Biotechnological Innovations in the Mineral-Metal Industry

Mining activities generate large quantities of wastes which pose threat to aquatic life, environment and human health, if left untreated. The generation of large quantities of wastewater with low concentrations of metals (for example: 10 mg/L Te(IV) in used solar cell leachate; 5–30 mg/L Cr, 0.14–21 mg/L Cu, 0.2–30 mg/L Ni, and 0.2–28 mg/L Zn in electroplating wastewater) makes the biological treatment processes more attractive, over physicochemical processes. Often, these wastes are laden with critical, scarce metals and are considered as resource due to their limited availability, cost and intended applications. Metal–microbe interactions through various redox reactions and acid-producing metabolism allow the extraction of base metals from ores. In the industrial biomining and bioleaching processes, microbes are employed for metal extraction from ores and the same can be applied for extraction of precious metals from low-grade ores, solid wastes and mine tailings. This book chapter presents an overview of metal–microbe interactions for potential biotechnological applications in the treatment of metal laden wastes generated in mining activities. These metal-microbe interactions include mobilisation (biomining) and immobilisation (biosorption, bioaccumulation, bioreduction and bioprecipitation) of metal ions present in different forms of wastes. Up to date studies on different microorganisms and biofilm systems employed for successful treatment and recovery of metals from wastes have been included along with underlying biochemical process. The chapter ends with a discussion on sustainable technological platforms such as bioelectrochemical systems, wherein the oxidation of organic contaminants in wastewater is coupled to the removal and recovery of metal ions from metal-bearing wastewater. Important studies on bioelectrochemical systems for the recovery of metal ions and associated removal mechanisms are provided.

Chalcopyrite is the main source of copper in the world, amounting to nearly 70% of the copper reserves. Nonetheless, chalcopyrite is highly recalcitrant to chemical and biological processing for copper extraction. Concentration by flotation and Cu recovery by pyrometallurgical techniques are still the main route for processing chalcopyrite concentrates, although they are unfeasible for copper extraction from low-grade ores that make up the most copper reserves. Acid bioleaching is a promising technique for extracting copper from low-grade copper ores, and the technology has been studied for decades, but there is still no commercial-scale bioleaching application for copper recovery from chalcopyrite concentrates. Bioleaching is practiced with low-grade chalcopyrite ores in heap leaching processes with ores of multiple sulfide minerals. Research in this area has probed electrochemical reactions, biological activities, and interactions with microbes and mineral surfaces to integrate operational models for chalcopyrite bioleaching. The purpose of this chapter is to review the evolution in the understanding of the chemical leaching and bioleaching of chalcopyrite in the last 20 years, and the progress achieved so far.

Despite nickel-bearing sulfide deposits having a large share of the world's nickel extraction, lateritic ore deposits contain more than 70% of the world's nickel reserves. Considering the limitations of producing nickel from sulfide reserves, the use of oxide reserves (laterites) for the production of nickel will be of great importance in the future. In this chapter, the applications of nickel and cobalt in various industries were described. Nickel and cobalt are mainly used in alloys of other metals. In addition, the most effective methods for extracting nickel and cobalt from lateritic nickel ores were examined. Due to the need for high energy, pyrometallurgical methods, as well as acid leaching, which uses a high amount of acid, are rarely used today. Therefore, the bacterial and fungal leaching methods (bioleaching), which is another hydrometallurgical process, and their mechanisms were explained. Bioleaching is a new prospective method for extracting valuable elements from hard-to-treat ores. The benefits of bioleaching low-grade ores are numerous in comparison to traditional methods due to their simplicity, using unskilled labor, low capital and operating costs, low energy consumption, and also the lowest negative environmental effects. In this processing operation, metals are dissolved from low-grade deposits by using microorganisms and their metabolic products. In addition, the final concentrations of iron in PLS can be decreased by biological methods. The most effective factors in the bioleaching process such as pH, size of sample particles, type of microorganism species, type of substrate, amount of inoculation, type of produced metabolic acid, the pulp solid to liquid ratio, salinity, temperature, and leaching time were explained. Heterotrophic bacteria such as Aspergillus, Penicillium, Pseudomonas, and Delftia were also successful at dissolving laterites, in addition to autotrophic bacteria such as At.ferrooxidans and At.thiooxidans. The presence of O₂ is considered a key factor in increasing the bio-reduction dissolution of nickel and cobalt of iron-containing minerals. In addition, high temperature, low density, and pH gained a higher dissolution rate of nickel and cobalt. The main mechanisms for autotrophic acidophilic (iron-oxidizing) and iron-reducing (dissimilatory iron-reducing bacteria) were acidolysis and redoxolysis. In general, biological dissolution and chemical control, respectively, had a greater effect compared with chemical dissolution and diffusion control on the dissolution rate of nickel and cobalt from the laterites. It was found that optimizing factors that affect the bioleaching of nickel and cobalt from nickel-containing laterites greatly increased the dissolution rate, recovered nickel and cobalt, and reduced iron dissolution.

Rare Earth elements (REEs) are a group of 17 elements, including 15 lanthanides, coupled with chemically similar yttrium and scandium. Due to their unique physical and electrochemical characteristics, they are applied in a wide variety of sectors of the global economy, standing as elements of strategic importance. The rapid increase in the demand, together with the limitations of their availability, have addressed the study of alternative, secondary sources of REEs as well as the development of eco-friendly processes to pursue their sustainable recovery. The need to set environmentally sound treatments has thus driven the scientific and technical interest towards bio-metallurgy, as a promising alternative to conventional methods. This chapter focuses on the application of biotechnological strategies to leach REEs from both primary and secondary sources. Biological-mediated leaching processes are discussed to point out the main mechanisms driving the extraction of REEs as well as the factors influencing their yields. The current state-of-the-art of REE bioleaching processes is figured out in order to highlight the potential for scale up as well as to address future research perspectives.

Lithium-ion batteries (LIBs) have emerged as the leading energy source for a diverse array of electronic devices, owing to their numerous benefits. Recycling LIBs is of significant importance since the ever-growing demand for them will shortly lead to massive disposal of spent LIBs and cause critical environmental problems. Spent LIBs can be considered as an excellent secondary source for various valuable metals since they approximately contain Mn (5–11%), Co (5%–25%), Ni (5%–10%), Li (5%–7%), Al (15–20%), Cu (5–7%), and graphite. Currently, LIBs’ recycling is mainly through the pyrometallurgical or high-temperature hydrometallurgical approaches, which have been substantiated to be effective for metal extraction. However, these processes come with some disadvantages such as inefficient energy consumption, high operational cost, toxic gas emission and production of secondary hazardous waste. The application of bio-hydrometallurgical methods has demonstrated remarkable efficacy in extracting metals from ores, flotation concentrates, tailings, and diverse waste materials. As an eco-friendly, low-cost, and energy-efficient method, bioleaching can be a superior replacement for conventional LIB recycling processes. In this chapter, new trends of LIB bioleaching, various factors influencing the LIB bioleaching, mechanisms, microorganisms, and regeneration of black mass have been thoroughly discussed. Moreover, the dominant challenges for industrial application of LIB bioleaching and several approaches for upscaling were summarized.

The increasing demand for various minerals and the limited high-grade mineral resources, concerning economic and environmental issues, has led to increasing research attention to the bio-beneficiation of low-grade mineral resources. Bio-beneficiation can be defined as employing microorganisms (including bacteria, fungi, algae, and yeast) in mineral processing and related industries. The high potential of microorganisms and their metabolites, especially extracellular polymeric substances (EPS), has been substantiated in bio-beneficiation processes. The bio-beneficiation is generally divided into two main categories: including bioflotation and bioflocculation. The bioflotation uses the microorganisms and their products (such as biomass and EPS) as flotation reagents. Microorganisms and their biomass can be applied as collectors, depressants, dispersants, and frothers in minerals floatation. Bioflocculation is another application of biotechnology in minerals processing. Almost all mineral processing techniques should be carried out in a wet environment. Therefore, dewatering and water recycling are essential steps in mineral processing plants. Microorganisms can be used as flocculants to decrease the dewatering time or minerals separation with high efficiency. Comprehensive information about flocculation, classification of flocculants, and the application of EPS as bioflocculant for selective bioflocculation of different minerals are provided in this chapter. The mechanism of the bioflocculation process and the effect of different parameters on the bioflocculation of various minerals have been investigated. Moreover, recent research on the application of bioflocculation in the selective separation or removal of minerals using different types of microorganisms has been briefly reviewed. Employing microorganisms for both bioflotation and bioflocculation can be a great strategy to save the environment and decrease process costs.

The key energy transition industries are reliant on critical minerals including but not limited to rare earth elements (REEs), copper (Cu), and lithium (Li). Furthermore, the ongoing COVID-19 pandemic, geopolitical conflicts, and climate change have exposed major bottlenecks in the security of global critical minerals and food supply chains. On the one hand, the major host minerals for REEs are primary and secondary phosphate minerals such as monazite and xenotime. On the other hand, phosphate and potash used in fertilizers are essential to improve the resilience of agricultural soils in a changing climate. Phosphate solubilizing microorganisms (PSMs) are often reported to be a major contributing factor for plant and soil nutrition by making insoluble phosphate into more soluble forms. Recent progress in understanding the molecular mechanisms of REEs solubilization from REEs-containing phosphate mineral, monazite, has suggested that in addition to protonation and complexation mechanisms either through organic acids production in heterotrophs or biogenic sulfuric acid in acidophiles, bacterial attachment has a pivotal role in bioleaching systems. This chapter highlights the recent application of PSMs for the bioleaching of critical minerals and emphasizes the significance of microbial function to narrow down potential microorganisms and associated dissolution pathways of these metals.

Surfactants are chemical compounds produced from petroleum feedstock, agro-based waste materials and microbial fermentation having wide variety of use in industries, pharmaceutical, agriculture, cosmetics, etc. These are amphiphilic moieties and chemically synthesised. These chemical compounds are toxic and are responsible for various harmful environmental problems. Recently, biosurfactants have gained lots of interest worldwide, because they are green-alternatives for surfactants. Biosurfactants are produced naturally from microorganisms like yeast, fungi and bacteria. These have both hydrophobic and hydrophilic groups which makes its unique and important in different industries. These organisms produce surface active metabolites or secondary metabolites and grow on water immiscible or oily surface. The surface active molecules help them to absorb, emulsify, wetting, solubilise and disperse the water immiscible substances. Biosurfactants are in demand and commercially promising due to their properties, i.e., low toxicity, higher biodegradability, environmental compatibility, foaming properties, shows stable activity at extreme pH, temperature and salinity, etc. Biosurfactants play very crucial role in mineral flotation. Heavy metal removal and mineral flotation is a very crucial process for industries (which commercially separates metals from ores by collecting them on the surface/froth layer—so the metals can be used commercially) and also for the environment. Biosurfactant mediated mineral floatation and heavy metal removal involves the metal ion sorption to sorbent material followed by floatation and floatation product collection. Using biosurfactants in replacement of surfactants for heavy metal removal and mineral floatation are actually effective, low cost, recyclable, reusable and environmental friendly. This chapter emphasises on removal of some metals from their respective ores using different biosurfactants. A probable mechanism of flotation by biosurfactant is also discussed.

Extraction of metals (leaching) is chemical or biochemical processes that utilize acids or microorganisms to enhance the suspension of metals from the primary and secondary sources by making them more amenable to dissolution in aqueous solutions (leachate). Recovery of metals from the leachates is an essential stage supported by additional purification processes such as precipitation of impurities, electrowinning, solvent extraction, chemical or biological adsorption, and ion exchange. In this study, especially biosorption and metal sulfide precipitation are overviewed and discussed. Biosorption is a process by which particular biomass such as bacteria, fungi, yeast, agricultural wastes, algae, and biowastes can able to bind with specific ions or other molecules from aqueous solutions. Metal sulfide precipitation can be highly effective in obtaining a high degree of separation of metal cations from complex leachates. Each of these techniques has advantages and drawbacks. Sometimes, a technique may not be effective in attaining higher metal recovery. Therefore, different recovery techniques are needed to recover the target elements from the complex leachates. Maybe a combination of two or three recovery techniques is required to recover metals from complex leachates. Additionally, the research activity highlighted that metal sulfide precipitation and biosorption processes have to limit factors that could hinder the process scale-up. Thus, more research is needed to evaluate the environmental impacts of metal recovery from leach liquors.

Acid mine drainage (AMD) is considered as a widely spread environmental problem that affects several countries involved in mining activities. Because of its high acidity as well as high metal(loid)s content generating environmental and health toxicity, AMD poses a threat to the surrounding ecosystems. Generally, when exposed to air and water, sulfide minerals undergo oxidative dissolution, which results in formation of AMD. Treatment of AMD at source is regarded to be an effective option; however, this might not be possible at all the sites. Technologies for treating AMD can be governed through the application of various physical, chemical, and biological processes to defuse acidity and remove metal(loid)s from the liquid streams. However, the physicochemical techniques are intended to achieve process viability and cost-effective when the treatment stream is of high volume and sulfate rich. In contrast to this, biological processes are economical to run and do not require a high concentrations of sulfate in the targeted stream. The present chapter critically reviews the state-of-the-art on available aerobic and anaerobic bioreactor technologies with an emphasis on anaerobic bioreactors for the treatment of AMD. In the remediation of AMD, the anaerobic process is a type of biological remediation that relies on neutralizing acidity and precipitating the metal contaminants by natural microbial consortia preferably the sulfate-reducing bacteria (SRB). However, as the AMD is associated with low organic matter, a supply of source of an external factor carbon that is required to complete the remediation process. Anaerobic bioreactors, such as membrane bioreactors, continuous stirred tank reactors, bioelectrochemical systems, up-flow sludge blanket reactors, are suitable bioreactor processes for the treatment of AMD wherein the syntrophic activity of both SRBs and other fermentative and few methane forming bacteria takes place. These anaerobic reactors through the application of SRBs are paving its path in the treatment of AMD because of its efficacy and cost-effectiveness. However, adding of external organic substances are required during the treatment of AMD with SRB which could play a pivotal role in determining the cost of the technology. This chapter describes briefly about the aerobic reactors and detailed information on the different types of anaerobic bioreactors available that can be made suitable for AMD treatment. Comparing the passive and active SRB-based alternatives, their substrate choice, and the recent advances in the anaerobic treatment of AMD along with future perspectives as an alternative to conventional techniques are discussed.

Several profound societal changes such as the shift towards renewable energies have created an ever-increasing demand for base and critical metals. Electronic wastes constitute a significant secondary source of such elements and a potential environmental hazard if disposed of improperly. In contrast to traditional methods of recycling e-waste, biohydrometallurgy is an environmentally friendly, low-cost, and energy-efficient alternative. Although processes developed in laboratories display promising yields, it is still premature to implement these biotechnological strategies on a larger scale as the bioleaching and biorefinery mechanisms are still poorly understood. Moreover, very few studies focus on fully biological processes, and most opt for more efficient hybrid approaches. Thus, this book chapter compiles the optimal parameters reported in recent studies, from waste pre-treatment to metal biorecovery, along with insights to complete and close the biohydrometallurgical recycling loop.

Bioreactors have proven capabilities to facilitate the biometallurgical extraction of important major and trace metal commodities, even from low-grade mineral ores and mine wastes. Yet, effective mineral processing with bioreactors requires a detailed and quantitative understanding of the underlying biogeochemical and mineralogical processes, the prevailing mass and energy transport limitations, as well as process control and monitoring concepts. In this chapter, we aim to introduce critical aspects of bioreactor design and operation, ranging from the pre-conditioning and properties of bioreactor material feeds, relevant geochemical reactions, kinetics, microorganisms and extraction conditions to process and performance control aspects. We also discuss select industrial applications, case studies and emerging technologies. We conclude that mineral processing with bioreactors is a challenging task that requires the input of concepts from various scientific and engineering fields and will play a critical role in satisfying the growing demand for metals and sustainable resource extraction in future.

This chapter reviews what has been accomplished in metal bio-extraction from so many secondary sources. In some cases, tailings were generated during processing of primary and weathered ores. It has been demonstrated that the use of native microorganisms, naturally present in drainages from mines where sulphide minerals are present, is very attractive in several locations, especially when it comes to the processing of ores with low levels of metals of interest as well as the tailings generated in these processes. In addition, several studies show the possibility of using the mineral substrates remaining in the rocks after such bio-extraction processes, for crops. This is a natural fertilization technique which uses such mineral substrates for augmenting the necessary nutrients for food production, in soils depleted by weathering/leaching or by the inappropriate and intensive use of chemical fertilizers, without affecting the balance of the environment. Following this line of research, there is also a need for technology to recover elements from electronic scraps, bearing in mind that some of them are also used as micronutrients for human beings, especially given the short lifespan of modern electronic equipment. Latterly, electronic waste can encompass dozens of different elements such as base metals, precious metals, rare earth and several heavy metals. Several processes have been used for extracting/recycling those metals. Bearing this in mind, the biotechnological approach plays a pivotal role as a very attractive and cost-effective way for processing such wastes and so many others being dumped in the environment, as natural resources are available in the environment and can be used without much expenses as it is the case of so many microorganisms.