Extraction of Precious Metals from Industrial Waste Using Microbial Technology

Table of Contents

1. Frontmatter

2. Chapter 1. Microbe Mediated Metal Recovery: A Sustainable E-waste Management Approach

   Sougata Ghosh, Sarbartha Chakraborty, Khalida Bloch

   Abstract

   Printed circuit boards (PCBs) used in electronic appliances contains significant amounts of metals, ceramics, and polymers. Various precious metals such as aluminium (Al), copper (Cu), gold (Au), silver (Ag), iron (Fe), lead (Pb), nickel (Ni), and palladium (Pd) are associated with the metallic components of the PCBs. More recently, diverse groups of microorganisms are employed for the metal recovery from the electronic waste. The bacteria, fungi, and microalgae can potentially biotransform or degrade the contaminants into simpler and less hazardous substances. The metal extraction from the electronic wastes (E-wastes) using microbes may involve several mechanisms that include processes such as bioaccumulation, biosorption, bioleaching, bioprecipitation, biooxidation and bioreduction. The most predominant process of bioleaching, may involve acidolysis, redoxolysis, and complexolysis. Hence, this chapter gives an elaborate account of role of various bacteria and fungi in the recovery of precious metals from the E-wastes. In some cases certain pretreatment is necessary before the microbes are brought into contact with the PCBs that enhance the efficiency of metal recovery. Certain acidophilic bacteria and filamentous fungi show more potent metal extraction ability. Moreover, the energy transfer for bacterial growth occurs through electron transfer that is responsible for responsible for the solubilisation of the metal present in the PCBs via oxidation. On the other hand, the bioleaching mechanism in the cyanogenic bacteria, is associated with the simultaneous generation of cyanide from glycine. Certain bacteria such as Acidiphilium acidophilum, Acidithiobacillus ferrivorans, Bacillus megaterium, Chromobacterium violaceum, Leptospirillum ferrooxidans, Magnetospirillum sp., and Pseudomonas putida with superior bioleaching properties are reported to recover metals from E-wastes. Similarly, the heterotrophic fungi from the genus like Aspergillus fumigatus, Candida, Penicillium, Phanerochaete, Purpureocillium, and Rhizopus are reported to play an effective role in the recovery of metals from PCBs. However, certain parameters such as type of microbe, incubation time, temperature, microbial density, pH, and carbon sources, should be carefully optimized for developing efficient metal recovery process from E-wastes which is a sustainable approach.

3. Chapter 2. Metal Solubilization Through Bioleaching: Microbial Action

   Sonia Sethi, Harshita Jonwal, Rishita Parihar

   Abstract

   Among the microorganism commonly studied for metal recovery, Acidothiobacillusferrooxidans is a well-known example that can oxidize iron and sulfur compounds, making it useful for the recovery of metals such as copper, zinc, and gold. Acidithiobacillusthiooxidans is another species of acidophilic bacteria that can oxidize sulfur compounds and leach metals such as copper and nickel from ores. Leptospirillumferrooxidans is a type of iron-oxidizing bacteria that is commonly used for the recovery of metals such as copper, gold, and zinc. Sulfolobusmetallicus is an archaeal species that thrives in extremely acidic environments and is capable of leaching metals such as copper, iron, and zinc from ores. Chromobacteriumviolaceum, a gram-negative bacterium, has been shown to accumulate silver and gold nanoparticles, making it a potential candidate for metal recovery. Pseudomonas fluorescens, a common soil bacterium, has been shown to have potential for the recovery of metals such as copper and nickel. One of the main advantages of microbial technology for metal recovery is its environmental sustainability. Unlike traditional metal extraction methods, microbial technology does not involve the use of toxic chemicals or generate harmful waste products. Additionally, this technology can be used to extract metals from low-grade ores that are not economically feasible to process using traditional methods. However, the use of microbial technology is not without its challenges. One major challenge is the optimization of conditions for microbial growth and metal recovery, which can be affected by factors such as pH, temperature, and nutrient availability. Another challenge is the need for large-scale infrastructure for microbial cultivation and metal recovery. In summary, microbial technology offers a promising alternative to traditional metal extraction methods, and ongoing research is exploring the potential of different microorganisms for this application. As this technology continues to evolve, it has the potential to become an important tool for sustainable metal recovery and contribute to the development of a circular economy.

4. Chapter 3. Biological Prospecting of Microorganisms for Metal Recovery

   Binu Gogoi, Rabina Gurung, Saurav Anand Gurung, Yadika Subba, Arun Kumar Rai, Arun Chettri

   Abstract

   Many litotrophic and organotrophic microorganisms are capable of metal recovery. Bacteria and fungi are capable of bioleaching, which is the conversion of solid compounds into soluble and extractable compounds. Platinum group metals (PGMs), rare earth metals (REEs) and different heavy metals such as Pt, Fe, and Zn, etc., can be absorbed by naturally occurring microbes rather than high metallurgical technologies because they use more energy and have a higher carbon footprint when compared to biotechnological and microbial approaches. Biomining and bioremediation are two widely employed technologies in biometallurgy involving the extraction, recovery and immobilization of metals, radionuclides from sites. This overview discusses the various microbe-metal interactions, biosorption, bioleaching, signficance of sourcing metals with the aid of microbes and biological methods given its low energy usage and minimal waste generated.

5. Chapter 4. Biorecovery of Metals from E-waste: An Elaborate Study

   Shristy Shreya, Vinod Kumar Nigam, Muthu Kumar Sampath

   Abstract

   In this digital era the increased manufacturing and consumption of electronics is causing major concern to environmentalists because of the nature and composition of the electronics that are discarded, i.e., e-wastes. The e-wastes are a serious cause for polluting soil mainly with metal toxicity. Discarded keyboards, mouse, RAM, mobile phones, refrigerators, televisions, and printed circuit boards (PCBs) are all in the category of e-wastes. These wastes are main reason for contamination of natural resources with metals like Cu, Ag, Ni, Mo, Au, Zn, Pb, Co, Cr, Sn, Fe, and Pd. But it has been researched that these metals can be removed using microbes, the technique of bioleaching. In the process of bioleaching, metals are extracted from ores and other materials containing metals. Major classes of bacteria involved in bioleaching are chemolithotrophic acidophiles (Acidithiobacillus ferroxidants, Acidithiobacillus thiooxdants, and Leptospirillum ferrooxidants and heterotrophs like Sulfolobus. Many factors are determinants of the bioleaching process; such as temperature, pH, aeration, microbe used, substrate used for growth of microbes and nutrients available to microorganism. ICP-MS is mainly used for determining the quantitative metal content in the e-waste samples being used for metal recovery.

6. Chapter 5. The Mechanism Behind Bio-recovery of Precious Metals from Industrial Wastes

   Shiwani Guleria Sharma, Nishu Sharma, Gurvinder Singh Kocher, Poonam Singla, Bimalpreet Singh, Amit Dhir

   Abstract

   Rapid Industrialization and the development of advanced technologies have hastened industrial activities. This generates millions of tonnes of waste annually, which is anticipated to ascend to about 2.2 billion tonnes per year by 2025. Several unrecovered metals in such a vast amount of waste are nonferrous metals such as aluminum, copper, chromium, etc., and precious metals such as silver, gold, and platinum. This improper management of waste generated may cause a consequential threat to mankind and is pernicious to the ecosystem. Contemporarily, industrial wastes are either disposed of in the environment, incinerated, or used in construction. Due to these malpractices, precious metals are lost and toxic compounds from wastes are leached into the environment. At present several methods are developed and devised for waste management along with metal recovery. It has been reported that metal recovery from industrial wastes is much easier and lesser power-consuming than from mineral ores. The use of microbial technology for the recovery of metals from industrial wastes has several advantages such as being environmentally friendly, high efficiency and economical. This chapter provides a comprehensive overview of the several methods and microbial-mediated mechanisms for recovery of precious metals from industrial wastes.

7. Chapter 6. Bio-recovery Approaches of Metals from Liquid and Solid Waste Streams

   Rym Salah Tazdaït, Djaber Tazdaït

   Abstract

   Over the last few decades, the waste products from urban and industrial activities have significantly increased worldwide. Solid waste includes all materials of solid consistency in their normal state resulting from human activities and discarded. Liquid wastes refer to chemically complex effluents that result from human activities. Solid waste recovery and recycling is an approach that reduces pollution related to the toxicity of waste, saves raw materials, and preserves the Earth's natural resources. Electronic waste, for instance, is considered one of the essential materials to be recycled because it contains different precious metals, such as Ag, Pt, Au, Pd, and Rh, and other metals, such as Cu, Hg, and Cd, which are known for their hazardous effects on human health and the environment. Recovering metal methods from liquid or solid wastes are based on physicochemical methods that use toxic chemicals and are energy-consuming. In response to stricter regulations and environmental concerns, research efforts are oriented toward practical and sustainable solutions to recover waste-containing metals. Biological-based methods (bioleaching, bioaccumulation, biosorption, biomineralization, etc.) using different groups of microbes offer a promising, eco-friendly, and effective approach to recovering metals from industrial and urban solid or liquid wastes. Thus, this chapter mainly focuses on current knowledge about the application of different mechanisms of bio-recovery to different waste-containing metals.

8. Chapter 7. Metal Recovery from Various Wastes: An Overarching Process for Wastes Management and Valorization

   Beauclair Nguegang, Phethego Gad Komane, Abayneh Ataro Ambushe

   Abstract

   Wastes are unwanted or unusable materials generated by various industries or living being. In the case of industries, wastes are any materials discarded after primary use and are generally worthless. However, wastes generated by various industries can be valorised since they contain a huge quantity of naturals resources and specifically metals of great economic values, which have been recovered using different technologies according to the type of wastes. In wastewater, metals are recovered using various methods including adsorption, membrane filtration, precipitation, cementation, ion exchange, ion flotation, sedimentation, desalination and bio-electrochemical methods. In solid and electronic waste (e-waste), various methods including plasma methods, electro winning, bio-cyanidation, chemical leaching, incineration and smelting, pyro metallurgical process, bioleaching, grinding and pulverizing techniques are widely applied to recover metals. The recovery of metals from various waste opens a route for waste valorisation and environmental pollution control. However, there are various drawbacks associated with the metals recovery process. Herein a detailed chapter on different types of wastes, their sources, their environmental, human health and socio economics impacts are presented. Different methods of metals recovery from various waste, advantages and drawbacks of metals recovering from waste considering future refinements and interventions are also elucidated.