Unlocking the potential of avocado seed activated carbon: rapid and efficient adsorption of Th(IV) ions for sustainable nuclear waste management

Activated carbon derived from avocado seeds (AVSAC) was evaluated for its ability to adsorb and desorb Thorium(IV) ions, targeting applications in nuclear waste management and environmental cleanup. Extensive characterization (FTIR, XRD, SEM, TGA/DSC, BET) confirmed structural changes upon Th(IV) uptake; notably, FTIR indicated hydroxyl and aromatic groups participate in binding, while SEM and BET showed significantly reduced porosity and surface area, consistent with effective adsorption. At pH 3.0, a fixed-bed column (0.50 g AVSAC; flow rate 0.25 mL min⁻¹; residence time 4 min mL⁻¹) treated 50 mL of 750 mg L⁻¹ Th(IV), achieving 97.3% removal (36.5 mg captured; 73 mg g⁻¹ working capacity). The adsorption was remarkably fast, sequestering 94% of Th(IV) within five minutes. Kinetic data fit a pseudo-second-order model well, and equilibrium data aligned with the Freundlich isotherm, consistent with PSO behavior on a heterogeneous surface; overall uptake is predominantly physical (thermodynamics/D-R), with localized Th-O coordination contributions. Thermodynamic analysis revealed a spontaneous and endothermic process. Regeneration studies showed that 1.00 M nitric acid could recover 70.5% of the adsorbed thorium. Overall, this work highlights AVSAC as a highly promising, efficient, and regenerable adsorbent for removing Th(IV) from aqueous solutions, offering valuable insights for treating contaminated water streams.