Nano Materials Induced Removal of Textile Dyes from Waste Water

The first chapter helps the reader to get acquainted with the basic features of the nanomaterials. Here, the basic properties of nanomaterials, basic synthesis processes, and different applications of nanomaterials are discussed. The novel features of the material are also mentioned. How the suppression of degrees of freedom of electrons that affects the electrical, optical, and other properties, has been discussed in detail. Special emphasis has been given to the resemblance of nanosystems in mother nature, and as a result, few examples have been mentioned. As the objective of the book is to discuss the nanomaterial-induced removal of dye materials from water, thus the interaction between water and the nanomaterials plays one of the major roles. Keeping this in mind, we have discussed the concept of surface tension, surface energy, surface energy components, hydrophobicity, and lotus effect in much depth with their consequences to different particular applications. The discussion has also been done on the concept of contact angle, hysteresis, porosity, and related topic. Thus, this chapter familiarizes the reader acquainted with the basic characteristics, properties, and applications of nanomaterials and provide useful information regarding the interaction of nanomaterials with water, which is the central theme of this book.

This chapter deals with the concept of nanomaterials, especially basic quantum mechanics and solid-state physics. It is now a well-established fact that the dynamics of materials in nano-regime cannot be described by simple Newtonian mechanics, and, therefore, one should opt for quantum mechanics. Thus, the focus of this chapter will be on basic quantum mechanics and solid-state physics in order to gain an understanding of the system's transport properties. A few characteristic phenomena of nanomaterials like the density of state, quantum confinement, excitonic radius, etc., will also be discussed in detail. To acquaint the reader with the Fermi energy and related properties, efforts will be made to provide a fundamental concept of statistical physics, specifically the Fermi-Dirac statistics. The authors have focused their efforts exclusively on dealing with different length scales, namely Ballistic transport and the associated Landauer-Buttiker formula of quantum transport in nanomaterials. Also, the relationship between exciton radius and quantum confinement and optical properties of nanomaterial has also been explained in detail. The concept of tunnelling, which is the foundation of quantum transport, has been explained, and an effort has been made to acquaint the reader with quantum conductance and Coulomb blockade.

It is not surprising that materials with nanoscale dimensions have existed since the creation of the universe. The reason is simple since all the materials are composed of different atoms or molecules, so an assembly of a few molecules can give rise to what one calls “nanomaterials”. The concept of nano, or more specifically, nanoscience and technology, is relatively new, as it requires a long journey of technological advancement to develop distinct optical devices that can see materials with dimensions of 10-9 metres and thus manipulate them for greater purposes. These special devices are commonly known as microscopes; however, they are not the same as traditional microscopes, which have a maximum resolution of 10-6 (micro) meters. In this chapter, the basic constructions and working principles of the more commonly used microscopes, rather than nanoscopes, will be discussed. Discussions on field emission scanning electron microscope (FESEM), high-resolution transmission electron microscopes (HRTEM), and scanning tunnelling microscope (STM) will also be done. Besides, the name and the main working principle of some other microscopic techniques will be mentioned. Apart from imaging, some other uses (if any) of these devices would also be mentioned.

In today's world, the textile industry is one of the most important sectors, both economically and in everyday life. The textile industry is one of the most important commercial sectors that require a significant amount of water and chemical ingredients for several types of processing needed during the conversion of fibres to final textile products ready for sale. Textile dyes are an important topic to discuss from both a positive and negative perspective, as dyes are an unavoidable part of colouring clothes or papers, but when they end up in the environment as a waste product from the industries mentioned above, they have a significant negative impact on the environment and the water ecosystem. Thus, it becomes necessary to handle the dyes properly and develop ways and means to remove/reuse them. However, in order to do so, one must have an in-depth understanding of the structures and properties of various dyes, as well as the treatment that should be applied. Keeping this in mind, we have discussed the basics of textile dyes in this chapter. The classifications of textile dyes, as well as their chemical structures and qualities, were also covered in this chapter. The in-depth discussion on the fundamental of textile dyes may help the workers handle dyes in a controlled way to protect the environment from the associated toxicity.

After the discussion of all the preceding sections/chapters, now we are in a position to review some typical nanomaterial systems that have established themselves as materials of immense potential in the field of water purification by successfully removing different textile dyes through different processes like catalysis adsorption or others. In this chapter, we will discuss a few such particular materials from different domains. The material will mainly include metal oxide nanostructures and related derivatives like zinc oxide, etc., and also carbon nanostructures like carbon nanotube, graphene, etc., and their hybrids. A detailed discussion regarding the dye removal ability of graphitic carbon nitride is also included here. In this regard, the results of other researchers will be accompanied by a few of our own findings, which will help the reader in better understanding the topic. Apart from these wellknown materials that have higher dye removal effectiveness, a few other less studied and newly evolved systems, such as silicon nanowire and p-type conducting oxides like copper borate, have also been discussed with a few established results.

The matter-energy reaction is the basis of a variety of fundamental scientific phenomena we have witnessed in nature. Photoreaction is related to the interaction of photons and the molecules of a substance. When the necessary photon in the ultra-violet or visible range of the electromagnetic spectrum is absorbed by the materials in concern, it may convert different poisonous elements into harmless substances, such as water and carbon dioxide. The study of photon physics and chemistry is fundamental for our understanding of the world we live in. The basic physiological processes through which the living species maintain their life cycles are also somehow related to the different photochemical reactions. Photo-catalysis happens to be a low-cost, versatile, and environment-friendly method that deals with a variety of harmful pollutants. Pollutants can be inorganic, organic, or even biological, and they can be found in both air and water. Photo-catalysis is a process in which the catalyst, light source, and contaminants must be in close proximity or contact. There have been numerous studies on the oxidation-induced removal of different organic pollutants as well as microorganisms, especially those found in water. In this chapter, we have covered the basics of photo-catalysis, the characteristics of various catalysts, their types, and photochemical laws, as well as the conditions and limitations of quantum yield.

Adsorption is one of the simplest ways and means to remove dyes from water. The process of adsorption simply involves the removal of water contaminants that come in contact with adsorbents, i.e., the materials of interest. The material should only have sufficient surface area, porosity, and adequate numbers of adsorption sites. Besides being one of the simplest means of dye removal, the process has further advantages in that the same material may be used many times, i.e., regarding the recyclability of the material. Keeping all these in mind in this chapter, a detailed discussion regarding the adsorption process has been included. The discussion not only covers the basic principle of the process but also unfolds the analysis technique regarding the performance of certain material as an efficient absorber. The quantification of removal efficiency will also be a topic of discussion. The setup for such a kind of measurement will be unveiled, and most importantly, different theoretical models for such a process will also be a topic of interest in this chapter. The different models include the Langmuir model, Freundlich model, Temkin model, and others. An effort has also been made to enlighten the readers with the different reaction kinetics like pseudo-first-order, or second-order reaction kinetics. In every subsection, a few experimental data will be shown and discussed.