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About this book

This book reports on the development of nanostructured metal-oxide-based electrode materials for use in water purification. The removal of organic pollutants and heavy metals from wastewater is a growing environmental and societal priority. This book thus focuses primarily on new techniques to modify the nanostructural properties of various solvent-electrolyte combinations to address these issues. Water treatment is becoming more and more challenging due to the ever increasing complexity of the pollutants present, requiring alternative and complementary approaches toward the removal of toxic chemicals, heavy metals and micro-organisms, to name a few. This contributed volume cuts across the fields of electrochemistry, water science, materials science, and nanotechnology, while presenting up-to-date experimental results on the properties and synthesis of metal-oxide electrode materials, as well as their application to areas such as biosensing and photochemical removal of organic wastewater pollutants. Featuring an introductory chapter on electrochemical cells, this book is well positioned to acquaint interdisciplinary researchers to the field, while providing topical coverage of the latest techniques and methodology. It is ideal for students and research professionals in water science, materials science, and chemical and civil engineering.

Table of Contents


Chapter 1. Dynamic Degradation Efficiency of Major Organic Pollutants from Wastewater

Due to the impact of photo-active materials on removal of disposed pharmaceutical waste and synthetic dyes from wastewater, attention of numerous researchers has been hugely turned onto dynamic degradation efficiency of various photocatalysts constituents. On the application of photo-active composites, they are predominantly synthesized from nanoparticles, and fabricated to photo-active semiconductors. At the center of overcoming limitations of photocatalysis technique which encompass rapid photo generation electron-hole pairs, high operational costs and utilization of small portion of solar energy, synergism of photocatalysist technique to electrochemical oxidation became a necessity for a better degradation efficiency. Hence, this chapter addresses a dynamic degradation efficiency provided by combined photocatalysists within variety of synthetic dyes and pharmaceutical products and application of photoelectrochemical oxidation technique. An emphatically sensitized discussion is on variety of synthetic dyes, pharmaceutical products, environmental concerns and photocatalysists. Overall, a degradation efficiency based on paramount factors has thoroughly been clarified.
Khotso Khoele, Onoyivwe Monday Ama, Ikenna Chibuzor Emeji, William Wilson Anku, Suprakas Sinha Ray, David Jacobus Delport, Peter Ogbemudia Osifo

Chapter 2. Synthesis and Fabrication of Photoactive Nanocomposites Electrodes for the Degradation of Wastewater Pollutants

On the endeavor of wastewater treatment, synthesis and fabrication of various nanoparticle metal oxides is the pillar of continuation. As metal oxides possess different pros and cons, they are presently applied in their singular compounds and combined forms so as to pin point their definitive distinction on the efficiency and effectiveness occur on wastewater degradation. Hence, synthesis of metal oxides from nanoparticles and their fabrication to photoelectrode is paramount for clarification. Within this chapter, nanoparticles are explained; photoactive metal oxides are listed and discussed. Most centrally, the synthesis of photo-active semiconductors from nanoparticles and a fabrication of the photoactive metal oxides to semiconductor electrodes are detailed.
Graphical Abstract
The purchased Nanoparticles are prepared as received through different steps. First, Nanoparticles are synthesized. Secondly, the intended Nanocomposites are formed using synthesis techniques such as sol-gel method. The formed Nanocomposite is characterized using different techniques. Thirdly, the Nanocomposite is pressed into a pellet. Fourthly, the copper wire is connected to the pellet using conductive silver paste. Finally, a transparent glass tube with opening at both ends sides was used.
Onoyivwe Monday Ama, Khotso Khoele, David Jacobus Delport, Suprakas Sinha Ray, Peter Ogbemudia Osifo

Chapter 3. The Essence of Electrochemical Measurements on Corrosion Characterization and Electrochemistry Application

Electrochemical measurements (EMs) are utilized on corrosion studies and electrochemistry applications. Corrosion is a naturally occurring phenomenon, and that negatively affect functionality of engineering components. To prevent and mitigate it, EMs such as Open circuit potential (OCP), Potentiodynamic Polarization (PDP) and Electrochemical Impedance Spectroscope (EIS) are carried out. Details on all EMs which are carried out to characterize corrosion are included in this study. As twenty-first century industrialization grows, production of inks and dyes for various industrial also grow in direct proportional order. From eventual usage of products manufactured with inks and dyes, different elements become present in wastewater. This phenomenon consists risk to human being, plant and animals. Hence, EMs is necessitated to remove pollutants from the wastewater. On a quite number of EMs, photoelectrochemical technique (PET) is worthwhile on disintegration of havoc in wastewater. PET is carried out within an electrochemical cell (EC). In demonstration of the EMs impact, materials which are used as anodes (photoanodes) within the EC and the engaged organic pollutant simulating solution are thoroughly profiled before and after EMs. All undertakings give necessary information needed on degradation of organic pollutants from the wastewater. Hence, this chapter explains the following important aspects on Electrochemistry application: (i) PET technique significance and its functionality which make it supersedes other techniques. (ii) A standard EC operation and the constituents elements for successful degradation of wastewater. (iii) Pre and post-measurements techniques which are used as underpinnings demonstrating effectiveness of EMs. (iv) Overall, significance of engaging EMs on wastewater treatment.
Graphical Abstract
Corrosion is a tendency of metallic materials returning back to their original states. Therefore; the electrochemistry is a study of electrons migration during metallic substrates application. This shows Corrosion and electrochemistry involve same techniques, but different interpretations.
Khotso Khoele, Onoyivwe Monday Ama, David Jacobus Delport, Ikenna Chibuzor Emeji, Peter Ogbemudia Osifo, Suprakas Sinha Ray

Chapter 4. Electrochemical Cells

The main goal of this chapter is to present an overview of electrochemical cell operations. An electrochemical cell is devices that use a spontaneous chemical reaction to produce electricity or conversely use applied electricity to bring about non-spontaneous useful chemical reactions. The electroactive species in the ionic conductor (electrolyte) through mass transport reaches the electrode surface where Faradaic and Non-faradaic Processes occurs. A Faradaic process such as redox reaction at the electrode-solution interface gives rise to reduction or oxidation reaction. Fick’s law gives the rate of diffusion of the oxidized or reduced species in terms of a concentration gradient. The electrified solution-electrode interface was modeled using Helmholtz compact layer model, Gouy-Chapman diffuse layer model, and the Stern model. Accepted definitions of certain physical quantities were also presented.
Ikenna Chibuzor Emeji, Onoyivwe Monday Ama, Uyiosa Osagie Aigbe, Khotso Khoele, Peter Ogbemudia Osifo, Suprakas Sinha Ray

Chapter 5. Properties and Synthesis of Metal Oxide Nanoparticles in Electrochemistry

The synthesis and study of “metal oxide nanoparticles”, has gain greater attention over the past 10 years among interdisciplinary researchers. The major interest may be as a result of their unique physical and chemical properties, which gives rise to their various industrial usage in the field of catalysis, electronics, solar energy conversion, and others. As the particle size diminishes, the ratio of surface atoms to those inherent rises, enabling the surface properties to dictate the overall properties of the nano-materials. Also, metal oxide nanoparticles manifest different optical and electrical properties in proportion to that of the bulk material. Hence, as the size of the solid becomes smaller, the band gap becomes larger. This, therefore, gave scientists the unique opportunity of nanofabrication synthesizing highly complex nanostructure with different electronic and optical properties just by manipulating its particle size.
Ikenna Chibuzor Emeji, Onoyivwe Monday Ama, Uyiosa Osagie Aigbe, Khotso Khoele, Peter Ogbemudia Osifo, Suprakas Sinha Ray

Chapter 6. Metal Oxide Nanomaterials for Biosensor Application

Metal oxide nanomaterials (MONMs) have captivated a lot of attention due to their unique analytical properties such as fast electron transfers kinetics, large surface area, catalytic ability, conductivity (enhancement of charge flow), biocompatibility and excellent electrochemical properties. These properties have allured scientists towards employing MONMs as an upcoming platform for the development of various biosensors for different electroanalyte, biological compounds, biological molecules or cancer biomarkers. It is important to highlight that the early detection of cancer biomarkers will assist in solving the long-standing health problems in the world. In view of this, the present chapter underscores the construction of different biosensors using metal oxide nanomaterials as a novel platform for the determination of various biological molecules.
Azeez Olayiwola Idris, Onoyivwe Monday Ama, Suprakas Sinha Ray, Peter Ogbemudia Osifo

Chapter 7. Metal Oxide Nanomaterials for Electrochemical Detection of Heavy Metals in Water

Metal oxide nanomaterials (MONMs) have gained much research attention as prospective materials of preference for modifying electrode surfaces intended for electrochemical sensing of heavy metal ions. MONMs have attracted much research interest because of their unique characteristics at nano dimensions compared to bulk species. In general, the unique electronic properties, high electron transfer kinetics, semi-conducting properties among others make them exceptionally smart materials for electrochemical reaction. Moreover, early detection of toxic metal ions in our water bodies will help to improve the standard of human living in the environment. Owing to this effect, the present chapter deals with the utilization of electrochemical techniques such as voltammetry and potentiometry among other electrochemical techniques for sensing of heavy metal ions in water bodies. The chapter also address the progress in the application of different metal oxide nanomaterial in terms of their frameworks, adsorption capacities, surface structure, chemical functional group attached, and how their use as preference of electrode materials affect electrochemical sensing of heavy metal ions in water.
Seyi Philemon Akanji, Onoyivwe Monday Ama, Suprakas Sinha Ray, Peter Ogbemudia Osifo

Chapter 8. Application of Metal Oxides Electrodes

The search for engineering materials that can withstand the high demands of the emerging technologies in the fields of bio-engineering, aerospace engineering, medicine, environmental protection, renewable energy and manufacturing industries continues to thrive and find relevance in the today’s world. Metal oxides-based electrodes possess exceptional properties which qualify them as suitable engineering materials with wide range of applications such as sensors, semiconductors, energy storage, lithium-ion batteries and solar cells. This paper focuses on the use of various metal oxide-based electrodes (metal oxide, transition metal oxide, mixed metal oxide, transition, and hybrid systems) and how they have improved certain parameters of energy storage such as life cycle, capacitance, nominal voltage in above mentioned application prospects. This paper describes the novel concept of lithium metal oxide electrode materials which are of value to researchers in developing high-energy and enhanced-cyclability electrochemical capacitors comparable to Li-ion batteries. In order to fully achieve the potential of metal oxide electrodes in the future, significant efforts need to be directed to producing low cost and environment-friendly materials.
Chikaodili Chukwuneke, Joshua O. Madu, Feyisayo V. Adams, Oluwagbenga T. Johnson

Chapter 9. Application of Modified Metal Oxide Electrodes in Photoelectrochemical Removal of Organic Pollutants from Wastewater

The scarcity of clean water due to the increase in ground and surface water pollution by numerous pollutants from municipal, industrial, and agricultural sources is considered to be the most pressing environmental problem and a threat to the survival of humans. Among the methods being tested for the sustainable removal of these pollutants from water before use or disposed into the environment is photoelectrochemical degradation. This technique is a combination of electrochemical oxidation and heterogeneous photocatalytic degradation and involves the use of metal oxide semiconductor-based electrodes in the presence of light. This process begins with the generation of electrons by the metal oxide semiconductors which react with oxygen and water molecules to produce oxidants including superoxide and hydroxyl radicals which are responsible for the degradation of the pollutants. The efficacy of this process is, however, hampered by the high rate at which the electrons recombine with the co-generated holes and the poor visible light activity of the semiconductors due to their wide band gaps. A number of modifications have been made to the semiconductors to resolve the above-mentioned problems and improve on the efficiency of the photoelectrochemical degradation process. This chapter dwells mainly on the various modifications that have been made to the metal oxides including the use of carbon-based and polymeric materials, doping with metal, doping with non-metals, co-doping with metals and non-metals and formation of mixed metal oxide/heterostructures.
William Wilson Anku, Onoyivwe Monday Ama, Suprakas Sinha Ray, Peter Ogbemudia Osifo

Chapter 10. Metal Oxide Nanocomposites for Adsorption and Photoelectrochemical Degradation of Pharmaceutical Pollutants in Aqueous Solution

The global deterioration of water quality which is associated with industrialisation, urbanisation, and a growing population is reaching critical levels and thus needs to be addressed urgently. Common pollutants that are discharged from industries and sewage plants include unknown toxic chemicals, heavy-metals and micro-organisms; these are well known and thoroughly studied. Of growing and great concern to both human and animal health is the new emerging class of pollutants known as endocrine disruptor chemicals (EDCs) or emerging organic compounds (EOCs); these are frequently associated with residues from pharmaceutical industries, i.e. they comprise of common drugs such as antibiotics, medication for chronic illnesses, pain killers. Regrettably, the traditional water purification systems cannot fully remove these pollutants, thus they are found in various water systems in minute concentrations. The danger is in the long run accumulative exposure to humans, animals and the environment. There are several methods that have been developed, reported and used for the removal of these pollutants. Several removal or remediation technologies have been studied and reported for the mineralisation of these emerging organic pollutants and of interest to this work is photocatalysis using light harvesting materials such TiO2 (i.e. semiconductors) and electrochemistry. The drawbacks associated with semiconductors are low quantum yields that emanate from rapid recombination of photo-generated electrons and holes with very low lifetimes. To overcome these drawbacks and to enhance degradation, an electrical external field can be applied across the catalyst or semiconductor to induce special separation of photo-generated electron hole pair to allow a sink for the electrons in a process called photoelectrochemistry. This chapter highlights the reported mineralisation of organic pollutants photoelectrochemistry using semiconductors; it also highlights the efficiency of photoelectrocatalysis when compared with photocatalysis alone.
L. Mdlalose, V. Chauke, N. Nomadolo, P. Msomi, K. Setshedi, L. Chimuka, A. Chetty


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