Preface

In the present era, environmental degradation has emerged as a major threat due to widespread urbanization and industrialization all over the world. Air, water, soil and all other natural resources are getting polluted by one or the other ways. The majority of industries use various inorganic and organic toxic chemicals and discharge them into nearby water streams as effluents without treatment. These pollutants severely influence the aquatic world as well as indirectly the human life. Global crisis due to depletion of natural resources that are not replenishable as well as degrade the environment leads to harmful consequences. Thus, environmental remediation has emerged as a significant field of research towards this direction. In recent times, nanomaterials have exhibited multifunctional properties in the fundamental arena of scientific activities because of their enormous applications especially their roles in environmental monitoring and remediation. The beauty of nanomaterials lies in their small size leading to real perfection, potency and wide range of applications. The inimitable properties of nanomaterials make them suitable for energy harvesting and removal of pollutants from the environment and ultimately cleaning up of the environment. They can be readily tailored for application in different environments and these properties make them unique for developing a new generation of efficient, cost-effective and environmentally friendly functional materials for energy harvesting and water treatment processes.

This book is an attempt to spread scientific awareness among the readers and discuss various methods needed to overcome the challenges faced during environmental remediation as well. The book comprises ten chapters. In this era of digitalization, the use of electronic devices has become an integral part of our everyday life. These devices used for sensing, analysing, and transmitting signals require a very small amount of energy. An alternative source to power these devices could be through harvesting the tiny mechanical motion associated with different motions. Chapter 1 presents a brief introduction to the need for nanomaterials for environmental remediation. Different nanoremediation pathways have been broadly catergorized into four categories: Adsorption, Photocatalysis, Nano-membrane, Nanosensors for different classes of nanomaterials. Nanomaterials for energy harvesting and storage applications have also been discussed in brief. Chapter 2 deals with the methods of preparation of spinel ferrites and their structural and magnetic characteristics. The importance of spinel ferrite in pollutant degradation for wastewater along with its recovery and reuse has been explored. The chapter also discusses the efficacy of adsorption and photocatalysis processes in conventional wastewater treatment techniques. Chapter 3 explains the significance of carbonaceous quantum dots in environmental remediation. In addition, the advantages of carbonaceous quantum dots over conventional quantum dots, methods for synthesizing carbonaceous quantum dots (top down and bottom up) their functionalization or doping to improve their selectivity and sensitivity, their applications in various fields such as sensing, photocatalysis, and bio-sensing have also been discussed. Chapter 4 explores the carbonaceous materials such as activated carbon, biochar, hydrochar, etc. for wastewater remediation. This chapter summarizes the role of carbonaceous materials, their importance and fabrication for their multidisciplinary applications. Chapter 5 deals with a systematic discussion of the role of pure and modified ferrites in the removal of various toxins and pollutants from the environment and their potential applications for environmental remediation. Chapter 6 deals with another material for wastewater remediation- Carbon Nanotubes. This chapter discusses functionalization or modification procedures, depending on the intended application and the chemical makeup of the target pollutants. Designer CNTs can significantly increase the effectiveness of contaminant removal and help with nanomaterial regeneration and recovery. Chapter 7 deals with cellulose-based nanomaterials in water remediation processes. In this chapter designing of various cellulose-based nano-materials has been depicted for the extraction of valuable metals from wastewater. Adsorption by various chemical transformations such as reduction, chelation and electrostatic interaction are discussed for the extraction of various metals. Lastly, composite systems consisting of cellulose and metal oxide nanoparticles have also been discussed for the extraction of rare earth metals from the mining industry. Chapter 8 discusses potential sources of energy harvesting by converting waste mechanical energies into useful electrical energy by nanogenerators. This chapter reviews the basic workings of different nanogenerators based on piezoelectricity, triboelectricity, pyroelectric, and flexoelectricity. This chapter attempts to present the energy management landscape of the country by developing cost-effective materials and devices that can harness both sunlight and vibrational energy and convert them into electricity is the need of the present day for a green and circular economy-driven future. Lead-free piezoelectric energy harvesting technology has been discussed in Chapter 9. The fundamental piezoelectric concept and several piezoelectric materials specifically KNN, BT, and BNT-based ceramics and their applications for energy harvesting are described and assessed in this chapter. Finally, based on their current developments, different challenges and future perspectives have also been encompassed. Chapter 10 aims to offer an overview of cold spray additive manufacturing including their advantages for sustainable manufacturing in terms of environmental concerns. Challenges associated with cold spray additive manufacturing have also been discussed. Chapter 11 aims to assess the ecotoxicity and risk associated with nanomaterials in environmental remediation. Overall, this chapter highlights the importance of careful consideration of the ecological impacts and risks of nanomaterials before implementing them in environmental remediation programs.

We believe this book has successfully targeted the fundamental issues and challenges regarding environmental remediation. Easy to read and pictorial illustrations have focussed on the theme and have justified its purpose. We anticipate that this book will be beneficial for students and academicians in broadening their horizons.