Chemistry Reference
In-Depth Information
assessed through measurements of critical properties such as removal of different
heavy metal ions as well as durability [
50
]. The amount of heavy metal ions
removed was higher at higher levels of grafting. The poly(methacrylamide)-
pregelled starch-graft-copolymers were more effective in removing Hg
+2
than all
other
metal
ions
in
question
and
follow
the
order:
Hg
+2
Pb
+2
.
An investigation was undertaken regarding the adsorption behaviours of copper
(II) and lead(II) ions from aqueous solutions by cross-linked starch-graft-
copolymers with aminoethyl groups, which were synthesised by grafting 2-
aminoethyl methacrylate onto cross-linked starch [
103
]. The dynamic adsorption
method was utilised to evaluate absorbability of graft copolymer under various
parameters such as metal ion concentration, adsorption time, grafting percentage
and adsorption temperature. The adsorption time reaching equilibrium for Cu(II)
and Pb(II) was found to be 2 h and 1 h, respectively. The adsorption capacity
increases with the increasing graft percentage and metal ions concentration. For the
starch-graft-copolymer with grafting percentage of 75.5 %, when the metal ions
concentration was about 5.0 mmol/L, the saturation adsorption capacity of Cu(II)
and Pb(II) is 21.05 mg/g and 144.08 mg/g (dry weight), respectively, and its
desorption percentage is about 95 %.
Eight levels of poly(
N
-vinyl formamide)-cross-linked pregelled starch-graft-
copolymers (graft yields in the range 11.5-55.3 %) were used for removing
different heavy metal ions from their solutions at a concentration of about
200 ppm [
42
]. The different heavy metal ions used were Cu
+2
,Pb
+2
,Cd
+2
and
Hg
+2
. The residual amount of heavy metal ions removed is governed by the %graft
yield as well as the nature of metal ion used (Fig.
3.14
). So, when the graft yield
increased from 11.5 to 55.3 % the residual removal of heavy metal increased
irrespective of the nature of metal ion used. It was also observed that poly(
N
-
vinyl formamide)-cross-linked pregelled starch-graft-copolymers were more effec-
tive in removing Hg
+2
Cu
+2
Zn
+2
Ni
+2
Co
+2
Cd
+2
>
>
>
>
>
>
than the other metal ions and followed the order: Hg
+2
>
Cd
+2
Cu
+2
. The relative atomic size, ability for metal ion to interact with
the polymer, metal ion charge density and reactivity of the metal ion affect the
adsorption behaviour.
An investigation was carried out to study the adsorption of basic violet 7, basic
blue 3, direct yellow 50 and acid red 37 from aqueous solutions by the water-
insoluble modified starch containing amidoxime groups and rice straw. The effects
of initial pH of the solution, pollutant concentration and treatment time on the
adsorption were studied and it was found that the maximum adsorption was at 1:2
(starch/acrylonitrile) at irradiation dose 30 kGy [
46
].
By grafting flexible poly(acrylic acid) chains onto the polysaccharide backbone,
it is possible to develop efficient and shear stable polymers for water treatment in
industrial effluents and mineral processing. In the flocculation of bauxite red mud
suspensions, starch-g-poly(acrylic acid) can be effectively used. A synergetically
acting new flocculant was synthesised by graft copolymerisation of corn starch
acrylamide and sodium xanthate using epichlorohydrin as cross-linking agent and
CAN as polymerisation initiator which exhibits excellent flocculation and capacity
Pb
+2
>
>
