dc.description.abstract |
During last three decades, calixarenes a family of macrocyclic oligophenols have
attracted much attention because of their unique molecular structure, simple one-pot
synthesis, stability and their application as recognition agents with high sensitivity toward
the ionic as well as neutral guest molecules. However, the present study comprise the
synthesis and derivatization of calix[n]arene based and/or simple polymeric resins by
anchoring different groups (i.e. esteric, nitro, amino or thiourea) along with their
analytical/environmental applications. The new synthetic compounds/resins were
characterized by various analytical techniques (i.e. FT-IR, NMR, SEM, elemental
analysis etc).
In the first phase of study, the synthetic work was carried out by synthesizing
5,11,17,23-p-tert-butyl-25,26,27,28-tetrahydroxycalix[4]arene (i) and 5,11,17,23,29,35-
hexa-tert-butyl-37,38,39,40,41,42-hexahydroxycalix[6]arene (ii) followed by their de-
tert-butylation from para-positions and Williumsons’ etherification to obtain iii, iv and
v, vi, respectively. The synthesis of iii and iv was achieved by the treatment of i and ii
with AlCl3 in the presence of phenol. Compounds v and vi, were prepared by the
reaction of bromoethyl acetate in the presence of K2CO3 in acetone while, the ligand v
was immobilized on to Amberlite XAD-4 resin (vii). The 5,11,17,23-p-tetranitro-
25,26,27,28-tetrahydroxycalix[4]arene (viii) was also synthesized from i by treating
H2SO4/ NaNO3 in chloroform. Furthermore, the ligand viii was used to obtain a new
derivative,
i.e.
5,11,17,23-p-tetranitro-25,26,27,28-tetramethoxycarbonylmethoxy-
calix[4]arene (ix).
The ligands (v,vi and ix) and resin (vii) were used in extraction (liquid-liquid
and/or solid-liquid) studies for a series of metal cations (i.e, Li+, Na+, K+, Cs+, Mg2+,
Ag+, Pb2+, Cu2+, Co2+, Cd2+, Ni2+, Hg2+, Al2+, Fe3+). The extraction results reveal that
both vi and vii are highly suitable extractants selective for Pb2+ while ix is for Hg2+ even
in the presence of other co-existing ions.
Consequently, the anion receptors were also synthesized; the ligand viii was
immobilized onto Marrifield resin to have x that was followed by catalytic reduction of
p-nitro groups of x to obtain a modified resin xi with amino groups. Finally, the p-amino
groups of xi were converted to thiourea binding sites in order to obtain resin xii.
The Amberlite XAD-4 resin (xiii) was modified to have nitro groups onto its
surface through nitration (xiv). The nitro groups were converted to amino groups by
catalytic reduction (xv) followed by conversion into thiourea (xvi) groups. for
comparison with above resins i.e. xi and xii.
In order to evaluate the fluoride extraction efficiency of newly synthesized
anionophoric resins (xi, xii, xv and xvi) solid-liquid extraction experiments were
performed. From the results it has been concluded that all resins have significant
extraction efficiency for fluoride from aqueous media. It has also been noticed that there
is no significant effect of co-existing anions (Cl-, Br-, I-, NO32-, NO2-, SO32-, PO42-, CO32-
and HCO3-) on the extraction behavior of these resins. A remarkable extraction efficiency
for fluoride has been observed with the calixarene appended resins (xi and xii) as
compared with the simply modified resins (xv and xvi). Moreover, the fluoride extraction
efficiency of the resins was also found satisfactory when these were applied on real water
samples collected from different places of Thar Desert. Thus, it has been deduced that the
resins could be used as adsorbent material for the removal of fluoride from the ground
water of Thar Desert. |
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