Metal contamination in the environment is a persisting global issue. The metal reservoirs in the earth have declined due to society’s needs and due to uncontrolled mining activities. Therefore, the idea to recover metals from waste streams has emerged. In this thesis, cost competitive technologies such as adsorption using agro-wastes and precipitation using an inverse fluidized bed (IFB) reactor were investigated, with special emphasis on the recovery of base metals. Groundnut shell showed good potential for metal (Cu, Pb and Zn) removal. From artificial neural network modeling, the performance of the sulfate reducing bacteria (SRB) was found to be strongly pH dependent; the removal efficiency of Cu and Zn in the IFB at pH 5.0 was >97%. Electronic waste is a good candidate as secondary metal resource. The recovery of Cu from computer printed circuited boards (PCBs) using biogenic sulfide precipitation was investigated as well. Using this technology, Cu could be recovered at ~0.48 g Cu/g PCBs.

Waste electrical and electronic equipment (WEEE) generation is a global problem. Despite the growing awareness and deterring legislation, most of the WEEE is disposed improperly, i.e. landfilled or otherwise shipped overseas, and treated in sub-standard conditions. Informal recycling of WEEE has catastrophic effects on humans and the environment. WEEE contains considerable quantities of valuable metals such as base metals, precious metals and rare earth elements (REE). Metal recovery from WEEE is conventionally carried out by pyrometallurgical and hydrometallurgical methods. In this PhD research, novel metal recovery technologies from WEEE are investigated. Using acidophilic and cyanide-generating bacteria, copper and gold were removed from crushed electronic waste with removal efficiencies of 98.4 and 44.0%, respectively. The leached metals in solution were recovered using sulfidic precipitation and electrowinning separation techniques. Finally, a techno-economic assessment of the technology was studied. This research addresses the knowledge gap on two metal extraction approaches, namely chemical and biological, from a secondary source of metals. The essential parameters of the selective metal recovery processes, scale-up potential, techno-economic and sustainability assessment have been studied.

This book presents an assortment of case-studies pertaining to the use of sustainable technologies for heavy metal removal and recovery from mining and metallurgical wastes, construction and demolition wastes, spent catalysts and electronic wastes. Wastewaters from diverse industrial and mining activities have caused pollution problems, but these sectors also serve as a hotspot for metal recovery. Several metal removal technologies based on physical, chemical and biological processes have been successfully implemented in full-scale operation, while metal recovery, which is beneficial for economic and environmental reasons, is still limited due to challenges arising from downstream processing. For instance, microbial recovery (bioleaching) of metals from their ores is an established technology with a number of full-scale applications. Bioleaching of electronic wastes to recover metals is also a highly promising technology with low environmental impact and high cost-effectiveness; yet, this technology is still at its infancy. As the individual chapters of this book focuses on the applications and limitations of different technologies, this book will serve as an excellent resource for chemical engineers, environmental engineers, mining engineers, biotechnologists, graduate students and researchers in these areas.

This book is offered as a practical primer on the hydrometallurgy of nonferrous metal reclamation from industrial wastes, as well as a brief discussion of pyrometallurgy, biological, and other separation processes. The objectives are to acquaint nontechnical readers with the subject as well as providing a detailed survey of current research and industrial practice to technical readers concerned with the management of industrial waste.

Metal contamination in the environment is one of the persisting global issues since it not only disturbs the environmental quality but also the environment and human health. The major contribution to this problem arises mainly from anthropogenic activities such as industries. Metal scarcity has become more severe lately where some elements have been predicted to be fully eradicated in several decades from the earth crust. Recently, researchers have focused their attention to recover these metals from the waste stream and reuse it in industrial production processes. The use of agricultural wastes as a potential low cost adsorbent for heavy metal removal from wastewater is one of the most versatile technologies. In this study among the different adsorbents tested, groundnut shell established high removal efficiencies with fewer requirements for further post treatment for Cu, Pb and Zn removal. Furthermore, the batch experiments on the main effects of process parameters (pH, adsorbent dosage, contact time and initial metal concentration) showed a major effect on metal uptake and removal efficiency. For material regeneration, 0.2 M HCl was the most effective desorbing solution that did not alter the efficiency, up to three cycles of adsorption and desorption. The use of sulfate reducing bacteria (SRB) in bioreactors is another technology that can be applied for the treatment of metal contaminated wastewater. The SRB reduce sulfate into sulfide which further reacts with metals to form metal sulfide precipitates. The inverse fluidized bed (IFB) bioreactor is the configuration which shows prominence in utilizing SRB technology for metal contaminated wastewater treatment. Two IFB bioreactors were operated at different pH (7.0 and 5.0). The sulfate reducing activity (SRA) at pH 7.0 was higher than at pH 5.0, which shows that pH is the main factor that affects SRA. However, thiosulfate showed a higher efficiency than sulfate as an alternate electron acceptor. The sulfide produced using thiosulfate as the electron acceptor was 157.0 mg/L, while only 150.2 mg/L was produced using sulfate and it required an adaptation period at pH 5.0 prior to successful operation. Moreover, the IFB had shown its high efficiency for Cu, Ni and Zn removal from synthetic wastewater. The removal of Cu and Zn were more than 90% at pH 7.0 and 5.0, at an initial metal concentration of 25 mg/L. On the other hand, Ni removal was not removed at an initial concentration of 25 mg/L as it showed toxic effects toward SRB. There are various types of metal contaminated waste streams which pose as a good candidate for metal recovery include electronics waste (e-waste). This e-waste has a high potential as secondary source of metal to recover especially base metals such as Cu, Ni and Zn. Printed circuit boards (PCBs) of personal computers were evaluated as the potential secondary source of Cu, Ni and Zn using hydrometallurgical and sulfide precipitation methods. The optimal conditions for metal leaching were 0.1 M HNO3 with a liquid to solid ratio of 20 using PCBs of 0.5 - 1.0 mm particle size at 60 °C which resulted in 400 mg Cu/g PCBs. With sulfide precipitation at a stochiometric ratio of 1:1 (Cu:S2-), the recovery of Cu was very effective up to 90% from the leachate which accounted to approximately 0.41 g Cu/g PCBs, while Ni and Zn recovery were 40% (0.005 g Ni/g PCBs) and 50% (0.006 g Zn/g PCBs) for leachate from an upflow leaching column, respectively. This indicates Cu can be recovered from PCBs using sulfide precipitation.

Increasingly stringent environmental regulations and industry adoption of waste minimization guidelines have thus, stimulated the need for the development of recycling and reuse options for metal related waste. This book, therefore, gives an overview of the waste generation, recycle and reuse along the mining, beneficiation, extraction, manufacturing and post-consumer value chain. This book reviews current status and future trends in the recycling and reuse of mineral and metal waste and also details the policy and legislation regarding the waste management, health and environmental impacts in the mining, beneficiation, metal extraction and manufacturing processes. This book is a useful reference for engineers and researchers in industry, policymakers and legislators in governance, and academics on the current status and future trends in the recycling and reuse of mineral and metal waste. Some of the key features of the book are as follows: Holistic approach to waste generation, recycling and reuse along the minerals and metals extraction. Detailed overview of metallurgical waste generation. Practical examples with complete flow sheets, techniques and interventions on waste management. Integrates the technical issues related to efficient resources utilization with the policy and regulatory framework. Novel approach to addressing future commodity shortages.

State-of-the-art metals treatment and recovery technologies to assist in identifying waste management options.

This book covers the principles, underlying mechanisms, thermodynamic functions, kinetics and modeling aspects of sustainable technologies, particularly from the standpoint of applying physical, chemical and biological processes for the treatment of wastewater polluted with heavy metals. Particular emphasis has been given to technologies that are based on adsorption, electro-coagulation, bio-precipitation, bio-solubilization, phytoremediation and microbial electrolysis. Metal contamination in the environment is one of the persisting global issues. The adverse health effects of heavy metals on human beings and its impact on the environment has been well-documented. Several physico-chemical and biological technologies have been successfully implemented to prevent and control the discharge of industrial heavy metal emissions. On the contrary, metal resource depletion has also accelerated dramatically during the 20th century due to rapid advances in industrial engineering and medical sciences, which requires large amount of raw materials. To meet the global metal demand, in recent years, novel research lines have started to focus on the recovery of metals from metal contaminated waste streams. In order to conflate both metal removal and recovery, new technologies have been successfully tested, both at the lab and pilot-scale. The target audience of this book primarily comprises of research experts, practicing engineers in the field of environmental/chemical technology and graduate students.

This book, besides discussing challenges and opportunities, will reveal the microbe-metal interactions and strategies for e-waste remediation in different ecosystems. It will unveil the recent biotechnological advancement and microbiological approach to sustainable biorecycling of e-waste such as bioleaching for heavy metal extraction, valorization of precious metal, biodegradation of e-plastic, the role of the diverse microbial community in e-waste remediation, genetically engineered microbes for e-waste management, the importance of microbial exopolysaccharides in metal biosorption, next-generation technologies, omics-based technologies etc. It also holds the promise to discuss the conservation, utilization and cataloging indigenous microbes in e-waste-polluted niches and promising hybrid technology for sustainable e-waste management. Revolution in the area of information technology and communication is constantly evolving due to scientific research and development. Concurrently, the production of new electrical and electronic equipment also thus uplifting in this era of revolution. These technological advancements certainly have problematic consequences which is the rise of huge amounts of electronic obsoletes or electronic waste (e-waste). Improper management of both hazardous and nonhazardous substances of e-waste led to a major concern in our digital society and environment. Therefore, a sustainable approach including microbial candidates to tackle e-waste is the need of the hour. Nevertheless, the continuous demand for new-generation gadgets and electronics set this high-tech evolution to a new frontier in the last few years. With this continuing trend of technological development, e-waste is expanding exponentially worldwide. In the year of 2019, the worldwide generation of e-waste was approximately 53.6 Mt, of which only about 17.4% of e-waste was collected and recycled, and the other 82.6% was not even documented. E-waste contains various heterogeneous waste complexes such as metals (60%), blends of many polymers (30%) and halogenated compounds, radioactive elements and other pollutants (10%), respectively. The sustainable, efficient, and economic management of e-waste is thus, a challenging task today and in the coming decades. Conventional techniques such as the use of chemicals, incineration and informal ways of e-waste dismantling trigger serious health risks and contamination to the human population and environment, respectively due to the liberation of toxic and hazardous substances from the waste. In this context, bio-candidates especially microorganisms could be sharp-edged biological recycling tools to manage e-waste sustainably. As microbes are omnipresent and diverse in their physiology and functional aspects, they offer a wide range of bioremediation.

The electrochemical plating of Cu, ln, Ni and Cd from aqueous solutions has been studied using standard plate type electrodes and improved efficiencies were attained with fluidized bed electrodes. Because direct electroplating from sludge was found to be inefficient, acid and base additions were made to solubilize the metals prior to plating. Little economic advantage wou1d be gained by recovering sludge constituents, since processing costs for the large volumes of dilute leachate would be high. Therefore, the removal of heavy metals from wet sludge to reduce their toxicity does not appear to be economically feasib1e. The meta1s and phosphorus in sludge incinerator ash can be solubilized with H2S04 in a countercurrent stepwise process which uses most of the acid. Further processing of the H2S04 leachate for recovery of va1uable constituents is complicated by the presence of large quantities of iron in the leachate. Neutra1ization of the leachate with NaOH precipitates all the metals and phosphorus. Electroplating can remove Cu, ln, Ni and Cd from the ammonia, leach and ammonium phosphate can be recovered from the solution after electrolysis. While processing costs for incinerator ash are much less that those for wet sludge, the procedure does not appear to be economically viable except for very large treatment plants.