Page 23 - Multifunctional Photocatalytic Materials for Energy

12 Multifunctional Photocatalytic Materials for Energy

Catalysis Environment
and remediation and
photocatalysis chemical
synthesis

Applications
Sensors,
health and of Batteries and
automobiles metal oxides supercapacitors

Clean energy DSSCs,
production, Solar cells and
H production fuel cells
2

Fig. 2.3 Possible applications for metal oxides.

waste materials from the paper industry, the leather and tanning industries, the food
industry, agricultural research, and pharmaceutical industries. The release of these
colored and toxic compounds in the environment has raised substantial concern be-
cause of their toxic effects on the environment, plants, and human beings. In ad-
dition, two classes of dyes, azo dyes and thiazine dyes, can cause serious health
risks. Some of the azo dyes are highly carcinogenic. The conventional wastewater
treatment plants cannot degrade the majority of these pollutants. Thus there has been
increasing interest in methods for decontamination of such products over the past
few decades [4,16,17].
The waste from the textile industry, paper industry, leather and tanning industries,
food industry, agricultural, and pharmaceutical industries has long been considered a
serious environmental issue. Most paper mills and textile industries produce waste-
water that contains aromatic dyes, which are highly toxic and difficult to decompose
because of their relatively stable chemical structures. Many dyes (methylene blue,
methyl orange) are used in industry for a range of purposes. Among them, methy-
lene blue (MB) is one of the most frequently used dyes for agriculture, textile, paper-
making, cosmetic, and pharmaceutical purposes [4,16–21].
Photocatalysts combined with ultraviolet light can oxidize organic pollutants into
nontoxic byproducts, such as water and CO 2 , and can sterilize certain bacteria. This
technology is very effective for removing hazardous organic compounds such as dyes,
VOCs, and TOCs and for killing a variety of bacteria and some viruses in secondary
wastewater treatments. Pilot projects have demonstrated that photocatalytic detoxi-
fication systems can effectively kill fecal coliform bacteria in secondary wastewater
treatments [4,14–19].
The excessive use of organic chemicals in both industrial manufacturing and nor-
mal household uses has led to their leaching into the environment, causing shocking