Development and Evaluation of NiAl LDH-based Beads for I– Sorption Under Aqueous Solution

Radioactive iodine isotopes (129I and 131I) from spent nuclear fuel pose significant environmental risks due to high radioactivity and mobility in aqueous systems. This study embedded NiAl Layered Double Hydroxide (LDH) within sodium alginate and poly vinyl alcohol matrices by crosslinking with CaCl2 to fabricate bead-type sorbents for I– removal. XRD and FT-IR analyses confirmed that the crystallinity of NiAl LDH was retained within the beads, indicating structural stability. However, the sorption capacity of NiAl LDH beads (0.2151–0.2489 mmol·g–1) was lower than that of pristine NiAl LDH powder (0.6750 mmol·g–1), primarily due to partial anion-exchange of interlayer NO₃– by Cl– during bead formation, as Cl– has a higher affinity than NO₃–. Despite this, effective I– sorption occurred. Zeta potential measurements revealed an increase in surface potential after I– sorption, which contradicted the typical behavior of electrostatic attraction. This suggests that structural rearrangement of the bead, driven by Na+–Ca2+ exchange under NaI used for I– solution, may have led to increased LDH surface exposure. This exposure enabled I– sorption via anion-exchange, allowing partial substitution of interlayer anions. These findings can offer insights for the design of bead-type sorbents optimized for radioactive iodine removal.