124 including pH, contact time, uranium concentration, and adsorbent dose, was systematically investigated to optimize the removal process. 2. MATERIALS AND METHODS Moringa Oleifera seeds were obtained from a local farmer in Setúbal, south of Portugal. The Chitosan was obtained from Thermo Fisher Scientific, with a CAS number of 9012-76-4 and a molecular weight of 100.000–300.000, as an off-white to yellowish-beige powder. For the laboratory experiments, the MOS shells were removed. The seeds were then washed with distilled water and dried in an oven at over 100 °C until a constant weight. The seeds were ground into powder using a small coffee grinder. The Chitosan was used as received, without any additional preparation. Two sets of experiments were conducted to assess the ability of Chitosan and Moringa Oleifera to remove uranium from water. Distilled water was spiked with a known concentration of uranium, yielding three 1-L samples at approximately 10, 40, and 400 μg/L. Three batch tests were performed using 1 g of crushed Moringa Oleifera seeds mixed with water containing uranium at different considered concentrations. The extraction steps were performed after 2 and 4 hours of contact time. Each test was conducted in a sealed beaker with continuous mixing. The beaker was then left to settle, and a 100 mL sample was extracted using an air pump from VIDROLAS-VL2 and a 55 mm 1240 filter paper from FILTER-LAB®. The extracted liquid was then poured into a 100 mL plastic bottle. The same procedure was employed for the Chitosan. The solution's pH was finally adjusted to 1.7 to preserve the samples and avoid precipitation. The samples were then sealed and left to settle for further testing of the final uranium concentration in the extracted liquids. The liquid extractions from the experiments were further prepared in accordance with ISO 13169:2018 at the Laboratory of Natural Radioactivity in Coimbra (LRN). Water samples were acidified with nitric acid to a pH of 1.7 ± 0.2, after which a complexing agent [bis(2-ethylhexyl) hydrogen phosphate, HDEHP] and the scintillation cocktail Optiscint (Revvity) were added. The mixture was stirred and left to stand until phase separation occurred between the aqueous layer and the less dense scintillation cocktail. The scintillation phase was collected in a vial and analyzed by liquid scintillation counting with the Quantulus 1220 and Quantulus GCT 6220 counters (Revvity). Process efficiency was determined using a natural-uranium standard supplied by the Czech Metrology Institute. 3. RESULTS The Chitosan (CS) used in this experiment was unmodified. As noted by Xu et al. (2015), unmodified Chitosan often yields limited results; however, chemical modification can alter its functional groups, significantly increasing its removal efficiency. Also, Shi et al. (2024) used CaCO3-Doped Chitosan modified with PO43– to effectively remove uranium from water. A recent
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