Agriculture Reference
In-Depth Information
authors also concluded that the rate of release of the pesticides from the pectin
polymer matrix was greater than from the alginate polymer matrix. In addition,
considerable effects on the release of both pesticides were only observed for
nanocomposites with montmorillonite clay.
Recently, Bortolin et al. (
2013
) obtained a novel nanocomposite based upon a
PAAm/methyl cellulose/montmorillonite hydrogel and evaluated its application as
a possible candidate to be used as a carrier vehicle in the controlled release of urea
fertilizer. The results indicated that the release process was strongly dependent
upon the hybrid nanocomposite hydrophilicity, the pH of the release medium, and a
hydrolysis treatment. The results showed that the release of urea was more
prolonged, approximately 192 times more slowly, for the hydrolyzed hydrogel
when compared to the control (pure urea). Additionally, according to the authors,
these nanocomposites were the first carrier vehicles to release 90 g of urea per gram
of dry hydrolyzed hydrogel used.
Novel hybrid nanocomposites based upon wheat gluten and three types of
commercial nanoclays (1 unmodified: sodium montmorillonite or HPS and 2 organ-
ically modified montmorillonites: Cloisite
®
30B or C30B; Dellite 72T or D72T),
using a bi-vis extrusion process, were developed by Chevillard et al. (
2012
). Ther-
mal, structural, and morphological properties of these nanocomposites were char-
acterized by differential scanning calorimetry, wide angle X-ray scattering analysis
(WAXS), and transmission electron microscopy (TEM) techniques, respectively.
The TEM results (Fig.
5.6
) showed that the best intercalation/exfoliation degree
was found for the WG-HPS-E hybrid nanocomposite (where E represents the
presence of the pesticide ethofumesate). The absence of the HPS nanoclay diffrac-
tion peak observed in the WAXS technique supported this conclusion. However,
the most important result about the controlled release of the ethofumesate pesticide
from these hybrid nanocomposites is shown in Fig.
5.6
. This figure shows that the
quantity of ethofumesate pesticide released in water for three different temperatures
from the wheat gluten-based hybrid nanocomposites
followed the order
WG-HPS-E
WG-E
WG-C30B-E
WG-D72T-E. This result is an important
>
>
>
indication that
the nanocomposite structures affected the pesticide release
mechanism.
Jafari et al. (
2014
) developed a system for the determination of pesticides based
upon polypyrrole/cloisite-Na
+
montmorillonite hybrid nanocomposites by an
electropolymerization method at a constant anodic potential of 0.95 V vs Ag/AgCl
using Ni-Cr wire, platinum electrode, and a pseudo Ag/AgCl electrode as the
working, counter, and reference electrodes, respectively. SEM micrographs,
presented in Fig.
5.7
, show that the coated layer of the Ni-Cr wire (Fig.
5.7a
) was
approximately 32
m. The polypyrrole (Ppy) film exhibited a dense morphology
when compared to the Ppy/nanoclay film. Additionally, Ppy/nanoclay
nanocomposites had a porous structure when compared to Ppy that was attributed
to the insertion of Ppy into the clay galleries.
According to the authors, this highly porous structure would significantly
increase the available surface area of the coated fiber and would enhance the
extraction efficiency in solid-phase microextraction (SPME), which was confirmed
μ
