Preface

Water pollution has emerged as one of the severe environmental threats globally. In recent years, the problem has become critical due to the mismanagement of natural water resources, population growth and rapid pace of industrialization. Among various water treatment technologies, ‘adsorption’ process is still one of the best methods available for the removal of diverse types of pollutants from water and wastewater. Several wastewater treatment plants all over the world are operating on the principle of adsorption. The technological and environmental importance of adsorption can never be in doubt.

Activated carbon, a universal adsorbent, has undoubtedly been the most popular and widely used adsorbent in water and wastewater treatment. Charcoal, the forerunner of modern activated carbon has been recognized as the oldest adsorbent known in wastewater treatment in removing diverse contaminants/pollutants such as metals, dyes, phenolic derivatives. However, in spite of abundant uses of activated carbon, its applications are sometime restricted due to its higher cost. Attention has therefore, shifted towards the use of non-conventional naturally occurring materials, agricultural and industrial waste products as low-cost adsorbents for water remediation. Recently, sorption onto low-cost materials such as carbons produced from wastes or natural by-products, natural sorbents, and biosorbents has been the focus of much attention. The purpose of this book is to present detailed reviews on the application of variety of adsorbents in water pollution control.

Chapter 1 presents a comprehensive review on the preparation, properties and use of activated carbon for wastewater treatment. The sorption mechanism of different pollutants by activated carbon has also been discussed. In Chapter 2, the most common equilibrium and kinetic models describing the adsorption at solid/solution interfaces have been discussed. Chapter 3 focuses on the removal of various pollutants from wastewater using different phases of iron oxide nanoadsorbents. The chapter highlights the main synthesis techniques of iron oxide nanoadsorbents, their types, advantages, and adsorption mechanisms

Chapter 4 highlights the different surface engineering strategies for enhanced and/or selective removal of different inorganic/organic pollutants from water iv bodies. Chapter 5 reviews the application of layered double hydroxides (LDHs) or hydrotalcite-like (HT-like) materials in water remediation. A brief introduction on LDHs, their synthesis methodologies, physicochemical characterization and their application potential in the removal of environmentally undesired oxoanions like phosphate, borate and chromate from aqueous solutions. A comparison on the anion-exchange removal capacity of LDHs with commercial anion exchangers is also discussed. Different mechanisms involved in the removal of phosphate, borate and chromate anions by LDHs are addressed.

Chapter 6 discusses the development of novel, highly ordered, mesoporous materials as active sorbents for mitigation of environmental pollutants. Chapter 7 reports the use of kaolinite as inexpensive adsorbent for industrial and mining wastewater treatment. In Chapter 8, the use of a common clay mineral, montmorillonite and its modified derivatives for adsorptive removal of toxic heavy metals from aqueous system has been reviewed. The review aims to give a comprehensive picture on the studies of isotherm of adsorption for metal removal on montmorillonites during the recent years.

Chapter 9 focuses on application of some natural materials (zeolites, siliceous materials, clays) as low cost adsorbents for water treatment. Chapter 10 reports the sorptive removal studies of humic acids, phenylureas and triazines herbicides by using zeolites such as phillipsite and chabazite. In Chapter 11, the application of agricultural solid wastes without any chemical treatments, i.e. identified as “low cost adsorbents”, has been reviewed for the removal of different pollutants especially heavy metals and organics. Chapter 12 presents a review on the use of biochars as low-cost adsorbent for wastewater treatment summarizing the concept, methods of production, property of structure, capacity and mechanism of adsorption for hazardous materials and some recommendations for future work.

Chapter 13 addresses the application of rice husk and bagasse ash as adsorbents to remove dyes from textile and printing wastewater and heavy metals, such as nickel, from electroplating wastewater. Chapter 14 discusses the use of Electric Arc Furnace (EAF) slag as a safe, effective and inexpensive end-of-pipe add-on solution for improving the treatment of urban stormwater runoff. Chapter 15 describes the use of Victorian lignite, a cheap natural energy resource from v southeast Australia, for methylene blue dye removal from aqueous solutions without the need of pretreatment. The kinetics of the adsorption process was examined using different kinetic models.

In Chapter 16, a detailed characterization of bone char is presented. Thermodynamic and kinetics aspects of adsorption using bone char in these systems are presented. The results depict a high affinity of bone char for both organic and inorganic compounds which makes it a potential adsorbent for chemically complex solutions. The adsorption mechanisms are also discussed. Chapter 17 briefly summarizes the progress and advances in adsorption technology for water remediation.

The intended audience for this e-book includes students, environmentalists, engineers, water scientists, civil and industrial personnel who wish to specialize in adsorption technology for water treatment. This e-book will be very helpful for the researchers who aspire to learn about recent developments on sorbent materials in order to promote further research toward improving and developing novel sorbents and processes for the efficient removal of pollutants from industrial effluents.

Finally, the editor would like to thank all the contributing authors of this e-book. I would like to thank Prof. S.J. Allen, for writing the foreword and Bentham Science Publishers, particularly Manager, Bushra Siddiqui, and Assistant Manager, Maria Baig, for their continuous support and efforts throughout this project.

Last but not the least, I would like to sincerely extend my heartfelt thanks to my parents and my lovely wife, Eva, who has put all her efforts to complete this project.