An Electrochemical Oxidation and Intercalation Strategy for Iodide Removal Using LDHs.

Area of Science:

• Environmental Science
• Materials Science
• Electrochemistry

Background:

• Radioactive iodide poses significant risks to ecosystems and human health, necessitating effective aquatic pollution mitigation strategies.
• Layered double hydroxides (LDHs) are cost-effective 2D adsorbents for anion pollutants, but show limited affinity for iodide.
• Efficient iodide removal and immobilization are crucial for managing radioactive liquid waste.

Purpose of the Study:

• To develop an electrochemical strategy for iodide removal and immobilization using layered double hydroxides.
• To investigate the transformation of iodide into species with higher affinity for LDHs.
• To assess the performance and adaptability of the developed method for practical applications.

Main Methods:

• Electrochemical oxidation of iodide on a NiFe-LDH/CC electrode at varying potentials (0.6 V and 1.0 V vs Ag/AgCl).
• Characterization of iodide transformation products (I₂/I₃^- and IO₃^-).
• Analysis of adsorption mechanisms, including surface adsorption and interlayer intercalation into LDHs.

Main Results:

• Iodide was electrochemically oxidized to I₂/I₃^- and IO₃^-, achieving high adsorption capacities (962 mg g^-1 and 355 mg g^-1, respectively).
• I₂/I₃^- adsorbed weakly on the NiFe-LDH surface, while IO₃^- intercalated into the LDH interlayers with strong affinity.
• The method demonstrated high adaptability to low iodide concentrations, a wide pH range, and excellent ion selectivity.

Conclusions:

• An electrochemical oxidation and intercalation strategy using NiFe-LDH effectively removes and immobilizes iodide.
• The high affinity of iodate for LDH interlayers is attributed to hydrogen bonding and coordination with Ni atoms.
• This approach provides a foundation for efficient iodide elimination from radioactive liquid waste.