Synthesis of surface ion‑imprinted polymer for specific detection of thorium under acidic conditions

A fibrous surface ion-imprinted polymer (IIP) was synthesized for thorium removal through direct electron beam radiation using thorium as a template. Polypropylene coated by polyethylene non-woven fabrics (PE/PP) was used as a substrate. The PE/ PP non-woven fabrics were irradiated in the presence of the phosphoric monomer (2-HMPA) composed of 2-hydroxyethyl methacrylic phosphoric acid diester (50%) and monoester (50%) emulsified with the crosslinker. Hence, the formation of the three-dimensional IIP-Th crosslinked network and complexation between thorium (template) and 2-HMPA was investigated. The emulsion stability and particle size distribution of emulsion were determined using dynamic light scattering (DLS). Various factors influencing the synthesis of the thorium ion-imprinted (Th-IIP) nonwoven PE/PP such as the absorbed radiation dose, monomer concentration, and type of crosslinker were investigated. The IIP-Th was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy–energy-dispersive X-ray (SEM–EDX), and X-ray photoelectron spectroscopy (XPS) and applied as an adsorbent for the removal of thorium using the batch adsorption method. The IIP-Th achieved a maximum distribution coefficient of 3.293 g/L and selectivity ratio (Th(IV)/U(VI)) of 9.5 after 90 min of contact time under acidic conditions. The adsorption kinetics of IIP-Th followed the pseudo-second-order kinetic model for both Th(IV) adsorption and U(VI) adsorption. The synthesized fibrous surface ion-imprinted polymer is a promising candidate for the selective removal of thorium ions from aqueous solution

Modification of kenaf fibers by single step radiation functionalization of 2-hydroxyl methacrylate phosphoric acid (2-HMPA)

Phosphorylated adsorbent is commonly used in the extraction of rare earth metals and radioactive waste because of its high affinity in acidic condition. In this study, adsorbent containing phosphoric acid groups was synthesized by one-step radiation-induced grafting of 2-hydroxyl methacrylate phosphoric acid monomer (2-HMPA) onto kenaf fibers. The kenaf fibers were pre-treated with sodium chlorite prior grafting process. The incorporation of poly (2-HMPA) in the bleached kenaf fibers was confirmed by Fourier transform infrared spectroscopy (FTIR), FT-IR chemical imaging and scanning electron microscopy (SEM). The structural property was investigated using X-ray diffraction (XRD). The result revealed optimum grafting yield of 91.3% with 10% 2-HMPA and 50 kGy at 40 °C for 3 h. The performance of the synthesized adsorbent showed almost complete thorium adsorption. The removal efficiency of 99.9% thorium from aqueous solution was achieved using fibrous adsorbent at an initial thorium concentration of 10 mg/L, a reaction time of 3 h, and pH of 3 at room temperature. This single step combining grafting and functionalization to modify kenaf fibers showed sufficient property for application of natural fibers as adsorbent

Radiation grafting of DMAEMA and DMAEMA-based adsorbents for thorium adsorption

Radiation grafting of two tertiary amine methacrylates; 2-(dimethylamino)ethyl methacrylate (DMAEMA) and 2-(diethylamino)ethyl methacrylate (DEAEMA) onto polyolefin non-woven fabric (PE/PP-NWF) was comparatively investigated in this study. In addition, the absorbent preparation process, grafting kinetics, and mechanism were investigated. The thermal properties were investigated by thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC). Fourier transform infrared (FTIR) spectroscopy was performed to confirm the successful grafting and incorporation of the two monomers functional groups onto PE/PP-NWF. X-ray diffraction (XRD) analysis was used to examine the differences between the crystal sizes and structures. Lastly, the adsorption of Th(IV) ion was investigated in batch mode. The results indicate that the radiation grafting of both DMAEMA and DEAEMA onto PE/PP-NWF required high activation energies with increasing temperatures from 313 to 333 K. Furthermore, P-DMAEMA and P-DEAEMA demonstrated different adsorption behaviours towards Th(IV). Results showed that P-DEAEMA exhibited lower Th(IV) adsorption capacity compared to P-DMAEMA, although both contain similar carbonyl and tertiary amino functional groups. These findings indicate that the molecular structure of the adsorbent was responsible. The molecular sizes increased with increasing branched carbon chains from the methyl to ethyl groups. Density functional theory (DFT) analysis indicated that induced steric effect eventually increases the inter-molecular repulsions caused by the additional CH2-groups in the structure, which reduces adsorption capacity