Current Trends and Future Developments on (Bio-) Membranes

Photocatalytic Membranes and Photocatalytic Membrane Reactors

Angelo Basile, Sylwia Mozia, Raffaele Molinari

• Publisher: Elsevier
• Year: 2018
• Print ISBN: 9780128135495
• eBook ISBN: 9780128135501
• Topic: Tecnologia e ingegneria
• Subtopic: Ingegneria chimica e biochimica

Current Trends and Future Developments on (Bio-) Membranes: Photocatalytic Membranes and Photocatalytic Membrane Reactors offers a comprehensive review on the state-of-the-art in the area of PMs and PMRs. The book gives an overview of the basis of photocatalysis and membrane separation and the basic aspects of photocatalytic membranes and photocatalytic membrane reactors, along with their applications, modeling, and the economic aspects of PMs and PMRs. The book addresses the main issues associated with PMRs design and tries to predict how long it will be before laboratory scale models can be scaled to the PMR industry.- Reviews new hybrid separation techniques based on photocatalysis and membranes- Offers a detailed description of the various photocatalytic membrane reactors and their function- Includes new membrane based separation techniques for the removal of emerging contaminants from water, such as pharmaceutical and personal care products- Discusses numerous reactor configurations and various membrane materials for photocatalytic membranes- Includes the modeling and economic aspects of various processes

Chapter 1

Heterogeneous Photocatalysis

A Promising Advanced Oxidation Process

Vittorio Loddo¹, Marianna Bellardita¹, Giovanni Camera-Roda², Francesco Parrino¹, and Leonardo Palmisano^{1 1}University of Palermo, Palermo, Italy ²University of Bologna, Bologna, Italy

Abstract

This chapter briefly presents the fundamentals of the processes of heterogeneous photocatalysis (PC). In particular, Langmuir–Hinshelwood and Eley–Rideal models that are often used to model the kinetics of heterogeneous photocatalytic reactions are described together with other models and equations derived. Moreover, some considerations about the dependence of the rate of PC on the light intensity, pH, and photocatalyst modification are done. Methods for photoreactor modeling are described, and the coupling of PC with other advanced oxidation processes (AOPs) using H₂O₂, O₃, and peroxydisulfate is discussed. It is highlighted that coupling different technologies results in a real intensification of the global efficiency only for specific ratios of the rates of the single processes. The suitability of the practical application of the AOPs must be based on a precise process efficiency assessment, which, as the results show, is a challenging but necessary task.

Keywords

Advanced oxidation process (AOP); Coupling photocatalysis-AOPs; Kinetics of photocatalytic processes; Photocatalysis; TiO₂

1.1. Introduction

Since the pioneering research of Fujishima and Honda in 1972 on the photocatalytic cleavage of water into H₂ and O₂ (Fujishima and Honda, 1972), basic and applied research have been devoted to heterogeneous photocatalysis (PC), especially for the oxidation of organic pollutants in water or in air (Schiavello, 1995; Fujishima et al., 1999; Augugliaro et al., 1997, 1999a,1999b, 2004; Maira Vidal et al., 1997). Heterogeneous PC is defined in the following way (Braslavsky et al., 2011): “Change in the rate of a chemical reaction or its initiation under the action of ultraviolet, visible, or infrared radiation in the presence of a substance, the photocatalyst, that absorbs light and is involved in the chemical transformation of the reaction partners.” The possibility of solar light exploitation makes PC in aqueous media a promising tool for green chemistry applications.

The occurrence of an oxidation reaction is linked to a transfer of one or more electrons from a reductant (electron donor) to an oxidant (electron acceptor).

These electron transfers result in a chemical transformation of both the oxidant and the reductant species. Sometimes chemical species with an odd number of valence electrons (radicals) are produced, and these species are highly unstable and reactive.

The radicals generated could further react with other species present in the reaction environment (both organic and inorganic) until thermodynamically stable oxidation products are formed.

The ability of an oxidant to react with other species is related to its oxidation potential. The most effective oxidants are fluorine, hydroxyl radicals (

OH), ozone, and chlorine with oxidation potentials of 2.85, 2.70, 2.07, and 1.49 eV, respectively (Dorfman and Adams, 1973). The final products of a complete oxidation (i.e., mineralization) of organic compounds are carbon dioxide (CO₂), mineral acids, and water (H₂O).

The phenomena occurring during an advanced oxidation process (AOP) are (1) formation of primary oxidizing species (e.g., hydroxyl radicals) and (2) reaction of these species with organic/inorganic contaminants in water (Glaze et al., 1987). Examples of advanced oxidation processes (AOPs) are processes that include O₃, H₂O₂, and/or UV light, cavitation, electron beam irradiation, and Fenton's reaction. Nevertheless, AOPs will be used also to refer to a more general group of processes that involve semiconductor PC.

The rationales of these AOPs are based on the in situ generation of the highly reactive transitory species aforementioned for mineralization of refractory organic compounds, water pathogens, and disinfection by-products (Esplugas et al., 2002; Pera-Titus et al., 2004).

Heterogeneous PC uses semiconductor oxides irradiated with UV, near-UV, or visible light at ambient temperature and pressure and i...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of Contributors
• Preface
• Chapter 1. Heterogeneous Photocatalysis: A Promising Advanced Oxidation Process
• Chapter 2. Membranes and Membrane Processes: Fundamentals
• Chapter 3. Materials and Design of Photocatalytic Membranes
• Chapter 4. PMRs Utilizing Pressure-Driven Membrane Techniques
• Chapter 5. PMRs Utilizing Non–Pressure-Driven Membrane Techniques
• Chapter 6. Performance of Reactors With PMs
• Chapter 7. PMRs in Photodegradation of Organic Contaminants: Water and Wastewater Treatment
• Chapter 8. PMRs in Photocatalytic Synthesis of Organic Compounds
• Chapter 9. How Far Are We From Large-Scale PMR Applications?
• Chapter 10. Modeling Photocatalytic Membrane Reactors
• Chapter 11. Economical Aspects in Photocatalytic Membrane Reactors
• Index