We synthesized and characterized amidoxime-modified Fe₃O₄/SiO₂ core-shell magnetic microspheres tailored for maximal U(VI) sorption efficiency from seawater. Through meticulous structure and spectroscopy analyses, the microspheres, which were designed with amidoxime functionality, exhibited remarkable U(VI) sorption capabilities compared to raw silica-coated Fe₃O₄ counterparts. The maximum percent uranium adsorption (98.57%) was achieved at 60 minutes with 0.05 g of adsorbent, using a synthetic solution of 25 mg L⁻¹ UO₂(CH₃COO)₂. 2H₂O at pH 7 and 25 C (298 K). The kinetic studies highlighted rapid equilibrium achieved within 1 hours. Following the pseudo-second-order model, the microspheres reflected a maximum sorption capacity of 24.286 mg g^-1 at pH 7 and 298 K. The U(VI)-loaded microspheres could be efficiently separated via an external magnetic field with adsorption efficiency of 91.67% at pH 6.5 and efficiently regenerated by HCl, indicating their potential for U(VI) preconcentration and separation from seawater. This research contributed to the development of high-performance sorbents for U(VI) removal and holds promise for solving the radioactive element elimination and enrichment, performing its stability, selectivity, and reusability across multiple cycles.

Initial research was focused on the production of calcium-based alginate-chitosan membranes from coral skeletons collected from the Gulf of Prigi. The coral skeleton's composition was analyzed using XRF, revealing a calcium oxide content ranging from 90.86% to 93.41%. These membranes showed the significant potential for salt adsorption, as evidenced by FTIR analysis, which showed the presence of functional groups such as -OH, C = O, C-O, and N-H involved in the NaCl binding process. SEM analysis showed the particle size diameter of 185.96 nm, indicating a relatively rough and porous morphology. Under optimized conditions, the resulting calcium-based alginate-chitosan membrane achieved 40.5% Na⁺ and 48.39% Cl^- adsorptions, using 13.3 mL of 2% (w/v) chitosan and 26.6 mL of 2% (w/v) alginate with a 40-minutes contact time. The subsequent we applied for the desalination potential of calcium alginate, revealing the efficient reduction of NaCl levels in seawater. The calcium of coral skeletons collected was 90.86% and 93.41% before and after calcination, respectively, affirming the dominant calcium composition suitable for calcium alginate production. We identified an optimal 8-minute contact time for calcium alginate to effectively absorb NaCl, resulting in an 88.17% and 50% for Na⁺ and Cl^- absorptions. We applied the addition of chitosan into calcium-alginate membranes and its impact on enhancing salt adsorption efficiency for seawater desalination.

We developed a Fe₃O₄/SiO₂/CaCO₃ magnetic nanocomposite adsorbent, with SiO₂ synthesized from sea sand and CaCO₃ derived from coral skeletons. The Fe₃O₄/SiO₂/CaCO₃ nanocomposite was characterized and employed as an adsorbent to reduce ammonia levels in shrimp pond wastewater where ammonia concentrations ranged from 11.9 to 38.8 mg/L. We further explored the effects of various parameters on the removal efficiency, adsorption capacity, thermodynamics, isoterm, and kinetics of the adsorption process. Specifically, we examined the influence of pH (3–8), adsorbent mass (0.025–0.25 g), temperature (27–60 ℃), and contact time (10–120 min). Ammonia concentrations in the filtrate were measured using the Nessler method. The synthesis of CaCO₃ from coral skeleton, SiO₂ from sand, and Fe₃O₄/SiO₂/CaCO₃ adsorbent was successfully achieved, as confirmed by XRF, FTIR, and XRD characterizations. The adsorption process adhered to the second-order kinetics model, exhibited spontaneous behavior with a negative ΔG value, and followed the Langmuir isotherm model (R² = 0.9267). The results indicated an optimal adsorbent mass of 0.025 g, achieving 89.3% adsorption at 60 minutes of contact time, a temperature of 27 ℃, and an optimal pH of 5. When applied to shrimp pond wastewater, the Fe₃O₄/SiO₂/CaCO₃ adsorbent demonstrated an adsorption efficiency ranging from 52.1% to 86.8% and an adsorption capacity between 6.2 and 30.9 mg/g.