Photocatalytic materials & surfaces for environmental cleanup

220 Pages·37.646 MB·English

by  Rahesh J Tayade

Photocatalytic Materials & Surfaces for
Environmental Cleanup
Edited by
Rajesh J. Tayade
Photocatalytic Materials
&
Surfaces for
Environmental Cleanup
Special topic volume with invited peer reviewed papers only.
Edited by
Rajesh J. Tayade
Copyright  2012 Trans Tech Publications Ltd, Switzerland

All rights reserved. No part of the contents of this publication may be reproduced or
transmitted in any form or by any means without the written permission of the
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Volume 712 of
Materials Science Forum
ISSN 1662-9760
Full text available online at http://www.scientific.net

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Preface

This Special Topic Volume is the results of the contribution of thirty four experts form the international
scientific community in the respective field of research. It thoroughly covers newly developed
photocatalytic materials, photocatalytic surface, photocatalytic reactors and their designs, for the
environmental cleanup applications as well as for hydrogen generation and storage. It gives the latest
and in-depth coverage to the physics, chemistry, nanomaterials, nano-composite, and engineering of
photocatalytic materials applications for environmental applications.

Nowadays, environment pollution and energy crisis are faced throughout the world. So to overcome
these problems it is an urgent task to develop technologies that can remove the pollution and can
provide alternative clean energies. Photocatalysis is one of the promising methods for both the
problems and becoming more and more attractive to industry today because global environmental
pollution has come to recognized as a serious problem that need to be addressed immediately.
“Photocatalysis” has potential to open one of the desirable technologies for environmental abatement
and production of next generation’s fuel. The photocatalysis is a phenomenon to promote chemical
reactions on a surface of irradiated semiconductor. The essence of the photocatalysis is attributed to
the property of photo-excited carriers (electrons and holes) with strong oxidization and reduction. That
finally contributes to the decomposition, deodorization, and sterilization of the hazard organics, as well
as decomposition of water to hydrogen and oxygen. The use of photocatalytic materials for the
environmental cleanup and hydrogen production by water splitting was stated after a remarkable work
published in Nature in 1972 and called Honda-Fujishima effect. A. Fujishima and K. Honda achieved
ultraviolet light-induced water cleavage using titanium dioxide (TiO ) photoanode in combination with
2
platinum electrode soaked in an electrolyte aqueous solution. This opened up the possibility of
photocatalytic degradation of organic pollutant and solar energy conversion. Intense research carried
out over past few decades has resulted in improved environmental cleaning and hydrogen production
using photocatalysts.

In order to reduce the environmental pollution and production of next generation fuel tremendous efforts
are under progress and they are mainly based on photocatalytic processes, as they are highly cost
effective and cheap as compared to other processes. But still to meet the global challenges, there is
need to focus on development of novel photocatalytic materials and surfaces for these applications.
Presently, many researchers are working on development of new photocatalytic materials, surfaces to
meet the pollution problem. Here in this volume development of visible light active photocatalytic
materials and surface have been covered some extent.

This volume is indeed the result of remarkable cooperation of many distinguished experts, who came
together to contribute their research work and comprehensive, in-depth and up to date review chapters.
I am very thankful to all contributing authors who, in spite of their busy life in research and teaching,
willingly accepted the call to contribute and sent their manuscript in time. I would also like to express
my gratitude to all the publishers and authors and others for granting us the copyright permissions to
use their illustrations. Although sincere efforts were made to obtain the copyright permissions from the
respective owners to include the citation with the reproduced materials, I would like to offer my sincere
apologies to any copyright holder if unknowingly their right is being infringed.

This volume contains twelve state-of-the-art research articles and reviews: Chapter 1, a review article,
focuses on the contribution of nanotechnology for removal of water pollutants and provides a critical
analysis of various reports on the degradation of pollutants by TiO nanotubular photocatalytic materials
2
and surfaces.

Chapter 2, is also a review article focuses on the application of TiO mainly for conversion of solar light
2
in to electrical energy and water splitting for hydrogen production. Chapter 3 is research article focuses
the modification of photocatalytic materials by doping with metal and study its properties for
photocatalytic degradation of dye. Chapter 4, demonstrate the use of photocatalytic materials for
development of auto-cleaning surface of buildings by addition of photocatalyst into cement. Chapter 5,
6, & 7 contains, the synthesis of nano-composite and modified metal ion doped photocatalyst for the
degradation of dye pollutants in water in presence of visible and ultraviolet light. Chapter 8 & 9, talks
about the photocatalytic thin film development by doping with diethanolamine (DEA), MCM-41 and
silver for photocatalytic degradation of dye and for gaseous hazard air pollutants such as benzene,
toluene, ethylbenzene and xylene (BTEX) under visible light. Chapter 10 & 11, are review article
summarizes the remediation of amines and photocatalytic degradation of carboxylic acids from waste
water. Chapter 12 is a review article based on the synthesis of photocatalysts and design of
photoreactors for treatment of industrial effluents and also brings out inadequacies associated with the
photocatalytic technology for wastewater treatment.

I would like to take this opportunity to express my sincere gratitude to Dr. P. K. Ghosh (Director, Central
Salt & Marine Chemicals Research Institute-CSIR, Bhavnagar). My special thanks to Dr. R. V. Jasra
(Vice Precident, Reliance Industries Limited, Vadodara) and Dr. H.C. Bajaj (Senior Principle Scientist,
CSMCRI, Bhavnagar). My special thanks to Mr. Sivakumar Thillai and Mr. Kalithasan Natarajan, without
their continuous encouragement and association with me during the this Special Topic Volume would
have not been brought into its final form. I would like to acknowledge the sincere efforts of Mr. Thomas
Wohlbier of TTP publishing Authority, in evolving this Special Topic Volume in to its final shape. Last
but not the least I am highly appreciative of the support of my all family members.

Rajesh J. Tayade
Discipline of Inorganic Materials & Catalysis,
Central Salt & Marine Chemicals Research Institute,
Bhavnagar
India
Table of Contents
Preface
The Contribution of Nanotechnology for Removal of Water Pollutants
S. Anandan 1
Application of Titanium Dioxide (TiO ) Based Photocatalytic Nanomaterials in Solar and
2
Hydrogen Energy: A Short Review
A. Al-Ahmed, B. Mukhtar, S. Hossain, S.M. Javaid Zaidi and S.U. Rahman 25
The Influence of Carbon Doping on TiO Nanoparticle Size, Surface Area, Anatase to Rutile
2
Phase Transformation and Photocatalytic Activity
P. Nyamukamba, L. Tichagwa and C. Greyling 49
Photocatalytic Cement by TiO Addition
2
P. Periyat, A.S. Divya and K.G.K. Warrier 65
Photocatalytic Activity of Sol-Gel Derived Bi O -TiO Nanocomposite
2 3 2
C. Karunakaran, P. Magesan and P. Gomathisankar 73
Photocatalytic Activity of Transition Metal Ion Doped Titania for Amaranth Dye
Degradation
N. Divya, A. Bansal and A.K. Jana 85
Photocatalytic Degradation Studies of J-Acid under Visible Light and Ultrasonic Activation
Using Dye Sensitised TiO
2
S. Kaur and V. Singh 105
Enhancement of Photocatalytic Activity of TiO Thin Film Using Diethanolamine and
2
MCM-41
A.K. Karki, N. Grisdanurak and S. Chiarakorn 117
Novel Photocatalytic Ag/TiO Thin Film on Polyvinyl Chloride for Gaseous BTEX
2
Treatment
P. Peerakiatkhajorn, C. Chawengkijwanich, W. Onreabroy and S. Chiarakorn 133
Treatment Methods for the Remediation of Amines: A Review
Pankaj, M. Verma, S. Goyal and P.K. Patnala 147
Titanium Dioxide Catalyzed Photocatalytic Degradation of Carboxylic Acids from Waste
Water: A Review
V. Gandhi, M. Mishra and P.A. Joshi 175
Photocatalysts and Photoreactors for Treatment of Industrial Effluents
N.N. Rao 191
© (2012) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/MSF.712.1
The Contribution of Nanotechnology for Removal of Water Pollutants
Sambandam Anandan
Nanomaterials and Solar Energy Conversion Laboratory, Department of Chemistry,
National Institute of Technology, Trichy 620015, India.
email: [email protected]; [email protected]
Keywords: Nanotubes, Semiconductor, Pollutants, Photodegradation

Abstract. The use of nanosized semiconductor particles in various forms for the photocatalytic
degradation of pollutants has been discussed. The aim of this review is to provide a critical analysis
of various reports on the degradation of pollutants by various semiconductor nanomaterials. It has
been shown that self-organized one-dimensional nanotube matrix creates a better opportunity to
remove pollutants more efficiently than the randomly oriented nanoparticles. The use of metal
doping and mixed semiconductor systems has also been analyzed. Although large improvements in
the present technology are required, the review points to focus on the advantages of nanomaterials
compared to bulk materials in efficient purification of water.

Introduction
Chemicals (dyes, pharmaceuticals, endocrine disrupting compounds, etc) used in a wide range of
applications in our modern society are produced on a large scale worldwide. Because of their
physical and chemical properties, many of these substances or their metabolites end up in the
environment, where they can induce adverse effects on ecosystem. Most environmental data focus
on the occurrence, fate, and transport of these compounds in waste water. However, during the
sewage process these inactive compounds are readily transformed into ones that are potentially
more harmful than original. The inadequate removal of such pollutants in waste water treatment
plants will ultimately find the way into the potable water thus causes environmental remediation [1,
2].
Sunlight photodegradation is just one of many possible processes that pollutants may undergo once
dispersed in the environment. On the other hand, the use of UV/vis radiation, alone or in
combination with different auxiliary oxidizing agents is the basis of advanced oxidation processes
(AOPs) [3]. In this context, the use of photosensitizers and/or photocatalysts has become a
requirement, since many common pollutants are relatively inert to direct UV/vis radiation. Hence
exploration of materials to identify effective photocatalysts for the decompostion of harmful organic
contaminants has grown into an intensive area of research in the past decade.
In this regard, the significance of semiconductor photocatalysis for the degradation of harmful
organic compounds was recognized for environmental remediation [4-10] because it is highly
stable, cost-effective and capable of mineralizing various organics has been studied by many
research groups. The limitations of a semiconductor as a photocatalyst for a particular use can be
surmounted by modifying the surface of the semiconductor. To date, three benefits of modifications
to photocatalytic-semiconductor systems have been studied: (1) inhibiting recombination by
increasing the charge separation and therefore increasing the efficiency of the photocatalytic
process; (2) increasing the wavelengths responsive range (i.e., excitation of wide bandgap
semiconductors by visiblelight) and (3) changing the selectivity or yield of a particular product. To
attain such properties in photocatalysis, the addition of noble metals to semiconductor can change
the photocatalytic process by changing properties of the semiconductor surface [11-13]. The metal
can enhance the yield of a particular product or the rate of the photocatalytic degradation.
2 Photocatalytic Materials & Surfaces for Environmental Cleanup
On the other hand, an exponential growth of research activities has been seen in nanoscience and
nanotechnology in the past one decade regarding semiconductor nanomaterials [14-18]. This is
because new physical and chemical properties emerge when the size of the material becomes
smaller and smaller, and down to the nanometer scale. Properties also vary as the shapes of the
shrinking nanomaterials change. Among the unique properties of nanomaterials, the movement of
electrons and holes in semiconductor nanomaterials is primarily governed by the well-known
quantum confinement and the transport properties related to phonons and photons are largely
affected by the size and geometry of the materials [14-18]. The specific surface area and surface-to-
volume ratio increase dramatically as the size of the material decreases [14,19]. The high surface
area brought about by small particle size is beneficial to many semiconductor based devices, as it
facilitates reaction/interaction between the devices and the interacting media, which mainly occurs
on the surface or at the interface and strongly depends on the surface area of the material. Thus, the
performance of semiconductor based devices is largely influenced by the sizes of the individual
building units, apparently at the nanometer scale. Many excellent reviews and reports on the
preparation and properties of nanomaterials have been published recently [20-32]. Chen and Mao
[31] summarized the necessity of photosensitive material (TiO2) for various applications [Fig. 1].
However, the current review primarily focuses on the recent development in the field of
semiconductor nanomaterials for removal of environmental pollutants.

Fig. 1, Schematic chart that briefly shows the historical survey on the synthesis (left) and
applications (right) of oxide nanotubes. Left: P sol–gel, electrochemical, N sol–gel,
hydrothermal, oxidation methods, ALD, and anodization methods. Right: Molecular
separation, hydrogen sensing, single-DNA sensing, hydrogen generation, and DSSC
respectively. [Ref: 31] Ref: Chem. Mater. 2008, 20, 756–767
Degradation of Environmental Pollutants using TiO nanotubes. Oxidation of many pollutants,
2
especially organic species, requires high potentials with the result that the valence band location at
the semiconductor-electrolyte interface has to be rather positive, as exemplified by TiO [8]. In
2
these instances, the photogenerated holes will have sufficient energy to oxidize the organics via the
generation of hydroxyl radicals. However semiconductors such as CdS, ZnO and α-Fe O do not
2 3
Rajesh J. Tayade 3
have long term stability and they undergo either photoanodic or photocathodic corrosion [9]. Hence
for the removal of organic pollutant, the best semiconductor is TiO . This is because the range of
2
organic pollutants that can be completely photomineralized by oxygen, using TiO as sensitizer, is
2
very wide and includes many aliphatics, aromatics, detergents, dyes, pesticides, and herbicides.
TiO in the anatase form appears to be the most efficient semiconductor for environmental
2
application. In the earlier days, TiO was produced by sol gel method by Dagan and Tomkiewicz
2
[33] to perform photoassisted oxidation of salicylic acid. Authors got enhanced photoactivity while
compared to commercial Degussa (P-25) TiO [Fig. 2]. The reasons for such enhanced
2
photoactivity may be due to such TiO2 aerogels have a porosity of
85 %, a BET surface area of 600 m2g-1, and a bulk density of 0.5 g/cm3. But Degussa (P-25) TiO
2
(non-porous mixture (anatase and rutile; 70:30 %) with a BET surface area of 55 ± 15 m2g-1 and has
a crystallite size of 30 nm in 0.1 µm diameter aggregates) has set the standard for photoreactivity in
many environmental applications [34-36]. Later, Khalik et al. [37] have shown that Hombikat
UV100 was better than Degussa in the case of photocatalytic reduction of Cr(VI) whereas Theurich
et al. [38] showed that in the case of photocatalytic degradation of 4-chlorophenol Degussa P-25
was better than Hombikat UV 100.

Fig. 2, Photodegradation profiles of salicylic acid on annealed (E ) and nonannealed (E) TiO
la l 2
aerogels as compared to a commercial powder (Degussa). [Ref: 33] Ref: JPC 97 (1993)
12651.

The photocatalyst (Degussa (P-25) TiO ) derives its activity from the fact that when photons of a
2
certain wavelength are incident upon its surface, electrons are promoted from the valence band and
transferred to the conductance band. This leaves positive holes in the valence band, which react
with the hydroxylated surface to produce OH• radicals which are the most potent oxidizing agents.
Thus the above mentioned photocatalytic oxidation of organic pollutants can be described via the
following reaction sequence [39-42]
TiO + hν TiO (e- + h+) (1)
2 2
TiO (h+) + H O TiO + •OH + H+ (2)
2 2 ad 2 ad
TiO (h+) + -OH TiO + •OH (3)
2 ad 2 ad