The removal and recovery of thorium(IV) [Th(IV)] ions
from aqueous
solutions were investigated using poly(methacrylic acid)-grafted-cellulose/bentonite
(PMAA-g-Cell/Bent) superabsorbent composite through batch adsorption
experiments. Surface characterizations of the adsorbent were investigated.
The adsorbent showed significant Th(IV) removal (>99.7%) at pH
5.0.
The influence of coexisting ions on the adsorption of Th(IV) was studied.
Mass transfer aspects of Th(IV) adsorption onto PMAA-g-Cell/Bent were
evaluated. The Sips adsorption isotherm described the adsorption data
very well, with a maximum adsorption capacity of 188.1 mg/g. Thermodynamic
parameters such as standard enthalpy (ΔH°),
standard entropy (ΔS°), standard free
energy (ΔG°), activation energy (E
a), isosteric enthalpy (ΔH
x
), and entropy (ΔS
x
) were calculated. Tests with a seawater
sample revealed the effectiveness of PMAA-g-Cell/Bent for adsorptive
removal of Th(IV) from aqueous solutions. Desorption experiments showed
that 0.1 M HNO3 can effectively desorb adsorbed thorium
ions with a contact time of 3 h. A single stage batch reactor is designed
for commercial applicability of the adsorbent.
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