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Abstract

Research on biohydrometallurgy of secondary metal resources is primarily focussed on the leaching of valuable metals. For secondary metal resources biological processing can be an economically more effective and environmentally friendlier alternative to traditional hydrometallurgical and pyrometallurgical processes. Therefore, Bioydrometallurgy is a rapidly evolving biotechnology that has already provided revolutionary solutions to old problems associated with recovery of metals by conventional pyrometallurgy and chemical metallurgy. This review evaluates various pr ocesses of recovery of metals from waste materials and commercial applications are di scussed. Case studies and future technology directions are reviewed. Keywords: Biohydrometallurgy; Metal recovery; Recycling; Secondary metal resources

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... Step4: Convert the semantic expression into the corresponding triangular fuzzy numbers through the semantic conversion table. electronic products is shortened in Turkey like other countries (Erust et al., 2013). Moreover, these products contain highly valuable and secondary materials such as gold, silver, and palladium (Sahin et al., 2012;Andersson et al., 2019). ...
... Moreover, these products contain highly valuable and secondary materials such as gold, silver, and palladium (Sahin et al., 2012;Andersson et al., 2019). However, their transformation to raw material in emerging economies such as Turkey is very difficult (Erust et al., 2013). Therefore, in this study, e-waste, which is a major source of urban mining in Turkey is discussed and evaluated barriers for urban mining by experts from the second largest city of Turkey using Fuzzy DEMATEL. ...
... Unlike emerging economies, in Turkey, besides avoiding the waste of resources, recycling waste and its effort to raise living standards for re-use it is not yet a fully developed state (Pekdemir et al., 2020). By considering Turkey waste generation, sectors such as construction and electronics has the potential to achieve much more than secondary sources (Erust et al., 2013). Also, in parallel with the increase in population in Turkey has increased the amount of waste and the use of packaged products has become an economic value in recoveries (Sahin et al., 2012). ...
Article
Urban mining is a management approach that can transform wastes into a secondary material resource based on the circular economy. It helps to provide secondary raw materials by recycling precious metals and raw materials, and also contributes to improve resource consumption and melioration in a circular economy and sustainability. However, it is difficult to implement urban mining due to various barriers such as lack of know-how, needed technology. Thus, the study aims to determine the barriers and challenges of urban mining in emerging economies both theoretically and empirically and to identify the various barriers and determine the causal relationships and the relative importance of these barriers that are critical to the success of urban mining, which provides resource melioration in circular economy. In the study, six main dimensions and eighteen barriers are analysed by five experts with using Fuzzy DEMATEL. According to the results, the most important barrier to urban mining in emerging economies from the e-waste perspective, which is in cause group, is the government's incentives and support. The barrier is followed by lack of regulations and lack of producer responsibility, respectively. Moreover, the lowest priority barrier, which is in effect group, is lack of product design and setting standards that encourage circularity.
... Biohydrometallurgy, bioleaching or biooxidation designates specific biomining process (Mahmoud et al. 2017). Bioleaching is the conversion of insoluble metals present in ores into soluble forms, for instance the conversion of sulfide into sulfuric metals in mines with the presence of sulfur (Campodonico et al. 2016;Erüst et al. 2013), whereas biooxidation is the decomposition of the mineral matrix by microorganisms, which encapsulates the metal of interest, exposing it and thus increasing its accessibility for further extraction. The most common sulfide minerals are pyrite (FeS 2 ), chalcopyrite (CuFeS 2 ), sphererite (ZnS), and galena (PbS). ...
... Bioleaching and biooxidation microorganisms, including their relations, have the greatest impact on the metal cycle in the mineralization environment mediating metal transformation, since the energy required for their metabolism is obtained from the metabolism of organic compounds or the oxidation of inorganic compounds-heterotrophs or autotrophs, respectively (Erüst et al. 2013). ...
... In addition, iron (II) and (III) ions should be available. However, this species does not oxidize sulfur and sulfuric compounds such as thiosulfate (Bosecker 1997;Erüst et al. 2013;Mahmoud et al. 2017). ...
Chapter
Mineral coal is one of the most employed natural resources that represent potential environmental issues. The mine tailing contains several valuable minerals such as zinc, molybdenum, vanadium, chromium, iron, and copper. Currently, the most part of mine tailings is disposed at large tailing ponds. Another important tailing from mineral coal is fly ash, the main residue from thermoelectric plants, which may also contain valuable minerals. Currently, the most part of coal fly ash produced is used as raw material for cement fabrication or disposed at ash ponds. In this sense, biomining and bioleaching is an economically and environmentally attractive technology that can be used for metal recovery from residues such as mine tailing and coal ash, in line up with the concept of green chemistry. There are sparse data available on bioleaching of coal ash using either autotrophic or heterotrophic microorganisms. Therefore, the aim of this chapter was to describe the key aspects related to biomining and bioleaching of mine tailing and coal ash, pointing out the state of the art and some future perspectives.
... 11 Several metal recovery techniques can be applied to PCBs, according to the metal content, including pyrometallurgy, hydrometallurgy and bio-hydrometallurgy. 12,13 Bio-hydrometallurgical techniques, such as bioleaching, are more suitable for metal recovery due to their eco-friendly nature, high selectivity for metals and lower operational costs. [14][15][16][17] Bioleaching has proven to be a successful method for dissolving metal sulfides (also successfully applied to secondary resources such as e-waste) owing the oxidative activity of certain chemolithotrophic microbes which are mainly sulfur and iron oxidizers; these microbes obtain their Table 1 Reported studies on bioleaching of metals from WPCBs by mesophilic acidophiles [18][19][20][21][22] Biological activity can be reflected by variation in redox (oxidation-reduction) potential (ORP) in leaching solution, and several attempts have been made to control ORP for efficient metal dissolutions (see Table 1). Maximal values of ORP can promote the interaction between bacteria and WPCB for metal recovery, 23 and this can be achieved by providing pH balance. ...
Article
BACKGROUND: The waste printed circuit boards (WPCBs), today, offer a wide array of metals and are of great importance because their metal concentration is much more than that in the ores. Largely, studies have been devoted to Cu bioleaching from WPCBs because it has the highest ratio among all metallic elements ( ̴ 10-30%). In the present study, an intensified mixed meso-acidophilic bacterial leaching of multi-metals has been studied from WPCBs of spent mobile phones, with the system operating under high oxido-reductive potentials (HORPs). ICP-OES, XRD and SEM-EDX characterization indicated the sample to have recoverable contents of Cu, Al, Ni & Zn which were targeted for bioleaching. RESULTS: Shake flask optimization studies, under HORP of >750 mV indicated dissolutions of Cu – 98.1%, Al – 55.9%, Ni – 79.5% and Zn – 66.9% under optimized conditions of 9 g/L Fe (II), 10% pulp density, 1.8 initial pH and 10% (v/v) as initial inoculum. Under these conditions, at ORP >650 mV, Cu – 97.3%, Al – 55.8%, Ni – 79.3% and Zn – 66.8% were achieved in bench scale (1L) bioreactor systems without any significant reduction in efficiency (compared to shake flasks) in 8 days of operation. CONCLUSION: Variations in the co-relatable parameters, to metal leaching, such as pH, ORP and Fe (II) concentrations indicated that these parameters significantly contributed to metal leaching. Operating the system under high and controlled ORPs is a faster and efficient way to leach multi-metals from WPCBs.
... The fast renewal of electronic products and the change of people's consumption concept continuously shorten the actual service life of electronic products, thereby leading to huge amounts of waste electronic and electric equipment (WEEE). It is reported that WEEE generation is 2 or 3 times faster than other municipal solid wastes [2]. According to the report released by the United Nations University in April 19th, 2015, global electronic waste in 2014 has an increase of 5.0% ...
... On the other hand, metal reserves may be replenished using secondary resources [5]. The search for secondary resources has became an urgent issue in the recent past [6][7][8]. For example, the European Commission has compiled a list of critical raw materials (with 27 currently listed), and its resource policy is more oriented towards recycling [9]; the "life cycle" of industrial materials should be extended so that disposal is no longer the "end-of-life." ...
Article
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Metallurgical wastes contain metals that are unrecovered during industrial processing. The disposal of these wastes is technically difficult due to the potential release of metals through weathering. Therefore, alternative management methods are currently sought. The high leaching susceptibility of these wastes combined with the need for alternative sources of rare and critical metals creates a need for residual element recovery. This study evaluated the leaching potential of lead matte and copper slag through chemical mineral acid leaching as well as indirect bioleaching with organic acids and direct bioleaching using Acidithiobacillus thiooxidans. The leaching efficiency of these acids was compared based on different normality equivalents. Additionally, the effects of pulp density (1–10%) and extraction time (24–48 h) were assessed. Slag toxicity was assessed with a germination test in concentrated and diluted leachates using Brassica juncea. The results demonstrated that copper slag is particularly suitable for chemical treatment because as much as 91 wt.% Cu and 85 wt.% Zn or 70 wt.% Cu and 81 wt.% Zn were extracted using HNO3 or bacterial leaching, respectively. The residual slag was characterized by significant metal depletion and the presence of gypsum, rendering it more suitable for further use or disposal. Lead matte released 65 wt.% Cu and 8 wt.% Zn using mineral acid leaching while 70 wt.% Cu and 12 wt.% Zn were released using bacterial leaching. Further process optimization is needed for lead matte to generate residue depletion in toxic metals. Toxicity assessment showed toxic characteristics in metal-loaded leachates originating from waste treatment that inhibited germination rates and root development.
... Bioleaching is a promising technology for extracting valuable metals from electronic waste (e-waste); because it has relatively low capital and operating costs and low energy consumption (Erüst et al. 2013;Sa et al. 2015;Fang et al. 2022). Currently, bioleaching is known as one of the main methods of biohydrometallurgy and plays an essential role in recycling various metals (Ferraro et al. 2019;Pourhossein et al. 2022). ...
Article
Full-text available
Manganese is extensively used in various advanced technologies. Due to high manganese demand and scarcity of primary manganese resources, extracting the metal from spent batteries is gaining increasing interest. The recycling of spent batteries for their critical metal content, is therefore environmentally and economically feasible. The conventional pyro- and hydrometallurgical extraction methods are energy-intensive or use hazardous chemicals. Bioleaching of manganese from spent batteries as secondary resource has been suggested to meet two objectives: reduce environmental footprint and turn waste into wealth. A bioleaching process can operate with less operating costs and consumption of energy and water, along with a simple process, which produces a reduced amount of hazardous by-products. Hence, this review discusses various approaches for bioleaching manganese from secondary resources using redoxolysis, acidolysis, and complexolysis. Candidate microbes for producing inorganic and organic biolixiviants are reviewed, along with the role of siderophores and extracellular polymeric substances as other effective agents in manganese extraction. The three main types of bioleaching are discussed, incorporating effective parameters with regard to temperature, pH, and pulp density, and future perspectives for manganese bioleaching and provided. Graphical abstract
... Microorganisms are playing a significant role in the extraction of metals from tailings, ores, concentrates, and e-Waste, and most of these processes are working at ambient temperature and pressure with mild conditions; thus, they are easier to be regulated and maintained (Erüst et al. 2013). Colmer and Hinkle isolated acidophilic autotrophic iron-and sulfur-oxidizing bacteria from acid mine drainage in 1947 and provided the first scientific evidence on the role of microorganisms in metal solubilization (Dave and Tipre 2011). ...
... The main technologies for the extraction of rare metals are the following: metallurgical methods (Jha et al., 2001), extraction methods (Kuang and Liao, 2018), methods of mechanical separation (Frohlich et al., 2017). Biological methods for the extraction of rare and precious metals are being actively developed: biohydrometallurgical (Erüst et al., 2013), bioelectrochemical (Nancharaiah et al., 2016), bioextraction (Watling et al., 2010). As a rule, these methods are used for the extraction of metals from ores. ...
Article
Full-text available
To study the mass transfer of metal compounds, a model of filtration combustion of metal-containing combustible mixtures is developed. Using cadmium-containing mixture as an example, the main characteristics of filtration combustion are determined when the gas pressure at the reactor inlet is constant. It is shown that under the conditions of a filtration combustion wave, a metal can evaporate into the gas phase and be transferred with gas through the reactor. Due to the evaporation and condensation of cadmium, it is transported and accumulated before the combustion front. The possibility of controlling the mass transfer of metal compounds under the conditions of a filtration combustion wave with the aim of concentrating them is shown. It is revealed that a 4-fold increase in the pressure difference at the open boundaries of the reactor can lead to a decrease in the maximum metal concentration by about 1.5 times. An increase in the concentration of metals due to mass transfer will subsequently make it economically feasible to extract them by traditional methods.
... Bioleaching is a promising technology that uses microorganisms to recover metals from PCB which is low cost and ecofriendly (Hong and Valix 2014). Among the all microorganisms being selected for bioleaching of metals from PCB, chemolithoautotrophs are commonly used for metal recovery from PCBs, such as Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, Acidithiobacillus thiooxidans (Erust et al. 2013) and Chromobacterium violaceum (Li et al. 2015). ...
Article
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Background E-waste management is extremely difficult to exercise owing to its complexity and hazardous nature. Printed circuit boards (PCBs) are the core components of electrical and electronic equipment, which generally consist of polymers, ceramics, and heavy metals. Results The present study has been attempted for removal of heavy metals from printed circuit board by metal-resistant actinobacterium Streptomyces albidoflavus TN10 isolated from the termite nest. This bacterium was found to recover different heavy metals (Al 66%, Ca 74%, Cu 68%, Cd 65%, Fe 42%, Ni 81%, Zn 82%, Ag 56%, Pb 46%) within 72 h under laboratory conditions. The metal content of PCB after bioleaching was analyzed by ICP-MS. The crude PCB and bioleaching residue were characterized by FT-IR, XRD, SEM for the determination of structural and functional group changes for confirmation of bioleaching. Conclusion The findings of the present study concluded that Streptomyces albidoflavus TN10 is a promising candidate for bioleaching of heavy metals from the printed circuit board as an eco-friendly and cost-effective process.
... These have been categorized as: firstly, ferric iron-generating prokaryotes which produce the mineral oxidant; secondly, sulfuric acid-generating autotrophs which maintain the low pH environment essential; and lastly, heterotrophic and mixotrophic prokaryotes, which degrade organic compounds seeped from autotrophic iron oxidizers and sulfur oxidizers, thereby escaping potential toxicity issues (Johnson and Hallberg 2008). Erüst et al. (2013) reviewed the possible applications of biohydrometallurgy to recover metals from spent batteries and catalysts. ...
Chapter
Global technology development and industrialization have led to the increased usage of electronic gadgets. Electronic waste or e-waste is one of the emerging environmental issues in the developing countries. Much of the e-waste globally generated is recycled in the unregulated informal sector and results in significant risk to environmental health. These wastes also consist of economically valuable minerals such as copper, silver, and gold. The multitude of toxic heavy metals present in the components of discarded electrical and electronic equipment such as cadmium, arsenic, antimony, chromium, lead, mercury, selenium, beryllium, brominated flame retardants, PAHs, and PCBs pose threats to the environment. The usage of microbes and plants in minimizing the toxicity of chemicals and metals in the environment is eco-friendly and cost effective. This chapter provides a concise overview of the volume of e-waste generated globally, disposal and reuse/recycle practices; forecasts e-waste production, and discusses environmentally sustainable remediation strategies. The principles, advantages, and disadvantages of bioleaching, biosorption, bioaccumulation, bioprecipitation, biomineralization, and phytoremediation techniques, which are recognized as biological strategies for remediation of contaminants released into different environmental matrices are presented.
... Currently, the mineral industry looks for new alternatives to withdraw impurities from metal ores using bio-hydro-metallurgical techniques, with well-known advantages such as precious metal enhanced recovery (Núñez-Ramírez et al., 2018;Shiers et al., 2016;Johnson, 2014;Rodríguez et al., 2001aRodríguez et al., , 2001b. Bioleaching is the process by which metals dissolve a liquid phase by means of microorganisms subjected to a highly oxidative environment (Zhang et al., 2019;Mikoda et al., 2019;Erüst et al., 2013). This process is low cost (to within 0.3-0.5 of the conventional process cost) and environmentally friendly whenever the bioleaching acid agent is treated correctly . ...
Article
The iron purity was increased by 3–4% by a bioleaching process. Zinc dissolution exceeded 50% during the first day of leaching. Bacteria concentration affects the rheological behavior of mineral pulps during bioleaching. The mineral pulp exhibited shear. The optimum bioleaching time was five days.
... Due to the fact that it has the potential to reduce operating costs and energy requirements, as well as being environmentally sound, bio-hydrometallurgical approaches to waste recycling have been increasing day by day. As seen in Table 1, iron and sulfur-oxidizing bacteria (e.g., Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans and Acidithiobacillus thiooxidans) are widely used in the bio-hydrometallurgical process to dissolve copper by a series of biological and chemical reactions (Brandl et al., 2001;Erust et al., 2013;Panda et al., 2013Panda et al., , 2017. ...
Article
Bioleaching of copper from electronic waste (e-waste) in the form of high grade waste printed circuit boards (WPCBs) collected from obsoletemobile phones is assessed using a consortium of iron (Fe2+) & sulphur (Sº) oxidizing bacteria in a semi-pilot reactor system. Results from the study indicated that the microorganisms were able to grow in the presence of WPCB and efficiently solubilize Cu from it. At a solid/liquid ratio of 10% (w/v)with a particle size of <250 μm, maximum bioleaching efficiency of around 95% Cu was observed in 8 days of leaching under oxidation-reduction potentials (ORP) of >600 mV and pH 1.8. In order to recover the metallic values, electrowinning (EW) of copper from the bioleach solutions was investigated in detail. Direct EW of the bioleach solution yielded low current efficiencies (66.1% over 4h.), ascribed due to the high concentrations of iron (i.e., 9.1 g/L). As a novel approach, a downstream purification and concentration process was further tested, that involved ferric hydroxide (Fe(OH)3) precipitation and solvent displacement crystallisation (SDC) to eliminate iron and increase the concentration of copper in solution prior to its application for EW. This significantly improved the current efficiency (by ~22%) during the EW of copper. A process flow-sheet for Cu recovery from WPCBs was developed and the downstream process was found to be profitable even though its margin was small with techno-economic analysis. It is believed that the two-step hybrid process i.e. bioleaching technique followed by the novel approach proposed (i.e., iron precipitation + SDC) can be suitably employed for the extraction of copper from WPCBs.
... The results were corrected for the content of sulfate sulfur in the ore dumps, which was determined using a boiling solution of Na2CO3 (the soda-extract method) and subsequent precipitation as BaSO4. 23 The sample of polymetallic ore contained 9.12 % Cu, 2.08 % Zn, 18 ...
Article
Full-text available
The aim of this study was to investigate the possibility of applying Acidithiobacillus sp. B2 to copper, zinc and gold recovery from a polymetallic ore flotation concentrate. The study was designed in two phases. The first phase was a classic biooxidation process in which the microorganisms oxidize sulfides, leaching copper and zinc while simultaneously concentrating gold in the ore. In the second phase, after elimination of the sulfide substrate, the rate of gold leaching by potassium cyanide was analyzed. The leaching was conducted using the shake flask testing technique during a period of 28 days at a temperature of 28 ?C. The percentage of copper and zinc leached at the end of this study was 37.63 % and 47.95 % respectively. The results obtained indicated 6- and 13-fold (for copper and zinc, respectively) higher metal leaching efficiency in the suspension with iron-oxidizing Acidithiobacillussp. B2 than in the control suspension. In the next phase of the study, after elimination of the sulfide substrate, gold was extracted with potassium cyanide from the remaining polymetallic ore concentrate. The results obtained showed that the efficiency of the gold extraction process was 80 %. According to the available data, this is the first study of the microbiological leaching of copper, zinc and gold from a polymetallic ore flotation concentrate from the Coka Marin deposit (Serbia).
... Bioremediation is described as the utilization of microorganisms to eradicate or change pollutants into non-hazardous or less-hazardous forms by utilizing their metabolic processes [83]. Microbial technologies operate at certain specific temperatures and in moderate environments, making them easier to control and maintain compared to other methods [84]. The use of biological technologies for the removal of heavy metals has received high attention as they are environmentally friendly, have less cost, and require less energy [85]. ...
Article
Full-text available
Around 50 million tonnes of electronic waste has been generated globally per year, causing an environmental hazard and negative effects on human health, such as infertility and thyroid disorders in adults, endocrine and neurological damage in both animals and humans, and impaired mental and physical development in children. Out of that, only 15% is recycled each year and the remaining is disposed of in a landfill, illegally traded or burned, and treated in a sub-standard way. The processes of recycling are challenged by the presence of brominated flame retardants. The different recycling technologies such as the chemical and mechanical methods have been well studied, while the most promising approach is the biological method. The process of utilizing microbes to decontaminate and degrade a wide range of pollutants into harmless products is known as bioremediation and it is an eco-friendly, cost-effective, and sustainable method. The bioremediation process is significantly aided by biofilm communities attached to electronic waste because they promote substrate bioavailability, metabolite transfer, and cell viability, all of which accelerate bioleaching and biodegradation. Microbes existing in biofilm mode relatable to free-floating planktonic cells are advantageous of bioremediation due to their tolerant ability to environmental stress and pollutants through diverse catabolic pathways. This article discusses the harmful effects of electronic waste and its management using biological strategies especially biofilm-forming communities for resource recovery.
... Biohydrometallurgy is an effort to develop an environmental process with a high potential to lower energy requirements and operational costs; it is gaining much interest in metal recovery from E-waste [7]. Bioleaching is the main field of biohydrometallurgy, which is defined as the leaching of metals using microorganisms [8]. ...
Article
The high amount of base metals poses an important challenge in gold bioleaching from spent printed circuit boards (PCBs). The best objective in the current study is the bioleaching of important base metals (Cu, Ni, and Fe) from a mixture of spent PCBs (E-waste) using adapted Acidithiobacillus ferrooxidans in the bubble column bioreactors. The adaptation process firstly is done from 1- 15 g/L in Erlenmeyer flasks in 187 days, then the concentration of E-waste increased to 40 g/L in the bubble column bioreactors in 44 days. The concurrent recovery of copper, nickel, and iron using adapted bacterium in a bioreactor was optimized by central composite design. Various effective parameters such as aeration rate, initial ferrous sulfate concentration, and solid waste loading that significantly affected bioleaching yields were studied. 54% of Cu (6% dissolution/d), 75% of Ni (8% dissolution/d), and 55% of Fe (6.1% dissolution/d) were recovered simultaneously under the optimum condition of 20 g/L of solid content, 1.5 vvm of aeration rate, and 40 g/L of the initial concentration of ferrous sulfate after only 9 days. The results proved 100% recovery of each metal is possible separately, 100% of Cu and Fe are extracted maximally on the 4th and 13th day, respectively. Ni is recovered maximally 96% on the 17th day. This is the first report of an ecofriendly method for bioleaching of important base metals from E-waste in bubble column bioreactor. Thus, the obtained results contribute to the knowledge of microbial hydrometallurgy on large scale.
... In the process of bioleaching of base and precious metals, the acidophilic group of bacteria plays a vital role in the recovery of valuable metals [36]. These sundry acidophiles like Acidithiobacillus ferrooxidans, Acidithiobacillusthiooxidans, Leptospirilliumferriphilum, Sulfolobusthermosulfidooxidans, etc. are being used in metal extraction from e-waste and also gave efficient results [37].Numerous types of microorganisms, used in the bioleaching process are shown in Table 3. ...
... Considering the priority of metal recycling, ecological factors, and economic prospective, it is crucial to choose an optimal metal recycling approach from WEEE (Priya and Hait 2018;Joshi et al. 2017). Compared with pyrometallurgical process and hydrometallurgical process, biometallurgical process avoids the risk of generating secondary pollution such as air pollution or water pollution Erüst et al. 2013). Meanwhile, in terms of economy, this technology can also extract metals from WEEE under the condition of low energy consumption and low cost. ...
Article
Full-text available
In the twenty-first century, the increasing demand for electrical and electronic equipment (EEE) has caused its quick update and the shortening of its service life span. As a consequence, a large number of waste electrical and electronic equipment (WEEE) needs to be processed and recycled. As an environmentally friendly method, biometallurgy has received extensive attention in the disposal of WEEE in recent years. Aspergillus niger is an acid-producing fungus with a potential applicability to improve metals’ recycling efficiency. This review article describes the latest statistical status of WEEE and presents the latest progress of various metallurgical methods involved in WEEE recycling for metal recovery. Moreover, based on the summary and comparison towards studies have been reported for bioleaching metals from WEEE by A. niger, the bioleaching mechanisms and the bioleaching methods are explained, as well as the effects of process parameters on the performance of the bioleaching process are also discussed. Some insights and perspectives are provided for A. niger to be applied to industrial processing scale.
... The application of these techniques for treatment of the waste costs more in comparison to the fi nal product. In that respect, bioleaching has been a promising alternative for metal recovery from low-grade ores and the waste (Cui and Zhang, 2008;Mishra and Rhee, 2010;Erüst et al., 2013;Johnson, 2014). The microorganisms which are primarily used for bioleaching belong to genus Acidithiobacillus due to their robust nature and ability to oxidize the inorganic ferrous (Fe 2+ ) and elemental sulfur (S 0 ) (Rawlings, 2005;Arshadi and Mousavi, 2014;Quatrini and Johnson, 2019). ...
Article
The microbial culture as well as the components of the bioleaching medium affects the efficiency of microbial leaching. The present study on mobile phone printed circuit boards (MPPCBs) was conducted to know that whether the addition of energy source is required during the microbial leaching or microorganisms can utilize the iron (Fe) content of the MPPCB. The study was conducted with pure Fe oxidizers in Fe supplemented (9g/L, pure Fe 9K), non-supplemented (0g/L, pure Fe 0K) medium and pure sulfur (S) oxidizers supplemented with 3g/L of elemental sulfur (S0). The copper (Cu) content of the feed material was 26.3% (w/w) by X-Ray Fluorescence (XRF) spectroscopy. The Cu recovery in pure Fe 0K and pure Fe 9K was 100% while with pure S oxidizers it was 39.41%. The acid consumption in pure Fe 0K and pure Fe 9K was 579.65kg/ton and 559.05kg/ton respectively. The bioleaching rate of Cu was 0.128g/L/h, 0.075g/L/h and 0.023g/l/h in order of pure Fe 9K> pure Fe 0K>pure S. Bioleaching with pure Fe oxidizers in 0K medium was found to be efficient and economical in terms of metal recovery and acid consumption. The present study reports that the addition of extra energy source is nevertheless required for bioleaching of PCB. Therefore, this study can be useful in large scale operations where the process cost for the treatment of the waste should be less than the cost of the final product. KEYWORDS: Bioleaching, Copper, 9K medium, 0K medium.
... In recent decades, iron and sulfur-oxidizing bacteria such as Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, and Acidithiobacillus thiooxidans have been some of the remarkably important microorganisms, which have attracted the attention of many researchers for electronic waste bioleaching [13][14][15][16]. Biohydrometallurgical processes include bioleaching of gallium from GaAs and GaN by heterotrophic bacteria, as reported by Maneesuwannarat et al. [17,18]. ...
... It can be clearly found that bioleaching is an important and clean technology in processing low grade and complex ores mainly due to its environmental and low-cost advantages (Anjum et al., 2012). It also may play an important role in processing solid wastes and secondary resources (Akcil et al., 2015;Asghari et al., 2013;Erüst et al., 2014;Hoque and Philip, 2011;Pant et al., 2012;Pathak et al., 2009;Watling, 2015), such as tailings, electronic waste, spent catalyst, sludge, sediment, fly ash and smelter waste, as well as an important bioremediation technology. In addition, its theory and technique would be extended to the other research areas of minerals processing and extractive metallurgy, biological environment, biomass conversion, biodeterioration, biogeochemistry and biomineralization. ...
Article
Chalcopyrite (CuFeS 2 ) is the most abundant copper-containing resource in the earth and is also widely distributed in solid wastes and secondary resources. Biohydrometallurgy (bioleaching) is considered as a promising minerals processing and extractive metallurgy technology because of its environmental and economic advantages over the conventional beneficiation-pyrometallurgy process, and the bioleaching of chalcopyrite is always a challenge because chalcopyrite can be easily passivated in bioleaching. Hence, it is important to understand the dissolution process and passivation mechanism of chalcopyrite in bioleaching. In this paper, the dissolution process and passivation mechanism of chalcopyrite bioleaching have been summarized and discussed according to previous publications. The reported possible passivating species are mainly S-containing species consisting of polysulfide (S n²⁻ ), elemental sulfur (S ⁰ ) and insoluble sulfate (SO 4²⁻ ). The effects of physicochemical properties of chalcopyrite and multiple factors on the dissolution and passivation mechanism of chalcopyrite bioleaching have been summarized. We particularly discussed the role of redox potential in chalcopyrite bioleaching and its controlling techniques.
... The low pH is favorable for metal extraction due to replacement of protons in metal-bearing phases (Lee and Pandey, 2012). Moreover, these organisms are able to proliferate in extreme environmental conditions, including pH (<1) and high metal concentrations (Erüst et al., 2013;Zhang et al., 2018). ...
Article
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Global economy faces an increasing problem of the supply risk of critical raw materials, therefore the search for secondary resources has become an urgent issue. Copper orebodies in Poland contain substantial amounts of metals deemed critical (e.g. Co, Mo, rare earth elements (REE) or V), which are not recovered during processing. The metals of interest are concentrated in metallurgical waste residues that should be classified as a secondary resource rather than as a waste. Bioleaching is a frontier technology promising for environment-friendly treatment of slags. Therefore, the objective of this work was to study the feasibility of metal (Co, Mo, REE, V) bioleaching from copper metallurgical wastes employing Acidithiobacillus thiooxidans bacterial strain as the leaching agent. The effect of particle size (fractions <0.25 mm and 0.25–0.5 mm) and pulp density (1%, 2%) was studied using three different slag samples (lead slag - LS, shaft furnace slag - SFS and granulated slag - GS). The bioleaching experiment was set up for 28 days under acidic conditions (pH t 0 = 2.5). The results revealed that the microorganisms can catalyze metal extraction from slags as compared to leaching achieved under abiotic conditions. The optimal bioleaching yield was achieved under conditions at 0.25–0.5 mm particle size and 1% pulp density, regardless of used type of slag. After 28 days, the extracted amounts of metals were: 88% Co, 40% Mo, 83% REE and 55% V from LS, 100% Co, 44% Mo, 70% REE and 70% V from SFS and 95% Co, 70% Mo, 99% REE and 93% V from GS. All examined slags showed good potential for bioleaching of valuable elements. However, optimization of initial parameters is still needed for further efficiency improvement, especially in terms of the process duration.
... A. thiooxidans was chosen as a mesophile bacteria to evaluate its ability to leach the metals of SCCs. This bacterium obtains its energy source through oxidation-reduction of sulfur compounds (Erüst et al., 2013). It can convert elemental sulfur to sulfuric acid and as a result, can help in heavy metals dissolution in the medium (Liang et al., 2010). ...
Article
The technology for recycling the spent coin cells is pressing needed due to a large amount of generated spent coin cells. However, there is little information about the recycling technology of spent coin cells. In this work, a two-step bioleaching method for recovery of metals from spent coin cells by Acidithiobacillus thiooxidans is performed for the first time. In this regard, the growth characteristics of A. thiooxidans was investigated in pure culture and during the two-step bioleaching approach. The highest recovery of Li, Co and Mn was achieved at a pulp density of 30 g L-1, in values of 99%, 60%, and 20%, respectively. The structural analyzes confirmed the progress of bioleaching process. In addition, the kinetics models showed that the chemical reaction was the rate-controlling step of the two-step bioleaching of spent coin cells. The comparative results between bioleaching and chemical leaching showed that Acidithiobacillus thiooxidans can enhance the leaching of metals. Toxicity characteristic leaching procedure of the spent coin cells powder demonstrated that the bioleached residue met the environmental limitations for safe disposal. In fact, bioleaching is an effective and promising route to reduce the environmental hazard of spent coin cells.
... The chemolithoautotrophs are widely used for bioleaching of PCBs (Erüst et al. 2013). Bioleaching studies using the mixed culture of chemolithoautotrophic iron (Fe)-and sulfur (S)-oxidizing microbes were found to be effective with good recovery of copper from waste PCBs (Wang et al. 2009;Liang et al. 2013). ...
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The present study was conducted to carry out bioleaching of waste mobile phone printed circuit board (WMPPCB) in a high redox potential-controlled fed-batch process compared to the low redox potential batch process. Concomitant additions of WMPPCB achieved high redox potential bioleaching of WMPPCB. The pH of the bioleaching slurry was maintained at 1.50 for both high and low redox potential experiment. High redox potential was controlled to allow more Fe-oxidizing activity compared to sulfur oxidation process. The primary element in the WMPPCB was Cu (26.3%) along with Ni, Zn, Al, etc., analyzed by XRF, while XRD revealed the presence of metal sulfide/oxides. Both experiments were carried out in a 2-L stirred tank reactor and regular measurement of pH, redox potential, planktonic viable cell count, Fe²⁺, Fe³⁺, Fe (total), SO 4²⁻, Cu²⁺ concentration. The change in pH and controlling with acid addition showed that fed-batch bioleaching consumes 1.35 times lower sulfuric acid per ton WMPPCB than the batch process. Both the batch and fed-batch bioleaching supported first-order reaction and also followed as similar type of intermediate leaching kinetics, which is neither chemically controlled nor diffusion-controlled type. The leaching yield of copper was found to be best (98–97%) in both leach residue and leach liquor analysis. The acid requirement/ton WMPPCB and the bio-residue weight loss state a better fed-batch process. The fed-batch bioleaching was comparatively better than batch process, when compared all bioprocess dynamics parameters and leaching yield of various metals.
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With the massive consumption of lithium-ion batteries in portable consumer electronics and electric vehicles, proper disposal of spent batteries is of paramount importance for sustainable development. In this study, biodegradable organic methanesulfonic acid (MSA) is investigated for the first time to leach valuable metals from waste LiCoO2 powders for battery material regeneration. Under the optimal conditions, leaching efficiencies of lithium and cobalt are achieved at nearly ∼100% and ∼100%, respectively. Comparison experiment indicates that MSA can achieve better leaching performance than previously reported organic acids (e.g. citric acid, malonic acid, succinic acid, oxalic acid) under the same conditions. Besides, strong leaching capability of MSA at high solid-to-liquid ratios (e.g. 81.2 g L⁻¹ and 163 g L⁻¹) is confirmed with satisfactory leaching efficiencies (ca. 92.4%–100%). Feasibility test of MSA utilization for proper treatment of spent batteries is demonstrated at the optimized conditions. Importantly, regeneration study suggests that the as-obtained leachate can be employed to synthesize Co3O4 anode and LiCoO2 cathode materials with micro/nanostructures. Excellent cycling performance and rate capability of the regenerated electrode materials are demonstrated in the repeated charge-discharge cycles. Overall, the proposed recycling strategy is of great significance for rational resource utilization of spent lithium-ion batteries.
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BACKGROUND Phosphor in discarded cathode ray tube (CRT) contained valuable metals, yttrium (Y) and europium (Eu), which are categorized as technology‐critical elements (TCEs) in terms of their supply risk and importance in emerging technologies. Microwave‐assisted leaching was applied to recover Y and Eu from waste CRT with sulfuric acid (H2SO4) solution as the leaching agent in the current study. It is aimed to develop an alternative leaching method of valuable metals from waste CRT phosphor. RESULTS The effects of microwave power and acid concentration on leaching efficiency of Y and Eu were investigated. Shrinking‐core model could describe the leaching kinetics of Y and Eu well and it was controlled by chemical reaction and diffusion through the product layer. Higher leaching efficiency was found when microwave power increased from 200 to 600 W, and was also found as acid concentration increased from 0.5 to 2 mol L⁻¹. Leaching efficiency of Y and Eu were 78.07% and 100%, respectively, for Y and Eu within 60 min at microwave power of 400 W, using 2 mol L⁻¹ of H2SO4 at 10 g L⁻¹ of solid to liquid ratio. Compared with conventional leaching, microwave‐assisted leaching is an alternative technology that could shorten reaction time significantly. CONCLUSIONS The concentration of acid and microwave power affected microwave‐assisted leaching of Y and Eu from waste CRT phosphor. Microwave‐assisted leaching could be an alternative process for rare earth elements recovery. © 2019 Society of Chemical Industry
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This work focuses on constructing a bio-electro-hydrometallurgical platform to efficiently recover cobalt (Co), lithium (Li), and manganese (Mn) from the cathode active materials (CAMs) of spent lithium batteries. A bioleaching process and selective adsorption by PC-88A/TOA-modified granular activated carbon were both incorporated into an electrokinetics approach to achieve excellent recycling performance. The technical feasibility was comprehensively investigated in terms of four aspects, including the domestication of microorganisms, the evaluation of the bioleaching process, the equilibrium adsorption of the adsorbent, and the electrokinetic recovery. Potential sulfur-oxidizing bacteria were screened and domesticated to a high concentration of pyrite pulp. The voltage gradient and the remediation time both had obvious influences on the recovery of the target elements in the electrokinetic process. Maximum recoveries of 91.45%, 93.64% and 87.92% for Co, Li, and Mn, respectively, were achieved from the CAMs of spent lithium-ion batteries via the electrokinetics process. The indirect oxidation of pyrite provided the necessary reductants for the platform. The transformation of sulfur (S) to H2SO4 as a result of bio-oxidation by bacteria strains supplied additional H⁺ ions to facilitate the reduction reaction, and acid dissolution mitigated the drawbacks caused by the uneven distribution of pH in the electrokinetics process.
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Slag produced as a byproduct in industrial processes, contains considerable metals contents, which need to be recovered to avoid environmental contamination. In present review, the types, applications, recovery of metals from slag and their hazardous effects have been discussed. Gravimetric, magnetic, floatation, pyrometallurgical and hydrometallurgical treatments are discussed for processing of charge chrome, steel, copper smelter, brass smelter, tin, incineration, ferrochrome and silico-manganese slags for the extraction of various metal ions (Mg, Cu, Zn, Pb, Cd, Ni, Co, Mn, Fe, As, Cr, Al, Nb, Ag, Au, Nb, Ta, Cu, Co, Ni, Fe, V, Cr). The possibility of biometallurgical processing of slags is also evaluated. Merits and demerits of extraction and purification techniques are highlighted with possible suggestions and possibility of integrated leaching techniques is also discussed.
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The high leachability of heavy metals and toxic organic components has severely discouraged the broader resource recycling of municipal solid waste incineration fly ashes. In this study, a recycling system combining water washing treatment, cationic buffer solution recovery, and electrokinetic remediation was designed based on pH controls and comprehensively explored in terms of strengthening the removal of heavy metals from samples and reducing the risk of environmental leaching of heavy metals in fly ashes. The water washing pretreatment removed a considerable amount of soluble minerals from the fly ash and lowered the initial pH of the electrochemical system to below 10. The dosing of buffer cations decreased the thickness of the diffuse double layer and ameliorated the mobility of the heavy metal species in the pore fluid. Cu was most sensitive to the changes in the operating factors during electrokinetics. The effects of the remediation times and voltage gradients were more significant on heavy metal removal than those of the nitric acid concentration in the electrokinetic optimization system. The leaching toxicities of zinc, lead, copper, and cadmium were reduced by 82.59%, 73.64%, 67.07%, and 93.13%, respectively. Generally, the recovery of the water washing leachate not only enhanced the performance of the electrokinetic remediation for the municipal solid waste incineration fly ash but also avoided downstream disposal of the effluent.
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Benefiting from lower operational costs and energy requirements than do hydrometallurgical and pyrometallurgical processes in metal recovery, the bioleaching of LiCoO 2 through the use of sulfur-oxidizing and iron-oxidizing bacteria has drawn increasing attention. However, the bioleaching mechanism of LiCoO 2 has not been clearly elaborated. In the present study, the effects of the energy source of bacteria, such as Fe ²⁺ , pyrite and S ⁰ , and the products of bacterial oxidation, such as Fe ³⁺ and sulfuric acid, on the chemical leaching of LiCoO 2 were studied. The results indicated that lithium was dissolved by acid, and cobalt was released by the reduction of Fe ²⁺ and acid dissolution. The recovery of Li ⁺ and Co ²⁺ could be significantly improved by pH adjustment. Finally, optimal recoveries of Li ⁺ and Co ²⁺ were observed in the pyrite group, reaching 91.4% and 94.2%, respectively. By using pyrite as the energy source, the role of bacteria in bioleaching of LiCoO 2 was investigated. The results showed that bacteria could produce sulfuric acid by oxidizing pyrite to promote the mobilization of Li ⁺ and Co ²⁺ . The recovery of lithium and cobalt could be increased to 100.0% and 99.3% by bacteria. Moreover, extracellular polymeric substances secreted by bacteria were found to be a factor for the improvement of Li ⁺ and Co ²⁺ recovery.
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Large amounts of waste electric and electronic equipment (WEEE) has been produced due to continuous technological innovation and the improvement of living standards. Based on the rich metal compositions, waste printed circuit boards (WPCBs) are considered as the most valuable component among WEEE. The recycling of metals from WPCBs with inappropriate methods or in informal sectors has been a profitable business, which, however, wastes resources and is harmful to environment and human health. Proper methods that are eco-friendly to recover metals from WPCBs are therefore urgent and essential for both industries and policy makers. In this article, the technology details of metal recycling processes are reviewed based on past research efforts to provide a complete image of the current status. The advantages and problems of several conventional methods are summarized and compared according to cost, environmental impact, and recovery efficiency. Possible approaches for improving mechanical treatment and bioleaching methods, are accordingly analyzed. Novel hybrid processes, such as chelation technology & bioleaching process, green adsorption & chemical leaching process, etc., are put forward to open up possibilities of multi-technology coupling processes for metal recycling from WPCBs.
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The recovery of copper from secondary waste resources (e.g. electronic wastes, slag, fly-ash, sludge and spent catalysts) via oxidative and reductive bioleaching becomes a running trend and a potential alternative to limited metal supply. The motive of this review is to ponder over recycling of secondary waste towards the circular economy to reduce environmental risks as well as to increase the economic profitability of the mining industry. The biochemistry of iron/sulfur minerals, bacteria–mineral interactions and adaptive behavior allowing the acidophiles to survive are among the key parameters to be optimized during the bio recovery of copper. The use of OMICS approaches such as genomics, proteomics, transcriptomics and metabolomics is also crucial to elucidate a comprehensive view of the bioleaching communities, their mechanisms and interactions with minerals. This handy information can act as a boon to develop potential strains by adopting synthetic biology and antiviral CRISPR-Cas9 technologies to efficiently control the bioleaching process. Furthermore, some of these recent discoveries to design bioelectrochemical system (BES) and to achieve higher rate of metal recovery are discussed. Finally, the objective of this study is to narrow the gap between fundamental and applied research to fully address scientific, technological and economic challenges and bottlenecks of bioleaching process in general and BES in particular.
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Copper slags can hardly be utilized because the fayalite in it produces silica gel during the dissolution process. This work proposes a new process on sulfuric acid treatment of copper slag (Jinchuan Group, Gansu Province, China.). The results show that over 98% of recovery efficiency of Cu²⁺, Co²⁺, Ni²⁺ and Zn²⁺ was achieved through the whole process cycle. Ammonia was used to control the pH of the solution in order to completely precipitate Fe²⁺, and then produce hematite powder. More than 85% of the non-ferrous metal ions were left in the solution, and the utilization method of stepwise extraction was evaluated. The generation of silica gel during the acid digestion of copper slag was not restricted, and the silica gel in the acid-leach residue was subsequently dissolved with NaOH solution to obtain sodium metasilicate solution. Acidification and other steps were carried out to produce high-purity silica with a purity of 99.9%. Magnetite and pyroxene were obtained by using a simple magnetic separation process to segregate the remaining slag phase. The whole process achieves the full resource utilization of copper slag, and exhibits great potential for the future industrial utilization of copper slag in an economically and environmentally friendly way.
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This review discusses physical, chemical and direct lithium-ion battery recycling methods in order to have an outlook on future recovery routes. Physical and chemical processes are employed to treat cathode active materials which are the greatest cost contributor in the production of lithium batteries. Direct recycling processes maintain the original chemical structure and process value of battery materials by recovering and reusing them directly. Mechanical separation is essential to liberate cathode materials that are concentrated in the finer size region. However, currently, the cathode active materials are being concentrated at a cut point that is considerably greater than the actual size found in spent batteries. Effective physical methods reduce the cost of subsequent chemical treatment and thereafter re-lithiation successfully reintroduces lithium into spent cathodes. Some of the current challenges are the difficulty in controlling impurities in recovered products and ensuring that the entire recycling process more sustainable.
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Agriculture plays a vital role in every national economy. It represents a substantial trading industry for an economically strong country. Remote sensing and geographical information system used to analyze and visualize agriculture environmentals have proved to be very beneficial to the farming community as well as inudstry. In this chapter, I tried to overview the application of remote sensing and geographical information system in agriculture and natural resource management. Application of different remote sensing technique are important for crop monitoring, crop condition assessment, and yield estimation for the sustainability of agriculture and natural resources. The spectral information is the important aspect of remote sensing data for crop modeling and it is strongly related to canopy parameters which are representative of crop health and crop growth stage. Remote sensing and GIS can also be used very effectively in land use, land cover analysis as well as damage assessment because of drought, floods, and other exteme weather events information on meteorology and vegetation are the two major important inputs into agriculture meteorology application of remote sensing technologies are an important and effective method to identify pests and disease. It is one of the effective tools for assesing and monitoring water resources.
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Society’s hunger for commodities is leading to an increased consumption of minerals considered critical or strategic. A range of minerals containing elements such as lithium (Li), cobalt (Co), rare earth elements (REEs) are considered critical and more important for strategic uses than others. In this paper we describe these as strategically important critical minerals (SICMs). However, their continuous depletion from primary sources coupled with supply risks due to geopolitical issues and geographical segregation is a major concern. As a consequence, recovering these valuable elements from non-conventional sources such as abandoned mine tailings has recently gained increased worldwide attention. In some part this is due to the fact that the potentially recoverable amount of these elements in abandoned mine tailings is often higher than the concentration in some primary ores. A review of the scientific literature reveals the use of modern recovery techniques such as tailored made hydrometallurgical and bio-hydrometallurgical processes can lead to effective recovery of these elements from low grade sources such as mine tailings. However, there remain some technical, economic and environmental challenges associated with recovering SICMs from mine tailings. This review critically analyzes these challenges and discusses the opportunities available for recovering SICMs from abandoned mine tailings using conventional hydrometallurgical techniques as well as bioleaching methods, which can offer significant advantages in reprocessing. This paper also concludes by providing an outlook of an integrated approach to the reprocessing of mine tailings where the recovery of SICMs as well as clean water production should be the combined overall reprocessing and recovery goal, helping to realize the full economic potential of the tailings.
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Ultrasonication has been mechanically applied widely in the recycling of spent lithium-ion (SLI) batteries while its influence on chemical pathways has barely been reported. In this study, ultrasonication and sulfate radicals were used in a coupling system to obtain efficient recoveries of Co and Li from SLI batteries. The synergistic effect of ultrasonication and sulfate radicals on recycling was quantitatively analysed by significance analysis and surface responses in a central composite design. The employment of persulfate significantly affected the whole recycling process during the sonication. Factors including acoustic time, operating powers, and temperature all had a significant effect on the recoveries of Co and Li. The maximum recovery efficiencies of Co and Li of 97.33% and 99.25%, respectively, and the minimum loss rate of Al of 4.13% were simultaneously obtained by the fitting predictor. The optimal combination of factors for the sonication system included an acoustic time (min) of 5.5, an operating power (W) of 168, a temperature (°C) of 86, and a ratio of cathode foil to S-solution (mg/mL) of 1:60. A moiety of cathode active material was directly separated from the aluminium collector by sulfate radical-related reactions. Co and Li cations dissolved from LiCoO2 by carbon dioxide radicals were reprecipitated by excess oxalate. The research demonstrated the positively synergistic influence caused by ultrasonication and sulfate radicals on achieving efficient recoveries of Co and Li from SLI batteries, explicitly expanding the technical choices for the recycling procedure.
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Inefficient waste management has led to the contamination degradation of various ecological resources. Several physicochemical techniques are already in place to remediate this issue. However, remediation through adsorption presents several advantages over existing physicochemical techniques in terms of cost‐effectiveness. Furthermore, biosorbents present the additional advantage of sustainability and offer remediation of affected natural resources. This chapter presents an overview of the deployment of biosorbents and their potential in conserving natural resources. This chapter also highlights the recovery of metals through used biosorbents. Finally, the chapter discusses current challenges in the implementation of biosorbents.
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Bioleaching is an eco-friendly and cost-effective technology for processing low-grade and complex ores and may also be an important bioremediation technology for processing solid waste and secondary resources such as tailings, electronic waste, spent catalyst, sludge, sediment, fly ash, and smelter waste. However, large-scale commercial applications of chalcopyrite bioleaching, especially heap bioleaching of chalcopyrite, are still developing slowly owing to the refractory nature of chalcopyrite. Some industrial practice cases of chalcopyrite bioleaching are summarized in this chapter, which provides a reference for its future industrial application. Key parameters and controlling techniques for chalcopyrite bioleaching, mainly including redox potential/oxidation-reduction potential, pH, temperature, and additives, are summarized and discussed.
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The increasing demand for metals and the concomitant depletion of the primary metallic resources is one of the most important environmental and societal challenges nowadays. Critical metals, rare earth elements, base and precious metals demand is growing day-by-day and driving many metals towards the edge of supply risk. On the other hand, the problems linked to waste generation (especially waste electrical and electronic equipment (WEEE)) are also increasing globally. These end-of-life electronic wastes contain significant concentration of critical raw materials accompanied by harmful substances. Spent Li ion batteries is a kind of WEEE stream, bearing considerable concentrations of valuable metals (like Co, Li, Mn and Ni). If the end-of-life Li ion batteries are not managed properly, there is a high risk that these valuable metals and toxic substances could end into the environment. In order to address the environmental complications, sustainable resource management and boost circular economy, it is important to properly manage and recycle these spent Li ionbatteries. Conventional methods based on high-temperature pyro-metallurgical routes together with hydro-metallurgical processing have been widely studied for the recovery of metals from spent LiBs. However, bio-metallurgical approaches have an edge over their counter parts because of their environmentally friendly nature. Microbe-metal interactions have received special attention both in terms of leaching metals from WEEE and also in recovering metal ions from aqueous streams. Microbial technologies are promising for removing metal ions because of less cost, technical feasibility for large scale applications and no need for addition of toxic chemicals thereby avoiding generation of toxic or hazardous byproducts. In this study, particular emphasis is placed on reviewing the progress made in biohydrometallurgy (i.e. bacterial and fungal leaching practices as one and two-step mode) for the leaching of critical metals from waste lithium ion batteries. Biotechnological methods (e.g. biosorption, bioprecipitation and bioelectrochemical treatment) for the recovery of critical metals from pregnant leachates and aqueous streams are also discussed.
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Recycling of spent lithium-ion batteries (LIBs) has become a global issue because of the potential environment risks raised by spent LIBs as well as high valuable metal content remaining in them. Although bioleaching is an environmentally friendly method to recover metals from spent LIBs, the commonly utilized bioleaching bacterial consortia or strains enriched/isolated from acidic environments cannot be applied at large scales owing to their long leaching cycle and poor tolerance to organic compounds. Here, two bioleaching consortia were enriched in 60 days from neutral activated sludge and were identified phylogenetically divergent from the documented bioleaching bacteria. The results showed that the novel consortia shortened the leaching cycle almost by half when compared to the previous reported consortia or strains, of which one consortium dominated by Acidithiobacillus ferrooxidans displayed high bioleaching efficiency on LiMn2O4, as 69.46% lithium (Li) and 67.60% manganese (Mn) were leached out in seven days. This consortium was further domesticated using cathodic materials for 100 days and proved consisted of three mixotrophs and two chemoautotrophs, three of which were novel species from the genera Sulfobacillus and Leptospirillum. More genes coding for proteins that utilize organic compounds were annotated in the metagenomic assembled genomes (MAGs) than previously reported. A mutualistic relationship between mixotrophs and chemoautotrophs was suggested to help the consortium surviving under either organic- rich or shortage environments. The results discovered that novel bioleaching bacteria with shorter leaching cycle and higher tolerance to organics could be enriched from non-acidic environments, which showed high potential for the metal recovering from spent LIBs or other organic-rich environments.
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Circular economy is considered a new chance to build a more sustainable world from both the social and the economic point of view. In this Essay, the possible contribution of inorganic chemistry towards a smooth transition to circularity in inorganic materials design and production is discussed by adopting an interdisciplinary approach. Circular economy, acknowledged as “an opportunity to rethink our economic future”, is considered a new chance to build a more sustainable world from both the social and the economic point of view. In this Essay, the perspective contribution of inorganic chemistry towards a smooth transition to circularity in inorganic materials design and production, to enable them to enter into the circular loop, is outlined by adopting a truly interdisciplinary approach, encompassing expertise in inorganic materials chemistry, modelling, materials engineering, circular waste management, metallurgy, and mineralogy.
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A bioelectrochemical system (BES) can produce energy in the form of electricity in microbial fuel cells or hydrogen in microbial electrolysis cells while treating wastewater or sequester carbon by reducing CO2 to long-chain organic products of high calorific or market value via a microbial electrosynthesis pathway. Augmenting the circular bioeconomy (CBE) models with BES can aid in bridging the gap between reality and the concepts. This chapter discusses the different variants of BESs and their constraints for understanding the feasibility of incorporating BES in the future CBE models. Suggestive measures such as minimized primary material consumption, utilization of waste-based materials for electrode and proton-exchange membrane synthesis, CO2 emission reduction, regeneration of spent electrodes and membranes, and bioelectrochemical mining of metals from waste stream for on-site reutilization and recovery have been discussed. A detailed scope for the future is also outlined for designing BES variants to fit in the futuristic circular bioeconomy models.
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Copper slag, generated mainly during copper smelting, and classified as a potentially harmful waste, is an important secondary resource containing not only valuable metals, such as Cu, Fe, Zn, Co and Ni, in abundant quantities, but also hazardous elements, such as Pb and As. Hence, in response of its potential economic performances and environmental benefits, copper slag needs to be subjected to further metallurgical recycling and cleaning instead of being dumped or abandoned without treatment. Here, a critical review of the generation mechanism, and chemical and physical characteristics of copper slag is provided. Details of the mainstream and recently developed routes for metallurgical recycling and further cleaning of copper slag are also summarised, such as flotation, leaching, and reduction roasting followed by magnetic separation, smelting reduction, and molten modification followed by physical separation. The technical challenges and developmental bottlenecks of the metallurgical processes are pointed out, which indicate that the improved processes characterised by high recycling efficiency, low energy consumption, and low secondary environmental pollution continue to be the focus of research and development in sustainable waste utilization of copper slag.
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Spent lithium-ion batteries (LIBs) are more hazardous due to the presence of several toxic metals such as cobalt, lithium, nickel, manganese, etc. as well as electrolytes such as LiPF6, LiBF4, or LiClO4. However, these spent LIBs are the secondary source of metals that can be extracted and reused in many ways to decrease their potential environmental risks. Metal extraction from the mixture of LiCoO2-based spent LIBs at a high pulp density by bioleaching is challenging because of microbial inhibition due to high metal toxicity and substrate (iron) limitation. In the present study, we have investigated the bioleaching of a mixture of LiCoO2-based LIBs at high pulp density (100 g/L) using cost-efficient autotrophic bacteria Acidithiobacillus ferrooxidans. By increasing the biogenic H2SO4 production in the culture media, as well as replenishing the bacterial culture for three cycles, we could recover 94% cobalt and 60% lithium in 72 h at 100 g/L pulp density. The X-ray diffraction (XRD), Scanning electron microscope (SEM), and Inductively coupled plasma - optical emission spectrometry (ICP-OES) analysis of LIB powder before and after bioleaching confirmed that more than 90% cobalt leached out from the LIB powder. This bioleaching process is an environmentally friendly way of extracting metals from the mixture of LIBs in gadgets and can be used for all types of spent LIBs.
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To improve the recovery of valuable metals (Li, Co, Ni, and Mn) from the cathode material of waste lithium-ion batteries (LIBs), a mechanochemical reduction technique is proposed in this research. The cathode material was mechanochemically ball milled with various reductive agents as a pretreatment and then subjected to a chemical leaching process for the recovery of valuable metals. The influence of mechanochemical ball milling parameters and leaching conditions on metals recovery, and the changes in physicochemical properties of cathode materials before and after mechanochemical ball milling were investigated. The results show that Zinc (Zn) powder was an effective co-grinding reagent forimproving the recovery of valuable metals from cathode materials. The crystal structure of the cathode material gradually shifted to an amorphous state with an increase in ball milling speed and time. Mn(IV) and Co(III) in the cathode material were mechanochemically reduced to Mn(III) and Co(II) after co-grinding with Zn, which was beneficial to their leaching. The activation energies of Ni and Co decreased from 30.47 KJ/mol and 31.99 KJ/mol to 5.58 KJ/mol and 7.15 KJ/mol, respectively. The leaching rates of Li, Ni, Co, and Mn increased from 72.0%, 42.5%, 31.2%, and 15.2% to 99.9%, 96.2%, 94.3%, and 91.0% under the optimum conditions of a cathode material to Zn powder mass ratio of 7:3, a rotational speed of 500 rpm, a milling time of 2 h, and a ball-to-powder mass ratio of 19: 1. This research presents a highly efficient and feasible approach for recovering valuable metals from waste LIBs.
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The application of end-of-life (EoL) strategies, especially in Waste Electrical and Electronic Equipment (WEEE) is becoming extremely relevant for sustainable development in manufacturing processes and circular economy models. Owing to this, printed circuit boards (PCBs) are important component embedded in WEEE. The present chapter deals with the bio-recovery and waste valorization describing innovative treatment, recovery and recycling technologies for bringing enormous economic benefits. Development and modification of bio-inspired techniques will provide high-efficient way to recover metals selectivity from PCB waste. A mechanistic insights and viable application of bio-leaching, bio-mineralization, bio-electrochemical and biosorption systems for simultaneous enhancing the critical metals recovery and energy-efficiency is also discussed. Henceforth, the present chapter is an effort to provide certain insights and assistance to researchers, policy makers, practitioners in PCBs recycling enterprises.
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Waste electrical and electronic equipment (WEEE) contains economically significant levels of precious, critical metals and rare earth elements, apart from base metals and other toxic compounds. Recycling and recovery of critical elements from WEEEs using a cost-effective technology are now one of the top priorities in metallurgy due to the rapid depletion of their natural resources. More than 150 publications on WEEE management , leaching and recovery of metals from WEEE were reviewed in this work, with special emphasize on the recent research (2015-2018). This paper summarizes the recent progress regarding various hydrometallurgical processes for the leaching of critical elements from WEEEs. Various methodolo-gies and techniques for critical elements selective recovery (using ionic liquids, solvent extraction, electrowinning, adsorp-tion, and precipitation) from the WEEEs leachates are discussed. Future prospects regarding the use of WEEEs as secondary resources for critical raw materials and its techno-economical and commercial beneficiaries are discussed.
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The origin of a rational (scientific) approach to extraction of metal values from ores with the aid of microorganisms (bioleaching) is traced. The removal by microbiological means of ore constituents that interfere with metal extraction (biobeneficiation), an outgrowth from bioleaching, is also traced. © 2004 SDU. All rights reserved.
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This paper presents the experimental results for the leaching of printed circuit boards (PCB) from obsolete computers for extracting and recovering tin and copper by means of leaching followed by precipitation. Printed circuit boards were dismantled, cut into small pieces, and fed into a cylinder mill. The powder obtained was leached by using the aqueous solutions 2.18N H2SO4, 2.18N H2SO4 + 3.0N HCl, 3.0N HCl, and 3.0N HCl + 1.0N HNO3. The lowest values for the percentage of metal extraction were obtained with 2.18N H2SO4 (2.7% for Sn and lower than 0.01% for Cu), while the 3.0N HCl + 1.0N HNO3 leach system exhibited an extraction of 98% for Sn and 93% for Cu. Precipitates were obtained at different pH values by neutralizing the leach liquors using NaOH. The 3.0N HCl + 1.0N HNO3 leach system presented the highest recovery values from the powder feed (84.1% for Sn and 31.9% for Cu), as well as from the leach liquor (85.8% for Sn and 34.3% for Cu).
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Previous studies have shown that various microorganisms can enhance the dissolution of silicate minerals at low (<5) or high (>8) pH. However, it was not known if they can have an effect at near-neutral pH. Almost half of 17 isolates examined in this study stimulated bytownite dissolution at near-neutral pH while in a resting state in buffered glucose. Most of the isolates found to stimulate dissolution also oxidized glucose to gluconic acid. More detailed analysis with one of these isolates suggested that this partial oxidation was the predominant, if not sole, mechanism of enhanced dissolution. Enhanced dissolution did not require direct contact between the dissolving mineral and the bacteria. Gluconate-promoted dissolution was also observed with other silicate minerals such as albite, quartz, and kaolinite.
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This paper deals with bioleaching of metals from hazardous spent hydro-processing catalyst by means of iron/sulphur oxidizing bacteria. The exhaust catalyst was rich in nickel (45 mg/g), vanadium (44 mg/g) and molybdenum (94 mg/g). Before bioleaching, the solid was washed by means of a mixture of Tween 80 and ethyl alcohol, for hydrocarbons removal. The effects of elemental sulphur, ferrous iron and actions contrasting a possible metal toxicity (either the presence of powdered activated charcoal or the simulation of a cross current process by means of filtration stages in series) was investigated. Ferrous iron resulted to be essential for metals extraction and for bacteria adaptation. Nickel and vanadium were successfully bioleached in the presence of iron, reaching extraction yields of 83% and 90%, respectively; on the other hand extractions around 50% for nickel and vanadium were observed both in biological systems in the absence of iron and in the chemical controls with iron. As concerns molybdenum, the highest extraction yields experimentally observed for molybdenum was about 50%, after 21 days bioleaching in the presence of iron, while a maximum extraction of 25 was observed in the other treatments. In conclusion, a bio-oxidative attack with iron could successfully extract nickel, vanadium and partially molybdenum. Further actions aimed at contrasting a possible metal toxicity resulted not to be effective and partially inhibited the metal extraction processes.
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A 3-phase computational ∞uid dynamics (CFD) model for heap bioleaching of chalcocite is investigated to identify and understand the efiect of oxygen ∞ow during air sparging. The study uses an existing one-dimensional model of liquid ∞ow, bacterial transport (including attachment/detachment of bacteria to ore particles), and the depletion of a copper-sulphide, coupled with a two-dimensional (2D) model of gas ∞ow in the heap. The CFD model includes the efiects of oxygen and ferrous ion consumption, coupled with leaching of copper-sulphide via a shrinking core model. The model is used to investigate the 2D efiects of air ∞ow in heap bioleaching with regard to oxygen limitation.
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According to the properties of bioleaching solutions of printed circuit boards (PCBs), copper in the leaching solution were recovery by ion exchange with macroporous styrene iminodiacetic acid chelating resin D401. The bed height of resin, flow rate, pH value on copper adsorption had been studied. Work Exchange Capacity (WEC) of copper increased with increasing bed height of resin and flow rate. The copper WEC of 7.88 mg/mL can be obtained with pH 2.5 and 200 mm bed height at flow rate of 2 mL/min. More than 99.5% of copper could be eluted from loaded resin to get the copper enriched solution by 1.0 M sulphuric acid at A/R ratio 20 in at flow rate of 2 mL/min. Results of the present investigation indicated that D401 resin can efficiently recovery copper from bioleaching solution of PCBs.
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Bioleaching studies of metals from a spent catalyst were conducted using both adapted and unadapted bacterial cultures. The bacterium used in this experiment was Acidithiobacillus ferrooxidans. A comparison of the kinetics of leaching was made between the two cultures by varying the leaching parameters, including the pulp density, particle size and temperature. Both cultures showed similar effects with respect to the above parameters, but the leaching rates of all metals were higher with the adapted compared to the unadapted bacterial cultures. The leaching reactions were continued for 240 h in the case of the unadapted bacterial culture, but only for 40 h in the case of the adapted bacterial culture. The leaching reactions followed first order kinetics. In addition, the kinetics of leaching was concluded to be a diffusion control model; therefore, the product layers were impervious.
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Book
The way municipal solid waste is handled greatly determines its impact on the local as well as the global environment. New technologies have emerged for the treatment of waste, for the recovery of raw materials and energy, and for safe final disposal. The environmental performance of technologies, their social acceptance and their economic viability are key issues to be considered in sustainable waste management. This book provides an overview of current practices in waste management and a synthesis of new developments achieved through interdisciplinary discussions of recent research results.
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Nowadays bioleaching occupies an increasingly important place among the available mining technologies. Today bioleaching is no longer a promising technology but an actual economical alternative for treating specific mineral ores. An important number of the current large-scale bioleaching operations are located in developing countries. This situation is determined by the fact that several developing countries have significant mineral reserves and by the characteristics of bioleaching that makes this technique especially suitable for developing countries because of its simplicity and low capital cost requirement. The current situation of commercial-size bioleaching operations and ongoing projects in developing countries is presented and discussed with especial reference to copper and gold mining. It is concluded that this technology can significantly contribute to the economic and social development of these countries.
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The mixed culture of acidophilic bacteria was used as the inoculant to bioleach waste printed wire boards. Meanwhile, bacteria in different leaching phases (0, 5, 24 and 60 h) were sampled, and denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR)-amplified 16Sr RNA genes was used to evaluate the change of microbial community structure during the bioleaching process. The results showed that the mixed culture of acidophilic bacteria could bioleach 96.36% copper from the boards in 48 h. The analysis of the bands selected from the DGGE gel revealed that the sequences of seven bands (Z1~Z7) had over 99% sequence similarity with Acidithiobacillus ferrooxidans. It meant that the seven strains were all clustered to Acidithiobacillus ferrooxidans genus. The relative abundance of Z1 to Z7 in the four samples was not changed significantly. Meanwhile, Z3 showed the highest relative abundance during the whole bioleaching process, which was 72.70%, 82.90%, 79.00% and 85.80%, respectively. Therefore, the microbial community structure changed a little bit during the bioleaching, which always consisted of Acidithiobacillus ferrooxidans strains and was dominated by strain Z3.
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The efforts made by several countries to resolve the environmental impact and health hazards produced by the electronic waste are discussed. Approximately 20 to 50 million tons of electronic waste are discarded annually worldwide where as 2 million tons of e-waste-laden with lead and other heavy metals go to the US landfills. State legislatures throughout the country have introduced several e-waste bills, and passed some of substantive laws. European Union (EU) has enacted legislation that makes electronics recycling mandatory and restrict use of certain hazardous substance. A e-waste bills has been passed by Washington, where the EU's recycling law requires manufacturers to participate finally in the recycling process.
Chapter
The most familiar and well-studied microorganisms indigenous to acidic mineral leaching environments are autotrophic sulfur- and iron-oxidizing bacteria such as Thiobacillus ferrooxidans, Thiobacillus thiooxidans and Leptospirillum ferrooxidans. Some photoautotrophs, such as the thermophilic rhodophyte Cyanidium caldarium, may also be present in extremely acidic environments that receive light. Other microorganisms which require pre-fixed (organic) carbon have been isolated from mineral leach dumps and acid mine drainage (AMD) waters. These heterotrophic microorganisms include eukaryotes, such as some fungi and yeasts1 and protozoa,2 as well as prokaryotic bacteria and archaea. It is somewhat paradoxical, given that heterotrophy is the most widespread form of metabolism among bacteria, that the first acidophilic heterotrophic bacterium which is indigenous and active in mineral leaching environments was isolated and characterized some 40 years after the iron/sulfur-oxidizing chemolithotroph T. ferrooxidans and 70 years after the sulfur-oxidizing acidophile T. thiooxidans.
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Tests of heavy metal extraction from municipal solid waste incineration fly ashes (MSWFAs) were conducted using Thiobacillus spp. strain TM-32. Six types of MSWFAs were collected from actual incineration plants. Despite different ash sources, the samples showed approximately the same percentages by heavy metal extraction. The percentages were 55.3-68.5%, 57.4-84.6%, 2.2-19.6%, and 38.8%-56.4% for Cd, Cu, Pb, and Zn, respectively. To treat large amount of ash, large sulfate accumulation was essential. Sulfur free culture was employed for the tests and showed approximately the same extraction percentage as original ONM media culture.
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The Acidithiobacillus ferrooxidans (At. f) and Acidithiobacillus thiooxidans (At. t) were used in bio-dissolution experiments of heavy metals in spent MH/Ni batteries. The influences of the initial pH value, the concentration of electrode materials, the temperature and substrate concentration on the leaching rate of heavy metal Ni, Co have been investigated. The obtained results indicate that the efficiency of nickel extraction and cobalt extraction is dependent on all of the mentioned factors. Especially, the initial pH value and the temperature have more effect than other factors for these microorganisms. In addition, the results show that the optimal leaching rate of Ni and Co in the spent MH/Ni batteries reaches to 95.7% and 72.4% respectively after 20 days under the conditions of the initial pH value 1.0, concentration of electrode materials 1.0%, temperature 30 °C and substrate (sulfur) concentration 4.0 g·L-1.
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In this study experimental conditions were expressed for a new process of recycling lead paste at relatively lower temperatures. Lead acid battery paste was reacted with the mixture of citric acid, sodium citrate and hydrogen peroxide solution in this process. The solution mixture provided the removal of sulphur content of the paste as well as the decomposition of lead dioxide. Complete transformation to lead citrate was achieved by experimenting hydrometallurgical conditions of leaching-crystallisation step. Then thermal behaviour of lead citrate was investigated accordingly. Lead citrate crystals were decomposed to lead oxide at around 300°C without any addition. Direct reduction of lead from lead citrate was also possible under specific conditions. Experimental results reflected the efficient recovery of spent lead acid battery pastes without the use of high temperature pyrometallurgy or energy intensive electrolysis techniques.
Article
The present work investigated the influence of Fe+2 initial concentrations in the bioleaching of copper from printed circuit board using Acidithiobacillus ferrooxidans-LR. Printed circuit boards were collected from obsolete computers and mechanically processed through size reduction followed by magnetic separation. The bacteria Acidithiobacillus ferrooxidans-LR were grown and adapted in presence of printed circuit boards. A shake flask study was carried out on the printed circuit boards samples (non-magnetic fraction) using a rotary shaker under the following fixed conditions (185 rpm, 30°C). The bioleaching efficiency was evaluated by comparison between the concentration in the initial sample and in the leached liquor, pH of the medium and concentration of ferrous iron produced. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to determine the metals concentration. The results showed that Acidithiobacillus ferrooxidans-LR leached 63% copper from printed circuit boards using supplemented medium with Fe+2.
Article
Bioleaching of metal sulfides isdis effected by bacteria like Thiobacillus ferrooxidans, Leptospirillum ferrooxidans, Sulfolobus/Acidianus etc. via the (re)generation of iron(III) ions and sulfuric acid. According to the new integral model for bioleaching presented here, metal sulfides are degraded by a chemical attack of iron(III) ions and/or protons on the crystal lattice. The primary iron(III) ions are supplied by the EPS, where they are complexed to glucuronic acid residues. The mechanism of degradation is determined by the mineral structure. The disulfides pyrite (FeS2), molybdenite (MoS2), and tungstenite (WS2) are degraded via the main intermediate thiosulfate. Iron(III) ions are exclusively the oxidizing agents for dissolution. Thiosulfate is consequently degraded in a cyclic process to sulfate, with elemental sulfur being a side product. This explains, why only iron(II) ion-oxidizing bacteria are able to oxidize these metal sulfides. The metal sulfides galena (PbS), sphalerite (ZnS), chalcopyrite (CuFeS2), hauerite (MnS2), orpiment (As2S3), and realgar (As4S4) are degradable by iron(III) ion and proton attack. Consequently, the main intermediates are polysulfides and elemental sulfur (thiosulfate is only a by-product of further degradation steps). The dissolution proceeds via a H2S*+-radical and polysulfides to elemental sulfur. Thus, these metal sulfides are degradable by all bacteria able to oxidize sulfur compotmds (like Thiobacillus thiooxidans etc.). The two mechanisms, based on the mineral structure of a metal sulfide, are summarized in the following Figure 1.
Article
Hydrotreating heavy oils produces catalysts that are contaminated with coke and with nickel, vanadium and iron. Regeneration may be possible but sooner or later irreversible deactivation occurs. Means of regenerating or disposing of spent catalysts are reviewed. Regeneration may or may not involve decoking, with selective removal of Ni, V and Fe being achieved by leaching with different reagents. Leaching of all metals from the spent catalyst may be achieved if disposal is required and the economic justification exists. The solid wastes must be encapsulated or stabilized before final disposal in order to meet environmental standards.
Article
The recent U.S. Environmental Protection Agency's (EPA's) memorandum clarified that spent catalysts resulting from 'dual purpose' hydroprocessing reactors are hazardous waste. This article provides insight into the definitions in the EPA regulations that refiners must follow when determining how spent hydroprocessing catalysts should be classified.
Article
Billiton Process Research has carried out extensive research over the past four years to develop new process technology using bioleaching for extraction of copper and nickel from their sulphide concentrates. Continuous pilot scale and laboratory batch testwork has been carried out with adapted mesophile bacterial cultures at 40°C-45°C, moderate thermophile cultures at 50°C-55°C and thermophile cultures at 65°C-85°C. Pilot scale work has demonstrated the commercial viability of mesophile cultures for bioleaching of secondary copper sulPhide and nickel sulphide concentrates. Moderate thermophiles offer benefits in terms of reduced cooling requirements for commercial reactors and, in the case of bioleaching of nickel concentrates, some selectivity over bioleaching of pyrite. Continuous pilot scale testwork has shown that thermophiles achieve efficient bioleaching of primary copper sulphide and nickel sulphide concentrates, giving much higher recoveries than achieved by bioleaching with a mesophile or moderate thermophile culture.
Article
Microorganisms are intimately involved in metal biogeochemistry with a variety of processes determining mobility, and therefore, bioavailability. The balance between mobilization and immobilization varies depending on the organisms involved, their environment and physicochemical conditions. Metal mobilization can arise from a variety of leaching mechanisms, complexation by metabolites and siderophores, and methylation, where this results in volatilization. Immobilization can result from sorption to biomass or exopolymers, transport and intracellular sequestration or precipitation as organic and inorganic compounds, e.g., oxalates (fungi) and sulfides. In addition, reduction of higher valency species may effect mobilization, e.g,, Mn(IV) to Mn(II), or immobilization, e.g., Cr(VI) to Cr(III). In the context of bioremediation, solubilization of metal contaminants provides a means of removal from solid matrices, such as soils, sediments, dumps and other solid industrial wastes. Alternatively, immobilization processes may enable metals to be transformed in situ and are particularly applicable to removing metals from aqueous solution. This contribution will outline selected microbiological processes which are of significance in determining metal mobility and which have actual and potential application in bioremediation of metal pollution. These include autotrophic and heterotrophic leaching mechanisms, reductive precipitation, sulfate reduction and metal sulfide precipitation.
Article
As an alternative using cyanide chemicals for gold extraction, the application of a cyanogenic bacterium viz. Chromobacterium violaceum (C. violaceum) in YP medium has been investigated. The catalytic roles of metal ions such as Na+, Mg2+, Fe2+, and Pb2+, as well as the effect of Na2HPO4 nutrient addition on the cyanide generation efficiency of the bacterium in this medium have been elucidated. While MgSO4 and FeSO4 added to the medium were equally effective for cyanide generation, improved efficiency was obtained in the presence of Na2HPO4 and Pb(NO3)(2). In order to examine the effectiveness of C. violaceum cultured in YP medium for the generation of cyanide ions, the dissolution of gold and copper from waste mobile phone printed circuit boards (PCBs), a good source of gold and copper in alkaline conditions, was tested at 30 degrees C, for various pH values and metal ion contents. Gold leaching was found to be 11% in 8 d at pH 11.0 in presence of 4.0 x 10(-3) mol/L MgSO4, whereas; copper recovery was high (11.4%) at pH 10.0. Addition of 1.0 x 10(-2) mol/L Na2HPO4 and 3.0 x 10(-6) mol/L Pb(NO3)(2) to the YP medium increased copper leaching to 30.3% and 38.1%, respectively, at pH 10.0 in 8 d. However, this effect was not observed for gold leaching.
Article
In previous studies it has been showed that bacterially produced sulphuric acid is a good leaching agent for laterite tailings. In this work we evaluated heavy metals leaching from low grade laterite ore for cobalt and nickel extraction using sulphuric acid produced in situ by Acidithiobacillus thiooxidans under different culture conditions. In studies where that material was initially added to the cultures, considerable percentages of metals were leached (100 % Mn, 70 % Co, 7.5 % Ni, less than 5 % of Cr and Fe) after 18 days of incubation at low pulp densities (1 % and 2.5 %) of overburden. The maximum percentages were reached when cultures pH was approximately or below than 1.5. At higher pulp densities material was added to the cultures after different pre-cultivating times; also higher sulphur amounts were assayed; in such way about 100 % Mn, 60 % Co, 9 % Ni and Fe and 2.5 % Cr were leached. Although toxic metals were not completely leached, sequential extractions results indicate that these metals are not readily available. All studies finally suggest that bioleaching is a suitable technology for recovery of valuable metals as Co and remediation of mining residues by extraction of heavy metals.
Conference Paper
Material and energy resource consumption is on the rise in both the industrialized and developing world (e.g., countries like India and China). In order to sustain this growth and provide resources for future generations, there is a need to design products that are easy to recover and recondition, thus enabling multiple use cycles. Processes are needed that can achieve this multi-use while producing zero (or very near zero) waste. There exist a number of barriers and challenges to achieving this vision of multi-use with zero waste; one such challenge is the development of a product recovery infrastructure that will minimize short-term impacts due to existing products and will be robust enough to recover products of the future. This paper identifies the barriers to developing such a recovery and reuse infrastructure. The aim is to achieve product multi-use and zero waste.