Efficient separation of strontium radionuclides from high-salinity wastewater by zeolite 4A synthesized from Bayer process liquids

Ivana Smičiklas,Marijana Nodilo,Slavko Smiljanić,Mihajlo Jović,Ivana Coha,Željko Grahek,Marija Šljivić-Ivanović

doi:10.1038/s41598-021-81255-y

Ivana Smičiklas, Marijana Nodilo + Show 5 more

Open Access

https://doi.org/10.1038/s41598-021-81255-y

Copy DOI

Abstract

The efficient, selective, and economical sorbents for the removal of Sr radionuclides are largely needed for the decontamination of effluents with high salinity. In this study, the removal of Sr was investigated using the zeolite produced from the Bayer process liquids. Based on the XRD, SEM/EDS analysis, the product was pure and highly crystalline zeolite 4A (Z4A). Removal of Sr was fast (5 min for 100% removal at 8.80 mg/L), with high maximum sorption capacity (252.5 mg/L), and independent on the initial pH in the range 3.5–9.0. Specific sorption of Sr by protonated groups on the Z4A surface was operating in addition to ion-exchange with Na ions. The selectivity of Z4A decreased in the order Sr > Ca > K > Mg > Na. 84% of Sr was separated from seawater within 5 min, at the Z4A dose of 5 g/L, while efficiency increased to 99% using the dose of 20 g/L. Desorption of radioisotope 89Sr from seawater/Z4A solid residue was very low in deionized water (0.1–0.2%) and groundwater (0.7%) during 60 days of leaching. Z4A is a cost-effective, selective, and high-capacity medium for Sr removal, which provides high stability of retained radionuclides.

Highlights

Liquid radioactive waste (LRW) streams from different sources display a range of radioactive substances with different types of radioactive decay, half-lives (t1/2), activity concentrations, and chemical p roperties[1], and a variety of inactive c onstituents[2]
Examples of LRW with seawater come from power reactors of civil and navy vessels[11] and arise following the nuclear accidents like the one at the Fukushima Daiichi nuclear power plant (NPP) where the seawater was initially pumped into the reactors to maintain cooling during the e mergency[12]
The X-ray diffraction (XRD)-based qualitative and quantitative analysis of zeolite 4A (Z4A) crystalline phases has been performed by Rietveld structural refinement (Fig. 1)

Summary

Introduction

Liquid radioactive waste (LRW) streams from different sources display a range of radioactive substances with different types of radioactive decay, half-lives (t1/2), activity concentrations, and chemical p roperties[1], and a variety of inactive c onstituents[2]. The amounts of Sr, removed by Z4A from the solutions with different initial concentrations, are presented in the form of the sorption isotherm (Fig. 4a).

Results

Conclusion