Evaluating Solid Sorbents for Recycling Wash Waters Containing Strontium and Calcium

Area of Science:

• Environmental Science
• Radiochemistry
• Materials Science

Background:

• The Integrated Wash-Aid, Treatment, and Emergency Reuse System (IWATERS) is designed for rapid reduction of radioactive contamination and recycling of contaminated waters.
• Initial development focused on cesium decontamination using salt and surfactant additives, with subsequent water recycling through selective sorbent filtration beds.

Purpose of the Study:

• To adapt the IWATERS for strontium decontamination by identifying suitable additives.
• To investigate the effect of calcium (Ca2+) as a potential additive on strontium removal efficiency.

Main Methods:

• Literature review to identify potential additives and assess existing research on sorbent performance.
• Batch tests to evaluate the effectiveness of various sorbents in the presence of calcium.
• Surface complexation modeling to understand the interactions between strontium, calcium, and sorbent materials.

Main Results:

• Calcium additives, while potentially beneficial for general decontamination, significantly impair the ability of many selective sorbents to remove strontium from wash water.
• Existing literature lacks data on sorbent performance at relevant (millimolar) calcium concentrations.
• Only silico-titanate sorbents demonstrated high distribution coefficients (Kd) for strontium in the presence of calcium, but these materials present challenges regarding cost and availability.

Conclusions:

• The presence of calcium ions poses a significant challenge for strontium removal in the IWATERS system.
• Further research is needed to identify alternative additives or sorbent materials that can effectively remove strontium in the presence of calcium, enabling in situ water recycling.