Kinetic and Equilibrium Profiles of Adsorptive Recovery of Thorium(IV) from Aqueous Solutions Using Poly(methacrylic acid) Grafted Cellulose/Bentonite Superabsorbent Composite

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 (Delta H degrees), standard entropy (Delta S degrees), standard free energy (Delta G degrees), activation energy (E-a), isosteric enthalpy (Delta H-x), and entropy (Delta S-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.