Preface

**Section 2 Photocatalyst for Photoreduction 127**

**VI** Contents

Chapter 8 **Photoreduction Processes over TiO2 Photocatalyst 129** Endang Tri Wahyuni and Nurul Hidayat Aprilita

> Photocatalysts are based on nanomaterials and their applications are extremely broad. This is a constantly growing research area and it has become an important research topic in the recent years. Solar light photocatalysis is currently one of the most blossoming interdiscipli‐ nary fields of science. Research in the development of efficient photocatalytic materials has seen significant progress in the last two decades with a large number of research papers published every year. Improvements in the performance of photocatalytic materials have been largely correlated with advances in nanotechnology. As photocatalysts have diverse applications, the interest on photocatalysis has accelerated and has attracted worldwide in‐ terest. Photocatalysts have potential to be used in photodegradation of several contaminants to solve environmental problems. Other important applications of photocatalysts are the de‐ velopment of self-cleaning products, air purification, CO2 conversion to hydrocarbon fuels as well as the production of highly effective fuels such as hydrogen.

> Hence, photocatalysis is a subject of key interest. Therefore, it was planned to present recent progress in photocatalysis in the form of a book to the scientific community. There are eight chapters in this book. In the first chapter, different methods for disinfection such as chlorina‐ tion, zone, ultraviolet light, chloramines, potassium permanganate, photocatalytic disinfec‐ tion, nanofiltration, and chlorine dioxide are discussed. The second chapter is related to the selective degradations using a titanium-based photocatalyst while in chapter three, some of the most recent works that have employed the doping, decoration, and structural modifica‐ tion of TiO2 particles for applications in photocatalysis have been reviewed. Additionally, the effectiveness of these dopants and/or modifiers in enhancing TiO2 photoactivity as well as some perspective on the future of TiO2 photocatalysis are also discussed. Chapter 4 presents modified materials such as alternatives for conventional photocatalysts as titanium dioxide. Discussion about silver/graphene nanoparticle-modified zinc oxide for degradation of pollutants such as triclosan or bisphenol A, both considered as endocrine disruptors, which affect the hormonal development of humans, is presented. In addition, bismuth oxy‐ chloride has gained attention during the last 5 years for photocatalysis. In accordance, the obtained results for phenol photodegradation, using such oxychloride, are also presented. In the chapter, characterization of the photocatalyst is reported along with the proposal for mechanisms of action for the modified ZnO photocatalyst and bismuth oxychloride. In Chapter 5, structural modifications in semiconductors have been proposed to enhance the photocatalytic activity, such as doping processes with elements that are capable of generat‐ ing superficial defects that capture the formed electrons, avoiding the recombination or in‐ creasing the density of –OH groups or water molecules on the surface of the catalyst, which can enhance the formation of hydroxyl radicals. Therefore, this brief review is proposed to show the role of lanthanides in TiO2 doping and the synthesis method applied, as well as the

results discussed in the literature. Chapter 6 presents the role of various carbon forms, i.e., activated carbon and carbon nanotubes/nanofibers as support for TiO2 in drinking water treatment is discussed. Also, the chapter discusses how TiO2 is supported on zeolite to act bi-functionally as a sorbent/photocatalyst for drinking water treatment. The main contami‐ nants of natural organic matter (NOM), arsenic species, and nitrogen compounds from drinking water sources by type of groundwater and surface water can be removed/degrad‐ ed by sorption/photocatalysis using TiO2 supported onto carbon and/or zeolite. TiO2 sup‐ ported on powdered activated carbon (PAC-TiO2), granular activated carbon (GAC-TiO2), and zeolite (Z-TiO2), namely supported TiO2, were synthesized through sol-gel method and TiO2 and multi-wall carbon nanotubes/carbon nanofibers dispersed within epoxy matrix (CNT-TiO2-Epoxy; CNF-TiO2-Epoxy), namely TiO2 composite, were obtained through tworoll mill method. Kinetics study results using specific mathematic models allowed the eluci‐ dation of some mechanistic aspects for sorption and photocatalysis for the application in drinking water. The intercalation of the carbon and zeolite supported TiO2 layers into a fil‐ tering system that allows to develop a self-cleaning filtering system in drinking water. Chapter 7 presents a review of the role of HAp in the TiO2/Hydroxyapatite composite in‐ cluding the adsorption ability of contaminations and the promoted impacts of the HAp component. Chapter 8 presents the study of the TiO2 photocatalyst for photoreduction of several reducible chemicals. The photocatalytic reduction of several toxic metal ions, includ‐ ing Ag(I), Cu(II), Cr(VI), Hg(II), and U(VI) in the presence of TiO2 , in order to decrease their toxicity, is described. Photodeposition of the noble metals, such as Ag(I), Au(III), Pt(IV), and Pd(II) for doping purposes by photocatalytic reduction over TiO2 is also addressed. Conver‐ sion of the greenhouse gas of CO2 into useful hydrocarbons and methanol by photocatalytic reduction using TiO2 photocatalyst is highlighted. Several operating parameters in photore‐ duction processes (photocatalyst dose, time of irradiation, pH of the solution, and the initial concentration of the substrates (the reducible chemicals)) are also reviewed.

> **Dr. Sher Bahadar Khan** King Abdulaziz University Jeddah, Saudi Arabia

**Section 1**

**Photocatalysts for Water Treatment**

**Dr. Kalsoom Akhtar** Ewha Womans University Seoul, South Korea **Photocatalysts for Water Treatment**

results discussed in the literature. Chapter 6 presents the role of various carbon forms, i.e., activated carbon and carbon nanotubes/nanofibers as support for TiO2 in drinking water treatment is discussed. Also, the chapter discusses how TiO2 is supported on zeolite to act bi-functionally as a sorbent/photocatalyst for drinking water treatment. The main contami‐ nants of natural organic matter (NOM), arsenic species, and nitrogen compounds from drinking water sources by type of groundwater and surface water can be removed/degrad‐ ed by sorption/photocatalysis using TiO2 supported onto carbon and/or zeolite. TiO2 sup‐ ported on powdered activated carbon (PAC-TiO2), granular activated carbon (GAC-TiO2), and zeolite (Z-TiO2), namely supported TiO2, were synthesized through sol-gel method and TiO2 and multi-wall carbon nanotubes/carbon nanofibers dispersed within epoxy matrix (CNT-TiO2-Epoxy; CNF-TiO2-Epoxy), namely TiO2 composite, were obtained through tworoll mill method. Kinetics study results using specific mathematic models allowed the eluci‐ dation of some mechanistic aspects for sorption and photocatalysis for the application in drinking water. The intercalation of the carbon and zeolite supported TiO2 layers into a fil‐ tering system that allows to develop a self-cleaning filtering system in drinking water. Chapter 7 presents a review of the role of HAp in the TiO2/Hydroxyapatite composite in‐ cluding the adsorption ability of contaminations and the promoted impacts of the HAp component. Chapter 8 presents the study of the TiO2 photocatalyst for photoreduction of several reducible chemicals. The photocatalytic reduction of several toxic metal ions, includ‐ ing Ag(I), Cu(II), Cr(VI), Hg(II), and U(VI) in the presence of TiO2 , in order to decrease their toxicity, is described. Photodeposition of the noble metals, such as Ag(I), Au(III), Pt(IV), and Pd(II) for doping purposes by photocatalytic reduction over TiO2 is also addressed. Conver‐ sion of the greenhouse gas of CO2 into useful hydrocarbons and methanol by photocatalytic reduction using TiO2 photocatalyst is highlighted. Several operating parameters in photore‐ duction processes (photocatalyst dose, time of irradiation, pH of the solution, and the initial

VIII Preface

concentration of the substrates (the reducible chemicals)) are also reviewed.

**Dr. Sher Bahadar Khan** King Abdulaziz University Jeddah, Saudi Arabia **Dr. Kalsoom Akhtar** Ewha Womans University

Seoul, South Korea

**Chapter 1**

**Provisional chapter**

**Disinfection Methods**

**Disinfection Methods**

Amjad Khan and Amjad Khan

Amjad Khan and Amjad Khan

http://dx.doi.org/10.5772/intechopen.80999

**Abstract**

disinfection

**1. Introduction**

appropriate process.

Muhammad Saqib Ishaq, Zobia Afsheen,

Muhammad Saqib Ishaq, Zobia Afsheen,

DOI: 10.5772/intechopen.80999

Water must be made safe to drink, and an important step in ensuring water safety is disinfection. Disinfectants are added to water to kill disease-causing microorganisms. Ground water sources can be disinfected by "The Water Treatment Rule," which requires public water systems for disinfection. Chlorination, ozone, ultraviolet light, and chloramines are primary methods for disinfection. However, potassium permanganate, photocatalytic disinfection, nanofiltration, and chlorine dioxide can also be used. Organic material is naturally present in water. Certain forms of chlorine can react with these organic materials and result in the formation of harmful by-products; the U.S. Environmental Protection

Agency has anticipated maximum levels for these contaminants.

**Keywords:** chlorination, chloramines, ozone, ultraviolet light, photocatalytic

Killing, removal, or deactivation of harmful microorganisms can be referred to as disinfection. Destruction or deactivation of pathogenic microorganisms results in stopping their reproduction and growth. People may fall ill by consuming the contaminated water containing the pathogenic microorganisms. Disinfection and sterilization are interrelated processes, but sterilization kills all the harmful and harmless microorganisms. Hence, disinfection is a more

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

#### **Chapter 1 Provisional chapter**

#### **Disinfection Methods Disinfection Methods**

Muhammad Saqib Ishaq, Zobia Afsheen, Amjad Khan and Amjad Khan Muhammad Saqib Ishaq, Zobia Afsheen, Amjad Khan and Amjad Khan

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.80999

#### **Abstract**

Water must be made safe to drink, and an important step in ensuring water safety is disinfection. Disinfectants are added to water to kill disease-causing microorganisms. Ground water sources can be disinfected by "The Water Treatment Rule," which requires public water systems for disinfection. Chlorination, ozone, ultraviolet light, and chloramines are primary methods for disinfection. However, potassium permanganate, photocatalytic disinfection, nanofiltration, and chlorine dioxide can also be used. Organic material is naturally present in water. Certain forms of chlorine can react with these organic materials and result in the formation of harmful by-products; the U.S. Environmental Protection Agency has anticipated maximum levels for these contaminants.

DOI: 10.5772/intechopen.80999

**Keywords:** chlorination, chloramines, ozone, ultraviolet light, photocatalytic disinfection
