Lanthanum and Cerium Adsorption Using Amino and Phosphate Groups Embedded in Pomegranate Peels from Their Solutions

Two low-cost adsorbents, R3 and R5, were prepared by embedding pomegranate peels and were applied for recovering rare earth elements (REEs) from their solutions. The two adsorbents were characterized by XRD, SEM, FTIR, BET, and XPS. The sorption factors of pH, initial rare earth ion concentration, contact time, and adsorbent dose were optimized. The optimal pH values were 3.5 for R3 and 4.0 for R5. The equilibration times were 90 and 120 min for reactions R3 and R5, respectively. The maximum uptake capacity reached 105 mg·g–1 for R3 and 87 mg·g–1 for R5. The adsorption data for both adsorbents fit the Langmuir and pseudo-first-order models, while thermodynamic studies indicated that the process was spontaneous and exothermic. Furthermore, the desorption efficiency was scrutinized using 1.0 M HCl, a 30 min time, and a 1:50 S/L phase ratio.