Quaternary phosphonium modified cellulose microsphere adsorbent for ⁹⁹Tc decontamination with ultra-high selectivity

Area of Science:

• Radiochemistry
• Materials Science
• Environmental Engineering

Background:

• Radioactive pertechnetate (TcO4-) removal from nuclear waste is critical for safe spent nuclear fuel reprocessing and environmental remediation.
• Separating TcO4- from complex waste streams containing excess competitive anions presents a significant challenge for existing adsorbents.

Purpose of the Study:

• To develop an economical and environmentally friendly adsorbent with ultra-high selectivity for TcO4-.
• To evaluate the adsorption capacity and selectivity of the novel adsorbent in simulated acidic waste solutions.

Main Methods:

• Modification of cellulose microspheres using pre-radiation induced grafting polymerization to create quaternary phosphonium-decorated adsorbents (CMS-g-VBPPh3NO3).
• Evaluation of adsorption capacity using a surrogate anion (ReO4-), achieving 251 mg g-1.
• Determination of selectivity factor against nitrate (NO3-) in nitric acid, yielding a factor of 168.

Main Results:

• The developed CMS-g-VBPPh3NO3 adsorbent exhibits exceptional anion-exchange selectivity for TcO4- over common anions like NO3-.
• Column studies demonstrated effective separation of TcO4- from simulated acidic waste solutions containing various radionuclides and metal ions.
• Tracer experiments confirmed superior adsorption selectivity of CMS-g-VBPPh3NO3 for TcO4- compared to ReO4-.

Conclusions:

• CMS-g-VBPPh3NO3 offers a promising solution for the selective decontamination of radioactive TcO4- from nuclear waste.
• The adsorbent's high selectivity and capacity, combined with its cost-effective and eco-friendly nature, make it suitable for practical applications in nuclear waste management.