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About this book

This book will be a guiding path to understand the photocatalytic process and mechanism for the deterioration of heavy metals, persistent organic pollutants and pathogens from wastewater. Environmental remediation is of crucial importance in the context of human sustainability in the present and future times. The unplanned anthropogenic activities and revolutionary industrialization end up in environmental contamination with noxious organic-inorganic and biogenic pollutants. The photocatalytic disinfection and detoxification is the only solution to preserve and restore the ecological balance. The main emphasis is to explore and enhance the photocatalytic potentials of solar active-materials.

Table of Contents

Frontmatter

Chapter 1. Role of Nano-photocatalysis in Heavy Metal Detoxification

Abstract
Heavy metal elimination from contaminated waterbodies is a worldwide concern. Their inherited property of causing toxicity with the metabolism of both aquatic and terrestrial life forms has been revealed. These metals are highly poisonous for flora and fauna even if they are present at very low concentrations due to their bioaccumulative capabilities. The detoxification of such contaminants is considered to be a prime concern in ecological remediation. Surface chemistry, photocatalysis and chemical engineering fundamentals in combination with advanced nano-engineered technologies spark up attractive prospects towards the treatment of water resources with heavy metal contamination. Products obtained through photocatalysis-assisted engineered nanotechnology have successfully proven upgraded performance characteristics like increased surface area, easy recovery, reuse capability, better volumetric potential, reduced mechanical stress, enhanced shelf life, excellent sorption behaviour, stability under operational conditions, easy separation, no secondary pollution and many more. The present chapter is contemplated to display an overview of the mechanisms and promising research activities on photocatalytic nanoparticles assisted heavy metal detoxification. This will thereby provide researchers and individuals with a profound intuition and bridge the research gaps of the exquisite nanomaterial-induced heavy metal removal techniques.
Ankita Mazumder, Souptik Bhattacharya, Chiranjib Bhattacharjee

Chapter 2. Solar Photocatalysis Applications to Antibiotic Degradation in Aquatic Systems

Abstract
Contaminant such as pesticides, veterinary products, industrial compounds, food additives, personal care products, and pharmaceuticals may cause a negative effect when comes into contact with the environment. The presence of these compounds can be generated toxic effects in the aquatic system and cause an irreparable ecological alteration. Antibiotic compounds are one of the main pollutants found in the aquatic systems, because they are often inadequately prescribed and as a part of antibiotics is not completely consumed or degraded in human and animal bodies. Their residues can be entered in aquatic systems by wastewater treatment plants. The presences of antibiotics in aquatic systems have been linked to increasing microorganism antibiotic resistance through different mutations. Advanced oxidation processes have been proposed for the treatment of antibiotic in aqueous systems, including solar photocatalysis. Several parameters are necessary to take into account in solar photocatalysis treatment to eliminate antibiotics, since these compounds display different physicochemical and biological properties. This chapter discusses the effect of parameters and pathways (transformation products) of solar photocatalysis of antibiotic groups usually found in aquatic systems as macrolides, sulfones, lincosamides, and quinolone.
Margarita Jiménez-Tototzintle, Enrico Mendes Saggioro

Chapter 3. Biomass-Based Photocatalysts for Environmental Applications

Abstract
In recent years, advanced oxidation process has shown a new frontier environmental friendly and sustainable wastewater treatment technology to replace the conventional treatment methods. Heterogeneous photocatalysis is a promising approach in environmental remediation. Among the popular photocatalysts, semiconductor oxide photocatalysts have been widely explored due to their durability and chemical and physical properties. However, the practical application of semiconductor oxide is limited because of its expensive cost, large bandgap energy and rapid recombination of the photoinduced electron-hole pairs. This chapter addresses the main advancements in overcoming the barriers accompanied by pure semiconductor oxide by incorporating with biomass-derived carbonaceous materials for fabrication of effective visible light-responsive semiconductor oxide-based photocatalysts.
The utilization of these biomass-derived photocatalysts provides a greener synthesis route for environmental purifications. This chapter firstly highlights the types, properties and conversion of biomass into biochar, activated carbon (AC) or any other carbonaceous materials. The general methods for preparing biomass-based support and the mechanisms are also presented in details. Finally, the latest research papers on modification or functionalization of a biomass-based photocatalyst for the removal of organic pollutants have also been comprehensively discussed. There is still a lack of published information on the fundamental knowledge of biomass-derived photocatalyst to understand the complex photocatalytic mechanisms especially on the reactions occurring on the heterogeneous biomass surfaces. Therefore, further theories and hypotheses need to be investigated to fill these gaps in order to address all full potentials of the biomass-derived photocatalyst for environmental applications.
Yean Ling Pang, Chin Woei Lim, Katrina Pui Yee Shak, Steven Lim, Wai Chong Cheam, Chai Hoon Koo, Ahmad Zuhairi Abdullah

Chapter 4. Application of Bismuth-Based Photocatalysts in Environmental Protection

Abstract
Photocatalysis by use of advanced oxidation processes (AOPs) is gaining attention as an effective method of air purification and water treatment. Undoubtedly, photocatalysis can also be applied to produce useful fuels from photocatalytic reduction of CO2 and splitting of water, or it can be utilized as a “green” technology in industrial production. Despite recent research into other photocatalysts (e.g., TiO2 and perovskites), bismuth-based semiconductors such as Bi2O3, BiPO4, (BiO)2CO3, BiOX (where X = Cl, Br, and I), and pentavalent bismuthates (e.g., NaBiO3) are most promising because of their low cost, nontoxicity, and high oxidizing and reduction abilities in solar and visible light. Moreover, the conduction band edge and the valence band edge of Bi-based photocatalysts can be designed by using a suitable strategy for preparation of these materials. The photocatalytic activity of Bi-based materials can be additionally enhanced by heterostructures, e.g., using carbon or graphene quantum dots, Ag/AgCl, modified TiO2, or Fe3O4.
This chapter aims to highlight recent advancements in application of Bi-based photocatalysts and heterostructures in environmental protection. Albeit nonexhaustive, this review explores the progress made in the last 6 years by focusing on solar and visible light–driven degradation processes to eliminate such contaminants as antibiotics, nonsteroidal anti-inflammatory drugs, beta blockers, anticonvulsants, hormones, resorcinol, bisphenol A, and other derivatives of phenol, many of which have been detected in aqueous ecosystems. The application of Bi-based photocatalysts for removing NOx from indoor air using solar and visible light illumination is also presented. Finally, advances in water splitting and CO2 reduction to CO and CH4 with Bi-based photocatalysts are discussed.
Ewa Maria Siedlecka

Chapter 5. Phosphors-Based Photocatalysts for Wastewater Treatment

Abstract
Every day a large amount of products has been released by chemical and pharmaceutical industries threatening the environment and human health. Moreover, their removal using conventional oxidation methods is difficult because a lot of pollutants are biorecalcitrant. Photocatalysis, an advanced oxidation technology, appears one of the most viable solutions due to its ability to oxidize a wide range of toxic organic compounds into harmless compounds such as CO2 and H2O by irradiation with UV light. Organic pollutants can be removed from water by a UV-driven photocatalytic process involving nanoparticles with semiconducting properties. However, their use in a photoreaction system suffers of the disadvantage due to the no-uniform photon distribution inside the reactor core.
The chapter describes a possible solution for enhancing the photon distribution inside the photoreactors, using inorganic and organic light-emitting particles (phosphors) coupled with photocatalysts to be applied in water and wastewater treatment. The chapter also underlines the difference between inorganic particles having down-conversion, up-conversion, and long-afterglow luminescence properties. Additionally, the use of up-conversion organic phosphors has been proposed. Finally, some examples concerning the use of semiconductors coupled with different photoluminescent materials in the removal of pollutants from water and wastewater are presented.
Olga Sacco, Vincenzo Vaiano, Diana Sannino

Chapter 6. Nanocarbons-Supported and Polymers-Supported Titanium Dioxide Nanostructures as Efficient Photocatalysts for Remediation of Contaminated Wastewater and Hydrogen Production

Abstract
Organic contaminants (textile dyes, pesticides) in industrial wastewater have adverse effects on the environment and human health. Such environmental pollutants are resistant in the environment and are difficult to completely remove through treatment techniques. Therefore, titanium dioxide (TiO2) nanostructure-based photocatalytic processes have received much attention due to their environmentally green nature with high efficiency for complete photodegradation of organic pollutants to produce safe and clean water.
In this chapter, zero-dimensional to three-dimensional TiO2 nanostructures functionalized with various polymeric and nanocarbon hybrid materials are discussed as low-cost, nontoxic, and highly efficient photocatalytic materials for photodegradation of chemical pollutants, in comparison with pristine TiO2, through expansion of the visible light photoresponse and regulation of the bandgap properties of TiO2. Various chemical synthesis methods, surface modifications with various polymers and nanostructured carbons, compositions, morphological structures, growth mechanisms, physicochemical properties, electronic and optical characteristics, and photocatalytic mechanisms (e.g., reactive oxygen species generation) of various heterostructured TiO2-based photocatalysts are discussed in terms of their prospects and future challenges in the fields of photocatalytic environmental remediation and hydrogen generation.
Kakarla Raghava Reddy, M. S. Jyothi, A. V. Raghu, V. Sadhu, S. Naveen, Tejraj M. Aminabhavi

Chapter 7. Investigation in Sono-photocatalysis Process Using Doped Catalyst and Ferrite Nanoparticles for Wastewater Treatment

Abstract
Industrialization and urbanization affect the environment directly, and water is one of the primary natural resources which are affected significantly. With rapid development of science of nanotechnology, the use of nanomaterials in environmental applications, especially water treatment, has attracted the scientific community in the last decades. Nanomaterials have unique properties, for example, surface-to-volume ratio, quantum effect, low band-gap energy, etc., which give extra features in catalytic performance.
This chapter gives a brief introduction of nanomaterials including their classification, shape and structure, type of nanomaterials and their applications in degradation of recalcitrant organic contaminants. Moreover, an attempt was made to emphasize the role of catalyst surface in degradation mechanism in the presence of transient metal ions or other elements and an external oxidant such as H2O2. Additionally, we have also discussed process intensification using sono-hybrid advanced oxidation processes of sono-photocatalysis and heterogeneous Fenton-like reaction for wastewater treatment. Some of our investigations revealed that nanophotocatalyst such as ZrFe2O5 possesses dual characteristic and it contains α-Fe2O3 phase which acts as a centre of recombination for holes and electrons resulting to low photoactivity. However, this phase promotes Fenton-like reaction in presence of H2O2 leading to higher degradation. Therefore, the dual activities of photo and Fenton, ZrFe2O5, were found to be better catalyst for hybrid advanced oxidation processes than other conventional photocatalysts. On the other hand, the doping of transition metal ions into nanophotocatalyst helps to generate more OH radicals which attack the organic molecules adsorbed on the catalyst surface and enhanced the degradation efficiency. In sono-hybrid advanced oxidation processes, such photocatalysts exhibit negative synergy as the intense shock waves generated due to the transient collapse of cavitation bubbles influence the desorption of organic molecules from the solid surfaces. As a result, low degradation efficiency was seen due to reduction of interaction probability between radicals and organic molecules.
Sankar Chakma, G. Kumaravel Dinesh, Satadru Chakraborty, Vijayanand S. Moholkar

Chapter 8. Magnetic-Based Photocatalyst for Antibacterial Application and Catalytic Performance

Abstract
Photocatalysis using magnetic-based photocatalyst in water and wastewater treatment offers a green and effective technique for the disinfection of harmful microorganisms along with its unwanted chemical pollutants. Introduction of magnetic materials to the catalytic material composites allows for the convenient magnetic separation, hence providing more economical, effective and environmentally friendly water decontamination processes. In this work, we disclosed a brief review on the effect of various magnetic-based photocatalyst nanomaterials on the application of the photocatalytic disinfection and degradation processes. The influencing factors including photocatalyst concentration and light intensity, nature of microorganism, solution pH, initial bacterial concentration and physiological state of bacteria of such processes were presented along with the disinfection mechanisms. The mechanism of magnetic-based photocatalyst was mainly ascribed to the surface generation of reactive oxygen species as well as free metal ion formation. Additionally, the potential utilization of the magnetic-based photocatalyst as visible light nanomaterials was discussed, and their magnetic recoveries were reviewed. It was worth noting that the combined disinfection and decontamination processes will greatly improve the use of magnetic-based photocatalysts as potential alternative to conventional methods of water purification.
Sze-Mun Lam, Jin-Chung Sin, Abdul Rahman Mohamed

Chapter 9. Antimicrobial Activities of Photocatalysts for Water Disinfection

Abstract
Water is an essential element for the survival of humanity and the continuity of the planet’s development. Impacts of human activity on water resources have been a growing concern because of environmental contamination and public health problems. For that reason, strategies and technologies to promote water sustainability and ensure water availability for current and future generations, with suitable quality for its respective uses, are being researched and developed, with priority being given to modern, efficient, inexpensive, and fast techniques that can achieve adequate water disinfection. Water disinfection is an efficient process for removal, deactivation, or killing of microorganisms that are responsible for waterborne diseases, and it is applied in public water supply and reuse systems. Among disinfection techniques, a promising and efficient method used against a wide range of different species of organisms is photocatalytic water disinfection using a photocatalyst activated by ultraviolet (UV) or visible radiation for generation of reactive oxygen species (ROS) that damage microorganisms. We performed a review of the literature on the mechanisms of photocatalytic water disinfection and photocatalysts with microbial activity. It was found that disinfection may occur due to (1) attack by ROS on bacterial cells, (2) the effects of metal ion release on cellular proteins, (3) direct interactions between nanoparticles and bacterial cells, and (4) mechanical damage to cell membranes. Generation of ROS in the presence of light occurs with activation of the photocatalyst with appropriate radiation; however, the mechanism of disinfection when it is performed in the absence of light has not yet been completely defined. In order for industrial application of photocatalytic water disinfection to become feasible, it is necessary to develop photocatalysts that exhibit high antimicrobial activity and can be activated preferentially with solar radiation. Among the different types of photocatalysts are pure photocatalysts and nonmetals, halogens, metals, and rare earth–modified photocatalysts, as well as photocatalytic films, biofilms, and nanocomposites. Modified photocatalysts, especially fluorine- and cobalt-modified zinc oxide and silver- and nitrogen-modified titanium dioxide, are more efficient than pure oxides under visible radiation, which makes their use promising in solar-induced photocatalytic water disinfection because modified photocatalysts can be reused and are not harmful to human health and the environment, being in accordance with the principle of green chemistry. Photocatalytic films, biofilms, and nanocomposites include silver- and copper-modified potassium hexaniobate film; silver orthophosphate, titanium dioxide, and magnetite film; and titanium dioxide and tungsten(VI) oxide anchored on a reduced graphene oxide nanocomposite, which demonstrate high antimicrobial activity with a mortality rate higher than 97%. As few studies have been performed with native microorganisms and under real conditions, a case study was performed experimentally by the authors, involving application of a supported photocatalyst for disinfection of wastewater from whey processing during exposure to UV radiation. The photocatalyst, constituted by hematite and titanium dioxide supported on a glass sphere, showed high bacteriostatic activity against mesophilic microorganisms and irreversible damage to psychrophilic microorganisms’ cell walls and their components. Therefore, this chapter contributes to the knowledge about use of photocatalysts as water disinfection agents and for control of waterborne diseases, especially those that are activated by solar radiation, thus making photocatalysis an efficient, viable, and environmentally safe alternative.
Veronice Slusarski-Santana, Leila Denise Fiorentin-Ferrari, Mônica Lady Fiorese

Chapter 10. Medicinal Applications of Photocatalysts

Abstract
With the help of nanotechnology and nanoscience , future devices and technologies will be small and possess advanced features; photocatalysis is an important area of application. This chapter discusses the importance of photocatalysts and their medicinal applications for human beings in daily life. The properties of photocatalysts as a result of their nanoscale are discussed. The main medicinal applications of photocatalysts—antifungal, antimicrobial, anticancer, and several another applications—are also focused on in detail.
Busra Balli, Aysenur Aygun, Fatih Sen

Backmatter

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