ArticleLiterature Review

A greener approach for resource recycling: Manganese bioleaching

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Abstract

In view of unremitting diminution of mineral resources, rising energy economics along with increasing global consumption of Manganese (Mn), development of environment friendly technologies for tapping alternate sources of Mn has gained importance lately. Mn recovery from mining residues using conventional approaches is extremely expensive due to high capital and energy costs involved. However lean grade ores present in millions of tons awaits the development of competent and cost effective extractive process. Mn recovery by biomining with diverse microbes is thereby recommended as a superior and green alternative to the current pyro metallurgical techniques. The synergistic effects of different factors are known to influence microbial leaching of mineral ores which includes microbiological, mineralogical, physicochemical and process parameters. Bacterial bioleaching is mostly due to enzymatic influence, however fungal bioleaching is non enzymatic. Genomic studies on microbial diversity and an insight of its metabolic pathways provides unique dimension to the mechanism of biomining microorganisms. The extraction of Mn has a massive future prospective and will play a remarkable role in altering the situation of ever-decreasing grades of ore. This review aims to encompass the different aspects of Mn bioleaching, the plethora of organisms involved, the mechanisms driving the process and the recent trends and future prospects of this green technology.

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... Manganese (Mn) is principally found in its oxide form and is available as a major constituent in many naturally occurring minerals [1]. It is also an important enzyme cofactor and provides protection to bacteria cells against reactive oxygen species. ...
... The extensive use of Mn leads to the generation of a substantial amount of waste, among which a considerable quantity does not possess any market value [7]. Some of this waste is discharged into the environment leading to its contamination [1]. The excess Mn in terrestrial and aquatic ecosystems is known to have many toxic effects on organisms. ...
... For example, Marinomonas sp. S11-S-4 isolated from sediment collected from the Arctic Ocean was able to grow when the Mn 2+ concentration was up to 100 mM [33], while strains isolated from Sanindipur mines (Odisha, India) showed visible growth at a concentration up to 500 mM of Mn [1,6]. Interestingly, Acinetobacter sp. ...
Article
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Manganese (Mn) is widely used in industry. However, its extensive applications have generated a great amount of manganese waste, which has become an ecological problem and has led to a decrease in natural resources. The use of microorganisms capable of accumulating Mn ions from contaminated ecosystems offers a potential alternative for the removal and recovery of this metal. The main aim of this work was an investigation of removal potential of Mn from soil by isolated bacterial. For this purpose, eleven bacterial strains were isolated from the soil from metallurgical waste heap in Upper Silesia, Poland. Strain named 2De with the highest Mn removal potential was selected and characterized taking into account its ability for Mn sorption and bioaccumulation from soil and medium containing manganese dioxide. Moreover, the protein profile of 2De strain before and after exposition to Mn was analyzed using SDS/PAGE technique. The 2De strain was identified as a Pseudomonas sp. The results revealed that this strain has an ability to grow at high Mn concentration and possesses an enhanced ability to remove it from the solution enriched with the soil or manganese dioxide via a biosorption mechanism. Moreover, changes in cellular protein expression of the isolated strain were observed. This study demonstrated that autochthonous 2De strain can be an effective tool to remove and recover Mn from contaminated soil.
... Bioleaching processes result from catalysis by microorganisms during the dissolution of mineral ores as the microorganisms transfer electrons for survival purposes, and metals are released without requiring an external energy supply. In this type of process, high activation energies are not necessary; as proof, the reactions take place at low pressure and low temperature (Ghosh et al. 2016;Diao et al. 2014;Rodríguez et al. 2001;Lombardi and Garcia 1999). ...
... As a result of related research, various applications and technologies have been developed that allow bioleaching to work under various weather conditions (humidity, temperature, precipitation, etc.) and operational conditions (pH, pulp density, residence time, particle size, mass transfer rate, etc.) at different scales (flask level, pilot plant, and industrial scale), and the extraction of valuable metals (gold and silver), basic metals (copper and iron), and even radioactive metals (uranium) has been achieved (Rana et al. 2019;Ghosh et al. 2016;Zhou et al. 2009;Acevedo 2002;Mathur et al. 2000;Salameh et al. 1999). Most of these microbiological processes are aerobic and are commonly carried out in an aqueous medium containing salts and organic substances (Ghosh et al. 2016;Govender and Gericke 2011;Liu et al. 2006;Çalik et al. 2004;Kinzler et al. 2003). ...
... As a result of related research, various applications and technologies have been developed that allow bioleaching to work under various weather conditions (humidity, temperature, precipitation, etc.) and operational conditions (pH, pulp density, residence time, particle size, mass transfer rate, etc.) at different scales (flask level, pilot plant, and industrial scale), and the extraction of valuable metals (gold and silver), basic metals (copper and iron), and even radioactive metals (uranium) has been achieved (Rana et al. 2019;Ghosh et al. 2016;Zhou et al. 2009;Acevedo 2002;Mathur et al. 2000;Salameh et al. 1999). Most of these microbiological processes are aerobic and are commonly carried out in an aqueous medium containing salts and organic substances (Ghosh et al. 2016;Govender and Gericke 2011;Liu et al. 2006;Çalik et al. 2004;Kinzler et al. 2003). ...
Article
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Bioleaching is suggested as a methodology with benefits in ex situ/in situ bioremediation for reducing metal contamination in dredged sediments. The process of bioleaching assisted by microorganisms in a stirred tank is widely used, among other biohydrometallurgical techniques, for the efficient extraction of metals of interest if the recovery costs of valuable metals allow it. Measurement of the mass transfer capacity of oxygen in an aerobic bioreactor is of vital importance; this factor determines the productivity of the system, since it promotes microbial growth and hence enables a bioconversion process at the mineral surface takes place. The main objective of the present research was to determine the volumetric oxygen transfer coefficient (kLa) during the manganese bioleaching process in a stirred tank reactor using silicone oil as a vector to improve the transfer of gaseous substrates. Experiments were carried out in triplicate with a 22 factorial design analyzing temperature (30 and 40 °C) and stirring speed (300 and 500 rpm). The effect of viscosity on the system was also determined by modifying the concentrations of mining waste (30, 40, and 50%), ferrous sulfate (FeSO4 · 7H2O) (2, 4, 8, and 14%), and silicone oil (0, 5, and 10%) at 0 and 24 h of mixing. The results showed an increase in the value of kLawith respect to time, from kLa(0 h, 30 °C, 500 rpm) = 8.75 s−1 to kLa(24 h, 40 °C, 500 rpm) = 18.18 s−1; ANOVA statistical analysis was performed with the Fisher and Tukey tests and showed that there were statistically significant differences.
... The drawbacks of these methods include incomplete removal of whole metals from spent batteries, high operating costs, hazardous chemical solvents that produce toxic sludge, large amounts of energy, and water (Naseri et al. 2019a;Pourhossein et al. 2021). Additionally, the chemical method of oxidizing manganese introduces harmful pollutants into the environment (Ghosh et al. 2016). ...
... 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). The unique benefit of bioleaching over conventional recovery is that it can remove and recover low concentrations of manganese from ores (primary resources) and secondary resources (Ghosh et al. 2016;Işıldar et al. 2019). ...
... Also, the presence of enzymes in microorganisms plays an essential role in the dissolution of manganese. Table S2 shows the list of enzymes and genes in the microorganism involved in manganese dissolution processes (Ghosh et al. 2016). ...
Article
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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
... The process of extraction of manganese from ores using bacteria can be aerobic or anaerobic. Some organisms might reduce manganese directly as a part of their life process, while others might produce acids which dissolve the manganese into solution [26,29]. Convincing evidence for MnO2 reduction by microbes which will perform this process anaerobically has so far been demonstrated only in enrichment cultures with lactate, succinate, and acetate as electron donors [8]. ...
... Manganese plays an important role in microorganism life functions and takes part in various redox reactions. MnO2 is used as a final electron acceptor during respiration in some manganese reducing bacteria in the absence of oxygen during the direct reduction process [26,27]. Since bacteria can take up manganese in their cell membranes [28], there is usually a maximum tolerable concentration of manganese in which bacteria can survive. ...
... Indirect reduction of manganese oxides usually involves the production of organic acids by microorganisms, which in turn digest the ores to make Mn 2+ ions available in the solution [26,27,29]. The microorganisms involved here have been found to be various types of fungi along with bacteria [9,11,12,26,31,32]. ...
Article
The increasing demand of manganese in the industries and various hindrances in its production from low grade ores by conventional method has made it imperative for researchers around the world to develop a method of manganese extraction from low grade ores that is both environment-friendly and economical. Bioleaching has shown significant potential in manganese extraction and efficiencies of extraction have been found to be 70–98% with the help of various bacteria and fungi. This study focuses on extraction of manganese with the help of mixed bacterial strains that have been collected from their natural anaerobic environment where manganese reducing activity was evident. The extraction of manganese from reagent grade manganese dioxide and high grade manganese ore has been studied over 180 days in an anaerobic environment at room temperature and pH around 5, without the addition of any mineral acids. Highest concentrations of dissolved manganese have been found to be 928.58 mg Mn/L for reagent grade manganese dioxide and 864.54 mg Mn/L for ore grade manganese, corresponding to 650 mg and 400 mg of cumulative manganese, respectively.
... Additionally, Figs. 1 and 4 show positive bacteria-oxalate-Fe(II) and bacteria-Fe(II) interactions, similar to those reported previously for jarosite dissolution where iron chelates may be acting as redox mediators (González et al., 2016). Since A. cryptum JF-5 is a nonfermenting bacterium (Küsel et al., 1999), manganese dissolution must be supported by a direct electron transfer, or an iron-(or iron-chelate) mediated process (Lovley et al., 2004) rather than by the synthesis of organic acids (Ghosh et al., 2016;Zhang and Cheng, 2007). ...
... Finally, the results obtained in this research contribute to shedding light on the role of A. cryptum in manganese cycling and AMD generation (Sağlam et al., 2016). Additionally, they may contribute to the development of greener technologies for mining and recycling this metal (Dunbar, 2017;Ghosh et al., 2016). ...
Article
Microorganisms contribute to metal mobilization by catalyzing the dissolution of diverse compounds in both acidic and circumneutral environments. Since Mn(II) is more soluble than Mn(IV), acidophilic iron-reducing microorganisms, such as Acidiphilium cryptum, may increase the manganese contained in acid mine drainage from both active and abandoned mines. Two low-grade manganese ores (7% and 25% Mn) were used to perform dissolution tests with A. cryptum JF-5 in medium amended with oxalic acid, dissolved iron and thionine. The statistical analysis performed with a 99% confidence level demonstrated that the presence of Acidiphilium cryptum was the most important factor for manganese dissolution, increasing the process rate up to sevenfold (from 23.2 to 175.8 nmol/L·d). Pareto charts showed that the oxalate alone and the interaction of bacteria-Fe(II)-oxalate were also relevant in the dissolution process. The sulfuric acid used for pH control was proportional to the extracted amounts of manganese and iron, obtaining a consumption of 1.3 mol of H2SO4 per mol of metal. In the presence of A. cryptum, oxalic acid led to the selective dissolution of manganese, while thionine increased the dissolution of iron and decreased the process selectivity. Deoxygenation of the culture medium limited the bacteria proliferation and dissolution processes. Although the mechanism used by A. cryptum to dissolve both ores was not identified, the synthesis of bacterial appendages, or an iron- (or iron-chelate) mediated process may be essential when performing manganese dissolution.
... Currently, microbiological mining technologies on an industrial scale are used for extraction of copper, uranium and gold from low-grade and complex ores [14][15][16] Research works on biomining manganese from low-grade ores and manganese-containing wastes are underway [17][18][19]. For several years, the authors of this study, together with colleagues, also intensively investigated the possibilities and technological features of microbiological leaching of manganese from secondary technogenic resources of the metallurgical industry of Georgia [20][21][22][23][24], but still have not studied the processes of bioleaching of manganese from rocks and their enrichment wastes. ...
... (18)] lags behind the sulfur release intensity [Eqs. (17), (19), (21)]. Unlike soluble ferrous ions, which easily penetrate the outer of the A.ferrooxidans cell and penetrate its periplasm, relatively volumetric and hardly soluble elemental sulfur encounters a steric obstacle, which slows down the reaction. ...
Article
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In Georgia, the amount of manganese-bearing industrial wastes is estimated at 15 million tons, of which over 10 million tons are mine wastes of Chiatura deposit. The resource potential of these technogenic formations makes 1.5 million tons of pure manganese. Every year the volume of these wastes increases by one mln t on average. An economic loss from non-utilization of this valuable manganese stock is great. Also great is an environmental damage. Analysis of a possibility of recycling manganese-bearing waste indicates the prospects of using environmentally safe and profitable biotechnological processes of utilizing this technogenic raw material. For intensifying the known methods of manganese biomining, the authors have developed a new technological leaching scheme, which, at the first stage, for processing the stock provides for its desilicalization by silicate bacteria B.mucilaginosus. The result of this stage is an increase in the content of manganese in the raw material by 25–30%, with an increase in the cumulative response surface for applying bacteria A.ferrooxidans at the next stage. One of the main distinctive features of the proposed scheme is also integration of the manganese leaching process with the copper and zinc recovery process. The advantage of this combined process consists in the application of the afterproduct of leaching of these nonferrous metals—a ferrous (II) sulfate compound for speeding up the manganese extraction, and, vice versa, in the application of ferric (III) sulfate produced upon manganese leaching to activate copper and zinc extraction. The advantage of the use of the bicultural solution A.ferrooxidans-R.phaseoli in manganese leaching instead of the monoculture one (A.ferrooxidans) is also substantiated. As a result of practical realization of the proposed technical novelties, the manganese extracting degree can be increased to 98–99%, while the length of leaching can be reduced to 14–21 days. The commercial exploitation of the proposed combined technological scheme of manganese biomining will increase the resource base of Georgian manganese, for it will create a new possibility for recycling environmentally harmful wastes and cut-off grade ores of Chiatura deposit.
... Conventionally, synthetic manganese dioxide is mainly produced from pyrolusite (MnO 2 ) or rhodochrosite (MnCO 3 ) ores. Pyrolusite ore has to be reduced before leaching, or it can be directly leached through a reductive leaching process [14]. After leaching and filtration, the leach liquor contains a variety of impurities, such as alkali metals, iron, nickel, and so on. ...
Article
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The ferromanganese (FeMn) alloy is produced through the smelting-reduction of manganese ores in submerged arc furnaces. This process generates large amounts of furnace dust that is environmentally problematic for storage. Due to its fineness and high volatile content, this furnace dust cannot be recirculated through the process, either. Conventional MnO2 production requires the pre-reduction of low-grade ores at around 900 °C to convert the manganese oxides present in the ore into their respective acid-soluble forms; however, the furnace dust is a partly reduced by-product. In this study, a hydrometallurgical route is proposed to valorize the waste dust for the production of battery-grade MnO2. By using dextrin, a cheap organic reductant, the direct and complete dissolution of the manganese in the furnace dust is possible without any need for high-temperature pre-reduction. The leachate is then purified through pH adjustment followed by direct electrowinning for electrolytic manganese dioxide (EMD) production. An overall manganese recovery rate of >90% is achieved.
... Manganese (Mn) is rarely found in its elemental state, being encountered mainly in its oxide form as a key constituent in naturally appearing minerals such as manganite (MnOOH) and birnessite (dMnO 2 ) Ghosh et al. 2016). Mn has fundamental applications in industries such as steel, glass, and batteries (Das et al. 2012) and its reserves are spread out over in many countries. ...
Chapter
Mining is one of the most important economic activities on Earth and has played an important role in human existence. Minerals and metals are crucial for a large number of services and infrastructures that are used by society. However, extensive mining and industrial activities have led to production of large volumes of wastes and management of these materials, such as tailings and waste rock which is an environmental challenge. Moreover, the growing worldwide demand for ores has made developing processes for economic recovery from secondary sources increasingly important. In this scenario, the development of environmentally friendly technologies for valorizing mining wastes is mandatory. This chapter thus intends to provide a current overview of an alternative and green approach for valorization of mining waste and tailings by microbial means, that is, biomining.
... There is also a crucial need to look into waste reservoirs (soils, sludge, slag and ash from incineration, bottom sediments, soils from landfills, waste from ore mining etc.) that are fully contaminated with metals and nutrients as potential secondary stocks of such valuable constituents. This lead us into the topic of the paper and introduction of the "Beyond the zero waste concept" which encourages recovery of all materials lost during the entire life cycles of different products manufactured, which are still available in different sinks (landfills, sediments of rivers, ocean, etc.) (Bhatnagar et al., 2013;Burlakovs et al., 2016;Ghosh et al., 2016;Kriipsalu et al., 2008). The long-term goal is to apply such innovative approach in an environmental and economic efficient way, making use of the accumulated knowledge, including reuse/recycling of materials bound in urban and rural structures. ...
Article
Existing schemes of solid waste handling have been improved implementing advanced systems for recovery and reuse of various materials. Nowadays, the ‘zero waste’ concept is becoming more topical through the reduction of disposed waste. Recovery of metals, nutrients and other materials that can be returned to the material cycles still remain as a challenge for future. Landfill mining (LFM) is one of the approaches that can deal with former dumpsites, and derived materials may become important for circular economy within the concept ‘beyond the zero waste’. Perspectives of material recovery can include recycling of critical industrial metals, including rare earth elements (REEs). The LFM projects performed in the Baltic Region along with a conventional source separation of iron-scrap, plastics etc. have shown that the potential of fine-grained fractions (including clay and colloidal matter) of excavated waste have considerably large amounts of potentially valuable metals and distinct REEs. In this paper analytical screening studies are discussed extending the understanding of element content in fine fraction of waste derived from excavated, separated and screened waste in a perspective of circular economy. Technological feasibility was evaluated by using modified sequential extraction technique where easy extractable amount of metals can be estimated. Results revealed that considerable concentrations of Mn (418–823 mg/kg), Ni (41–84 mg/kg), Co (10.7–19.3 mg/kg) and Cd (1.0–3.0 mg/kg) were detected in fine fraction (<10 mm) of waste sampled from Högbytorp landfill, while Cr (49–518 mg/kg) and Pb (30–264 mg/kg) were found in fine fraction (<10 mm) of waste from Torma landfill revealing wide heterogeneity of tested samples. Waste should become a utilizable resource closing the loop of anthropogenic material cycle as the hidden potential of valuable materials in dumps is considerable.
... This technology has been widely investigated for toxic metals removal from soils (Diaz et al., 2015;Huang et al., 2015;Nareshkumar et al., 2008), sediments (Akinci and Guven, 2011;Chen and Lin, 2009a;Hoque and Philip, 2011), and mine tailings (Lee et al., 2015;Liu et al., 2008;Seh-Bardan et al., 2012). Bioleaching was widely applied for removal and recovery of Mn from mining waste residues (Ghosh et al., 2018(Ghosh et al., , 2016Ghosh and Das, 2017;Mohanty et al., 2017;Sanket et al., 2017). Especially, bioleaching was also effective with mine tailings highly contaminated with As (Lee et al., 2015;Park et al., 2014) and As-containing minerals (Zhang et al., 2015. ...
Article
Mine wastes from tungsten mine which contain a high concentration of arsenic (As) may expose many environmental problems because As is very toxic. This study aimed to evaluate bioleaching efficiency of As and manganese (Mn) from tungsten mine wastes using the pure and mixed culture of Acidithiobacillus ferrooxidans and A. thiooxidans. The electrochemical effect of the electrode through externally applied voltage on bacterial growth and bioleaching efficiency was also clarified. The obtained results indicated that both the highest As extraction efficiency (96.7%) and the highest Mn extraction efficiency (100%) were obtained in the mixed culture. A. ferrooxidans played a more important role than A. thiooxidans in the extraction of As whereas A. thiooxidans was more significant than A. ferrooxidans in the extraction of Mn. Unexpectedly, the external voltage applied to the bioleaching did not enhance metal extraction rate but inhibited bacterial growth, resulting in a reverse effect on bioleaching efficiency. This could be due to the low electrical tolerance of bioleaching bacteria. However, this study asserted that As and Mn could be successfully removed from tungsten mine waste by the normal bioleaching using the mixed culture of A. ferrooxidans and A. thiooxidans.
... Alternatively, some quarry wastes are both rich in aluminosilicates and have the proper mineralogy, which allows their application as precursors to produce geopolymer cement and similar synthetic materials. Geopolymers are alternative binders which have diverse applications in various fields such as coatings and adhesives [14], fiber composite production [15], decorative stone artifacts [16], thermal insulations [17], building materials, low-energy ceramic tiles [18], waste encapsulation [9], thermal shock refractories [16], biotechnologies [19], etc. Geopolymers were first introduced by Joseph Davidovits in the early 1970s, where his primary aim was producing nonflammable and noncombustible plastics. During his studies he discovered that the synthesis of some organic plastics in alkali solutions as well as mineral zeolites and feldspathoids were driven by the same hydrothermal conditions. ...
Article
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Carbon footprint reduction of paving materials could be explored through recycling mining by-products into different applications, which will preserve natural resources and decrease environmental issues. One possible approach is to reuse quarry dust and mining ore waste as precursors in geopolymer applications. geopolymers are mineral polymers rich in aluminosilicates with an amorphous to a semi-crystalline three-dimensional structure. The current review aims to summarize the studies conducted during the past decade on geopolymers containing quarry dust and mine tailings. The first section discusses various precursors used for geopolymer cement production such as metakaolin, ground granulated blast furnace slag (GGBFS), fly ash, and quarry/mining ore wastes including silt, tungsten, vanadium, copper, gold, zinc, marble, iron, basalt, and lithium. Different calcination treatments and curing conditions have been summarized. In some cases, the precursors are required to be calcined to increase their reactivity. Both ambient temperature and elevated temperature curing conditions have been summarized. Less attention has been paid to room temperature curing, which is necessary for field and industrial implementations. Engineering properties such as compressive strength, density, durability and acid resistance, water absorption and abrasion of geopolymers containing mining waste were reviewed. One of the main barriers preventing the widespread use of waste powders, in addition to economic aspects, in geopolymers could be due to their unstable chemical structure. This was shown through extensive leachate of Na + or K + cations in geopolymer structures. The review of over 100 articles indicated the need for further research on different aspects of quarry waste geopolymer productions before its full industrial implementation.
... ferrooxidans) is by far the most widely used bioleaching microorganisms in ore leaching, including for Ni, Cu, Au, V, and Mn ores [7][8][9]. Additionally, a corrosion cell is the most common method in manganese oxide minerals and sulfide minerals for extracting valuable metals [10]. Many previous research studies have focused on the pyrite-pyrolusite coupled bio-leaching system. ...
Article
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Efficient extraction of Ni, Co, Cu, and Mn from low-grade and refractory ores is a common technical challenge. The present study proposes an Acidithiobacillus ferrooxidans-coupled leaching of Ni, Cu, Co, and Mn from oceanic polymetallic nodules and low-grade nickel sulfide ore, and focuses on the electrochemical behavior of the ores in simulated bio-leaching solutions. In the dissolution of polymetallic nodules, A. ferrooxidans facilitates the diffusion of H+ and accelerates electron transfer, producing a decrease in charge transfer resistance and promoting the Mn(IV)-preceding reaction. The use of A. ferrooxidans is beneficial for lower impedance of sulfur-nickel ore, faster diffusion rate of product layer, and better transformation of the Fe3+/Fe2+ couple and S0/S2− couple. A. ferrooxidans increases the potential difference between the nodule cathode and sulfide anode, and increases electron liberation from the sulfide ore. This motivates a significant increase in the average extraction rates of Ni, Co, Cu, and Mn in the bacterial solution. The bio-leaching efficiencies of Ni, Co, Cu, and Mn were as high as 95.4%, 97.8%, 92.2% and 97.3%, respectively, representing improvements of 17.1%, 11.5%, 14.3% and 12.9% relative to that of the germ- and Fe(III)-free acidic 9 K basic system.
... The inclusion of metal bioavailability as a freshwater quality component has been recommended in mining-impacted rivers as a more precise indication of mining pollution, preventing the underestimation of metal concentrations in pH-buffered rivers [56]. Moreover, besides the fact that pH and microbial enzymes influence metal solubility in freshwaters [57], the site-specific physicochemical environment (e.g., the presence of dissolved organic carbon or cationic stress) enhances the ecotoxicity of low zinc concentrations [55]. Metal phase distribution is also affected by pH variations, inducing metal precipitation or affinity to a matrix [56]. ...
Article
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Water quality assessments provide essential information for protecting aquatic habitats and stakeholders downstream of mining sites. Moreover, mining companies must comply with environmental quality standards and include public participation in water quality monitoring (WQM) practices. However, overarching challenges beyond corporate environmental responsibility are the scientific soundness, political relevance and harmonization of WQM practices. In this study, a mountainous watershed supporting large-scale gold mining in the headwaters, besides urban and agricultural landuses at lower altitudes, is assessed in the dry season. Conventional physicochemical and biological (Biological Monitoring Water Party-Colombia index) freshwater quality parameters were evaluated, including hydromorphological and land-use characteristics. According to the indicators used, water quality deterioration by mining was absent, in contrast to the effects of urban economic activities, hydromorphological alterations and (less important) agricultural pollutants. We argue that mining impacts are hardly captured due to the limited ecological knowledge of high-mountain freshwaters, including uncharacterized mining-specific bioindicators, environmental baselines and groundwater processes, as well as ecotoxicological and microbial freshwater quality components. Lessons for overcoming scientific and operational challenges are drawn from joint efforts among governments, academia and green economy competitiveness. Facing a rapid development of extractive industries, interinstitutional and multidisciplinary collaborations are urgently needed to implement more integrated freshwater quality indicators of complex mining impacts.
Article
Electrolytic manganese residue (EMR) is characterized by high silicon content, and thus, is an important silicon source. While considerable research has been conducted on bioleaching EMR for silicon recovery, sufficient information is not available on the impact of specific silicate mineral structures in EMR on silicon bioleaching. In the present study, the mineral composition of EMR was determined firstly, and then the leaching effect of Paenibacillus mucilaginosus on these different silicate minerals were investigated by shake flask experiments. Results showed that the silicon in EMR was mainly composed of quartz, sericite, muscovite, biotite, olivine and rhodonite; Paenibacillus mucilaginosus had a significantly different weathering and decomposition effects on different silicate minerals. Among them, sericite, muscovite and biotite with layered structure had the most obvious silicon leaching effect, followed by rhodonite with island structure, while silicon leaching from olivine with chained structure and quartz with frame structure was much more difficult. One can roughly judge the adaptability of bioleaching of silicon in EMR using Paenibacillus mucilaginosus if the main form of silicate minerals in EMR is determined.
Article
A bioleachate containing high-content Mn and low-content Fe is required for the production of electrolytic manganese metal (EMM). To produce the qualified bioleachate, bioleaching of Mn from a low-grade MnO2 ore by a mixed autotrophic culture in presence of combined energy matters of pyrite and sulfur and simultaneous removal of Fe using waste electrolytic manganese anolyte (WEMA) containing high concentration of NH4⁺ as both nitrogen source and iron scavenger were investigated. The optimal conditions for both the maximum Mn release from the MnO2 ore and the maximum Fe precipitation from the bioleachate were determined via Plackett-Burman design, Steepest Ascent design and Box-Behnken design, which were listed as follows: 6% (v/v) of WEMA addition, 140 rpm of shaking speed, 250 mesh of ore particle size, 1.0 g L⁻¹ of KH2PO4, pH value adjustment at 2.4, ratio of pyrite to sulfur at 14:10 (g·L⁻¹), incubation temperature at 31 °C, and bioleaching period of 14 days at a fixed pulp density of 100 g L⁻¹. The predicted values were 79.6% for the Mn extraction efficiency and 0.69 g L⁻¹ for the total Fe residual concentration respectively, being very close to the measured values of 78.5% and 0.73 g L⁻¹ in the confirmation experiments. The addition of 6% WEMA instead of (NH4)2SO4 resulted in an increase of 41% in the cell density from 1.20 × 10⁸ to 1.69 × 10⁸ mL⁻¹ after 14 days of culture, displaying that the WEMA was competent to be an nitrogen source for the bioleaching. On the other hand, the addition of WEMA enhanced the formation of more ammoniojarosite to greatly reduce the Fe residual concentration from 2.19 to 0.73 g L⁻¹, accompanying 7% of loss rate in Mn extraction due to possible Mn adsorption onto the ammoniojarosite. The present study demonstrated that the WEMA as a byproduct of EMM industry is qualified to be both the nitrogen source for efficient bioleaching of low grade MnO2 ore and the Fe scavenger for simultaneous removal of Fe from the bioleachate, which is advantageous for both reduction of bioleaching cost and the closed loop recycling of waste in preparation of EMM.
Article
Currently, bioleaching of manganese (Mn) from Mn-poor ore (e.g. pyrolusite) is facing the challenges of low leaching efficiency and high cost of leachant and process operation. In this study, a new process was developed that uses Microbacterium trichothecenolyticum Y1 (bacteria Y1) and waste molasses to bioleach Mn from pyrolusite or pure MnO2 (for comparison). Results indicate that the innovative process can be operated at normal temperature/pressure and a weak acidic condition (pH = 3.5) with a much improved Mn bioleaching efficiency (about 98% in 6–8 days) as compared with the previously-reported efficiencies (only 60–80%). The optimal conditions were found as the solid-liquid ratio of 1 kg of mineral powder to 20 L of leaching liquid, pH 3.5, anaerobic, stirring speed of 80 rpm, temperature 45 °C and waster molasses dose of 2.5 g L⁻¹. The associated mechanism was elucidated with the help of different equipment and methods. The leaching process first reduced Mn(IV) in MnO2 to Mn(II) as MnO in the solid phase and then dissolved Mn(II) into the liquid phase. Bacteria Y1 could produce a large number of tyrosine-like substances in the system, which promoted the decomposition of sugar and Mn(IV) reduction. Weak acid (pH = 3.5) could destroy biofilm and manganese oxides (e.g., MnO) on mineral surfaces to promote the leaching process. Kinetic studies show that the pyrolusite leaching process belongs to mixed control by solid film diffusion control and chemical reaction control. The innovative process may be cost-effective and green, with a great potential for future applications.
Chapter
A mature technology of lithium-ion batteries (LIBs) is applied in various electronic devices. The wide application of LIBs has brought large quantities of spent batteries, which has become a global problem. Owing to unfavorable effects of spent LIBs on the economic and environmental aspects, much effort has been made in many countries to manage and recycle the waste batteries. Owing to several restrictions in conventional recycling methods, the use of microorganisms has attracted increasing attention. The bio-hydrometallurgical approaches realize the win-win situation of environmental and economic benefits. In this chapter, the information available on the basic principles and recent developments of the bioleaching of metals from LIBs are reviewed in detail. Additionally, this chapter gives an overview of the previous studies performed in this field. Furthermore, the challenges, limitations, and potential solutions for applying more efficient bioleaching approach for recovery of metals from LIBs are highlighted.
Article
End of life waste Lead (Pb) acid batteries are one of the largest sources of secondary lead production globally. Recycling lead by melting down used batteries is a commercial trade all over the world; but, regrettably, reprocessing lead from end of life batteries is reported for anthropogenic lead exposures causing harsh human health consequence and environmental pollution. The current research intends to isolate and identify Lead (Pb) solubilizing bacteria from automobile waste deposits from Agartala city in Tripura state of India. Scanning Electron Microscope equipped with energy-dispersive X-ray characterization of the grounded lead sample was carried out, and the micrographs demonstrated scattered structures across the matrix. The X-ray diffraction (XRD) spectrum indicates the presence of Lead Oxide (PbO), Lead dioxide (PbO2), and Lead sulfate (PbSO4) in the collected samples. A single bacterium viewing observable growth on Pb supplemented plates was isolated and its Pb recovering capability was estimated through ICP AES analysis. Molecular characterization of the bacterium was investigated using 16S rRNA sequencing along with isolated culture was taxonomically grouped as Cupriavidus sp. The genomic DNA sequences were submitted in NCBI GenBank with the accession number MG171197. In the present case of inspection, the ability of the bacterial strain to recover Pb from end life battery waste was carried out in laboratory scale on a shake flask for 20 days. The experiment conducted under optimum bioleaching parameters with initial pH 6, 5% w/v of microbial culture, 2% pulp density and 2 g/100 mL dextrose concentration at 30 °C temperature with a speed of 200 RPM resulted in 67% Pb recovery from the battery sample. This investigation emphasizes the significance of Pb recycling ability of native bacterial isolate for efficient Pb bio-recovery from end of life waste batteries.
Article
Conventional leaching methods for Manganese (Mn) recovery require strong acids and are threatening to the environment. Alternatively, the use of microbes for Mn recovery is environment friendly in nature. The present investigation compares the capacity of pure and mixed cultures of native bacterial strains for bioleaching of low grade Mn ores. The ability of the isolated microorganisms to recover Mn was evaluated in shake flasks for 20 days under optimized conditions of pulp density (2%), sucrose concentration (2/g/100 ml), initial pH 6.5 and 30 °C incubation temperature. In pure culture form, Acinetobacter sp. MSB 5 (70%) was found to have a higher bioleaching potential than Lysinibacillus sp. MSB 11 (67%). Mixed culture of Acinetobacter sp. MSB 5 and Lysinibacillus sp. MSB 11 was found to perform better than the pure cultures with 74% extraction of Mn. The presence of mixed culture increased the dissolution rate and the recovery percentage of Mn. The respective growth pattern of the cultures was in synchronisation to their Mn bioleaching performances. This study underlines the importance of mixed cultures and, Mn solubilising activity of native bacterial strains for efficient Mn biorecovery.
Article
Electrolytic manganese residue (EMR) is a solid waste generated in filters after sulfuric acid leaching of manganese carbonate ore, which contains manganese, ammonia nitrogen and heavy metals that cause damage to environment. In fact, leaching and recovery of manganese and ammonia nitrogen from EMR is the key to the harmless treatment and resource utilization of EMR. In this study, electric field was applied to leach manganese and ammonia nitrogen from EMR. In addition, carbonate precipitation and struvite precipitation methods were used to recover manganese and ammonia nitrogen from leaching solution. The results showed that the leaching efficiencies of manganese and ammonia nitrogen were 88.07% and 91.50%, respectively, when the current density was 35 mA/cm², the mass of H2SO4 and H2O2 were 9.15 wt% and 3.33 wt%, solid-liquid ratio was 1:5 at temperature of 40 °C leached for 120 min. All heavy metals content in leached EMR except Ni and Cd were below national standard (GB 15618–2018) by electric field enhanced leaching. Meanwhile, manganese and ammonia nitrogen in leaching solution were fractional recovered by MnCO3 and struvite, and the recovery efficiency of manganese and ammonia nitrogen was 98.6% and 98.0%, respectively. This study provides a direction for the effective harmless treatment and resource utilization of EMR.
Article
Manganese is a strategically important metal that is widely used in industrial applications such as steel, catalysts, and batteries. Manganese generally presents as manganese dioxide (MnO2) in most of the ores. As MnO2 is stable in acid or alkaline oxidizing conditions, manganese extraction must be performed under reducing conditions to convert the insoluble Mn(IV) to soluble Mn(II) in aqueous medium. In this regard, two processes are followed viz. reduction roasting followed by leaching and reductive leaching. The major disadvantage of the reduction roasting process is the intensive energy consumption, high investment and operating costs as well as the occasional release of harmful gases. The hydrometallurgical reductive leaching method possesses the advantages of energy conservation and one-step leaching process. The reducing agents used for leaching are either pure inorganic or organic chemicals or sometimes new kinds of reducing agents such as agricultural and biomass wastes. The present review summarizes the process developed for extraction and recovery of manganese from ores using different kinds of reducing agents. The parameters affecting the leaching of manganese and reactions involved are reviewed and discussed.
Article
Present work deals with synthesis of copper nanoparticles at the room temperature, using two aqueous extracts prepared from green and dry leaves of Aloevera and Geranium ( Pelargoniumgraveolens ). Finely cut leaves were placed in the flask with the distilled water. The mixture was boiled for 15 min at the temperature of 60°C. After boiling, the mixture was centrifuged and pure extract was used for copper nanoparticles synthesis. The source of copper ions was leaching solution obtained from the bioleaching of copper shale (Kupferschiefier) using chemolithotrophic bacteria such as Acidithiobacillusfrerooxidans . The bioleaching procedure was performed in the column reactor.
Research
Mineral resources have been counted as public assets with economic benefit since time immemor-ial. Due to the rising issue of decreasing mineral deposits, recovery of metals from several waste residues has become progressively more essential. Novel and efficient recycling processes have been on the rise globally. Manganese (Mn) as the fourth most industrially applicable metal generates an extensive quantity of metallic waste which not only leads to loss of precious metal but also results in environmental toxicity. Globally, around 7 million tons of high-grade ores are produced , whereas 8 million tons of Mn alloys are produced yearly. Therefore, it is of greater significance to recover and recycle Mn from various waste residues. Various physical and biological techniques have been developed for recycling Mn from waste residues. Traditional Mn extraction processes are costly and labor intensive in nature, on the contrary, bioleaching techniques using diverse microorganism's, form the basis of an efficient, eco-friendly, and economically sustainable process of metal recovery. The quick progress in current methodologies to counteract the fast consumption of innate mineral resources involves the proper utilization of unused waste residues containing industrially important metals like Mn. This review focuses to enumerate diverse features of Mn recovery, efficient methodologies, bioleaching of Mn, merits of Mn bioleaching, and applications of recycled Mn along with the futuristic applications. Manganese recovery by means of biol-eaching will play a major role in changing the present situation where innate assets are quickly diminishing and substitute for metal recovery methodologies are the demand of this time. ARTICLE HISTORY
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To extend the knowledge on the microbial diversity of manganese rich environments, we performed a clone library based study using metagenomic approach. Pyrosequencing based analysis of 16S rRNA genes were carried out on an Illumina platform to gain insights into the bacterial community inhabiting in a manganese mining site and the taxonomic profiles were correlated with the inherent capacities of these strains to solubilise manganese. The application of shot gun sequencing in this study yielded results which revealed the highest prevalence of Proteobacteria (42.47%), followed by Actinobacteria (23.99%) in the area of study. Cluster of orthologous group (COG) functional category has 85,066 predicted functions. Out of which 11% are involved in metabolism of amino acid, 9% are involved in production and conversion of energy while Keto Encyclopedia of Gene and Genomes (KEGG) functional category has 107,388 predicted functions, out of which 55% are involved in cellular metabolism, 15% are environmental and information processing and 12% are genetic information processing in nature. The isolated microbial consortia demonstrated visible growth in presence of high concentrations of Mn. Solubilisation studies resulted in 86% of manganese recovery after 20 days. The result presented in this study has important implications in understanding the microbial diversity in manganese contaminated mine tailings and their role in natural geochemical cycling of Mn.
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With the depletion of high-grade manganese ores, Mn ore tailings are considered valuable secondary resources. In this study, a process combining high-gradient magnetic separation (HGMS) with hydrometallurgical methods is proposed to recycle fine-grained Mn tailings. The Mn tailings were treated by HGMS at 12,500 G to obtain a Mn concentrate of 30% Mn with the recovery efficiency of 64%. The Mn concentrate could be used in the ferromanganese industry. To recover Mn further, the nonmagnetic fraction was leached by SO2 in an H2SO4 solution. Hydrogen peroxide was added to the leachate to oxidize Fe²⁺ to Fe³⁺, and the solution pH was adjusted to 5.0–5.5 with ammonia to remove Al, Fe, and Si impurities. The purified solution was reacted with NH4HCO3, and a saleable product of MnCO3 with 97.9% purity was obtained. The combined process can be applied to Mn recovery from finely dispersed weakly magnetic Mn ores or tailings.
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The commercial application of copper bioleaching, an environmentally-friendly approach for low-grade and secondary mineral resources recycling, has increased worldwide since the 2000s. As the world's second-largest economic entity and the largest developing country, China has the largest demand for metal resources, significantly advancing the theory and industrial technology of copper bioleaching. This paper reviews the exploration and application of copper bioleaching in China. Two typical bioleaching applications and technological processes, bioheap leaching at the Zijinshan Copper Mine and bioheap leaching at the Dexing Copper Mine, are introduced. The considerable research completed by researchers is summarized, especially focusing on the isolation and identification of leaching bacteria, the bioleaching mechanism and interface reactions, multistage percolation behavior, bioleaching system reconstruction, the multiphysics coupled model, and enhanced copper bioleaching from waste printed circuit boards (WPCBs). Based on this investigation in China, key trends and prospects in copper bioleaching-such as efficiency improvement, environmental protection, and improved technology applications-are proposed.
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Electrolytic manganese residue (EMR)is a kind of solid waste generated along with the production of electrolytic manganese, with a high content of quartz and metals. The former can be used as silicon fertilizer for crops after activation, while the latter may cause harm to surrounding environment due to their toxicity. The aim of this study was to investigate the effects of bacterial on the activation of silicon and fixation of heavy metals in EMR by using microbe-mineral direct contact and indirect contact methods. Mixed cultures of Bacillus mucilaginosus (BM)and Bacillus circulans (BC)were used to achieve activation of silicon in EMR, and the leaching concentration of Mn, Co and Ni and their chemical forms in the leaching residue were also investigated. The results show that the microbe-mineral direct contact method has better performance for the activation of silicon in EMR with the available silicon in the leaching solution up to 163.27 mg L ⁻¹ than the indirect contact method. The metals (Mn, Co and Ni)remaining in the residue mainly exist as the stable state after bioleaching, with lower leaching concentration after bioleaching of 20 d. And the effect of silicon bacteria on activation of silicon and the fixation mechanism of metals including the effect of silicate and silicate bacteria is confirmed, and it is verified by the identification of metabolites and the analysis of chemical reaction process. This study investigates the treatment of EMR by using mixed silicate bacteria, and reveals the mechanisms of bacteria on the activation of silicon and fixaion of heavy metals in EMR. The bioleaching method not only provides silicon source for soil but also can realize the reclamation of EMR.
Article
Microscopic fungi (micromycetes) play an important role in rock alteration, often leading to the formation of insoluble biogenic oxalates on their surface. Oxalate crystallization under the influence of fungus Aspergillus niger (one of the most active stone destructors) was studied in vitro conditions on following Mn,Ca-bearing minerals of manganese ores: todorokite (Na0.36,Ca0.09,K0.06,Sr0.03, Ba0.02)0.56(Mn5.53,Mg0.47)O12∙3–4H2O and kutnohorite (Ca0.77,Mn0.23)(Mn0.74,Fe0.14,Mg0.11)(CO3)2. The underlying minerals and the products of their alteration were investigated via powder and single-crystal X-ray diffraction, optical microscopy, SEM and EDX methods. It was shown that more intense leaching of Ca-ions (compared to Mn-ions) from todorokite and kutnohorite leads to an earlier crystallization of calcium oxalates (predominantly whewellite) compared to manganese (lindbergite, falottaite). Crystallization of manganese oxalates on the surface of kutnohorite occurs in a more acidic (compared to todorokite) medium through the formation of mycogenic Mn,Ca-bearing oxides, which are close in composition and structure to todorokite. The possibility of structural evolution within the manganese oxalate crystalline phases caused by hydration and dehydration processes, which are responsible for changes in proportions of lindbergite and falottaite, derives from the similarities of falottaite and lindbergite crystal structures. The amorphization of falottaite in the temperature range of 70–80 °C suggests that formation of linbergite by falottaite dehydration occurs via amorphous precursor. The result can be used for developing efficient biotechnologies using fungi for industrial enrichment of poor manganese ores and environmental bioremediation.
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New magnetic materials for energy and information-processing applications are of paramount importance in view of significant global challenges in environmental and information security. The discovery and design of materials requires efficient computational and experimental approaches for high throughput and efficiency. When increasingly powerful computational techniques are combined with special non-equilibrium fabrication methods, the search can uncover metastable compounds with desired magnetic properties. Here we review recent results on novel Fe-, Co- and Mn-rich magnetic compounds with high magnetocrystalline anisotropy, saturation magnetization, and Curie temperature created by combining experiment, adaptive genetic algorithm searches, and advanced electronic-structure computational methods. We discuss structural and magnetic properties of such materials including Co- and/or Fe-X compounds (X = N, Si, Sn, Zr, Hf, Y, C, S, Ti, or Mn), and their prospects for practical applications.
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Probiotics are potential health-promoting microorganisms representing a significant health aid with diverse pharmaceutical applications. But its role in modulating the human gut microbiome necessities a profound analysis. Undoubtedly, the human gut is a reservoir of infinite species such as bacteria, viruses, fungi, etc. But host with chronic illness bids enrichment of the pathogenic strain which may alter the composition gut microbiome. Culture-based techniques are providing unclear taxonomic data where the possibility of the discrepancy is very high. Therefore the use of next-generation sequencing (NGS) analysis helps to explore depth understanding of the curd microbiome and can generate big genomic data. The present investigation aims to explore the microbial diversity of curd samples from different local dairy farms of Odisha, India using a metagenomic approach. The data read comprising 304,725 sequences totaling 148,546,295 base pairs were interpreted. Taxonomical distribution at different levels unfolded the absolute abundance of phylum, class, order, family, genus, and species within each microbial community. The most dominant species found to be Lactobacillus at order level is 49%, whereas phyla proteobacteria and firmicutes have shown taxonomic percentage abundance of 50.01% and 48.77%, respectively. However, nearly 26.41% of unclassified species from the Lactococcus genus were identified in the sample at different taxonomic levels. The metagenomics sequence data has been deposited to sequence read archive (SRA) of NCBI database under Bioproject PRJNA383620. The present study has vital implications in understanding the microbial diversity in curd samples with their role in human health and application in future pharmaceutical probiotic research.
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The coupled leaching of ocean polymetallic nodule and low-grade nickel sulphide ore in sulphuric acid solution was investigated, especially in performance on selective extraction of Ni, Cu, Co, and Mn. This work can be divided into three parts. First, the advantageous selective metal extraction conditions, parallel to the optimal coupled leaching conditions, were measured by coupled leaching tests which adopted the Ni, Mn, Cu, Co, and Fe dissolution efficiency. Under the optimal conditions, the extraction ratios of Ni, Mn, Cu, Co, and Fe are 96.8%, 97.3%, 92.2%, 97.9%, and 28.9%, respectively. Second, electrochemical tests revealed that multi-metal simultaneous extraction from two ores depends on the reduction-oxidation dissolution of a corrosion cell of the nodule cathode and the sulphide ore anode. The results showed that acidity and Fe³⁺ ion affected dissolution of both ores significantly; high valence manganese oxide reduction takes precedence which is in control of the Ni, Mn, Cu, and Co dissolution of the nodule; Ni, Cu, and Co extraction from the nickel ore is a course of sulphide minerals oxidative conversion which significantly affected by Fe²⁺-containing sulphide oxidation. Third, the separation performance of iron substance in the solution was determined by the transformation of minerals phases of the leached residues, showing that Fe-bearing minerals dissolved to Fe³⁺ ion then precipitated as iron vitriol or oxide during the selectively coupled leaching. The selectively coupled leaching of low-grade multi-metallic sulphide ore and oxide ore mainly rests with the transformation of Fe-containing species in the system.
Article
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The effect of Fe ³⁺ ions on the ocean manganese nodule reductive leaching in imitated sulphuric acid solutions was investigated.
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Electrolytic manganese residue (EMR), a by-product of the electrolytic manganese metal production process, contains several hazardous components such as ammonia nitrogen (NH3-N), soluble manganese, and heavy metals. In recent years, although a great number of treatment methods have been proposed, there is no mature and economical industrial process for treating EMR. Therefore, previous studies on separation/extraction (S/E) and solidification/stabilization (S/S) treatments of EMR are reviewed and are of great significance for further studies. The various treatment methods are summarized and evaluated, and the existing problems or prospects are given. The use of external field enhancement methods and appropriate auxiliary leaching agents in the S/E process can effectively improve the leaching efficiency. In the S/S treatment, it is found that the synergism of multiple solid wastes can increase the waste treatment capacity, which has significant environmental benefits and even can realize resource utilization. The research on manganese treatment has been found to have achieved remarkable results, but the problem of ammonia nitrogen in EMR still cannot be ignored and future research still has challenges. Further, based on the existing problems with harmless treatments of EMR, some suggestions are provided and the remaining challenges for future research are identified.
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A major apprehension is over microplastic pollution in the aquatic environment. These microplastics particles represent a novel medium in the aquatic environment, providing a substratum for various organic contaminants and for colonization of microorganisms. Microorganisms form a biofilm on the exterior of pollutants, consequential in a region known as a plastisphere, in which they interrelate and generate acid and different enzymes for microplastic degradation. The use of microbes for microplastic degradation has become a contentious exit indication as society focuses more on environmentally friendly pollution reduction methods. After both substantial and elemental degradation, biodegradation occurs, weakening the arrangement of polymers. Natural resource microbes have a significant effect on the reduction of plastic waste in the environment. The current review article discusses microbial colonization and degradation of microplastics present in aquatic ecosystems and the processes involved. While studying and considering how these microplastic particles have now turn out to be a recent environmental position within various aquatic environments, we emphasized the significance of colonization and microbial-assisted degradation of aquatic microplastics in this article.
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Biomining through bioleaching and bio-oxidation aims at recovering desired metals at the required specifications with lower environmental impact and costs from ores and waste streams. Research and developments related to the process technology and efficient implementation of this approach are advanced worldwide. Small particles of gold, a metal of higher interest, are mostly found in a matrix of sulfide-based minerals and not affordably recovered with conventional approaches encompassing cyanidation, pyrometallurgy, extreme heating (roasting), oxidation of ore samples at high pressure. Recently, advances in bio-oxidation have been made in addressing scientific and technical challenges that arise during the pilot and demonstration scales in the operations units in bioreactors and heaps. Through including high-throughput bacterial growth data and better process knowledge of the extraction and recovery approaches, bio-oxidation becomes more economically feasible and efficient. More advancements are necessary to evaluate the wide range of mineralogical structure of ores being processed, microbiological, and physicochemical that can significantly influence the bio-oxidation reaction within the different types of reactors (heap and continuously stirred tank reactors), the microbial interactions between metal and microbes, geographical localizations of the mining sector, economic as well as data interpretation by using advanced artificial intelligence methods toward obtaining optimized operation and efficiency. This review covers important advances and developments and associated industrial and academic research and challenges from the past few years for gold bio-oxidation.
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As the world’s second largest economy experiencing rapid economic growth, China has a huge demand for metals and energy. In recent years, China ranks first, among all the countries in the world, in the production and consumption of several metals such as copper, gold, and rare earth elements. Bioleaching, which is an approach for mining low grade and refractory ores, has been applied in industrial production, and bioleaching has made great contributions to the development of the Chinese mining industry. The exploration and application of bioleaching in China are reviewed in this study. Production and consumption trends of several metals in China over the past decade are reviewed. Technological processes at key bioleaching operations in China, such as at the Zijinshan Copper Mine and Mianhuakeng Uranium Mine, are presented. Also, the current challenges faced by bioleaching operations in China are introduced. Moreover, prospects such as efficiency improvement and environmental protection are proposed based on the current situation in the Chinese bioleaching industry.
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The release of petroleum and petroleum derivatives, such as polycyclic aromatic hydrocarbons (PAHs), in the environment owing to anthropogenic activities, has become a major global threat to human health and ecological equilibrium. It causes a number of diseases and petroleum hydrocarbon (PH) compounds bind to soil components, making their removal very difficult. In order to find an eco-friendly, convenient, and non-expensive way, indigenous PH degrading microorganisms are employed. Biofilm, being a syntrophic association plays an important role in PAH degradation. The three-dimensional structure of the biofilm matrix is found to facilitate the efficient and rapid degradation of PAH. Various physicochemical parameters of biofilm are found to regulate the efficacy of PAH degradation. In order to amend certain drawbacks of biofilm mediated remedi-ation, these days microbial electrochemical systems are increasingly being used for redressal of PH contamination, where the solid anode functions as an endless electron acceptor and the microbial activity is stimulated by bio-current in situ to guarantee the PH removal from contaminated soil and water. Following uptake of emulsified PH, it may be denatured by biofilm-associated enzymes or by biosurfactant molecules (such as rhamnolipids). The biomolecules synthesized by the bacterial cells further help in the expression of the specific genes thereby helping in the enhancement of PH degradation. ARTICLE HISTORY
Article
In this study, we analyzed toxic metals in leaves and marine sediment samples from the black mangrove in Sepetiba Bay to measure contamination and the use of Avicennia schaueriana leaves as bioindicator of toxic metal environmental pollution. The concentrations of heavy metals, namely cadmium (Cd), chrome (Cr), cobalt (Co), copper (Cu), lead (Pb), manganese (Mn), molybdenum (Mo), and zinc (Zn), were determined by using inductively coupled plasma optical emission spectrometry (ICP-OES). High concentrations of Mn were found in the leaves, while high concentrations of Mo and Zn were found in sediments. A. schaueriana leaves showed a tremendous capacity to absorb toxic metals, tolerating high concentration of manganese and may be used as phytoremediator for this toxic metal in impacted coastal marine environments. Herein, we reported for the first time the utilization of Avicennia schaueriana as a highly efficient accumulator for Mn.
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Synthetic microfbers (SMFs), tiny particles which gets fragmented from large fragments of large synthetic fbers having less than 10 µm in diameter, have gathered ubiquitously in each and every corner of the earth. After their release into the aquatic environment, they remain there without natural degradation. Furthermore, it can be anticipated that foating units are transported along the food chain leading to bioaccumulation. It has been esti- mated that approximately 10–20 Mt of large fabric products as garbage enter into aquatic system per annum. Recently, these synthetic fragments have been investigated as transport- ers of heavy metal ions (HMs) showing diferent types of interactions. Yet, the underlying mechanism of these types of interaction is not known, especially the factors stimulating this process and how badly they afect biotic communities. Through this article, a detailed sur- vey was carried out on the sources of microfbers and HMs into the aquatic environment, adsorption of diferent types of HMs on the SMF surface, mechanics favors these HM-MF interactions, particularly highlighting the signifcant roles of interaction on microbial bio- flm formation. Their collaborative efects which possess harmful efects on aquatic as well as terrestrial organisms was also discussed. Lastly, the future investigations should focus on rigorous research in this feld. This article to the best of our knowledge briefy describes the current research developments and emphasizes the vital function of the microorgan- isms on MFs-HMs interactions with the encouragement for rigorous research in this feld to reveal accurate mechanisms and decrease the hazards related with MF presence
Article
Ferruginous rhodochrosite with high impurity is difficult to be utilized by traditional beneficiation process due to the complex characteristics. Herein, a bioleaching process driven by Acidithiobacillus ferrooxidans was proposed to recover Mn and Fe in ferruginous rhodochrosite with economic and environmental benefits. The biogenic Fe³⁺, H⁺ and extracellular polymeric substances produced in bioleaching process significantly promoted the metal recovery and reduced the H2S emission. Optimal metal leaching efficiencies (95.94% of Mn and 97.54 % of Fe) were achieved in bioleaching group. Furthermore, the Mn and Fe mixed leaching solutions could be directly adopted to fabricate Mn-Fe oxide based materials (MFO). When applied as catalysts for peroxymonosulfate (PMS) activation, the as-synthesized MFO performed well for sulfathiazole (STZ) degradation with a 98.66% removal efficiency in 40 min. Both radical process and non-radical process occurred in the advanced oxidation process, which induced the generation of abundant active species of ̇OH, SO4⁻ and ¹O2. Meanwhile, charge transfer also contributed to STZ degradation. Favorably, MFO-3 exhibited good reusability in recycle study and showed adaptability towards various natural water matrixes. This research not only provided novel insights into the utilization of recalcitrant ferruginous rhodochrosite resources, but also enriched the strategy of PMS activator design for environmental remediation.
Article
Electrolytic manganese residue (EMR) has become a barrier to the sustainable development of the electrolytic metallic manganese (EMM) industry. EMR has a great potential to harm local ecosystems and human health, due to it containing high concentrations of soluble pollutant, especially NH4⁺ and Mn²⁺, and also the possible dam break risk because of its huge storage. There seems to be not a mature and stable industrial solution for EMR, though a lot of researches have been done in this area. Hence, by fully considering the EMM ecosystem, we analyzed the characteristics and eco-environmental impact of EMR, highlighted state-of-the-art technologies for EMR reduction, pretreatment, and reuse; indicated the factors that block EMR treatment and disposal; and proposed plausible and feasible suggestions to solve this problem. We hope that the results of this review could help solve the problem of EMR and thus promote the sustainable development of EMM industry.
Chapter
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Extensive allocation of synthetic microfiber (SMF) particles in the environment has harmful ecological impacts. These are tiny threads of synthetic fabrics having diameter less than 10 μm and are categorized under secondary microplastics, which are mainly composed of polyester, nylon, acrylic, polyethylene terephthalate, and polypropylene. These micropollutants are of increasing concern, especially due to their release into aquatic environments, including rivers and ocean. Primary sources of these tiny particles are laundering of apparel products, household sludge, direct throwing away of unused garments into the rivers and oceans, cosmetics, and cleaning agents. Approximately 13 million tons MFs all over the world along with coastal waste are entering the ocean yearly from which around 3 million tons are entering through rivers. Once these particles enter into aquatic sources, these are mistakenly ingested by various aquatic species and finally enter into the human body through consumption of MF-contaminated aquatic foods. Advanced microscopic and spectroscopic techniques are inspected for the successful detection of these synthetic micropollutants. Recent researches are focusing on the degradation of synthetic fibers using microbial enzymes that can be employed as an effective method. Strategies for plummeting microfiber pollution mainly focus on capturing these particles at source and consequently scheming of cost-effective remediation technologies. In the future, investigations are also required to develop techniques for an in situ remediation of these pollutants by enhancing natural attenuation using native microorganisms.
Article
This research aimed to address the issue of residual manganese in electrolytic manganese residue (EMR), which is difficult to recycle and can easily become an environmental hazard and resource waste. This research developed a method for the efficient and selective recovery of manganese from EMR and the removal of ammonia nitrogen (ammonium sulfate) under the combined action of ball milling and oxalic acid. The optimum process parameters of this method were obtained through single-factor experiment and response-surface model. Results showed that the recovery rate of manganese can exceed 98%, the leaching rate of iron was much lower than 2%, and the leaching rates of manganese and ammonia nitrogen after EMR ball grinding were 1.01 and 13.65 mg/L, respectively. Kinetics and mechanism studies revealed that ammonium salts were primarily removed in the form of ammonia, and that insoluble manganese (MnO2) was recovered by the reduction of FeS and FeS2 in EMR under the action of oxalic acid. Iron was solidified in the form of Fe2O3 and Fe2(SiO3)3. The technology proposed in this research has great industrial application value for the recycling and harmless treatment of EMR.
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.
Article
Challenges in the course of sustainable development, predominantly dearth of natural resources and waste management have suggested scientific community across the globe to seek novel processes to reduce ecological disturbances. For this purpose, microbial leaching process; a commercial application of bio-hydrometallurgy, could be a better option as it serves as a potential candidate for the retrieval of precious metals from low grade ores containing very low metal concentration, and sulfide minerals. It can also effectively remove excess of metals from soil and sediments and even recover metals from discarded solid waste. The present article intends to highlight the valuable metals which are being recovered by the process of microbial leaching from various kind of solid waste, the mechanism by which metals are mobilized, commercially used bioleaching processes along with their benefits and shortcomings, conditions and factors necessary for the optimization of the microbial leaching process. Emphasis is also being given to the extraction of metals from metal polluted soil and sediments using leaching organisms. It is to be concluded that microbial leaching is a revolutionizing technique bringing out both recovery of metals from solid materials including metal contaminated soil as well as remediation of soil using micro-organisms.
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The related microbial metabolomics on biological recovery of manganese (Mn) from Electrolytic Manganese Slag (EMS) has not been studied. This study aimed at open the door to the metabolic characteristics of microorganisms in leaching Mn from EMS by using waste molasses (WM) as carbon source. Results show Microbacterium trichothecenolyticum Y1 (Y1) could effectively leach Mn from EMS in combination with using waste molasses as carbon and energy sources. For the first time, Y1 was identified to be capable of generating and then metabolizing several organic acids or other organic matter (e.g., fumaric acid, succinic acid, malic acid, glyoxylic acid, 3-hydroxybutyric acid, glutaric acid, L(+)-tartaric acid, citric acid, tetrahydrofolic acid, and L-methionine). The production of organic acids by Y1 bacteria was promoted by EMS with the carbon source. This study demonstrated for the first time that metabolic characteristics and carbon source metabolic pathways of Y1 in bioleaching of Mn from EMS.
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The rapid decrease of natural resources and generation of huge amount of metallic wastes from mining industries has led to the focus of researchers to shift to alternative methods of waste benefaction and resource recycling. This study aims at the development of an eco friendly technique to recover Manganese (Mn) from mining waste residues using Acinetobacter sp. Bioleaching experiments were conducted in shake flasks at initial pH 6.5, 5% w/v inoculums and 2% pulp density at 30 °C with agitation speed 200 RPM and Acinetobacter sp. as inoculum. Mn recovery of 76% was recorded in 20 days. The analysis of the changes in cellular protein expression and conformation was carried out through sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE) and fourier transform infrared spectroscopy. The results reveal that bioleaching can alter protein expression and also result in conformational changes in protein structure. The present study sheds light on the greener alternative to recover and recycle manganese from wastes native bacteria. Exciting prospects for the utilization of mining wastes are in store in the near future; providing an economic and ecologically sound alternative to pyrometallurgical processes.
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There has been alarming depletion of manganese (Mn) reserves owing to the ongoing extensive mining operations for catering the massive industrial demand of this element. Moreover, the mining operations have been leading to the generation of Mn-rich waste, thereby contaminating both terrestrial and aquatic bodies. The current scenario necessitates the development of alternative processes for bioremediation as well as economic recovery of Mn from mining wastes. The present investigation aims to report the bioleaching of Mn by Lysinibacillus sp. from mining waste residues in the context of mine waste remediation. Results confirmed that the native isolate had a high Mn biosolubilization potential with a solubilizing efficiency of 84% at the end of a 21-day study under optimized conditions of pulp density 2% (< 150-μm particle size), pH 6.5, and temperature 30 °C. Fourier transform infrared spectroscopy (FTIR) studies followed by liquid chromatography mass spectrometry (LC-MS) analysis were used to ascertain the change in microbial protein conformation, configuration, and protein identification. The results revealed the expression of heat shock proteins (HSP) from the family HSP which is predominantly expressed in bacteria during stress conditions. This study represents the application of native bacterial strain in Mn biosolubilization. We foresee the utility of proteomics-based studies to provide a methodological framework to the underlying mechanism of metal solubilization, thereby facilitating the two-tier benefit of recovery of Mn from alternative sources as well as bioremediation of waste having high manganese content.
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A comprehensive study on fungus assisted bioleaching of manganese (Mn) was carried out to demonstrate Mn solubilization of collected low grade ore from mining deposits of Sanindipur, Odisha, India. A native fungal strain MSF 5 was isolated and identified as Aspergillus sp. by Inter Transcribed Spacer (ITS) sequencing. The identified strain revealed an elevated tolerance ability to Mn under varying optimizing conditions like initial pH (2, 3, 4, 5, 6, 7), carbon sources (dextrose, sucrose, fructose and glucose) and pulp density (2%, 3%, 4%, 5% and 6%). Bioleaching studies carried out under optimized conditions of 2% pulp density of Mn ore at pH 6, temperature 37 °C and carbon dosage (dextrose) resulted with 79% Mn recovery from the ore sample within 20 days. SEM-EDX characterization of the ore sample and leach residue was carried out and the micrographs demonstrated porous and coagulated precipitates scattered across the matrix. The corresponding approach of FTIR analysis regulating the Mn oxide formation shows a distinctive peak of mycelium cells with and without treated Mn, resulting with generalized vibrations like MnOx stretching and CH2 stretch. Thus, our investigation endeavors’ the considerate possible mechanism involved in fungal surface cells onto Mn ore illustrating an alteration in cellular Mn interaction.
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The study of the microbial ecology in extreme acidic environments has provided an important foundation for the development of mineral biotechnology. The present investigation reports the isolation, identification and molecular characterization of indigenous Manganese (Mn) solubilizing acidophilic bacterial strains from mine water samples from Odisha, India. Four morphologically distinct bacterial strains showing visible growth on Mn-supplemented plates of varying pH were isolated and identified. Mn solubilizing ability of the isolates was tested by growing them on Mn-supplemented agar plates. The appearance of lightening around the growing colonies of all the isolates demonstrated their Mn solubilizing ability in the medium. 16 S rRNA sequencing was carried out and the bacterial isolates were taxonomically classified as Enterobacter sp. AMSB1, Bacillus cereus AMSB3, Bacillus nealsonii AMSB4 and Staphylococcus hominis AMSB5. The evolutionary timeline was studied by constructing Neighbor-Joining phylogenetic trees. The ability of acidophilic microorganisms to solubilize heavy metals is supported by five basic mechanisms which include: enzymatic conversion, metal effluxing, reduction in sensitivity of cellular targets, intra- or extracellular sequestration, and permeability barrier exclusion. Such ecological studies undoubtedly will provide insights into Mn biogeochemical processes occurring in leaching environments. The application of acidophilic microbiology in mineral bio recovery and benefication has a large future potential.
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The current work was off-shoot of an attempt to isolate a thermophilic pyritic sulfur degrading bacteria in selective medium from a coal mine dump. This thermophilic bacteria (archaea) classified as Sulfolobus was tested for its feasibility to bioleach copper from a low grade Indian chalcopyrite ore (0.3% copper). With its prevalent ability to preferentially attack pyrite (a major phase in the ore), bioleaching was investigated at various parameters of pH, pulp density (PD), particle size, and temperature. A reflective high 85% copper recovery was obtained using <50 μm particles at 20% (w/w) pulp density, pH 2.0, 75 °C in 30 days. The copper dissolution was facilitated by iron (III) available in the leach liquor because of bacterial oxidation of pyrite present in the ore under acidic conditions. The biogenically generated Fe (III) ions enhanced copper dissolution from the chalcopyrite ore. The bioleaching of copper appeared to follow chemical control kinetic model with the reaction of lixiviant-Fe (III) and acid on the surface of the solid. Phase identification by XRD and SEM study corroborated the above mechanism of copper leaching.
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The requirement for manganese (Mn) has augmented extensively owing to the intense production of steel and the mounting paucity of natural deposits. The widespread mining, mineral processing, and further human activities have faced a severe consequence in the generation of massive quantity of manganese mining waste residues. The inappropriate supervision and unprocessed liberation of these wastes have resulted in the spread of Mn to the contiguous atmosphere, soil and groundwater pollution, and loads of severe ecological tribulations. Chronic and acute exposure of this metal pollutant leads to lethal consequences and is clinically categorized by the multiple symptoms of neurotoxicity including cognitive and psychiatric symptoms, Parkinson’s disease, manganism, motor system dysfunction, and other neurodegenerative diseases. The advancement of bioremediation technology focuses on accomplishing successful removal of these metal pollutants by increasing the effectiveness of microbes related to metal-solubilizing activities. This chapter describes a complete advance in the research on manganese environmental pollution, manganese compound-induced toxicity, and recent approaches for the microbial remediation of manganese pollutants.
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Manufacturing of manganese (Mn) compounds, their industrial applications as well as mining overburden, has generated a potential environmental pollutant. Occupational exposure to elevated levels of Mn occurs during mining, welding, smelting and other industrial anthropogenic sources. Chronic and acute exposure of this metal pollutant leads to adverse consequences and is clinically categorized by various symptoms of neurotoxicity including cognitive, psychiatric symptoms, Parkinson's disease, extra pyramidal signs, manganism, dystonia, and motor system dysfunction. The aim of this review is to summarize the possible mechanism underlying Mn compounds-mediated neurotoxicity leading to neurodegenerative diseases. Our review endeavours to examine recent advances in research on Mn-related environmental pollution, Mn-induced poisoning, molecular mechanisms underlying Mn-induced neurotoxicity with case studies as well as current approaches employed for treatment and prevention of Mn exposure.
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The purpose of this study is to test the feasibility of using mixed culture of iron and sulfur-oxidizing bacteria for the dissolution of metals from high-grade zinc and lead sulfide ore. Considering that the roll crusher could reduce the ore size to less than 2 mm, this size fraction was selected in order to study the possibility of removing mill circuit. Effects of parameters such as pulp density, initial pH, Fe2+, oxidation–reduction potential (ORP), and pH fluctuations were investigated, as well. The maximum Zn dissolution was achieved under the conditions of initial pH 2, initial 75 g/L FeSO4 · 7H2O, and pulp density of 50 g/L. The results indicated that under the optimum conditions, about 68.8% of zinc was leached during 24 days of bacterial leaching treatment. The lead recoveries were low (about 1%), because of precipitation of Pb as lead arsenate chloride. Furthermore, the surface studies by using SEM images showed that during chemical leaching the ore dissolution starts from surface discontinuities, but in bacterial leaching all surface becomes involved. In addition, in another process the ore was leached separately with sulfuric acid and sodium hydroxide, and then final results were compared to the bacterial leaching tests in order to find the optimum hydrometallurgical method to extract zinc and lead from these ores.
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Structural models determined by X-ray crystallography play a central role in understanding the catalytic mechanism of enzymes. However, X-ray radiation generates hydrated electrons that can cause significant damage to the active sites of metalloenzymes. In the present study, crystal structures of the multicopper oxidases (MCOs) CueO from Escherichia coli and laccase from a metagenome were determined. Diffraction data were obtained from a single crystal under low to high X-ray dose conditions. At low levels of X-ray exposure, unambiguous electron density for an O atom was observed inside the trinuclear copper centre (TNC) in both MCOs. The gradual reduction of copper by hydrated electrons monitored by measurement of the Cu K -edge X-ray absorption spectra led to the disappearance of the electron density for the O atom. In addition, the size of the copper triangle was enlarged by a two-step shift in the location of the type III coppers owing to reduction. Further, binding of O 2 to the TNC after its full reduction was observed in the case of the laccase. Based on these novel structural findings, the diverse resting structures of the MCOs and their four-electron O 2 -reduction process are discussed.
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The application of leaching process to extracting Mn from a low-grade manganese ore was investigated using a software based design of experiments. Four main parameters, i.e. sulfuric acid concentration, oxalic acid concentration, time and temperature were considered in a central composite response surface design. The recoveries of Mn and Fe were selected as response of design. The optimum conditions under which the Mn and Fe recoveries were the highest and the time and temperature were the lowest were determined using statistical analysis and analysis of variance (ANOVA). The results showed that Mn and Fe recoveries were 93.44% and 15.72% under the optimum condition, respectively. Also, sulfuric acid concentration was the most effective parameter affecting the process. The amounts of sulfuric and oxalic acid were obtained to be 7% and 42.50 g/L in optimum condition and the best time and temperature were 60 min and 65°C.
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In recent years, the comprehensive utilization of low-grade manganese oxide ores has received much attention due to the shortage of high-grade manganese ore resources. In this study, low-grade manganese oxide ores were treated by reduction roasting using chemically pure sulfur as a reductant. Then, the roasted samples were subjected to sulfuric acid leaching to extract manganese (Mn). The effects of roasting temperature, roasting time, S/Mn mole ratio, sulfuric acid concentration, leaching temperature, stirring rate, leaching time and liquid-to-solid ratio on the Mn and Fe leaching were discussed. The leaching efficiencies of 95.6% for Mn and 14.5% for Fe were obtained under the following optimized conditions: 550 °C of roasting temperature, 10 min of roasting time, 0.50 of S/Mn, 1.0 mol/L of sulfuric acid concentration, 25 °C of leaching temperature, 200 r/min of stirring rate, 5 min of leaching time and 5:1 of liquid-to-solid ratio.
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Manganese leaching and recovery from pyrolusite ore, was investigated by using H2SO4 as a leachant and H2O2 as a reducing agent. The effects of agitation, H2O2 concentration, H2SO4 concentration, liquid/solid mass ratio, leaching time and reaction temperature on manganese recovery were studied. The optimal leaching conditions were determined as 4.0M H2SO4 and 0.8M H2O2 using liquid–solid mass ratio of 5.0 for 90min at 40°C and ore particle size of 44–37μm. Under these conditions, the leaching efficiency was 92.0% for Mn. It was found that the use of H2O2 as a reducing agent for the reductive leaching of manganese increased the leaching rate. Analysis of the experimental results indicted that the leaching process is fitted by a chemical reaction model in temperature range 20–40°C, and at higher temperature, 45–70°C, the diffusion reaction model prevails. Activation energies for these models were calculated to be 49.5kJ∙mol−1 and 10.6kJ∙mol−1, respectively. Based on the experimental results, a separation method and flow sheet were developed and tested to separate high purity MnSO4.H2O (>99.4%). Comparison between the present results and that reported in the literature are given.
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Bacterial biomass, potential bacterial production and ectoenzymatic activity were measured at 4 stations along a trophic gradient at the Atlantic Barrier Reef off Belize (Central America). We investigated the changes in the trophic status of this system, which we hypothesized would also lead to changes in the bacterial community. The bacterial community of the oligotrophic station was characterized by low biomass (mean 7.2 mug C l-1) and low potential production rates (mean 9.2 mug C l-1 d-1) as determined by seawater cultures whereas at the most eutrophic station bacterial biomass (mean 18.6 mug C l-1) as well as potential bacterial production (mean 15.5 mug C l-1 d-1) was significantly higher. Oligotrophic bacteria exhibit high potential turnover rates (1.5 d-1). Ectoenzymatic activity measurements with fluorogenic-substrate analogs showed distinct differences in the expression of certain enzymes at different trophic conditions. Alpha- and beta-D-glucosidase activity declined from eutrophic to oligotrophic in both per volume and per cell while leucine-aminopeptidase activity per cell was inversely correlated with the trophic status of the environment. Differences in ectoenzymatic activity are indicated by differences in both v(max) and K(m). K(m) values of leucine-aminopeptidase clearly reflect the trophic situation. Substrate affinity was found to be higher in oligotrophic waters by 2 orders of magnitude as compared to eutrophic environments. Potential activity (v(max)) of the extracellular enzymes tested was found to be correlated to potential bacterial production and bacterial biomass.
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Pure manganese dioxide was successfully produced from low grade pyrolusite ore (β-MnO2) and sulphur slag. First, the reduction of β-MnO2, introduced as pure pyrolusite was studied using different ratios of elemental sulphur at different temperature (300–400°C), in air or in closed stainless tube. The reduction process was followed by leaching of Mn with H2O, 0.1, 0.5 or 1 M H2SO4. β-MnO2 was found to undergo a reduction process at obviously low temperature giving Mn3O4, MnS and MnSO4 depending on the applied conditions. The efficiency of Mn leaching ranged from 40 to 99%. The optimum conditions of reduction and leaching were applied to low grade pyrolusite from Um Bogma, Sinai and sulphur slag remained from the sulphuric acid industry. MnSO4 was prepared by concentrating the liquor extract. γ-MnO2 was produced either by precipitation from the liquor extract using ammonium peroxodisulphate or by electrodeposition on platinum anode. The products were characterised by X-ray diffraction, thermal and chemical analysis.
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This paper presents results of a feasibility study of recycling manganese furnace dust generated in production of ferromanganese and silicomanganese at Tasmanian Electrometallurgical Company, Australia. Dried man- ganese furnace dust contains about 20 wt% of carbon, in average 33.4 wt% of manganese and 1.3 wt% of zinc. Manganese in the dust is in the form of MnO, Mn 3 O 4 and MnCO 3 ; zinc is mainly in the form of ZnO and ZnSO 4 . Analysis of the zinc balance with dust recycling showed that to keep zinc intake at the acceptable level, it should be partly removed from the dust. In the reduction laboratory experiments, zinc oxide was reduced to zinc vapour by tar of the dust. Reduction of zinc oxide started at 800 o C and zinc removal rate increased with increasing temperature; removal of zinc was close to completion at 1100 o C. Optimal conditions for removing zinc from the dust include temperature in the range 1000-1150 o C, inert gas atmosphere and furnace dust frac- tion in the furnace dust-manganese ore mixture above 60%. In the sintering of manganese ore with addition of manganese dust in the sintering pot, zinc was reoxidised and deposited in the sinter bed. Removal of zinc in the sintering pot tests was in the range 4-17%. Up to 30% zinc removal was achieved from the bottom layer of the sinter bed. It can be concluded that zinc removal will be low during the processing of manganese fur- nace dust in the sinter plant. The zinc removal rate will be the highest when pelletised manganese furnace dust is added to the bottom layer of the sintering bed.
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Manganese is oxidized by a wide variety of bacteria. The current state of knowledge on mechanisms and functions of Mn2+ oxidation in two strains of Pseudomonas putida, in Leptothrix discophora SS-1, and in Bacillus sp. strain SG-1 is reviewed. In all three species, proteins bearing resemblance to multicopper oxidases appear to be involved in the oxidation process. A short description of the classification of Cu centers is followed by a more detailed review of properties and postulated functions of some well-known multicopper oxidases. Finally, suggestions are made for future research to assess the potential role of multicopper oxidases in bacterial Mn2+ oxidation
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The demand for metals is ever increasing with the advancement of the industrialized world. On the other hand, worldwide reserves of high grade ores are close to depletion. However, there exists a large reserve of metals in low and lean grade ores and other secondary sources. Metal recovery from low and lean grade ores using conventional techniques such as pyrometallurgy, etc. requires high energy and capital inputs which often result in the secondary environmental pollution. Thus, there is a need to utilize more efficient technologies to recover metals. Biohydrometallurgy, which exploits microbiological processes to recover metal ions, is regarded as one of the most promising and revolutionary biotechnologies. The products of such processes are dissolved in aqueous solution , thereby rendering them more amenable to containment, treatment and recovery. On top of this, biohy-drometallurgy can be conducted under mild conditions, usually without the use of any toxic chemicals. Consequently, the application of biohydrometallurgy in the recovery of metals from lean grade ores and wastes has made it an eco-friendly technology for enhanced metal production. This paper reviews the current status of biohydrometallurgy of low grade ores around the world. Particular attention is focused on the bioleaching of black shale ore and its metallogenic diversity in the world. The review assesses the status of bioprocesssing of metals to evaluate promising developments. Bioleaching of metals is comprehensively reviewed with the emphasis on the contribution of microbial community, especially fungal bioleaching coupled with ultrasound treatment. In this manuscript, the principles of bioleaching, their mechanisms, and commercial applications are presented. The case studies and future technology directions are also reviewed.
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Bioleaching is technologically feasible for extraction of manganese from low grade ores (containing manganese less than 35% by weight). The principle involves the non-enzymatic reduction of pyrolusite [Mn(IV) oxides] to +2 oxidation state by fungi with the production of metabolites such as oxalic acid and citric acid. In the present investigation, a fungal strain, Penicillium citrinum was isolated from top soil of Joda East manganese mine area, Tata Iron and Steel Company(TISCO), Orissa. Growth of the fungus was determined in terms of the final pH of the growth medium, biomass dry weight and total acid produced by the fungus. These data were used to evaluate the growth kinetics. Finally, it was used for bioleaching of low grade manganese ore. Effect of various parameters on in-situ leaching of manganese ore with P. citrinum such as (a) particle size (b) pulp density (c) sucrose concentration (d) inoculum size and (e) duration of leaching were studied. The maximum solubilisation of manganese (64.6%) was obtained with particle size of -45μm of the ore at pulp density of 2% (w/v), sucrose concentration 10% (w/v) and inoculum size of 10% (v/v) in a period of 30 days.
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Manganese recoveries from low-grade ores using organic acids as reducing agents were investigated in the present work. The acid leaching potential of both oxalic acid and citric acid were estimated. Manganese leaching amount were measured by using standard manganese curve and estimated by titration method. Effects of various acid concentrations on leaching efficiency were studied. The observed result suggested prominent manganese recovery of 66% by oxalic acid at 2 M concentration whereas citric acid had less effect on leaching showing leaching percentage upto 40% in 6 days. Acid leaching of manganese ore with both the acids gave a comparative data stating that oxalic acid leached better than citric acid.
Chapter
The “manganese-oxidizing group” is a phylogenetically diverse assemblage, which is characterized by the ability to catalyze the oxidation of divalent, soluble Mn(II) to insoluble manganese oxides of the general formula MnOx (where X is some number between 1 and 2). This results in the accumulation of conspicuous and easily detectable extracellular deposits of insoluble brown or black manganese oxides. Many different organisms have the ability to catalyze Mn oxidation, including a diverse array of bacteria, fungi, algae, and even eukaryotes (Ghiorse, 1984b). Among the prokaryotes, the ability to oxidize Mn is also quite widespread (Ehrlich, 1981; Ghiorse, 1984b, 1988; Marshall, 1979; Nealson, 1983); included are members of many phylogenetic and physiological groups: e.g., cyanobacteria, a diversity of heterotrophic rods and cocci, the sheathed (Leptothrix-like) and budding (Hyphomicrobium-like) bacteria, some purported autotrophic strains related to Pseudomonas species and the still-controversial Metallogenium group. The anaerobic lactobacilli, which utilize the Mn oxidation reaction as a protection against oxygen toxicity (Archibald and Fridovich, 1981, 1982) are not included, as they do not precipitate extracellular Mn oxides, but rather accumulate millimolar levels of protein-associated Mn in the cytoplasm. This chapter focuses on the process of Mn oxidation and also considers why so many bacteria have been identified as Mn oxidizers. It also offers suggestions that may help to clarify this complex area. Since there is no evidence of any advantage that Mn oxidation confers on bacteria, one might well ask the reason for the widespread distribution of this trait. The answer may lie in the Mn oxidation reaction itself. Under the conditions characteristic of most of the environments in which microbes are abundant, Mn is a very active element. Some critical features of Mn chemistry are summarized in Fig. 1 and are also discussed in more detail elsewhere (Ghiorse, 1988; Mulder and Dienema, 1981; Nealson et al., 1988, 1989; Pankow and Morgan, 1981). The oxidation of Mn(II) to Mn(IV) is thermodynamically favored under aerobic conditions, with a negative free energy of approximately 16 kcal/mol (Stumm and Morgan, 1981; Ehrlich, 1981; Nealson et al., 1988). However, the large activation energy of Mn(II) oxidation renders Mn(II) very stable in most aquatic environments (Stumm and Morgan, 1981). The activation energy barrier can be overcome by raising the pH (see Fig. 1) or by the addition of Mn-binding components, including Mn oxides themselves, which are excellent chelators of Mn(II) (Stumm and Morgan, 1981). The catalysis of Mn(II) oxidation by Mn oxides (autooxidation) makes it difficult to distinguish between chemically and microbially catalyzed Mn oxidation, especially in natural environments where organic chelators and Mn oxide particles may be abundant. Mn is, therefore, an element whose distribution and chemical speciation is kinetically controlled, thus allowing for the intervention of microbes and microbial products into the system. Some of the ways in which microbes might oxidize Mn(II) are shown in Table 1. If the pH or Eh of the environment is raised, if oxidants are produced by cells, or if binding of Mn(II) occurs so as to lower the activation energy, Mn(II) oxidation can rapidly proceed. With this in mind, it is not surprising that so many different bacteria have been identified as Mn(II) oxidizers, since the mechanisms of Mn oxidation are quite diverse (Ghiorse, 1988; Nealson et al., 1988, 1989). A true understanding of the “Mn-oxidizing bacteria” will likely await the time when it is possible to identify those reactions that confer some advantage to the bacteria and to disregard those that occur simply because of the dynamic chemistry of Mn(II). With regard to this, some of the recent studies of the mechanism of Mn(II) oxidation by cells, which include the isolation of Mn(II)-binding proteins (both intra- and extracellular) and polysaccharides, are particularly encouraging (Ghiorse, 1988; Nealson et al., 1989).
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Dumping of low-grade chalcopyrite encompasses several environmental problems. Despite slow dissolution rate, meso-acidophilic bioleaching is preferred for the extraction of copper from such ores. In the present study, meso-acidophilic bioleaching of a low-grade chalcopyrite in presence of an acid-processed waste newspaper (PWp) is discussed for the first time. The study illustrated a strong catalytic response of PWp with enhanced bio-recovery of copper from acid-conditioned chalcopyrite. A maximum of 99.13% copper recovery (0.36% Cu dissolution/day) was obtained in 6 days of bioleaching in presence of 2 gL- 1 PWp in contrast to only 5.7% copper in its absence. FTIR analysis of bioleached residues revealed similar spectral patterns to the original acid-conditioned ore in presence of PWp, thus indicating less development of passivation layer which was also confirmed through a complementary raman characterization of the bioleached residues. Further, a reaction mechanism (chemistry) was proposed suggesting the possible role of PWp as the electron donor under oxygen limiting conditions which facilitated microbial reduction of Fe (III). The resulting biochemical changes provided an energy source for the bacteria, thus allowing free flow of electrons through the ore surface, thus contributing towards enhanced bioleaching of copper.
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Fifty percent of sludges produced by wastewater treatment plants in the Province of Québec (Canada) cannot be spread on agricultural land because of their heavy metal content. In this study, leaching of heavy metals by bacteria (Thiobacillus) was achieved for the first time using an aerobic digested sludge. This was done in batch experiments with the addition of a substrate. Different options were tested with reference to time periods required for metal solubilization and sludge digestion. Metal solubilization simultaneous with sludge digestion proved to be a process both slow and difficult to apply. In aerobic digested sludges, metal solubilization took place within one day at a rate of 7·7 mg Cu per liter per day and at initial concentration of 1022 mg/kg dry sludge. Oxidation-reduction potential and pH affect copper solubilization. The importance of the ORP in copper solubilization explains the great rapidity with which this element is made soluble in aerobic sludges. Metal solubilization in aerobic sludges is thus possible and the high rates obtained in this study suggest that 1 day in a continuously-stirred tank reactor (CSTR) or 1 to 2 days in a batch reactor would suffice to to achieve high solubilization efficiencies.
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A combined novel process was developed to extract valuable metals from manganese–silver ore. The preferential dissolution of manganese from the primary materials was achieved through reductive leaching in dilute sulfuric acid medium with sodium sulfite as the reductant. Silver, which was enriched in the reductive leaching residue, was leached by complexation dissolution with hydrochloric acid and calcium chloride solution. Effects of process parameters on manganese extraction in the reductive leaching process were investigated, including the average particle size, the amount of sodium sulfite addition, sulfuric acid addition, liquid/solid ratio, leaching temperature and time. As for the silver extraction, the effects of Cl− concentration, hydrochloric acid addition, leaching temperature and time were also addressed. The results suggested that the extraction of manganese and silver could reach 99% and 92% respectively at the optimum conditions, while the high silica-containing product was obtained as the final residue.
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The contamination of aquatic sediments with metals is a widespread environmental problem. Coastal aquatic ecosystems with low hydrodynamics need to be periodically dredged in order to maintain the navigation depth and facilitate sailing; consequently large volumes of contaminated sediments need to be managed. Conventional remediation strategies include in-place sediment remediation strategies (e.g. in situ-capping) and relocation actions; in particular, landfill disposal and dumping at sea are still widely applied. Both this options are becoming unsustainable, due to problems associated with contaminant transport pathways, the uncertainties about long-term stability under various environmental conditions, the limited space capacity, costs and environmental compatibility. Alternative approaches have received increased attention; treatment and reuse of contaminated sediments is politically encouraged, but its application is still very limited. Because of the potential human health and environmental impacts of contaminated sediment, different chemical treatments are conventionally applied for contaminated sediments before reuse in other environmental settings. Environmentally friendly techniques developed for soils and other environmental matrices have been investigated for applications with sediments. Biotechnological approaches are gaining increasing prominence in this field and they are often considered as a promising strategy for the eventual treatment of contaminated sediments. In this paper an overview of the main treatment strategies potentially available for sediment contaminated with metals is given, together with a brief overview of the issue associated with the problem of the sediment management.
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Lateritic nickel ore from the Sukinda Mines, Orissa, India, was leached using Thiobacillus ferrooxidans, Bacillus circulans, Bacillus licheniformis and Aspergillus niger at 5% (w/v) solid: liquid ratio for 5-20 days. Maximum leaching of Ni was achieved with B. circulans (85%) and Aspergillus niger (92%) after 20 days. Bacillus circulans showed significantly higher rate of leaching than the other organisms giving 80% Ni extraction after 15 days. The importance and usefulness of heterotrophic organisms in metal extraction are discussed.
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One hundred and five strains isolated from aquifer sediments andEscherichia coli ML30S were tested for their ability to reduce manganese oxides. Eighty-two strains, includingE. coli, reduced manganese. In most cases the bacterial activity decreased the pH and Eh below 6.75 and 350 mV, respectively, enhancing a spontaneous and nonspecific reduction of manganese. However, for 12 strains the reduction was specifically catalyzed by bacteria; the high pH and Eh values would not permit a spontaneous reduction of manganese. Some of the most active strains were identified as genera common in soils and waters, i.e.,Pseudomonas, Bacillus, Corynebacterium, andAcinetobacter. Two strains were studied in detail. One of the strains, identified asPseudomonas fluorescens, required contact between the cells and the manganese oxides for reduction to occur. The reduction was inhibited by 15 mM of sodium azide. The other strain, identified asAcinetobacter johnsonii, catalyzed manganese reduction by an inductive and dialyzable substance which was excreted by the bacteria. The mechanism involved has not been previously demonstrated.
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A lab-scale circulation process of electrolytic manganese production with low-grade pyrolusite leaching by SO2 was introduced, exploring its feasibility and stability. Material balances of manganese and sulfur in circulation process were investigated. Results showed that the circulation process was entirely feasible. SO2 absorption efficiency of 99.66% and Mn extraction rate of 95.5% were obtained when a two-stage continuous countercurrent leaching process was used. The electrolytic manganese, meeting the needs of national industry grade standards, could be produced using purified leaching solution. 32 days' continuous running test proved good stability of the circulation process with the current efficiency of 78.1%, electricity consumption of 5396 kW h/t and total Mn recovery rate of 81.77%. The circulation process realized that the electrolytic manganese production with low-grade pyrolusite, has a wide prospect in industrial applications due to the advantages of stable performance, high efficiency and low consumption.
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Pressure leaching of manganese smelter dust with air as pressurized gas in a sulfuric acid medium was investigated. Optimum operating parameters were established as follows: liquid-to-solid ratio (mL/g), 5:1; initial sulfuric acid concentration, 120 g/L; leaching temperature, 120 °C; air pressure, 0.8 MPa; ore ratio (manganese smelter dust amount/pyrite amount), 1:0.5; leaching time, 2 h; and agitation speed, 500 r/min. Extraction rates of manganese and iron were obtained at 96.1% and 7%, respectively, under these conditions; and residual percentage of final acid was about 34.9%. Manganese can be effectively separated from impurities, such as iron, through leaching process. Leaching efficiency of manganese increased from 72.9% to 96.1%, whereas that of iron and the residual percentage of final acid both decreased with increase in leaching time from 40 min to 120 min. Pyrite was coated by elemental sulfur when temperature was higher than 119 °C, resulting in its inability to act as a reductant and to react with manganese dioxide. Therefore, leaching temperature must be lower than 120 °C. Pressure leaching technique for manganese smelter dust was proven to be effective and reliable.