Agriculture Reference
In-Depth Information
remove anionic contaminants from water. Hexadecyltrimethylammonium bromide
(HDTMABr), a cationic surfactant, was used for surface modification of zeolite,
and results showed that at HDTMABr loading maximum of 200 mmol kg
1
,
corresponding to 200 % of the zeolite
s effective cation exchange capacity, a
surfactant bilayer would form and the surface was reversed to positive (Li and
Bowman
1997
).
Li et al. (
1998
) revealed that SMZ has been studied extensively in the last
15 years due to its high capacity of sorption and retention of oxyanions. The
surfactant molecules (HDTMABr) form bilayers on zeolite external surfaces with
the lower layer held by electrostatic interaction between the negatively charged
zeolite surface and the positively charged surfactant head groups, while the upper
layer is bound to the lower layer by hydrophobic forces between the surfactant tail
groups in both layers (Bowman
2003
). Surface modified zeolite showed that
positive results have been reported on the retention of chromate (Krishna
et al.
2001
) and phosphate (Bansiwal et al.
2006
). Li and Zhang (
2010
) reported
that the loading capacity of sulfate compared to nitrate on SMZ may be attributed to
the charge effect of the anions. Each HDTMABr molecule contributes one positive
charge, which needs only one negative charge to balance. Sulfate is divalent and
thus needs two HDTMABr molecules to neutralize. Meanwhile, the HDTMABr
surface configuration is not rigid because of the surfactant tail-tail interaction.
Thus, bridging two HDTMABr molecules with one sulfate may be less favored
compared to 1:1 neutralization of HDTMABr by nitrate.
'
3.3 Characterization of Nano-fertilizers
Synthesized nano-fertilizers are to be characterized using particle size analyzer
(PSA), zeta analyzer, Fourier transform infrared spectroscopy (FTI-IR), Raman
spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM),
energy dispersive X-ray spectroscopy (EDAX), transmission electron microscope
(TEM), and atomic force microscope (AFM) to confirm the size, shape, charge
distribution, functional groups, elemental composition, surfactant attachment, and
sulfate attachment. The synthesized nano-fertilizers have been characterized using
the set of equipments listed above. Extensive studies had been undertaken to
characterize nitrogenous (Subramanian and Sharmila Rahale
2013
; Mohanraj
2013
; Manikandan and Subramanian
2014
), phosphatic (Bansiwal et al.
2006
;
Adhikari
2011
; Behnassi et al.
2011
), potassic (Subramanian and Sharmila Rahale
2012
), sulfatic (Selva Preetha et al.
2014
; Thirunavukkarasu
2014
), and zinc
(Subramanian and Sharmila Rahale
2012
) fertilizers.
