Ultra-effective modified clinoptilolite adsorbent for selective thorium removal from radioactive residue

Abstract

This study investigated the efficacy of using phosphate-modified zeolite (PZ) as an adsorbent for removing thorium from aqueous solutions. The effects of various factors such as contact time, adsorbent mass, initial thorium concentration, and pH value of the solution on the removal efficiency were analyzed using the batch technique to obtain optimum adsorption condition. The results revealed that the optimal conditions for thorium adsorption were a contact time of 24 h, 0.03 g of PZ adsorbent, pH 3, and a temperature of 25 °C. Isotherm and kinetics parameters of the thorium adsorption on PZ were also determined, with equilibrium studies showing that the experimental data followed the Langmuir isotherm model. The maximum adsorption capacity (Qo) for thorium was found to be 17.3 mg/g with the Langmuir isotherm coefficient of 0.09 L/mg. Using phosphate anions to modify natural zeolite increased its adsorption capacity. Furthermore, adsorption kinetics studies demonstrated that the adsorption of thorium onto PZ adsorbent fitted well with the pseudo-second-order model. The applicability of the PZ adsorbent in removing thorium from real radioactive waste was also investigated, and nearly complete thorium removal was achieved (> 99%) from the leached solution obtained from cracking and leaching processes of rare earth industrial residue under optimized conditions. This study elucidates the potential of PZ adsorbent for efficient removal of thorium from rare earth residue via adsorption, leading to a reduction in waste volume for ultimate disposition.

Adsorption and safe immobilization of Sr ions in modified zeolite matrices

“…As shown in the table, the specific surface area of natural zeolite is 29.74 m 2 /g that after modification of natural zeolite using H 2 L ligand the specific surface area of natural zeolite was decreased by 12.6%. The modification of natural zeolite may have resulted in pore blockage, leading to a decrease in specific surface area, but this modification also introduced additional adsorption sites, thereby enhancing the adsorption capacity of the modified zeolite 19 .…”

Thorium Removal, Recovery and Recycling: A Membrane Challenge for Urban Mining

“…For the current work, which involves obtaining thorium from industrial residues or by-products (waste), the diagrams in Figure 2 present, as narrow technological points, the filtration and extraction operations likely to be replaced to avoid environmental pollution [ 73 , 74 ].…”

Disposal Strategy of Ion-Adsorption Rare Earth Elements Low-Level Radioactive Residues: Reduction Emission and Recovery for Aluminum and Uranium by Alkaline and Alkalescent Media

“…Rare earth elements (REEs), as a strategic resource, have drawn great attention due to their significant applications in high-tech fields. − Ion-adsorption rare earths ore (IREO) contributes approximately 80% to the global supply of REEs resources . As associated natural radioactive elements, such as uranium (U) and Thorium (Th), their enrichment , in IREO residues is followed throughout the production process of IREO. , As reported, the total radionuclide activity of IREO residues was approximately 5–300 Bq/g, which was higher than the exemption level (>1 Bq/g, GB 27742-2011) and belonged to low-level radioactive waste (<400 Bq/g, GB 02013-2017), named as ion-adsorption rare earth elements low-level radioactive residues (IREEs-LRR), leading to an increased risk of environmental pollution and health hazards. , …”

“…It is documented that the disposal and utilization of IREEs-LRR is critical for mitigating marked hazards to the environment and populace Generally, two tons of IREEs-LRR are produced for each ton of IREO, , which mainly contained aluminum-containing compounds (∼25 wt % Al 2 O 3 ), a small amount of REEs (∼1 wt % REO), and the associated radioactive elements such as uranium (∼0.05 wt % U ) and trace of Th.…”