In this chapter, we have made an overview of the whole book and summarized the environmental pollutions and their treatment with new materials and technology. We highlighted how to resolve the old challenges with new solutions. We reviewed different methods used for environmental remediation and highlighted the importance of nanomaterials in environmental remediation. Different processes related to the management of waste water polluted by bacteria, organic, inorganic pollutants, and toxic metal ions, etc. have been discussed. We discussed how nanomaterials are economical solutions for the resolution of the old challenges related to waste water treatment. We also deliberated that the waste water containing harmful metal ions, organic pollutants, bacteria etc. can be treated with nanomaterials and for this purpose, development of novel nanomaterials is paramount because nanomaterials have revolutionized the scenario of emerging catalytic and adsorption technologies with recently certified efficient removal of pollutants along with the low cost and high stability. Therefore, the molecular engineering of nanomaterials to use them to reach stable state-of-the-art efficiency for the removal of pollutants as adsorbent and catalysts is vital and the high efficiency coupled with low cost and easy treatment process of the developed nanomaterials has probability to compete and replace the established technologies.

Recent years have witnessed the devastating impact of climate change on mankind and environment. Explosive growth in human population, indiscriminate burning of fossil fuels and rapid expansion of industrial sector have significantly contributed in worsening the current status of environment and the situation is highly anticipated to aggravate on extended time scale. To avert any further extreme environmental deterioration, adaptation of eco-friendly and cost effective alternatives is indispensable in order to address the global challenges in energy, industry and environmental sectors. These concerns have led to numerous scientific endeavours from multidisciplinary areas aimed at modifying existing technologies and designing new approaches with distinct economic and environmental benefits. Nanotechnology is genuinely one such revolutionary field of science with unlimited potential applications. This is evident from some of the greatest breakthroughs in the area of environmental protection, remediation and pollution prevention. With this idea, the present chapter is set to explore the fundamental aspects and promising applications of nanotechnology with emphasis on its role in environmental sustainability. In short, nanotechnology has significantly contributed in benefiting society and shaping the nature of modern life, hence it would be appropriate to consider it as the “Realm of Wonders”

The basic concepts of photocatalysis are explored in this chapter. Various parameters which control and influence the photocatalytic process are studied in relation to the mechanistic approach. Metal oxides like titanium dioxide, zinc oxide, cerium oxide, tungsten oxide and bismuth oxides play an important role in photocatalysis for environmental remediation, water splitting and solar cells. The phenomenon of photocatalysis is dependent on wavelength of incident light. However, the efficiency of most of the metal oxides is limited in the UV range. It is needed to modify their band gap energy levels. These modifications can be achieved by doping or coupling of metals, non-metals, metal oxides and carbon based materials. Metal oxides morphologies also affect the photocatalytic process due to enhanced surface area and surface defects providing more accessible sites for the diffusion of organics. Some new types of materials like perovskite and metal organic framework (MOF) are used as efficient photocatalysts. The role and mechanism of these materials have been discussed. All these nanomaterials are used for the environmental remediation, dye sensitized solar cells, air purifications, hydrogen production and self-cleaning process.

In the modern world, the quality of the environment (water, soil, and air) is greatly compromised by numerous pollutants and contaminations from diverse sources. The situation is even exacerbating on daily basis. Tracking and treating the existing contaminants while preventing further pollution may maintain and improve the quality of environment. Clays and clay based nanocomposites provide an efficient and cost effective solution to this end. In this chapter, we begin by introducing clays, composition of clay, clay minerals and various tools used for characterization of clays and clay based nanocomposites. The role of clay based nanocomposites for environmental protection is presented. In particular, the removal of heavy metal ions, toxic organic compounds, hazardous dyes and antibiotics from aqueous environment has been discussed and recent studies are summarized. Purification and remediation of contaminated soil and air with the help of clay based nanocomposites are also discussed.

The material with small size and high efficiency is the topic of the future. It is valuable and important in the field of separation and purification science. This chapter discusses ion-exchange materials, natural, synthetic, organic, inorganic and organic-inorganic nanocomposite. In this chapter, we discussed about the chromatography of ion-exchange particularly cation-exchanger and its uses as desalination and ion-selective electrode. The Estimation of the impact on the manufacturing procedure on the environment requires a systemic approach and suitable metrics for the quantitative valuation of environmental threats. Thus, this chapter starts with an overview on cation exchange materials for green technology as well as the metrics starting the procedure. Therefore, there are many applications of cationexchange materials and their derivatives have been explained in this chapter. In addition, the technological advancement in inorganic nanocomposite, cation-exchange materials from old era to modern age of nano are also explained as green chemistry and can be implemented to actual developments. Specifically, two elements are highlighted: (a) the usage of new resources for the facilitation of selective and active chemistry and the implementation of the said materials for the removal of hazardous materials for environment.

Iron oxide and its derivatives have been receiving importance and broad scale applications during the last two decades, due to their specific characteristics and use. There are many types of ferrous oxides have been characterized, whereas iron (III) oxide (Fe2O3), Fe(II)-deficient magnetite (Fe2O3, γ-Fe2O3) and ferrous-ferric oxide (Fe3O4) are, indeed, the relevant types of untainted ferrous oxides. Many hydroxides, such as ferric hydroxide (Fe(OH)3) and oxyhydroxide (Fe(O)OH), are also of industrial importance, being precursors of pure or complex oxides. As for the compound iron oxides, ferrites are essential ferromagnetic materials. Among all the ferrites, the iron oxides and ferrite magnetic nanoparticles with appropriate surface chemistry are prepared either by wet chemical methods such as colloid chemical or sol-gel methods or by dry processes such as vapour deposition techniques. The conventional granulometric technique does not form nanoparticles (NP), and is often desired to assemble or pattern ferrous oxide nanoparticles to give magnetic or optogenetic functions. This review summarizes the comprehensive study of ferrous based nanomagnetic particles preparation together with a comparison of synthesis techniques and their characterization, particularly regarding magnetism properties, particle size and morphologies. Moreover, in this review, a recent study of modified microwave assisted system for nanomagnetic particles preparation has also been highlighted.

Since the last century, polymeric membrane technology has been offering economical and efficient solutions for emissions control and energy security. However, polymeric membranes in separation and purification environment, are facing challenges such as correct material selection, polymer modification for the resolution of permeability, selectivity, low resistance to fouling and low mechanical strength. Among all these problems, the three types of fouling i.e., inorganic, organic and biological are the critical applications of membrane issue. Technically, organic and inorganic fouling can be controlled or minimized but the practical approaches to control biological fouling, particularly the membranes, used in the seawater desalination application are still facing issues, and the limitations to control biofouling. Recently, nanoparticles have shown real potential for the improvement of the membrane life. This chapter gives a comprehensive review of the critical aspects of the preparation and use of polymeric membranes in combination with standard additives and their influence on membrane permeability and selectively. The recent development of polymeric membranes loaded with nanoparticles against bio-fouling has also been reviewed in this chapter.

Nanocatalysts have received much attention because of their vast applications in various organic pollutants removal as well as their selectivity, ease in separation, eradicating the expensive materials and hazardous chemicals. Nanocatalysts are the heart of scientific field because of their vast applications in multidisciplinary sciences. This chapter provided a brief knowledge using nanocatalyst for the removal of organic toxins, for instance nitrophenols and dyes, which are at alarming condition. The readers will be benefited from this chapter and will learn about photocatalysis and its application. The use of semiconductors is appropriate in photocatalysis, therefore, much information is available about semiconductor. An important morphological nanocatalyst is the layered double hydroxide; also worked as a solar catalyst for the removal of contaminants and various support are present for these material to enhance its catalytic performance. Supported materials in nanocatalysis are required to stabilize the nanoparticles (Nps) from being aggregated and also offer any easy route in separating the catalyst after the reaction. Such criteria are highly demanded at industrial level.