Environmental Engineering Reference
In-Depth Information
20.1 Introduction
The extent and dispersion of contaminants in drinking water has generated immense
interest from scientists and policy makers in understanding their trend. This is due to
the increased deterioration of environmental ecosystems caused by population growth,
increased industrial activities, and the advent of modern technologies. The increase in
human population has resulted to population density swelling in areas that are in prox-
imity to rivers, lakes, or other sources of freshwater. Moreover, many agricultural and
industrial activities are located in areas close to major water sources since water is highly
needed in these sectors. The overall outcome of this trend will no doubt add massive loads
of both domestic and industrial wastes to these water sources.
All these activities will certainly affect the state of water quality, resulting in waterborne
diseases worldwide with the consequences being more intense in the developing world. To
counter this problem, strategies to ensure that clean and safe water is available and accessi-
ble to all have been put in place, and guidelines and regulations for various contaminants
(physical particulates, organic chemicals, inorganic chemicals, pathogens, etc.) have been
stipulated by the relevant national and international authorities. A number of technologies
have been developed for remediating contaminated water sources, and these are classiied
as either thermal, physico-chemical, or biological methods. These methods, however, are
known to offer high eficiencies when employed to solve very speciic problems of water
pollution. Of late, nanotechnology has been in the forefront among other technologies that
are employed for the purpose of treating water from both physiochemical and biological
contaminants.
The use of different types of nanomaterials for water treatment has been reported by
many researchers in various places, with some being in various stages of development. An
attractive feature of these nanomaterials is that they are synthesized with speciic func-
tionalities that give them the desired peculiar properties, such as high surface area to
volume ratio, which, in turn, increases the preconcentration/enrichment factors, resulting
in high adsorption capacities for targeted contaminants. Some of the nanomaterials and
nanoparticles that have been reported in water puriication strategies include zerovalent
and bimetallic iron particles, single-walled, double-walled, and multiwalled carbon nano-
tubes, titanium oxide, magnesium oxide, self-assembled monolayer on mesoporous sup-
ports, and nanoiltration membranes.
20.2 Polymer-Clay Nanocomposites
Polymeric composites are polymers that have been illed with synthetic or natural inor-
ganic compounds in order to improve their chemical and physical properties or to reduce
cost by acting as a diluent for the polymer.
1-3
In this context, the polymer is called a matrix.
If the iller is in the nanometer range, the composite is called a nanocomposite. These
nanocomposites are a new class of composites, and they possess unique properties that are
typically not shared by their more conventional microscopic counterparts.
2
Many illers have been used in nanocomposites preparation; however, clay (hydrous
layer silicates) and layered silicates have been most widely used.
4-6
Clay-based nanocom-
posites, which are the subject of this research, have received considerable scientiic and
