrode in Na-ion capacitor application can be incalculable step towards ecofriendly, cost-effective energy storage systems, additionally it also pave way to recycling other waste like used mask or covers.
Microorganisms play an essential role in the sustainable management of waste by driving biochemical processes that degrade, transform, and detoxify a wide range of pollutants found in municipal, industrial, agricultural, and biomedical wastes. This chapter reviews the fundamental microbial mechanisms involved in waste degradation, including aerobic and anaerobic pathways, enzymatic activities, and microbial consortia interactions. It explores practical applications of microbes in wastewater and solid waste treatment, highlighting composting, bioremediation, and advanced microbial technologies such as microbial fuel cells and genetically engineered strains. Emerging innovations in metagenomics and synthetic biology are also discussed, showcasing their potential to optimize microbial communities for improved efficiency and resource recovery. The environmental and economic benefits of microbial waste treatment, such as pollution reduction, greenhouse gas mitigation, and cost-effectiveness, emphasize the importance of integrating microbiology into waste management strategies. Challenges related to microbial stability, pollutant complexity, and scalability are acknowledged, with future prospects aimed at enhancing sustainability through interdisciplinary approaches. This synthesis underscores the critical role of environmental microbiology in transforming waste treatment into an eco-friendly, economically viable, and circular process vital for global environmental health.
The incineration rate of combustible household waste discharged using standard waste bags in Seoul city increased by about
6 times compared to about 20 years ago, reaching 58% as of 2022. From 2018 to 2022, the waste metals mixed in standard
waste bags of Seoul city are the source of incinerated-iron, the discharge of which increases every year. However, the
proportion recovered as incinerated-iron is varied, ranging from 4.7% to 39.7%, and the recovery rate is decreasing over the
years. The proportion of incinerated-iron recovered from bottom ash is 1.2% to 2.1%, and the proportion of incinerated-iron
among the recovered metals is 94.3% to 99.6%. All recovered incinerated-iron is sold, but its price is lower than the market
price. The low recovery rate and low selling price are the current problems of incinerated-iron of Seoul. The recovery rate
can be affected by the type of incoming waste, the performance of the magnetic separator, and the size and shape of
incinerated-iron, and continuous research is needed to analyze these interrelationships. In addition, the low sales price of
incinerated-iron is related to its quality and use. Incinerated-iron is recovered as iron oxide and sold with the incineration
bottom ash still on the surface, greatly reducing usage. Future research is needed to improve the recovery quality of
incinerated-iron and expand its uses.
Heavy metals pose a significant threat to public health and economic stability in Ethiopia, contaminating various environmental media, including water, soil, and air. This paper aimed to provide an overview of the public health and economic burden of heavy metals in Ethiopia. Exposure to heavy metals such as lead, mercury, cadmium, and arsenic has been linked to numerous adverse health effects, including neurological disorders, renal failure, cardiovascular diseases, and cancer. In Ethiopia, populations are particularly vulnerable to heavy metal exposure due to various factors, such as artisanal mining, industrial activities, agricultural practices, and inadequate waste management systems. The economic burden of heavy metal contamination manifests through increased healthcare costs, loss of productivity, and environmental remediation expenses. Furthermore, the impact extends to sectors such as agriculture and tourism, affecting national development goals and exacerbating poverty levels. Efforts to mitigate the public health and economic burdens of heavy metals in Ethiopia require multidisciplinary approaches, including policy interventions, regulatory enforcement, public awareness campaigns, and investment in sustainable development practices. Strengthening monitoring systems, implementing pollution control measures, and promoting research on alternative technologies for waste management are essential steps toward addressing this pressing issue. In conclusion, addressing the public health and economic challenges posed by heavy metal contamination in Ethiopia necessitates concerted efforts from the government, industry, academia, and civil society to safeguard human health, preserve the environment, and promote sustainable development.
biztosított támogatással, a VÁLLALATI KFI_16 pályázati program finanszírozásában fémekkel szennyezett környezeti közegekből, szennyvíziszapokból, meddőhányókból és ipari hulladékokból történő fémvisszanyerés lehetőségeit elemezte. A laboratóriumi vizsgálatokkal és később félüzemi berendezésekkel sikeresen kidolgoztunk egy olyan technológiát, mely egyes toxikus nehézfémek, ritkaföldfémek és egyéb iparilag fontos fémes elemek biohidrometallurgiai (BHM) eszközökkel történő kinyerését valósítja meg, lehetőséget adva ezen anyagoknak újra hasznosítására. Ebben a közleményben a BHM technológiák hatékonyságát befolyásoló környezeti tényezőket tekintjük át.
Sustainable agriculture is an effective approach towards environmental conservation. While agriculture provides food and livelihood for millions of people it also contributes to deforestation, habitat loss, soil erosion, etc. Additionally, the sector is a significant source of pollution, with pesticides and fertilisers contaminating waterways and disrupting ecosystems. Agricultural expansion often leads to the encroachment of wild lands, driving down prices and contributing to poverty. To address these challenges, sustainable agricultural practices are essential. This chapter explains how cutting-edge techniques can help reduce agriculture’s negative environmental effects and ensure long-term food production. These techniques include crop breeding, carbon sequestration, microbiome management, and climate smart irrigation. Reducing reliance on natural resources and using inputs more effectively are two ways to promote sustainable agriculture. Sustainable agriculture takes a holistic approach to farming by integrating three key objectives: social equity, economic profitability, and environmental health. By adopting these principles and leveraging technological advancements, the future of environmental conservation and sustainable agriculture looks promising. Environmental conservation is paramount for sustainable agriculture. We can reduce the damaging effects of agriculture on the environment while ensuring long-term food production and security by implementing sustainable practises, such as organic farming and climate-smart agriculture. Prioritising the adoption of these strategies is essential if we are to create an agricultural system that is resilient and sustainable for both the present and the future.
Industrial wastewater contains a variety of hazardous chemicals as well as high metal concentrations. Metal-contaminated wastewater is hazardous to the environment and can have serious health consequences if it enters biological systems. However, the recovery of metals from wastewater can increase the sustainability of treatment processes and enhance cost-effectiveness. There are numerous conventional treatment methods for recovering metals from wastewater, including physical, chemical, and even biological methods. Physical and chemical processes are primarily energy and chemical-intensive. New-age research uses novel bio-recovery methods to extract and remove metals from wastewater. Various methods like sorption, biomembranes, bioelectrochemical techniques, etc., have been discussed in this chapter in a summarized form. Further, insights into energy-efficient recovery methods and their applications have been elaborated.
Since enzymes are bioactive chemicals, they are of interest to scientists all over the world. Demand for microbial enzymes is rising rapidly across a wide range of sectors as their importance in ensuring the security, sustainability, and efficiency of biotech processes becomes more widely recognised. Media optimization is a powerful tool to enhance production capacity from biological sources (microorganisms). In this present study, samples were collected from mangrove-rich sources such as Borivali Monari Creek and Jhow Island, Maharashtra, western India. Samples collected were mangrove-associated soil, mangrove root, and sea water. The type of sampling was random. Samples were collected with prior permission from the mangrove cell maharashtra government. A total of 30 samples were processed, from which 62 isolates were obtained. These isolates were all screened for industrially important enzymes (protease, amylase, and cellulase), and the best protease producer was selected for further studies. The method of optimization was "ONE VARIABLE AT A TIME OVAT" and method is a well-known optimization technique. Optimization was carried out for parameters like inoculum size, pH of the growth medium, various carbon sources, varied nitrogen sources, and metal ions and cations. Casein was used as substrate, and casein was prepared in various pH buffers for the enzyme assay. At 5 minutes after incubation of enzyme substrate mixture, enzyme activity was at its peak, and substrate degradation in the medium was minimal as compare 65 minutes set. Enzyme activity decreased dramatically as substrate pH increased (between 11 and 12 pH). This optimization supports maximizing the yield of protease production and is of great benefit to the biotech industry. The present study shows that with time stability of enzyme reduces and residues of degraded substrate increases within the reaction mixture. Here in our experiment variation in substrate pH were studied, which showed that protease from Bor S17B13 isolate has optimum enzyme activity at substrate pH 10 at highly alkaline pH then 10 pH, activity of enzyme was reduced. A phenomenon called dissociation of substrate (casein) was seen at casein solution 13pH.
This study suggests the effective recycling method of sludge waste from various industrial fields to synthesize uniform colloidal silica nanoparticles. In detail, polymers are removed from the sludge waste to attain sludge-extracted silica (s-SiO 2) micron-sized particles, and ammonia assisted sonication is applied to s-SiO 2 , which has effectively extracted the silanol precursor. The nano-sized silica (n-SiO 2) particles are successfully synthesized by a typical sol-gel method using silanol precursor. Also, the yield amounts of n-SiO 2 are determined by the function of s-SiO 2 etching time. Finally, n-SiO 2-based slurry is synthesized for the practical CMP application. As a result, rough-surfaced semiconductor chip is successfully polished by the n-SiO 2-based slurry to exhibit the mirror-like clean surface. In this regard, sludge wastes are successfully prepared as valuable semicondutor grade materials. 초 록: 본 연구에서는 반도체를 포함한 다양한 산업 분야에서 발생하는 슬러지 폐기물을 활용하여 고부가 가치의 균일한 콜로이달 실리카 나노입자를 제조하고자 하였다. 상세히는 슬러지 폐기물에서 고분자를 용해하여 추출한 실리카(s-SiO 2)를 분리하였고, 암모니아와 소니케이터를 활용한 에칭을 통해 실라놀 전구체를 추출하였다. 실라놀 전구체를 활용하여 졸-겔법으로 균일한 약 50nm 크기의 실리카 나노입자(n-SiO 2)를 성공적으로 합성되었음을 확인할 수 있었다. 또한, s-SiO 2 의 에칭 시간에 따른 n-SiO 2 의 수득량을 확인하였으며, 8시간의 에칭 시간에서 가장 많은 n-SiO 2 가 제조되는 것을 확인할 수 있었다. 최종적으로 n-SiO 2 를 기반으로 한 CMP용 슬러리를 제조하여, 반도체 칩의 연마에 활용하였다. 그 결과, 반도체 칩의 표면에 존재하던 빗살 무늬의 데미지들이 성공적으로 제거되었으며, 이를 통해 슬러지 폐기물에서 고부가 가치의 반도체 급 n-SiO 2 소재가 성공적으로 제조되었음을 확인할 수 있었다.
Cyanide-based baths are generally used industrially to produce silver and gold coatings via electroplating. Baths containing ([Au(CN)2]⁻) and ([Ag(CN)2]⁻) are used for the deposition of gold and silver coatings, respectively. However, due to the severe toxicity, the technical personnel involved in work are at risk. Additionally, the disposal of cyanide-containing wastes poses a significant threat to the environment as they pollute various natural resources. The coatings produced from alkaline cyanide-based baths cause embrittlement of electronic circuit patterns. Due to these reasons, many cyanide-free baths have started to replace the existing cyanide-based baths. In the cyanide-free baths, the primary cyanide complexing agent is replaced with eco-friendly alternative compounds like sulphite, thiosulphate, thiourea, DMH, EDTA, and ionic liquids (ILs). This review article provides an overview of the various cyanide-free electroplating baths available for electroplating silver and gold that are either used for commercial practice or are developed for laboratory-scale use.
It is no longer a discovery that mechanochemistry positively influences the extractive metallurgy and other allied industries’ circular economy. However, a pertinent use and control of its processing route and parameters need to be looked into for effective sustainability of the industries and resources involved. The application of Mechanical activation (MA) in the extractive metallurgical process (hydrometallurgy) has vehemently improved the conversion of waste to wealth compared to other pretreatment methods. Some industrial wastes are hazardous and they are heap-dumped, negatively influencing the environment they occupied. This present work reviewed the hazardous industrial solid wastes (HISWs) from which economically valuable metals (EVMs) were recovered and the economic and environmental benefits of recovering via the Mechanical Activation Hydrometallurgical process. The influence of both MA and leaching parameters on the recovery efficiency was shown. The detailed analysis of the optimum conditions of these MA-leaching processes was also reported on the ground of critical evaluation of the scientific literature scrutiny. This study aims to present a direction and guidance flow sheet based on an extensive literature survey for effective recovery of EVM from secondary resources (HISW) via the MA-hydrometallurgical process addressing the drawbacks of MA-assisted leaching.Graphical Abstract
The waste X-ray/ photographic films contain 1.5 - 2 % (w/w) black metallic silver which is recovered and reused. Around 18-20% of the world's silver needs are supplied by recycling photographic waste. Since silver is linked to gelatin in the emulsion layer, it is possible to break the same and release the silver using proteolytic enzymes. Alkaline protease from Conidiobolus coronatus was investigated for enzymatic hydrolysis of gelatin from waste X-ray films. At the end of the treatment, gelatin layer was completely removed leaving the polyester film clean and silver was recovered in the hydrolysate, both of which can be reused. Various parameters such as pH, temperature, enzyme concentration, time etc on silver removal from the film were studied. Gelatin hydrolysis was monitored by measuring increase in turbidity in the hydrolysate, which was accompanied by release of protein and hydroxyproline. Gelatin layer was stripped completely within 6 min with 1.35 U ml -1 of protease at 40°C, pH 10. Rate of gelatin hydrolysis increased with increased in protease concentration. The enzyme could be effectively reused for four cycles of gelatin hydrolysis. Silver in hydolysate was around 3.87% (w/w) based on total weight of sludge. Key words: Silver recovery; X-ray films; gelatin hydrolysis; alkaline protease; Conidiobolus coronatus DOI: 10.3126/kuset.v6i1.3311 Kathmandu University Journal of Science, Engineering and Technology Vol.6(1) 2010, pp60-69
Free powders as well as compact shapes of molybdenum and cobalt have been successfully recovered from spent hvdrogenation and desulphunzauon catalysts. A process flow sheet was followed involving crushing, milling .particle sizing, hydrometallurgical acid leaching, roasting of the obtained salts in an atmospheric oxygen to obtain the respective oxides. These were reduced by hydrogen gas at I IOO°C and 900°C respectively. Parameters affecting the properties of the products and the recovery efficiency value such as acid concentration, particle diameter of the solid catalyst, , temperature . time , under a constant mass flew rate of the hydrogen gas, have been investigated. A mixture of cone, sulphuric and nitric actds(3:1 by volume) achieved adequate recovery of both metals. The latter increased with the increase in acid concentration, time up to 3 hours and temperature: IOO°C and with the decrease in particle diameter of the spent catalyst. The pH of the obtained filtrate was adjusted to 2 with ammonia to precipitate insoluble ammonium molybdate and a solution of cobalt sulphate. Cobalt hydroxide can be precipitated from the latter solution at apH=7.6 using excess ammonium hydroxide solution. The obtained results showed that the metallic products are technically pure meeting the standard specifications. Compact shapes of molybdenum acquire density values increasing with the increase of the pressing load whereby a maximum density value of 2 2 SO kg/m3 is attained at > 0.75 MPa. Maximum recovery efficiency amounts to 96%.
A process for the recovery of gold from processed gold-plated printed circuit boards, gold-coated bangles and gold-coated mirrors is described. It is based on heating the scrap material along with an “eco-friendly” or “green” reagent, 20% (v/v) formic acid solution to boiling temperature to separate the inorganic component from epoxy resin in gold-coated mirrors. Dissolution of base metals is affected using a strong oxidizing agent, 20%(w/v) potassium persulphate, which is also “eco-friendly” or “green”; and heating to boiling temperature. Recovery of gold is achieved by melting. The recovery efficiency is on par with the cyanidation process. The process can be scaled up and adopted by all categories of industries.
Aspergillus niger is known to be capable of bioleaching heavy metal ions from municipal solid waste (MSW) incineration fly ash. The objective of this study was to investigate the bioleaching kinetics of the fungus in the presence of the fly ash at various pulp densities (1–6%) in a batch system. The growth of the fungus was modeled using the modified Gompertz model. Since the metals present in the fly ash are toxic and inhibit microbial growth, an inhibition kinetic model using the generalized Monod growth kinetics was evaluated. In a two-step bioleaching system where the fly ash was introduced into the culture two days after inoculation, citric acid production and the leaching of the metals aluminium, iron and zinc from the fly ash were examined. The kinetic parameters in the system were estimated using the least square method. Results showed that the modified Gompertz model fit the experimental data well. The specific growth rate decreased with increasing pulp density, with a maximum specific growth rate (μmax) of 0.115day−1 for the control. The critical inhibitor (i.e. fly ash) concentration (CI*) above which no growth occurred was found to be 6.0%. Results also showed an increase in metal concentration leached with a concomitant increase in the citric acid production at various pulp densities.
We have used the solid‐phase MetPLA TE, an enzyme assay that is specific for heavy‐metal toxicity, to investigate metal toxicity of soils that have been amended with urban wastewater sludges or contaminated with dry deposition from metal‐plating industries. We have shown that soil toxicity, using MetPLA TE, ranged from 21 to 72.5% inhibition of enzyme activity. Evin soil, which displayed the highest toxicity, also had the highest concentrations of Pb and Zn. Metal uptake studies with ryegrass grown on Evin soil, showed Zn, Cd, and Pb accumulation in the plant that exceeds the standard levels reported for grasses
Solid‐phase MetPLA TE was also used as a tool to study the reduction of heavy‐metal toxicity following soil amendments to immobilize metals in soil and thus reduce their toxicity. It was found that the addition of 1% hydrated manganese oxide significantly reduced dissolved metals in soil, their accumulation by ryegrass, and soil toxicity as shown by MetPLA TE.
Municipal Solid Waste (MSW) incineration fly ash was collected in the industrial facilities in the city of Toulouse, equipped with recent gas scrubbing equipment which collects daily 15 t of lime treated fly ash. The fly ash contains a large proportion of water soluble chlorides, besides trace elements such as iron, zinc, titanium and copper. Presently, the fly ash is landfilled after a cement solidification process. Matrix stability and leaching behavior of heavy metals (Cd, Cu) from samples of doped MSW fly ash were examined before and after chemical and thermal treatments. A new phosphate process leading to hydroxylapatite formation is described. To evaluate it's performance as a stabilization process, cupric and cadmium ions were added as typical pollutant tracers and their distribution was studied as a function of different treatment parameters. The hydroxylapatite process used effectively removes chloride ions in the water extract and retains most of the added metal ions in the solid residues. Evaluation of this procedure as a cold process shows 50% reduction in leachable metal ions. Calcination of the solid residues at 900°C results in agglomerated particles with increased resistance to metal ion dissolution. This is attributed to heavy metal incorporation in the hydroxylapatite matrix formed during the thermal treatment. Thus, combined chemical and thermal treatments are efficient for heavy metal stabilization in MSW fly ash.
Two heavy metals, Cd and Ni, have been separately recovered from spent AA-size Ni–Cd batteries by the potentiostatic electrodeposition and chemical precipitation methods, respectively. Various types and concentrations of HCl, H2SO4, and HNO3 acids had been used as leach extractants. Experimental results indicate that the acid with the best leach capability is 4 M HCl. Three complexing reagents of NH3, sodium acetate, sodium citrate have been chosen and tested. The most effective buffer is sodium citrate. The optimum mole ratio of metallic ion to citrate ion is 1:1. The recovery process for Cd metal is conducted by the potentiostatic electrodeposition in a leach electrolyte with a sodium citrate complex. The optimum applied potential for Cd recovery is in the range −1100 to −1120 mV (versus saturated calomel electrode (SCE)). The current efficiency for the recovery process is between 70 and 90% and depends strongly on the process parameters, e.g. liquor, concentration, applied potential, temperature, type of complex reagents, mole ratio, mass-transfer rate.
Abstract Society uses metals derived from primary and secondary sources. Secondary sources include all metals that have entered the economy but no longer serve their initial purpose. The environmental benefits of increasing reliance on secondary metal production include conserving energy, landscapes, and natural resources, and reducing toxic and nontoxic waste streams. A variety of technologies are used to recover and process metals from waste streams and their use for metal production influences the amount of secondary metal that reenters the system. Environmental regulation also affects secondary metal production through laws that control emissions and govern the classification and treatment of metal-loaded wastes. Industry must develop better technology to isolate and recover maximum value from metals in waste streams, and governments must institute policies that remove barriers to their economically and environmentally sound recovery. Only through a concerted effort can society recover a maximum amount of metal from the industrial/social system to benefit the environment.
The present work was aimed at studying the bioleachability of metals from electronic scrap by the selected moderately thermophilic strains of acidophilic chemolithotrophic and acidophilic heterotrophic bacteria. These included Sulfobacillus thermosulfidooxidans and an unidentified acidophilic heterotroph (code A1TSB) isolated from local environments. Among the strategies adapted to obtain enhanced metal leaching rates from electronic scrap, a mixed consortium of the metal adapted cultures of the above-mentioned bacteria was found to exhibit the maximum metal leaching efficiency. In all the flasks where high metal leaching rates were observed, concomitantly biomass production rates were also high indicating high growth rates. It showed that the metal bioleaching capability of the bacteria was associated with their growth. At scrap concentration of 10 g/L, a mixed consortium of the metal adapted cultures was able to leach more than 81% of Ni, 89% of Cu, 79% of Al and 83% of Zn. Although Pb and Sn were also leached out, they were detected in the precipitates formed during bioleaching.
A different enzymatic method was developed for stripping the silver from waste X-ray photographic films. The silver having purity of > 99% was recovered by smelting the obtained slurry in the presence of borax. Enzyme extract, obtained from Bacillus subtilis ATCC 6633 by modifying Horikoshi medium, was used for stripping the silver layer. The metal impurities (Al, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb and Sn) in the recovered silver were determined using the ICP-MS method. The results were compared those in with literature for high purity silver using the same method.
Cadmium was recovered from scrap domestic, sealed NiCd batteries by the use of chlorination. The technique was efficient and economic and gave recoveries of almost 100%. The work also demonstrated that it is feasible to recirculate the chlorinating gas, making the process environmentally acceptable. Chlorine and hydrogen chloride were found to be suitable chlorinating agents. The latter was produced by the controlled combustion of polyvinyl chloride scrap, thus allowing the recycling of a toxic, commercially valuable material while disposing of two waste materials. The technique and equipment used were simple, enhancing the prospects for a pilot-scale version of the process.
Batrec AG operates an industrial plant for recycling of used dry batteries with a production capacity of 3200 tons per year. The process consists essentially of the following three process stages: • Pyrolysis of the organic part of the waste in the shaft furnace at temperature up to 700°C where the mercury is also evaporated. • Reduction of the metallic parts in the melting furnace at temperature of 1500°C. The metals are either molten (Fe, Mn, Ni) or evaporated (Zn, Pb, Cd). • Recovery of the gaseous metals (Zn, Pb, Cd) in the splash condenser. This Technology permit us to treat hazardous waste without the formation of new waste. As an demand we have seen, that other heavy metal containing wastes could be treated in this plant. Today Batrec AG is able to treat the most mercury contaminated wastes from dental waste to track field coverings and from sludge to contaminated scrub.
Hydrochloric acid leaching, chloride evaporation, acetic acid leaching, and biological leaching were evaluated and compared as processes of heavy metal removal for municipal solid waste incineration fly ash(MSWFA). Six factors, namely, energy consumption, process efficiency, process handling, process cost estimation, cost reduction potential, and study progress, were used in order to find out their advantages and disadvantages and to help develop a better recovery process of heavy metals from MSWFA in terms of treatment of the waste material. Hydrochloric acid leaching process was found to be most balanced among the evaluated processes. It showed superiority on energy consumption, process cost estimation, and study progress. On the other hand, despite of its excellency in process efficiency, chloride evaporation process was most unfavorable mainly due to heavy energy dependence. Biological process, with huge potential of cost reduction, was concluded to be the second best process.
The separation of nickel and cadmium from highly concentrated solutions by means of non-dispersive solvent extraction (NDSX) has been studied in this work. Extraction and back-extraction processes were carried out simultaneously in a batch mode using two parallel modules and the organic phase flowing in a closed circuit. Starting with concentrations of 0.37 M of Cd and 0.37–0.68 M of Ni in the feed aqueous phase, 1 M of H2SO4 in the back-extraction phase, and using D2EHPA as extradant, the viability of the separation-concentration of Cd from that mixture has been confirmed. Under the experimental conditions, the separation process was run at a constant rate of mass transport, thus leading to a selectivity factor in the concentration step ρ=67 mol Cd/mol Ni.
The demand for heavy metals is ever increasing with the advance of the industrialized world, whereas worldwide reserves of high-grade ores are diminishing. However, there exist large stockpiles of low and lean grade ores that are yet to be exploited. In addition, heavy metals that are present in a spectrum of waste streams including mine drainage, industrial effluents, river sediments, electronic scraps and ashes are also available for recovery and utilization. Heavy metal recovery from low and lean grade ores using conventional techniques such as pyrometallurgy, etc. chemical metallurgy encompass several inherent constraints like, high energy and capital inputs, and high risk of secondary environmental pollution. As environmental regulations become ever more stringent, particularly regarding the disposal of toxic wastes, the costs for ensuring environmental protection will continue to rise. Therefore, there is a need to utilize more efficient technologies to recover heavy metals from secondary sources in order to minimize capital outlay, environmental impact and to respond to increased demand. Biohydrometallurgy, which exploits microbiological processes to recover heavy metal ions, is regarded as one of the most promising and revolutionary biotechnologies. The products of such processes are deposited in aqueous solution thereby rendering them to be more amenable to containment, treatment and recovery. On top of this, biohydrometallurgy can be conducted under mild conditions, usually without the use of any toxic chemicals. Consequently, the application of biohydrometallurgy in recovery of heavy metals from lean grade ores, and wastes, has made it an eco-friendly biotechnology for enhanced heavy metal production.
In compliance with Directives 91/157/CEE and 91/338/CEE about spent batteries with dangerous, the paper proposes some laboratory electrochemical methods for valuable metals recovery like Ni and Cd from Ni-Cd spent batteries. The paper describes quick analyses and control methods for Ni and Cd, by AA spectroscopy, carried out on a novAA 400 G atomic absorption spectrometer - Analytik Jena, with graphite oven, with WinAAS 3.17.0 software for evaluation, control and result presentation, a so-called cookbook, for every element, and a HS 55-1 hydride generator. The components of the deposits were determined by SEM-EDAX electron microscope Inspect S - FEI-Holland.
The feasibility to recover the gold present in alluvial material, by means of a chlorination process, using chlorine as a reactive agent, has been studied. The influence of temperature and reaction time was studied through changes in the reactant solid. The techniques used to characterize the mineral samples and the reaction residues were stereomicroscopy, X-ray diffraction, X-ray fluorescence and scanning electronic microscopy. Results indicate that gold extraction is favored by increasing, both, the temperature and the reaction time. The best recovery values were of 98.23% at 873K and 3600s and of 98.73% at 873K and 5400s, with very low attack of the matrix containing the metal. The powder of pure gold was not chlorinated at this temperature level.
This article discusses a method to recover silver from waste X-ray films with the spent fixing bath. At first, the silver in the waste fixing bath was reduced by KBH4 at pH 8~9. Then the silver-free fixing bath was oxidized by air and some main components were replenished. As a leaching solution, the silver-free spent fixing bath was used to recover silver on the waste X-ray films. The total silver recovery from the spent fixing bath and waste X-ray films was 98.0% and 95.8%, respectively. The purity of recovered silver was more than 99.5%. The spent fixing bath can be reused again in the present method. The discharging of wastewater can be reduced and the polymer substrate of waste X-ray films can also be recycled.
In this work the effect of reaction temperature, sulfuric acid concentration, liquid-to-solid ratio and Fe2+ concentration on sulfuric acid leaching of gallium from phosphorus flue dust was studied. The results showed that gallium extraction increased with the increase of temperature, sulfuric acid concentration and liquid-to-solid ratio. Fe2+ concentration did not significantly affect the recovery of gallium. The acid-soluble gallium could be completely extracted with simulated spent acid containing 20% sulfuric acid and 0 to 50 g/L Fe2+ at temperature of 80 °C, and liquid-to-solid ratio of 10:1. The effect of phosphate concentration, reaction temperature and pH on the precipitation of gallium and ferrous iron was also studied in order to determine the optimum conditions for the recovery of gallium from simulated spent acid leach solution. It was found that under optimum precipitation conditions, when all gallium precipitated from the simulated spent acid leach solution containing 31 g/L ferrous iron and 0.1 g/L gallium, the precipitation of iron was less than 2%, the ratio of iron-to-gallium decreased from 310:1 in the leach solution to 5:1 in the precipitate. Gallium was therefore concentrated in the precipitate.
The improving awareness of environmental problems associated with the toxicity of heavy metals keeps the recycling of spent nickel–cadmium batteries an important assignment due to the presence of cadmium, nickel and cobalt on the electrode material. While cadmium from batteries is one of the major sources of cadmium contamination of the environment, the other heavy metals contained on the electrode material have a considerable economic value. Therefore a complete and valorising solution to the management of this type of residues is not possible through the existing pyrometallurgical processes because the treatment of complex materials in order to recycle all materials is difficult. An integrated process based on physical and hydroelectrometallurgical operations seems to be more efficient because it is possible to recover the three metals, Cd, Ni and Co, present on the electrode material. The study here presented deals with the first chemical stage of an integrated process, the leaching of spent nickel–cadmium electrodes with sulphuric acid. The electrode materials essentially composed of Ni, Cd and Co hydroxides were readily solubilised in 0.5 h with low acid concentrations (pH∼1) at ambient temperature. At higher pH values the solubilisation of metal hydroxides was inefficient, except when using long residence times. The leaching of nickel present in the metallic form, in the electrodes, was more difficult due to kinetic constraints, applying high temperature (e.g. 95 °C) and acid concentration (e.g. 2.5 M H2SO4) in order to obtain complete conversions in acceptable time (∼4 h).
Lead, tin and indium were successfully recovered from alloy wire scrap containing these metals by acid/alkali leaching. The scrap material was leached with hot HCl–HNO3 solution. Upon cooling down to 10°C, 71.8% of lead initially present was separated as lead chloride. The major part of the remaining lead content (22.9%) was recovered by cementation with indium powder of 1.5 equivalents per equivalent of lead at 45°C. Tin was recovered from the acidic solution as hydrated tin oxide by using NaOH at pH 2.0–2.8. Indium was recovered from the remaining solution by two different methods. The first method involved precipitation of indium as phosphate using H3PO4 at pH 3.91, converting the phosphate to the oxide by leaching with NaOH solution. In the second method, sponge metallic indium was recovered by cementation with zinc powder of 1.2 equivalents per equivalent of indium at 30°C. Parameters controlling the recovery processes, such as temperature, time, pH and metal equivalent were investigated. ICP and X-ray analysis were carried out to estimate the purity of the products. Results obtained are explained, knowing that the stated salts have the least solubility and highest purity under the given experimental conditions. Lead, tin and indium, having purities of >99, 99.7 and 99.8%, respectively, are obtained. The recovery of these metals are found to be 94.7, 99.5 and 99.7%, respectively. The recovery processes are favored at a temperature of ≤45°C for a maximum duration of 8 h and at a pH≤2.4.
Used X-ray film contains a large number of silver particles in its gelatin layers. With the aim of developing an efficient enzymatic process for the recovery of silver and polyester film from used X-ray film, hydrolysis experiments were performed using a stirred-tank reactor in batch operation. On the bottom of the tank a sheet of X-ray film was fixed so that only one of the film surfaces would be exposed to a solution containing the alkaline protease B21-2 from alkalophilic Bacillus sp. The time courses of gelatin hydrolysis, measured by using unexposed film which was prepared by developing X-ray film without exposure to light and which did not contain any silver, showed that at any stirring speed there existed induction periods in which hydrolysis was very slow. When the stirring speed was higher, the induction period and the time required to complete the hydrolysis were shortened due to an increase in the transfer rate of the enzyme through the liquid film. The rate of gelatin hydrolysis of unexposed film increased with the enzyme concentration. The time courses measured using exposed film, which was prepared by developing X-ray film after it had been exposed homogeneously to light and which contained fine silver particles, showed that the induction periods for the release of silver particles were much longer than those for gelatin hydrolysis. The presence of silver particles did not significantly affect the gelatin hydrolysis. The above experimental results on gelatin hydrolysis were well explained by a proposed model which took into consideration a number of physical processes, such as diffusion of the enzyme and hydrolysis products through the liquid film on the surface of the gelatin layer, in addition to the chemical processes.
Metal recovery and/or rejuvenation technologies of the spent catalysts resulting from various sources are reviewed. The fluid cracking catalyst (FCC), resid fluid cracking catalyst (RFCC), hydrodesulfurization (HDS) catalyst, supported and unsupported precious metal containing catalysts, i.e., reforming catalyst, auto catalyst and other catalysts from a variety of industrial processes are targeted. The precious metal recovery technologies such as the processes using aqua regia, chlorination, segregation and Rose (metallurgical) method are discussed in detail. A series of the FCC demetalation/regeneration processes such as Met-X, Demet, Demet II, Demet III and Demet IV is also described from the view point of the developmental history. Two physical processes using the high gradient magnetic and density grading separator are also reviewed.
Fly ash is produced in massive quantities by fossil fuel based power plants and waste incinerators, and contains high levels of potentially toxic chemicals. Various leaching tests exist to determine the available fractions, but the outcome is strongly dependent on the experimental conditions, and these have not yet been harmonised at the international level. In order to test existing protocols for heavy metals, several intercomparisons were organised within the framework of an EU-INCO project "ANALEACH", in which seven institutes from five countries participated. Two existing reference materials were made available for the project and test batches of two new fly ash reference materials were produced. Availability tests, leaching tests and pH-stat tests were studied and critical steps in the procedures were identified. Fly ashes can also contain large amounts of inorganic sulphur and nitrogen compounds, and the determination and leaching behaviour of these compounds were also studied. In one intercomparison for metals, inorganic S and N-compounds were also included. A five-step leaching test was optimised for fly ash in order to link metal fractions to different types of binding. Column leaching experiments were carried out to investigate leaching from fly ash into soil, mimicking the effects of (acid) rain on fly ash deposited on topsoil after atmospheric transport. The major fraction of the leached metal ions was retained by the soil. Also large numbers of organic compounds (including many toxic ones) were identified in fly ash extracts, especially in city waste incinerator ash. Leaching procedures based on ultrasonic extraction were developed for organic compounds and an intercomparison exercise was organised. In a field study at the river Nitra(Slovakia) numerous organic pollutants were found at elevated levels downstream from a major fly ash dump site.
The present work investigates a hydrometallurgical process for silver recovery from spent silver oxide button cells. The effects of acid concentration, reaction temperature, reaction time and shaking rate on the silver dissolution are investigated in detail. In addition, an investigation regarding the dissolution kinetics of silver is undertaken, and the activation energy is found to be 26kJ/mol. Silver is selectively precipitated as silver chloride using potassium chloride solution, ensuring that other impurities remain in the solution. Silver chloride is subsequently reacted with metallic zinc powder in 1.0M HCl to yield metallic silver of 99.99% purity. The process is proven to be easy, straightforward and environmentally friendly.
In recent years, recycling of household batteries has attracted much attention mainly with respect to environmental aspects in addition to the savings. Small silver oxide primary cells used in electric watches become a waste after their life is over. Recycling procedures are needed to prevent any environmental impact from these wastes and to recover the value inherent in the scrap. Smelting and electrolytic methods are discussed for silver recovery from this battery waste. Acid leaching of waste batteries and precipitation of silver as silver chloride followed by smelting at 1000°C yields a silver recovery of about 83%. An electrolytic route is studied as an alternative to the smelting operation and involves the electrodeposition of silver with higher purity from a silver thiosulfate complex prepared from silver chloride. The electrolysis is potentiostatically controlled at a potential of −0.400 to −0.600V (SCE) for avoiding side-reactions such as the sulfiding of silver. Although recovery methods have been identified in principle, their suitability for mixed small battery waste and economic factors have yet to be demonstrated.
The mechanism and kinetics of β-Ta2O5 chlorination, mixed with sucrose carbon, have been studied by a thermogravimetric technique. The investigated temperature range was 500 °C to 850 °C. The reactants and reaction residues were analyzed by scanning electronic microscopy (SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller method for surface area (BET). The effect of various experimental parameters was studied, such as carbon percentage, temperature, chlorine partial pressure, and flow, use of the multiple sample method, and carbon previous oxidation. The carbon percentage and previous treatment have an effect on the system reactivity. The temperature has a marked effect on the reaction rate. In the 500 °C to 600 °C temperature interval, the apparent activation energy is 144 kJ/mol of oxide, while at higher temperatures, the activation energy decreases. With high chorine partial pressures, the order of reaction is near zero. The kinetic contractile plate model, X=kt, considering carbon oxidation as the controlling stage, is the one with the best fit to the experimental data. A probable mechanism for the carbochlorination of β-Ta2O5 is proposed: (1) activation of chlorine on the carbon surface, (2) chlorination of Ta2O5, (3) oxidation of carbon, and (4) recrystallization of β-Ta2O5.
Biological activated carbon treatment is applied to a type of wastewater collected from plating industries. The water contains small amounts of refractory organic pollutants, such as anionic surfactants, small amounts of heavy metals, such as cupric and chromic ions, and large amounts of sodium salts. It is found that the thickness of biofilm formed around activated carbon particles increases with time, even though the existence of heavy metals is unfavorable to the growth of microorganisms. As a result, about 50% of organic substances are removed from the water. Present removals for the ionic species of copper and chromium are about 80% and 30%, respectively. Heavy metals are removed from the wastewater by uptake in the bodies of microorganisms, while organic substances are removed by biological decomposition and partly by adsorption.
The increasing acceptance of biological processes for the treatment of refractory gold-bearing concentrates should be considered as a positive move both in terms of process flowsheet development and its commitment to the environment. Research and development is now focusing on the application of moderately thermophilic and extremely thermophilic acidophiles in the treatment of both refractory gold-bearing and base-metal mineral sulphide concentrates. Current literature on the application of biological processes is still dominated by studies of mesophilic bacteria such as Thiobacillus ferrooxidans and Leptospirillum ferrooxidans although literature is becoming more prevalent with respect to the higher temperature acidophiles.This current experimental study highlights the problems of arsenic toxicity to certain strains of moderately thermophilic bacteria when oxidising both refractory gold and base-metal sulphide concentrates. It also concludes that these bacterial strains were capable of readily oxidising a chalcopyrite/pyrite concentrate (typical of base-metal sulphide concentrates).A mini literature review discusses some of the current and potential applications of acidophilic bacteria both within the minerals industry and in allied disciplines including treatment of metalliferous mine wastes, acid mine waters and sulphurous flue gases. Conclusions are drawn for both the experimental work presented and the literature reviewed.
Sulfur oxidizing bacteria were used to leach metals bound in municipal solid waste incineration fly ash. Pure or mixed cultures of Thiobacilli with or without addition of anoxic sewage sludge were incubated with various amounts of fly ash for several weeks. Co-cultures with Thiobacilli and sewage sludge grew faster than pure cultures of T. thiooxidans or cultures with only sewage sludge as inoculum. The addition of sewage sludge increased the rate of growth of sulfur oxidizing bacteria and simultaneously enhanced the acidification of the suspension. As a result, the time for fly ash processing was reduced by 50%. Thiobacilli were able to grow in the presence of up to 8% (w/v) fly ash. Depending on the amounts of fly ash added, the final pH, and the concentration of sulfuric acid formed, different amounts of metals were leached: over 80% for Cd, Cu, and Zn, 60% for Al and approx. 30% for Fe and Ni (totally, approx. 50% of the heavy metals present in the fly ash) were extracted.
Microbiological processes were applied to mobilize metals from electronic waste materials. Bacteria Thiobacillus . . thiooxidans, T. ferrooxidans and fungi Aspergillus niger, Penicillium simplicissimum were grown in the presence of electronic scrap. The formation of inorganic and organic acids caused the mobilization of metals. Initial experiments showed that microbial growth was inhibited when the concentration of scrap in the medium exceeded 10 g Ly1. However, after a prolonged adaptation time, fungi as well as bacteria grew also at concentrations of 100 g L y1. Both fungal strains were able to mobilize Cu and Sn by 65%, and Al, Ni, Pb, and Zn by more than 95%. At scrap concentrations of 5-10 g L y1, Thiobacilli were able to leach more than 90% of the available Cu, Zn, Ni, and Al. Pb precipitated as PbSO while Sn 4
The main concern of the present study is to find a more feasible and economical method to extract metal ions from low grade discarded ores like black shale by Aspergillus niger. A.niger exhibited a good potential in generating varieties of organic acids effective for metal ions solubilization. The effectiveness of organic acids was enhanced when sulphuric acid was added to the medium. Different agricultural wastes as substrates were evaluated. Maximum solubilization of copper (68.5%), zinc (49.0%) and cobalt (60.4%) was achieved in the media containing mango peel, rice bran and glucose as substrates. The extraction of low concentrations of metal ions from this ore indicated that this low grade discarded ore may be a potential source for metal ions in the future.
A spent processing catalyst from an Iranian oil refinery was initially characterized physically and chemically. Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans were used to mobilize Al, Co, Mo and Ni from the spent catalysts under optimized conditions in batch cultures. The characteristics of the bioleach solution (pH, Eh, cell concentration and Fe(II)/Fe(III) concentration) were determined along with the concentration of metal values extracted from the catalyst. The results showed that after bioleaching using A. ferrooxidans in the presence of ferrous sulfate, maximum extractions of 63% Al, 96% Co, 84% Mo and 99% Ni were achieved after 30 days at pH 1.8–2.0. However, the highest extractions using A. thiooxidans in the presence of sulfur were 2.4% Al, 83% Co, 95% Mo and 16% Ni after 30 days at pH 3.9–4.4. The recovery of these metals decreases the environmental impact of the waste catalyst and the recycled product can be further used for industrial purposes.Research Highlights► Bioleaching of the spent catalyst was conducted using various adapted strains. ► The one step bioleaching of spent catalysts using acidophilic bacteria was optimized. ► The highest metal extraction value was related to Ni, Co, Mo and Al respectively.
This paper reviews the current status of commercial biomining operations around the world, identifies factors that drive the selection of biomining as a processing technology, describes challenges to exploiting these innovations, and concludes with a discussion of biomining's future. Biomining is commercially applied using engineered dumps, heaps and stirred tanks. Overcoming the technical challenges of lowering costs, processing low-grade, low-quality and complex ores and utilizing existing capital investments at mines requires better understanding of microbial activities and innovative engineering. Surmounting biomining commercial challenges entails improved mining company/biomining innovator cooperation and intellectual property control.
Zinc containing wastes/secondaries viz. zinc ash, dross, flue dusts, sludge, residue etc. are generated in various chemical and metallurgical industries. The materials contain different level of impurities depending on the source. The hydrometallurgical processing is effective and flexible for treating such materials as it can control the different level of impurities. Depending on the nature and composition of the secondaries, a suitable lixiviant could be selected to dissolve the desired metals leaving gangue in the residue. In the present paper, the hydrometallurgical processes have been described for the recovery of zinc from the secon-daries using sulphuric acid, hydrochloric acid, ammoniacal solution and sodium hydroxide etc. as lixiviants. The leach solution thus obtained has been purified with respect to dissolved impurities using precipitation, ion exchange or solvent extraction method. The metal or salt is produced from the purified solution by electrolysis or crystallization. © 2001 Elsevier Science B.V. All rights reserved.
This study investigates the bioleaching of the complex Pb/Zn ore/concentrate using mesophilic (at 30 jC), moderate (at 50 jC), and extreme thermophilic (at 70 jC) strains of acidophilic bacteria. The effects of bacterial strain, pH, iron precipitation, and external addition of Fe 2 + on the extraction of zinc were evaluated. The results have shown that the ore is readily amenable to the selective extraction of zinc and lead using the acidophilic strains of bacteria [i.e., majority of lead (>98%) reports to the residue]. Moderate thermophiles displayed superior kinetics of dissolution of zinc compared with the other two groups of bacteria. The pH was found to exert a profound effect on the leaching process controlling the bacterial activity and precipitation of ferric iron mainly as K-jarosite. The K + released presumably from the alteration of the silicate phases such as K-feldspar present in the ore appeared to promote the formation K-jarosite in moderately thermophilic leaching systems. The external addition of iron was shown to be required for the bacteria to efficiently drive the extraction of zinc from the bulk concentrate. These findings place the emphasis on the prime importance of ferric iron for the dissolution of zinc and of mineralogical properties (i.e., iron and silicate content) of an ore/concentrate to be treated via bioleaching processes. D 2004 Elsevier B.V. All rights reserved.
An obligate alkalophilic Bacillus sphaericus strain, isolated from alkaline soils in the Himalaya, produced an extracellular protease which was optimally active at 50-55 degrees C and pH 10.5. The enzyme was stable in presence of 500 mg chlorine l(-1) and as a detergent additive. Its stability in presence of laundry detergents was comparable to that of commercial proteases. The gelatin layer in 25 g of used X-ray films was efficiently hydrolyzed within 12 min at 50 degrees C, pH 11.0 and 25 U protease/ml.
We describe the reduction of vanadium (V) to vanadium (IV) in cultures of Thiobacillus thiooxidans on elemental sulfur, for initial vanadium (V) concentrations up to 5 mM. The vanadium (V) is reduced by intermediate compounds
generated by bacterial oxidation of elemental sulfur. The limit of initial vanadium (V) allowing bacterial action seems to
be related to the inhibition caused by such vanadium species, rather than connected to the vanadium (IV) species, which did
not show inhibitory effects up to concentrations of about 0.1 M. This reduction mechanism of vanadium (V) is potentially applicable
in the recovery of vanadium from spent solid catalysts, by a low-cost methodology.
A strain of Basidiobolus (N.C.L. 97.1.1) was isolated from plant detritus which secreted alkaline protease optimally active at pH 10.0. It is the first report of a protease from Basidiobolus, which is stable to and active under high alkaline conditions. When incubated under stationary conditions in broth cultures containing salts such as ammonium chloride, 'darmform' morphogenesis was readily induced through enlargement and internal division of the hyphal segments. Secretion of high activity alkaline protease was obtained in cultures initiated with darmform morphogenesis whereas cultures initiated from mycelial inocula grew as large pellets in submerged cultures, with little or no protease secretion. Cultural conditions favoring alkaline protease secretion have been optimized and a preliminary characterization of the enzyme is presented. Compatibility of the alkaline protease with commercial detergents as well as its potential application in recovering silver from spent photographic films have also been investigated.
The food, chemical, petroleum, petrochemical and other industries generate thousands of tons per year of spent catalysts containing up to 35% valuable metals such as Co, Cr, Cu, Ni, Mo, Ti, V, W. The recycling of these materials will lead to provision of significant quantities which are currently imported from outside the EC countries and could contribute to the improvement of the environment.Selective chlorination of these spent catalysts with different chlorinating gas mixtures between 300 and 600°C is investigated for the recovery of their valuable elements. Depending on the experimental conditions, it is possible to recover up to 98% of the Ni and Co, as chlorides from the chlorination residue and about 98% of the Mo, Ti & W and 80% of vanadium compounds in the condensates. The catalyst support chlorination could be limited to less than 5%. Besides the reaction temperature and time, the oxygen partial pressure in the chlorinating gas mixture is a key factor for the selectivity of the chlorination.
Catalysts are widely used in petroleum refining and chemical industries. Among secondary resources, spent catalysts are undoubtedly very important because of not only their large amounts and enormous economic values, but also because of the environmental concerns if disposed off. Spent hydrodesulphurisation catalysts usually consist of molybdenum sulphide mixed with sulphides of vanadium, cobalt and nickel on an alumina carrier. A wide variety of metallurgical processes are used to treat these catalysts. The processes vary in their selectivity for metals and complexity of operation, but adopt one of the following approaches: 1. acid leaching with either H2SO4, HCl or (COOH)2, often after roasting; 2. caustic leaching with NaOH, sometimes after roasting; 3. salt roasting with Na2CO3, NaCl or NaOH followed by leaching with water or Na2CO3; 4. smelting either directly or after calcination; 5. anhydrous chlorination; 6. bioleaching.Roasting followed by sulphuric acid leaching seems to be the best option since all of the valuable metals dissolve. However the downstream processes to produce separate products with high purity are relatively complex. Sodium carbonate roasting followed by water leaching is a good option since molybdenum and vanadium are selectively extracted over aluminium, nickel and cobalt. Bioleaching offers good prospects for recovering valuable metals and at the same time, generates much less environmental pollution. However, much more research work is needed before it can be commercialised.After leaching, the metals in leach solutions have to be separated and purified by conventional separation techniques such as precipitation, adsorption, ion exchange and solvent extraction. Part II of this review considers the application of these methods, especially, solvent extraction for treating such leach solutions.
Solvent extraction separation and recovery of cadmium(II), cobalt(II) and nickel(II) from sulphate leach liquor of spent Ni–Cd batteries was investigated using phosphorus based extractants such as TOPS 99, Cyanex 923, Cyanex 272, Cyanex 302 and Cyanex 301 diluted in kerosene. The composition of the leach liquor used for the present study contains (g/L): Cd, 2.40; Ni, 5.94; Co, 0.05. Among the phosphorus based extractants screened at 0.1 M concentration as a function of aqueous phase equilibrium pH, Cyanex 301 showed selective separation of Cd(II) from Co(II) and Ni(II). On the other hand, stripping of metal from Cd–Cyanex 301 loaded organic (LO) phase needs high acid solution. Two-stage counter-current extraction with 0.06 M Cyanex 301 at unit phase ratio and three-stage stripping of the metal from LO with 6 M HCl at an aqueous to organic (A:O) phase ratio of 2 yielded >99.9% Cd(II) extraction and stripping efficiency. However, Cd(II) concentration in strip solution was reduced to half. Cobalt(II) extraction efficiency of ∼99% was achieved from cadmium raffinate at an equilibrium pH of 6.25 with 0.03 M Cyanex 272 in two counter-current stages at an A:O ratio of 2:1. Complete stripping of metal from LO containing 0.15 g/L Co(II) was carried out using a strip solution pH of 1.0 in two stages at an O:A ratio of 1.75. The enrichment of cobalt during extraction and stripping operations was ∼5.2 times. Complete process flowsheet for the separation and recovery of Cd(II), Co(II) and Ni(II) was proposed.
All life forms have absolute requirements for a wide range of metals. For some prokaryotic microorganisms, metals have not only a nutritional requirement but also pivotal roles in energy generation, by acting as electron donors or electron acceptors. In the last half of the twentieth century, scientific technologies emerged that harnessed the abilities of microorganisms to transform metals, and many of these bioprocesses are increasing in scope in the new millenium. This review considers the impact that biohydrometallurgy has on the environment, and vice-versa. The various ways in which microorganisms transform metals, and the continued importance of natural environments as sources of biological systems that have potential in optimising existing operations or for developing new biotechnologies, are described. Abandoned mines are, from a biological perspective, dynamic ecosystems and often develop their own unique complex food webs, in which metals (and sulfur) often play central roles. Finally, the major issue of pollution associated with past and present mining activities is considered, in particular the problem of acid mine drainage. New biologically based approaches that are currently being developed not only to remediate affected water courses, but also to recover metals, are discussed.
A comprehensive copper mass balance for waste management in Europe has been carried out, including municipal solid waste, construction and demolition waste, wastes from electrical and electronic equipment (WEEE), and end-of-life vehicles (ELV). The recycling efficiency of the current waste management system in Europe was quantified and the sources of copper scrap used for secondary copper production were determined. Additionally, an assessment of copper losses to the environment from incinerators and landfills was undertaken. As a final step, select parameters were varied to test the sensitivity of copper waste generation results to the uncertainties in the data. The total flows of copper into the European waste management system consists of 920 Gg/y domestic copper waste and of 300 Gg/y imported old scrap, of which 740 Gg/y are recycled and 480 Gg/y are landfilled. In Europe 2 kg per capita of copper waste is generated annually. WEEE and ELV are the most important domestic waste streams from the perspective of copper contents. They contain 67% of the total copper throughput, but only make up 4% of the mass of total waste generation. Because WEEE is the fastest growing waste category, this finding emphasizes the need for efficient WEEE recycling strategies. The overall recycling efficiency for Europe for copper in all types of waste, excluding prompt scrap and scrap imports, is 48%, with a range of 5–58% depending on the country. This shows further potential for increased recycling activities in the future. Emissions of copper to the environment are under 5 Gg/y but several new sources for emissions are not yet quantified. Uncertainties in waste generation rate and composition for some waste categories (WEEE, C&D) are high, and additional analysis is needed to confirm the above findings.
Hydrometallurgical processes have been proposed for selectively leaching nickel, then copper from non-mounted printed wiring boards, which contain considerable amounts of heavy metals, such as copper, nickel and gold in metal strips printed on the resin substrates, while at the same time recovering solid flakes of gold in high purity. Among the leaching reagents examined, nitric acid showed a great possibility of recovering gold flakes and its leaching performance was evaluated in terms of such experimental parameters as concentration, temperature, time and solid–liquid ratio. With the advance of the leaching of the base metals, gold flakes were detached spontaneously from the boards and recovered easily in high yield with excellent purity. For the separation of copper and nickel, both two-step leaching and solvent extraction have been examined. In the former process, nickel was selectively leached with 0.1 M HNO3 solution in the first step of leaching, and the remaining copper was transferred into 1.0 M HNO3 solution in the second step of leaching. In the latter process, copper could be selectively extracted from the leach solution with LIX984 reagent as extractant, while leaving nickel in the raffinate solution. Stripping was carried out successfully with 4.0 M HNO3 solution, giving pure copper solution of over 10 000 mg/L. An overall separation scheme has been proposed.