Page 633 - Polymer-based Nanocomposites for Energy and Environmental Applications

584 Polymer-based Nanocomposites for Energy and Environmental Applications

photosynthesis, ability to deplete dissolved O 2 , and toxicity to flora, fauna, and human
beings. If synthetic dyes such as azo dyes are degraded anaerobically, aromatic amines
are generated, which are very toxic, carcinogenic, and mutagenic. The organic dyes
are also typically complex aromatic compounds with substantial structural diversity
[59]. Their properties are generally improved to give a high degree of biological,
chemical, and photocatalytic stability, which are resistant to degradation [60]. There-
fore, the direct release of colored effluents into the aquatic ecosystems causes various
types of health problems. Thus, dye removal has been an important but challenging
area of wastewater treatment. Adsorption has been found to be one of the most popular
physicochemical treatment methods for removing dyes.
The adsorbents must have high adsorption capacity [61]. Polymer nanocomposites
are being frequently used as an adsorbent for dye removal from wastewater, but the
major challenge is the separation of adsorbent from the water after adsorption [61].
Magnetic separation of dispersed particulate adsorbents has become a promising tech-
nique for this purpose because they can be easily separated with the help of a magnet.
The potential of iron-oxide/polymer composite adsorbents with a large surface area
for the removal of organic components was studied using methylene blue (MB) as
a test substance. Adsorption isotherms fitted well with the Langmuir isotherm model
and the adsorption capacity of MB on this adsorbent was found to be high. The iron-
oxide/polymer nanocomposite could be easily separated from the aqueous solution by
placing a permanent magnet near the glass bottle, thus enabling separation, recovery,
and reuse of the adsorbents [62].
Removal of cationic and anionic model dyes depends on the pH of the solution.
Dye removal abilities of malachite@clay nanocomposite have been studied by taking
MB and congo red (CR) as cationic and anionic model dyes. The malachite@clay
nanocomposite exhibited excellent adsorption capacities in wide concentration ranges
for both the dyes. Enhanced removal was observed in acidic range for CR, while MB
removal was higher in alkaline range (Fig. 21.14) [60].

21.6.2.2 Pesticides

The term pesticide covers a wide range of compounds including insecticides, fungi-
cides, herbicides, rodenticides, molluscicides, nematicides, plant growth regulators,
and others. Pesticides often kill or harm organisms other than pests, including humans.
Pesticides can reach surface water through runoff from treated plants and soil. Con-
tamination of water by pesticides is widespread. Removal of permethrin pesticide
from water has been carried out by chitosan’zinc oxide nanocomposite [63].

Cl
O
Cl O
O
Structure of permethrin