Removal of ¹⁰⁶Ru from Actual Low‐Level Radioactive Waste Solutions Using Polyaniline as Anion‐Exchanger

Abstract

Polyaniline (PANI) was found to exhibit high affinity for ruthenium (Ru) with comparatively easy desorption and recovery. Based on this, both batch and column experiments were carried out to assess the feasibility of using PANI for the removal of radioruthenium (¹⁰⁶Ru) in low‐level radioactive waste (LLW) streams. Various experimental parameters such as pH, contact time, ratio of PANI:volume of solution, and desorption of Ru from PANI were studied using inactive (spiked with known amount of Ru) and actual LLW solutions. In the case of inactive experiments, inductively coupled plasma‐mass spectrometry (ICP‐MS) was used for the estimation of ruthenium whereas the high purity Germanium gamma detector (HPGe) detector was used for the assay of radioruthenium in active experiments. Quantitative (>95%) removal of Ru occurs at pH>4.5 with high K_d (∼8300) values in both the cases. Kinetic studies showed that a contact time of 10–15 min was sufficient to reach equilibrium. Column experiments demonstrated that the polyaniline is capable of removing about 29±2 mg/g of Ru from actual LLW solutions, with near complete removal of active ruthenium from treated samples. The sorbed Ru from the column could be leached out using 4 M HCl. The regenerated sorbent exhibited relatively the same initial binding capacity of Ru even after five cycles of reuse. Polyaniline appears very effective for the removal of radioruthenium from actual LLW solutions.

Keywords:

• ICP‐MS
• Polyaniline
• ¹⁰⁶Ru
• low‐level radioactive waste

Acknowledgment

The authors thank Dr. T. Mukherjee, Associate Director, Chemistry Group, BARC, and Shri Kanwar Raj, Head, Waste Management Division, BARC, for their support and encouragement. The help provided by Dr. B. S. Tomar, Head, Actinide Chemistry Section, Radiochemistry Division, BARC, is gratefully acknowledged. The authors thank Shri Sanjiv Kumar for his help during the preparation of polyaniline.